For Defence, this creates a strategic challenge. Traditional acquisition, training and doctrinal development cycles were designed for an era where capability evolved over decades. Modern conflict increasingly demands adaptation measured in weeks and months. This challenge is particularly pertinent when considering deception. Historically, deception could often be achieved through a single effect, whether physical, electronic or informational. Modern sensor fusion has changed that reality. Adversaries increasingly combine radio frequency (RF), thermal, acoustic, visual and radar signatures to identify, classify and target forces. As a result, Electronic Warfare Deception alone is no longer sufficient. Effective deception must become integrated, combined and multi-spectral.

Mission Partners such as Team FORTITUDE have a critical role to play in supporting this effort, working alongside military operators, trainers and capability developers to accelerate experimentation, training and operational learning. Equally important are interoperability standards that enable emerging capabilities to communicate and operate together without creating unnecessary barriers to innovation.

To explore these challenges and opportunities in greater depth, download Winning the Adaptation Battle: Multi-Spectral Deception, Interoperability and the Role of the Mission Partners and discover how innovation, collaboration and interoperability are helping shape future Defence capabilities.

The post Winning the Adaptation Battle: Multi-Spectral Deception, Interoperability and the Role of the Mission Partners appeared first on Filtronic.

Digital Intermediate Frequency (DIF) or ‘RF-over-IP’ technology offers the opportunity for satellite data communications to scale up rapidly and cost-effectively, while preserving signal quality and improving resilience in the face of growing demand for data.

By encoding analogue RF signals into standard Internet Protocol (IP) packets, data can be transported more reliably and securely, at scale and with minimal signal degradation over fibre cables, even over long distances. In a digitised system, analogue RF signals are encapsulated as IP packets (digitised) at source and transmitted over standard ethernet connections to the antenna station. Here, signals are reconstructed back into RF (de-digitised), upconverted to the relevant frequency, and amplified for transmission via the antenna to satellites.

This approach removes the need for signals to be modulated and demodulated by modems and associated equipment at the antenna station. Using RF-over-IP not only streamlines signal transport, but also facilitates the integration of RF systems into modern digital infrastructures, marking a significant advancement in satellite communications technology.

Figure 1: DIFI implementation

Why is digitisation needed in satellite communications?

The continued exponential growth in data traffic means that satellite communications need to rapidly increase capacity, resilience and security. The transition to DIFI directly addresses these pressures, particularly for operators wishing to move into higher mmWave frequencies which typically use wider bandwidth modulation such as at Ka, Q/V, E and W bands.

The huge growth in demand for data has seen the rapid expansion of LEO satellite constellations and high-throughput satellites (HTS) to deliver the necessary high-speed, high-capacity connectivity across non-terrestrial networks. However, current analogue ground systems are struggling to keep pace and cannot be scaled up quickly enough to meet future demand. These legacy hardware-heavy ground architectures are reaching their limits in terms of bandwidth, cost, capacity, scalability and flexibility.

Transforming to digital infrastructure and transitioning towards higher frequencies solves these issues and will enable satcom operators to rapidly and cost-effectively scale up their operations to meet growing demand.

How it works

Digital IF provides a streamlined, secure, high-capacity transport system for RF signals. In the ground segment of a traditional satcom system, antenna sites require routers, modems, IF matrices and cross-site cabling to handle incoming IF signals and convert them into RF signals for transmission up to satellites (see Figure 2a).

DIFI moves this capability back to the source of the data (for example, a data centre or hub) so that instead of sending the data to multiple antenna locations and modulating at the terminal, the data is sampled and encapsulated into IP packets at source using a single piece of digitisation hardware. In future this could even be a virtualised modem, since the RF to IP conversion can be done in the cloud.

The IP packets are transmitted over standard ethernet networks to the antenna station, where a simple de-digitisation unit reconstitutes the digital IP packets back into RF signals for transmission to satellites. This process happens in reverse for signals received by the antenna from satellites. It means that antenna terminals will no longer need to have routers, modems, cross-site cabling and associated infrastructure on site (see Figure 2b).

This is all replaced by a single digitiser/de-digitiser. This device extracts the RF signals from the incoming digital signals, which then pass through block upconverters (BUCs) and power amplifiers (SSPAs) to the antenna. In the other direction, RF signals received from satellites travel via low-noise amplifiers (LNAs) and block downconverters (BDCs) into the digitiser to be converted into IP packets for transmission to terrestrial destinations.

Figure 2a: Traditional satcom ground terminal layout (analogue system)

Figure 2b: Satcom ground terminal layout following DIFI upgrade

Advantages of digital over analogue RF systems

By eliminating a whole swathe of analogue hardware and cabling currently used to process signals at the antenna station, the switch to Digital IF reduces capital expenditure and operating expenditure, simplifies installation, operation and maintenance, improves signal quality and security, and increases network capacity.

– Capex savings

Much of the antenna terminal infrastructure, from baseband modems to IF/RF cross-site cabling, as well as some aspects of up and down conversion, can be replaced by a single digitiser/de-digitiser. This can be located close to the antenna, alongside existing upconverters and downconverters – removing the need for a separate terminal building to house the analogue hardware.

The wholesale removal of hardware translates to significantly lower capital expenditure in the development of new ground-segment infrastructure. It also equates to a significant reduction in deployment times for these new assets, since DIFI equipment is much simpler and faster to install.

– Opex savings

For existing antenna sites that need to be upgraded for the Digital IF environment, the removal of legacy hardware and cabling results in long-term savings in operating and maintenance costs. With no need to retain a terminal building at the antenna site, ongoing rental and building-related costs are also eliminated. In practice, these savings in operational costs are more than sufficient to fund the conversion to DIFI.

– Signal quality

By digitising signals at source and de-digitising them close to the antenna, signal quality is maintained and losses in transmission significantly reduced. In analogue systems, IF signals sent over long distances inevitably experience degradation, due to losses in the coaxial cables.

– Improved security

Coaxial cables used in analogue systems can radiate signals, making them vulnerable to interception. Moving to RF-over-IP and transporting signals via ethernet cables significantly improves data security. Digital signals can be further encrypted, adding another layer of protection. The structure of DIFI networks also means that ground segment teams can focus their efforts on protecting one centralised secure facility where analogue signals are encapsulated as IP packets, rather than having to guard against vulnerabilities at each individual antenna site.

– Greater flexibility

In a digitised system, more aspects of signal transmission can be managed by software, rather than hardware, making it more flexible and easier to implement and upgrade. It also enables traditional RF systems to be integrated into modern digital cloud infrastructures.

 – Increased capacity

Digitisation increases data capacity in the network, allowing satcom ground segment operations to scale up as demand for data increases. It means ground infrastructure can quickly ramp up capacity to keep pace with the expansion of high-throughput satellites (HTS) and LEO satellite constellations.

DIFI for industry-wide interoperability

To facilitate the widespread adoption of Digital IF systems, all participants in the satellite ground segment market need to adopt an agreed, universal digital RF/IF standard. This will enable full interoperability across all hardware in the sector.

The Digital Intermediate Frequency Interoperability (DIFI) consortium was established to support the digital transformation of space, satellite and related industries by providing just such a “simple, open, interoperable Digital IF/RF standard that replaces the natural interoperability of analogue IF signals and helps prevent vendor lock-in.”

As a member of the DIFI consortium, Filtronic has been closely involved in the evolution of the DIFI standard. Most of the industry has now adopted IEEE-ISTO Std 4900-2021 v1.3 July 2025 and members of the DIFI consortium, including Filtronic, are participating in regular interoperability trials.

High-throughput, high-bandwidth solution from Filtronic

To support the digital evolution of the satcom industry and open the door to RF-over-IP for satellite ground operations, Filtronic has developed an advanced digitiser/de-digitiser. By combining digitising and de-digitising functions in one unit, our device provides a compact solution that can be deployed both at antenna sites to toggle signals between analogue and IP formats, and at data sources on the ground to encapsulate RF signals as IP packets prior to transmission.

What sets our new device apart is the combination of wide bandwidth and high channel count. The platform features six transmit-and-receive RF channels, each capable of interfacing to carriers of over 2.5GHz of instantaneous bandwidth on IF carrier frequencies up to 6GHz. The RF signals can be sampled at 8 to 14-bit level and the encapsulated RF signals are transmitted over IP via a 100Gbit ethernet port. A second port can be enabled if additional data rates are needed. This exceptionally wide bandwidth provides a substantial performance advantage over existing solutions on the market.

Our solution has also been designed with a modular architecture, so it can be tailored to specific frequency bands and, where required, incorporate up/down conversion within the unit. An internal RF mezzanine board can be customised with tailored IF filtering for block upconverter and block downconverter applications, giving operators the flexibility to adapt the system to the specific needs of their ground segment.

Future-proofing the satcom ground segment

Digital IF is a pivotal technology for the future of satellite communications, and its adoption marks a major step forward in enabling truly virtualised, cloud‑ready architectures.

Satcom industry technology suppliers must prepare to future-proof their products for an increasingly digitised environment. Every component, from solid-state power amplifiers and block upconverters to channelisers and digitisers will need to have built-in capability to interface with the DIFI ecosystem, enabling seamless interoperability across the wider satcom network.

In the near future, satcom operators will expect all ground segment hardware to be compatible with the DIFI environment, and for all equipment to conform to the agreed DIFI standard. This will allow operators to connect DIFI-enabled hardware from any manufacturer into their ground segment infrastructure, future-proofing their networks for secure, reliable performance in the emerging digital era. 

To find out more about the transition to DIFI and the possibilities of new RF-over-IP technology for the satcom industry, please contact Filtronic.

The post Reducing cost and Complexity in Satcom: The power of RF-over-IP appeared first on Filtronic.

Synopsis:
Transmitting clear, distortion-free satellite signals requires amplifiers with high power and excellent linearity. This paper explores the importance of power linearity (Plin)—the amplifier’s ability to boost signals without distortion—and how it differs from power saturation (Psat) and P1dB compression. It outlines key measurement methods such as spectral regrowth, third-order intermodulation (IM3), and noise power ratio (NPR), and compares the performance of travelling wave tube amplifiers (TWTAs) with solid-state power amplifiers (SSPAs). With the advent of gallium nitride (GaN) technology, SSPAs now achieve high power and linearity close to saturation, surpassing traditional TWTAs. As a result, GaN SSPAs are becoming the preferred choice for modern satellite uplinks, enabling scalable, reliable, and distortion-free communications across higher frequency bands.

Transmitting clear, strong and undistorted communications signals from the ground to orbiting satellites requires amplifiers with high power output, and excellent linearity. Specifying the right amplifiers for demanding, multi-channel satellite uplink applications requires an understanding of power saturation, power linearity and compression and how this affects digitally modulated signals. In this white paper, we explore power linearity in high-power satcom applications, how it is measured and how it is delivered by the two main amplifier technologies: travelling wave tubes and solid-state power amplifiers.

Power linearity is critical in satellite communications because it determines the ability of an amplifier to increase the signal level without creating distortion. Linearity can be described as the degree to which an amplifier’s output is an accurate, undistorted representation of its input signal. The power linearity (Plin) of an amplifier is different to its power saturation (Psat), which is the maximum power output the amplifier can produce. At the saturation point, linearity is severely compromised and output signals are highly distorted.

Why linearity matters for satcom signal amplifiers  

With digital signal modulation, it’s vital to keep signals as linear as possible throughout the transmission chain, for both the uplink and downlink to and from  the satellites. That means ensuring amplifiers or any other devices in the chain are not operated under compression. To avoid compressing signals, amplifiers must be operated at a level below their power saturation point (backed off) so that linearity is maintained and signals are not distorted.

Assessing the power linearity (Plin) of amplifiers is not always straightforward, given that the stated power rating for amplifiers usually relates to saturated power (Psat). While Psat is an important specification, a more practical measure of useable power is often the P1dB point, where gain drops by 1dB from its constant value and signals are more linear and less distorted. This is the point that marks the boundary between an amplifier’s linear and non-linear operational regions.

The extent to which power needs to be backed off from the saturation point to achieve linearity differs between the two main amplifier technologies – travelling wave tube amplifiers (TWTAs) and solid-state power amplifiers (SSPAs). We’ll explore these differences later, but first it’s useful to understand the different ways power linearity is calculated for amplifiers handling multiple signals, to help specifiers make well-informed, like-for-like comparisons when reviewing amplifier capabilities.    

Useful definitions

Power saturation (Psat) is the maximum power output of an amplifier. It is the point at which the amplifier is saturated and can no longer increase its output power, even if the input power is further increased.

P1dB is the compression point of an amplifier at which its output power is 1dB less than it would be under ideal linear conditions. It’s a specification that indicates the upper limit of an amplifier’s linear operating range, where the gain begins to compress and the output power no longer increases in direct proportion to the input power.

Power linearity (Plin) is the ability of an amplifier to increase the power of a signal without distortion. A perfectly linear amplifier will increase the power of the output signal in direct proportion to the input power. If there is just one signal (or carrier) within an amplifier, the maximum power linearity can be the same as P1dB. However, for amplifiers handling signals from multiple carriers, power linearity can be defined in three different ways: spectral regrowth, 3rd order intermodulation (IM3) or noise power ratio (NPR).

How to measure power linearity (Plin) for satellite communications

For satellite communications, specifiers need to understand the differences between saturated power and linear power, and the relationship between linear power and P1dB to ensure the most appropriate amplifier technology is chosen. For amplifiers carrying multiple signals, there are three different ways to measure power linearity:

1. Single modulated carrier – spectral regrowth

This method of defining linearity is typically used for a digitally modulated single carrier being transmitted through a high-power amplifier (HPA). This definition is commonly used when multiple transmitters from different sources are transmitting to the same satellite, with each transmission having a defined bandwidth in which to operate. The aim is to prevent interference in adjacent channels. Outside of each defined bandwidth there is a maximum stated level at which the modulation energy (spectral regrowth) is observed. This is particularly visible for a QPSK carrier, but harder to see for higher order modulations.

Satellite operator Eutelsat established the original spectral regrowth specification, for situations where multiple carriers were sent to a satellite transponder split into 28 MHz wide (or narrower in some cases) channels for direct-to-home (DTH) broadcast TV. This specification stated that the out-of-channel modulation should be less than 26dBc. It meant that amplifiers had to be operated considerably below their power saturation point to meet the 26dBc linearity specification. Operating an amplifier beyond this level causes the spectral regrowth to be at a higher level in the adjacent channel, thereby causing interference.

Where there are no adjacent carriers, an amplifier can be operated above this Plin level – typically to around the P1dB point, after which the signal tends to distort itself.

2. Two-tone or 3rd order intermodulation (IM3)

This is probably the most common method of specifying the power linearity of amplifiers marketed for satellite communications. It is typically specified where two or more carriers are being transmitted through an amplifier. It is directly related to the 3rd order intercept point of the amplifier. This intercept point is a mathematical concept and does not correspond to any practically occurring physical power level.

The specification required by most satellite operators is that the 3rd order intermodulations of two unmodulated tones of equal level spaced relatively close to each other (typically 10MHz spacing) should be no higher than 25dB below the level of those two unmodulated tones (or 28dB below the sum of the two tones).

3. Noise power ratio (NPR)

This method of quantifying amplifier linearity originated in the world of telecommunications. It tends to be used in satellite communications to define the required linearity of an uplink, or gateway, where the amplifier is transmitting a very wideband (typically 16-128APSK) carrier or multiple carriers of low level.

NPR is calculated as the ratio of the power in a wideband signal with a notched-out frequency band, to the power of the noise that fills that notch after the signal has passed through the amplifier. Essentially, a high NPR indicates better performance, as it means less noise has entered the notched-out frequency band due to non-linear distortion. Using this method, the Plin is typically specified as the power level at which 19dB NPR is achieved. It is usually a similar figure to the Plin level calculated using the two-tone method.

How does linearity vary between amplifier technologies?

A knowledge of these definitions of power linearity is helpful when it comes to assessing the performance of amplifiers for satellite applications. The calculation of power linearity and its relationship with power saturation is further complicated by the differences between TWTAs and SSPAs, their performance at different power and frequency levels, and the way power ratings are usually specified for these devices.

TWTAs were the original amplifier technology used in RF communications. They are well established, reliable and still widely used. TWTAs are structurally complex, vacuum-based electronic devices that are time-consuming and expensive to manufacture. The challenger technology is the SSPA. These semiconductor-based devices can be produced quickly and in high volumes, at dramatically lower cost than TWTAs.

Broadly speaking, SSPAs offer better power linearity than TWTAs. Tube-based amplifiers had traditionally been recognised as having excellent amplification qualities with very low distortion. But as the number or power of signals passing through amplifiers increased, TWTAs performed less reliably and needed to be backed off considerably from their power saturation point. SSPAs, by contrast, can be operated much closer to their power saturation point while maintaining linearity.

The first TWTAs operating in the satellite bands (C, Ku, Ka) needed to be backed off from their saturation point by around 7dB to achieve the required linearity. The first SSPAs, using gallium arsenide (GaAs) semiconductors, were inherently linear in operation and only needed to be backed off from saturation point by 3dB. That meant they delivered a much better like-for-like linear performance than TWTAs.

Subsequently, linearisers were developed for use with TWTAs, which improved their linear performance and meant they only had to be backed off by 4dB or 5dB. Although this didn’t quite match the linear performance of SSPAs, TWTAs remained the amplifier technology of choice for higher-power, higher-frequency operations due to their superior efficiency. GaAs amplifiers consume around three times as much power as TWTAs when used for high-power satellite communications. Consequently, SSPAs tended to be used primarily for lower power applications.

GaN levels up power efficiency for SSPAs

The advent of gallium nitride (GaN) semiconductors for SSPAs introduced more efficient and more reliable operation at higher frequencies. While GaAs SSPAs require low-voltage, high-current power supplies, GaN amplifiers require higher-voltage, lower-current supplies, and so offer improved efficiency and reliability.

However, unlike GaAs amplifiers, the first GaN amplifiers were not inherently linear. At a point well below power saturation, GaN-based amplifiers produced a deviation or ‘kink’ in the response between input power and output power, where an increase in input power did not correlate with a proportionate increase in output. This impaired linear operation and gave GaN amplifiers a shallower slope towards Psat, which meant they did not have a P1dB point. See figure 1 (green line).

That was until a new type of corrective lineariser was developed for GaN amplifiers which ironed out this ‘kink’ in power output. It enabled GaN amplifiers to produce very good linear performance. Since then, GaN amplifiers have been developed that have a maximum power linearity (measured by either the two-tone or NPR method) just 3dB below power saturation. See figure 1 (yellow line).

The result is that GaN high-power amplifiers have now become the first choice for satellite communication uplinks, since they combine efficiencies approaching those of TWTAs with significantly better linear performance. These amplifiers are now making inroads into the higher frequency bands where TWTAs had previously dominated, such as Ka, V and E-band.

Figure 1: GaAs P1dB and equivalent GaN gain response

Ensure like-for-like comparisons between amplifiers

It’s widely recognised that linearity is vital for digitally modulated signals. What is less well understood is that to achieve optimum linearity, amplifiers must be operated below their power saturation point, and often well below their 1dB compression point. This is particularly true for TWTAs, which cannot be used anywhere near their maximum power levels for communications applications. 

Satcom specifiers need to be aware of which power level is being advertised on any amplifier and to understand the relationship between saturated power (Psat) and useable ‘linear’ power (Plin) for any amplifier – so that like-for-like comparisons can be made.

Many amplifier specifications refer to Psat levels, and TWTA specifications traditionally describe the Psat level of the tube within the device, not the final packaged device itself. The actual saturated output power of the fully packaged TWTA will be below the Psat level of the tube within it. For example, a TWTA containing a tube with a Psat of 200W would only have a saturated output power of around 150W when operating at high frequencies. To achieve linearity, this would have to be backed off further to around 50-60W.

By contrast, the saturated output power stated for SSPAs is the Psat of the device as a whole, not any of its constituent parts. Furthermore, SSPAs require less ‘back off’ from Psat to achieve linearity. So, an SSPA with a Psat of 150W, for example, would have a maximum power linearity of at least 75W for high-frequency satellite communications. 

It’s also worth noting that amplifiers for lower-power applications in point-to-point terrestrial communications are marketed according their linear operating power, and not power saturation.

Bringing clarity and new capabilities to satcom amplifiers

At Filtronic, to avoid misunderstandings, we are moving towards using power linearity (Plin) in the specification of our SSPAs. We believe that transmitters, amplifiers and other RF devices used in satellite communications should be marketed according to their useable linear power, which is the critical characteristic for undistorted signal transmission.

GaN has proved to be a game changer in delivering reliable power linearity at higher frequencies. Filtronic is at the leading edge of this push to develop GaN SSPAs for the satellite market, using our proprietary chip designs and proven expertise to develop SSPAs that are now displacing TWTA’s at higher-power levels in the higher frequency bands such as Ka, V, E  and even W band

As demand for more and faster data accelerates, so the deployment of satellite constellations and their enabling technologies needs to keep pace. Legacy TWTA technologies will not be able keep up. TWTA’s are complex and time-consuming to manufacture, particularly at scale, and there are a limited number of TWTA manufacturers worldwide, resulting in long lead times.

The emergence of semiconductor-based SSPAs that can be manufactured consistently at scale and can now outperform TWTAs for efficiency and power linearity at higher frequencies, is a game changer. It gives satellite companies the chance to acquire the volume of amplifiers they need to expand satellite deployment in line with fast-growing global demand.

To find out more about improving amplifier power linearity or specifying GaN SSPAs for high-frequency satellite communications, please contact Filtronic at sales@filtronic.com

The post Understanding power linearity and its importance in amplifier specification for satellite uplinks appeared first on Filtronic.

Amplifiers are a critical component in any long-range communications system. Positioned before the antenna, amplifiers boost the power of communications signals so they can be sent over long distances. Amplifiers are the most power-hungry component in RF communications systems, making them a key focus for performance optimisation in terms of linearity, power output and efficiency.

Tube versus semiconductor solutions 

The original amplifier technology used in RF communication systems was the Travelling Wave Tube (TWTA). It is well established, reliable and still widely used – particularly in higher frequency, high-power applications. Travelling wave tubes are structurally complex, vacuum-based electronic devices that are complex and time-consuming to manufacture.

The challenger technology is the Solid-State Power Amplifier (SSPA). These semiconductor-based devices can be produced quickly and in high volumes, at dramatically lower cost than tube amplifiers. However, they have not traditionally been able to compete with TWTAs in higher frequency, high-power applications.

Displacing the incumbent technology  

Over time, SSPAs have replaced TWTAs at the lower end of the frequency and power range. As new SSPA devices have been developed offering greater power, they have displaced TWTAs in increasingly higher frequency applications. Filtronic has been leading the way in SSPA innovation, developing increasingly powerful amplifiers that are able to operate in higher frequency bands.

Nevertheless, TWTAs remain unmatched at the highest frequencies and are the preferred technology for use in space applications for their superior power and efficiency. But SSPAs are catching up. Before we examine the latest developments in SSPA technology, let’s consider the pros and cons of each type of amplifier.

TWTA: high power, high efficiency, limited lifespan

Tube technology offers several advantages, principally high power combined with efficiency, particularly at higher frequencies. TWTAs are lightweight and have a compact footprint. On the downside, they are complicated devices that cannot be manufactured repeatedly at scale. They require stringent, precision alignment and vacuum sealing, meaning it can take months to manufacture a single tube. This complexity equates to cost. TWTAs also have a limited lifespan of around 50,000 to 100,000 hours. Output power gradually declines with age, and tubes can fail at any time without warning. When the tube fails, the signal path is immediately interrupted. Tube amplifiers also consume a lot of power, and their efficiency significantly decreases at lower output levels.

SSPA: increasing power, low cost, long lifespan

The significant benefits of solid-state amplifiers include reliability, low-cost, longevity and repeatability. SSPAs have a lifespan of up to a million hours. In Filtronic’s Cerus range of amplifiers because a single amplifier combines multiple MMIC devices, the failure of a single device only slightly reduces overall amplifier performance leading to graceful degradation rather than link failure. SSPAs typically offer much better linearity compared to TWTAs. They are also immediately operational, with no warm-up time required. The manufacturing time for SSPAs is dramatically shorter than for tube devices, and they can be produced reliably in volume. The disadvantages of SSPAs include size and weight. SSPAs are heavier and larger than tube amplifiers with comparable output power. The energy efficiency of SSPAs is also currently inferior to that of TWTAs.

Final frontier for SSPA technology

As SSPAs have replaced TWTAs in many applications, the final frontier for this semiconductor technology is space and satellite communications. Amplifiers used for satellite uplink applications must combine high power with high-frequency capabilities, which are difficult to achieve with SSPAs.

But this is where Filtronic is breaking new ground. With proprietary, ultra-low loss waveguide combining we are developing solid-state amplifiers capable of operating efficiently at mmWave frequencies while delivering the power requirements only previously possible with TWTA devices.

New developments extend SSPA capabilities

Our specialists have been able to achieve these advances in SSPA capabilities thanks to two key developments:

1. Semiconductor processes have become available that offer much higher power densities alongside higher frequency capabilities. Gallium Arsenide GaAs and Gallium nitride (GaN) semiconductors are leading the way here. At Filtronic, we have our own MMIC design capabilities, which means we can design devices specifically for the end application, to maximise performance. This has enabled us to develop the best-performing MMICs at E-band on the market.

2. We have developed proprietary technology for combining multiple devices into a single amplifier. Higher power density alone is not enough, since individual devices only deliver around 1-3W (depending upon the semiconductor technology) each at higher frequencies. Achieving the high power output required for satellite applications means combining multiple devices. Achieving the desired multiplier in output power requires very low-loss combining. Our novel combining technique has enabled us to achieve an SSPA at E-band that combines 32 devices into a single output producing the highest power 81-86GHz amplifier in the market. With a clear roadmap for further improvements.

To combine effectively, it’s vital to ensure that all the devices have similar phase performance and magnitude performance. Because we own the technology and produce many wafers, we can select similar devices from a wafer and screen them to assess their performance optimising the performance of the SSPA.

Growing demand for solid state amplifiers

SSPAs are in high demand due to their reliability, repeatability and long-life performance. Large numbers of SSPAs are used in telecommunications, for backhaul applications and base station to end user communications. In aerospace and defence, they are widely used in communications and radar systems.

In recent years, the launch of mega-constellations of satellites into Low Earth Orbit (LEO) has led to a huge increase in demand for powerful amplifiers to be supplied in volume. These new satellites are helping to deliver the full potential of 5G and provide high-speed connectivity to remote parts of the world. Previously, only a small number of amplifiers were required in space communications, to transmit and receive signals between ground stations and relatively few Geostationary Equatorial Orbit (GEO) and Medium Earth Orbit (MEO) satellites. Here, TWTAs provided the very high power required, while the high cost of these amplifiers only represented a small percentage of the overall satellite programme cost.

Now, with vast constellations of small satellites being launched, the market is becoming far more cost driven. The cost of each device becomes a significant factor when you need to equip 50,000 satellites at a time. Here, the low-cost, repeatable quality and reliable performance of SSPAs make them an attractive option.

Amplifiers for satellite payloads

For payload amplifiers located on the satellites themselves, SSPAs are making headway at lower frequencies. Space compatibility is an important consideration for these applications, where tolerance to radiation is vital. Size, weight and power are also critical, given the very high launch costs. SSPAs offer benefits over TWTAs for payload applications due to their longevity and the absence of mechanical, moving parts – making them more robust and better able to withstand shock and vibration. Thermal management is a challenge for SSPAs, however, due to the high power produced in a very small area. This becomes particularly problematic in space, where there is no airflow to dissipate heat.

Filtronic has projects underway to develop SSPAs with innovative thermal-management systems for satellite payload applications. We are initially working to develop these space-qualified solutions at Ka and Q-band with a roadmap to E -band.

Amplifiers for satellite uplinks

Satellite uplinks present different challenges. Communications from ground stations require far greater power, due to the amount of data being transmitted. This is where the benefits of TWTAs have traditionally outweighed those of SSPAs.

However, Filtronic is redressing that balance. We are now pioneering SSPA technology for applications above 45GHz. In these high-frequency bands, SSPAs have not previously been able to achieve the high power required to send signals into space. We have now developed an SSPA solution operating at 81-86GHz (E-band), which we are successfully supplying to the satellite ground station market. This amplifier is based on gallium arsenide (GaAs) semiconductors and gives around 20W of output power.

Our next step will be to develop a gallium nitride (GaN) amplifier with an 100W power output to operate at V-band (47.2-52.4GHz) frequencies. Concurrently, we are working on a GaAs amplifier to extend operations into even higher frequencies. Following this, we plan to advance our GaN amplifier capabilities for E-band applications and beyond, continuously pushing the limits of performance and frequency.

By developing high-power SSPAs for these high-frequency applications, we are delivering precisely the technology required by satellite ground stations – and creating SSPAs that can finally rival TWTAs at the higher end of the power scale.

What next for SSPAs?

The demand for data is growing exponentially worldwide. To accommodate this demand and sustain the required data levels, satellite communications need to use all available frequency bands and also move into less-crowded higher frequency bands.

As the industry moves up the frequency scale, semiconductors hold the key to developing reliable, repeatable amplifier technology. To meet demand, we need the technology at semiconductor level to deliver the fundamental power required from a single MMIC. As you move up the frequency range, integrating components becomes more challenging.

At Filtronic, we are applying our knowledge, expertise and resources to develop the increasingly high-powered SSPAs required for higher frequencies – helping the space sector keep pace with demand for more and faster data.

The post Benefits of a Solid State Power Amplifier over a Traveling Wave Tube Amplifier appeared first on Filtronic.

The semiconductor compound gallium arsenide (GaAs) has been used to manufacture monolithic microwave integrated circuits (MMICs) since they were first developed in the mid-1980s. MMICs use compound semiconductors to enhance data communications in radio frequency (RF) systems across the microwave and mmWave frequency spectrum.

GaAs was chosen as an alternative to silicon in integrated circuits because of its improved performance at higher frequencies. Silicon-based devices experience greater losses at high frequencies and can deliver less power than their compound semiconductor counterparts. GaAs is now well-established in commercial and military applications and is used extensively in RF devices ranging from consumer electronics such as smartphones to radar systems.

The emergence of GaN as an alternative to GaAs

In the push to meet even more demanding performance requirements, often driven by the needs of the defence sector, gallium nitride (GaN) emerged as an alternative to GaAs. It offers greater power density, efficiency and operating temperature all properties of GaN’s wide bandgap.

GaN has been around for almost three decades, but the lengthy processes of research, trialling and development mean that it has only more recently become established as a viable alternative to GaAs at higher frequencies. Crucially, the cost of fabrication using GaN has now been reduced to commercially acceptable levels, as a result of scaling up small prototype devices onto bigger wafer sizes. GaN is now fabricated on the same wafer sizes as GaAs, meaning the costs of the two technologies are more comparable. That gives device manufacturers the opportunity to embrace GaN MMICs to achieve the power and efficiency gains required for cost sensitive applications.

What is the optimum frequency range for GaN?

GaN crystals can be grown on a variety of substrates, including silicon carbide (SiC) and silicon (Si). It offers particularly enhanced performance at frequencies between 6GHz and 80GHz, depending on the substrate used. (see Figure 1).

Figure 1: Compound semiconductor power and frequency range.

The frequency breakpoints between semiconductor materials are changing all the time, as new processes are developed. For example, developments to shrink node sizes are enabling higher frequencies to be reached with a given semiconductor compound. This development process is ongoing with silicon. GaN MMICs are now very stable at lower frequencies, but advances are still being made in the very high frequency range. GaN doesn’t have the wide frequency range of GaAS, but with node sizes shrinking to the level of 90 nanometres, GaN is starting to be used at E-band (71-86GHz) and even at W-band (92-114GHz) – the emerging frontier of GaN-based devices.

Power and efficiency benefits of GaN

At frequencies between 6GHz and 80GHz, GaN offers valuable benefits over GaAs. Firstly, it offers significantly greater power density. For the same-sized device, GaN offers around six to eight times the power of GaAs. It means GaN can be used to achieve the same power as GaAs within a much smaller die area. The other major advantage of GaN is efficiency. At lower frequencies, GaN is around twice as efficient as GaAs. GaN is also easier to match over wide bandwidths when compared to GaAs.

These benefits make GaN the ideal choice when size, weight and power (SWAP) are critically important, as they are in many defence, space and aerospace applications.

GaN as a drop-in replacement for GaAs

There are opportunities to replace GaAs MMICs directly with GaN MMICs in some RF systems. When it’s important to retain the existing size and dimensions of a device, GaN MMICs can be used to boost power and efficiency. Such applications include military radar systems, jammers and electronic countermeasure systems, in which greater power means greater range. There are huge benefits to increasing the reach of these assets, meaning a wider area can be covered by a single asset and enabling operatives to be located further away from potential threats.

Exchanging GaAs for GaN MMICs within existing devices, the power and efficiency of hardware can be significantly enhanced, without the need to re-engineer the housing or structure of the overall module. That is especially important for RF systems that are housed in fixed locations, such as in the nose cone of an aircraft, inside ground-based radar stations, or on-board military vehicles or ships. Replacing GaAs MMICs with GaN alternatives here is an effective way to deliver major upgrades to these devices within their pre-defined footprints.

GaN is also beginning to displace GaAs in telecommunications base stations. Here, the efficiency gains achieved by GaN can significantly reduce running costs. These facilities consume a huge amount of electricity to power both the RF devices they house and the air-conditioning systems required to cool them. Energy efficiency is a major concern for the telecoms industry, particularly since new 5G base stations consume up to twice the energy of 4G stations. Any technology that can improve energy efficiency is highly prized in this sector.

Developing smaller GaN-specific modules

Alongside developments that enable GaN to be used as a drop-in replacement for GaAs, there is a drive to develop GaN-specific products, particularly at the higher end of its frequency range. Here, the greater power density of GaN enables module size, weight and an overall system cost to be reduced – producing the same power from a smaller device. The improved efficiency of these products means they require smaller heatsinks, which means less metalwork, and smaller power supplies. It means that designing modules specifically for GaN MMICs creates overall system improvements, in addition to the performance improvements derived directly from GaN.

There are challenges associated with developing smaller modules with greater power density. One of which is overheating, since the same amount of heat needs to be dissipated in a smaller area. Dissipating heat requires advanced process engineering expertise to ensure devices perform optimally for their expected lifespan. That relies on getting the details right in the choice of die-attach materials such as epoxies or sintering materials. In addition to the material selection, process engineering controls are necessary to define curing recipes and dispense patterns to ensure good adhesion, sheer strength and to avoid voiding, which is key cause of reduced lifetime and device failure.  

Advanced packaging systems, such as plastic encapsulation, are an important feature of GaN-based devices, where low cost and low weight are critical. This is particularly important on military aircraft or drones, where the increasing number of sensors on-board, allied with a limited power supply, means that reducing the weight and improving the efficiency of devices is critically important.

One application at the frontier of GaN developments is space communications. The incumbent technology used within ground stations to power the data transmission up to near space is the travelling wave tube. Used to amplify RF signals, travelling wave tubes are the highest power consuming element in the system. Filtronic’s range of Cerus Solid state Power Amplifiers (SSPAs) are now a viable alternative to travelling wave tubes, and has already developed a GaAs version that leads the market. To fully displace the incumbent technology, we are working to develop GaN systems that could deliver a fourfold increase in power at E-band frequencies.

Building UK semiconductor capabilities 

Some of the best-quality GaN developments today are happening in Asia, where semiconductor expertise and resources are well established. This is where the vast majority of the low node size silicon fabricators are based.

There is a desire in the UK to move semiconductor fabrication closer to home, motivated to a large extent by geopolitical instability. Developing this sovereign capability is important to the UK economy and security – so much so that the government has developed a National Semiconductor Strategy to encourage investment with £1B to be invested in the next 10 years.

Within the UK we already have much of the underlying technology required, including production facilities for epitaxial (EPI) wafers. These base wafers are currently shipped to fabricators in Asia to be processed into MMICs. That is the missing piece of the UK jigsaw with only small scale R&D facilities. While the UK may never be a major player in low-node silicon fabrication, due to the high cost of setting up fabrication plants, there is a significant opportunity to develop niche processes, like GaN fabrication. This could benefit sectors like defence, which require relatively small numbers of wafers per year. With the right investment, the UK could develop boutique, leading-edge operations in high-quality GaN production to meet UK demand.

End-to-end design and development expertise

Filtronic is keen to see a thriving supply chain ecosystem developed in the UK, enabling the development of GaN-based devices entirely within the country. We are already working at the cutting-edge of developments in applications for GaN MMICs.

Our end-to-end capabilities mean we can support GaN projects from the very beginning, designing MMICs for integration into packages customised for specific applications. We have the process engineering expertise to ensure devices are integrated in optimal ways within a product, and we have the system design expertise to turn products into modules and subsystems. We understand every step of the design chain and have the capabilities to produce complex, precision-manufactured GaN-based devices to the highest standards.

If you are looking to develop higher-power RF applications, please get in touch with Filtronic to discuss the possibilities of GaN MMICs.

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It’s widely reported that the world’s limited natural resources are being depleted at an unsustainable rate – and huge efforts are underway globally to develop new sustainable solutions. But one finite commodity that’s rarely talked about – but which is increasingly central to the way we live today – is the radio frequency (RF) spectrum.

The functioning of almost every part of society and industry relies on signals transmitted by radio waves at microwave (MW) and millimetre wave (mmWave) frequencies. Demand for wireless broadband access is growing exponentially, with the number of 5G subscriptions due to surpass 1 billion by the end of 2022. By the end of 2027, 5G subscriptions are forecast to reach 4.4 billion. In 2022, the monthly average usage per smartphone is expected to exceed 15GB. (Source: Ericsson Mobility Report, June 2022).

Entire industries rely on fast and reliable mobile broadband access – and new industries will open up and expand when high-speed and low latency access becomes widely available. Remote surgical procedures could be carried out by surgeons anywhere in the world, but only if high-speed signals with extremely low latency (lag) can be guaranteed. Faster data transfers could allow high-frequency city traders to secure deals nanoseconds faster than the competition. Transport applications, such as driverless cars, need rapid uninterrupted data connections along every route. Key to these and many more applications are rapid transfers of large volumes of data at high speed, across multiple devices.

The limiting factor in all of these possibilities is the availability of RF spectrum for mobile applications. Very few people are aware that the capacity of the RF spectrum is finite, and existing licensed bands are becoming highly congested.

Solutions: How to make space for more data

There are a number of possible solutions to the problem of congested RF bands.

1. The first is to make better use of the existing licensed frequency bands. The use of dual polarisation can increase capacity through spectrum re-use. In the microwave bands, the use of very high-order modulation techniques can also be used, but there is a limit and a law of diminishing returns. Additional techniques like MIMO extend capacity further, as can more effective filtering to help separate existing frequency bands, in conjunction with software that can encode signals to improve channel separation.

However, at the lower frequencies, we are already operating in very narrow bands, which don’t provide the very high data rates required for some of the more challenging applications. Fundamentally, the existing licensed bands alone will not provide sufficient bandwidth to cope with growing demand.

2. It is possible to use frequencies outside the currently licensed channels. However, in this unlicensed environment, different users are likely to be competing for the same wireless bandwidth, which is why the licensed bands are so tightly regulated. In addition, the licensed bands occupy the frequencies with the lowest environmental absorption, making them the most effective and reliable frequencies for RF communications.

3. Ultimately, backhaul data traffic will need to move into the higher frequency bands that haven’t yet been widely exploited (above 86GHz). In these higher mmWave bands, there are wide open areas of uninterrupted bandwidth available. E-band frequencies (71-86GHz) have already been licensed in most countries, offering much higher capacity than lower frequency bands due to the much wider spectrum channels. As E-band itself becomes congested, it’s inevitable that licensing and technology will need to move into even higher frequency bands, such as W-band (92-114GHz) and D-band (130-174GHz) where atmospheric absorption remains reasonably low and opens up significant new capacity.

What’s the current situation?

The currently licensed microwave bands and the lower mmWave bands are rapidly becoming saturated, increasing the likelihood of signal failure or unreliability, especially in crowded environments. As well as being narrower, bands at the lower end of the spectrum include restricted bandwidths that are reserved for specific uses, such as the military or weather satellites. Traffic on the traditional frequency bands comes from many devices and applications besides mobile phones, including emergency services radios, Satcom and aircraft radar systems.

The problem of congested airwaves is even impacting space communications. The recent arrival of new mega-constellations of low earth orbit (LEO) satellites, all trying to use the same bandwidth, means that signals have already had to move up the frequency spectrum from Ku to Ka band. For feeder links there is now a push to move into Q, V and even E-band.

Congestion in the RF spectrum is becoming a significant problem in the defence sector. If these critical communications are disrupted by interference or jamming, lives could be at risk. Filtronic is working with the defence sector to address these issues through advanced filtering techniques and by moving into frequencies that are less congested. A good example would be a shift to E-band, benefits include signals at these frequencies being highly directional, less likely to face interference and harder to jam. Power is also difficult to achieve at these frequencies reducing the opportunity for long-range jammers – meaning they are less likely to be intercepted or blocked in critical situations.

Challenges of mmWave communications

Moving up to the higher frequency bands may be a necessity, but it brings with it some major challenges.

Firstly, the atmospheric absorption is higher, therefore the signal is attenuated more if the same power level is used, meaning the distance over which signals can be transmitted in the terrestrial environment is shorter than at lower frequencies. This can be overcome by increasing power or infrastructure, but there is an additional cost.

Sub-systems for higher frequency bandwidths are more difficult to manufacture. That’s because tolerances are much tighter, and the smaller size of geometries means that machining, part placement and wire bond formation become more intricate and challenging.

The commercial availability of suitable semiconductors is another issue at very high frequencies. However, the technology required is beginning to emerge. Transmit and receive functions at this level must incorporate tightly packed semiconductor components, and there have been huge advances in the packaging techniques required to build these units.

At Filtronic, we have been pushing the boundaries of RF technologies for ten years, and have developed a suite of products that solve many of the problems at 71-86GHz (E-band). We’re now engaged in the novel solutions required to overcome the challenges at higher frequencies.

How do we get to the next level?

To successfully move up into higher frequency bands a number of factors need to combine.

Firstly, licensing authorities need to release the required bandwidth. The higher mmWave frequency bands are well understood, and the licensing bodies associated with the telecoms industry are well organised globally. E-band is now licensed in most countries, but it has taken ten years since it was first made available to achieve widespread adoption. Now there is an urgent need to start moving into W-band and, eventually, D-band. To make this happen, major industrial nations need to come together to set standards and define how these frequency bands will be used.

At the higher frequencies, standard silicon semiconductor devices are unsuitable for transmit, receive and amplification functions. New compound semiconductor processes need to be developed so that devices can be created for the higher bands. Due to the greater losses associated with higher frequency communications, the fundamental problem is achieving sufficient power to transmit signals over a reasonable distance – typically 3 to 5km for links at E-band or W-band. Different semiconductor compounds offer different capabilities for delivering high power, high frequency, or both.

At Filtronic, we have exploited gallium arsenide (GaAS) as our compound semiconductor material of choice for many years, which offers scope for further development into the higher frequency bands. More recently we have seen gallium nitride GaN processes emerging that will support frequencies up to E-band with far higher power densities offering significant benefits in higher mmWave bands. We are also actively engaged with semiconductor manufacturers to overcome the challenges of moving into higher frequencies. We can only design new chipsets once the necessary semiconductor processes are available to deliver the power required. What’s more, these semiconductor processes need to be commercially viable, to meet the volume requirements of the telecoms and other industries.

The process of designing RF devices for higher frequencies takes at least two years, once suitable semiconductor processes are commercially available. It involves working through multiple runs of MMICs to ultimately create robust and effective devices.

Keeping pace with change

The pace of growth in this market is relentless. Before long, 6G will be here. But true 6G performance capability will only be possible if there are very efficient, uncongested RF communications networks in place.

Developing technology for mmWave communications is not for the faint-hearted. The costs are high, and the challenges become greater the higher up the frequency spectrum you go. Moving from E-band to W-band does not pose major obstacles in terms of technology, but progressing into D-band will demand some fundamental changes to transmit, receive and amplification technologies. D-band opens up significantly higher data rates but requires a complete change to the architecture of devices and the way they are manufactured.

At Filtronic, we are well advanced in this endeavour. Semiconductor processes for W-band are now becoming commercially available with sufficient power to enable us to develop initial chipsets for transmit and receive functions. At D-band, we eagerly await the development of suitable semiconductor processes. Meanwhile, we are working actively to solve some of the fundamental challenges associated with interconnects and packaging for D-band products. Our aim in both cases is to ensure that the technology is available by the time licences are granted. We expect to have products ready for the release of W-band licences and are on course to meet the needs of D-band in the years ahead. Once these challenges are resolved we will be in a position to manufacture these devices at scale, as we have been doing with E-band for over 10 years.

Innovation through collaboration

Filtronic is at the centre of efforts to optimise the available RF spectrum and enable whole industries to access higher frequency bandwidths as demand grows and applications proliferate.

The telecoms industry is in the spotlight, but the problem of frequency saturation affects many other industries that rely on RF communications, including defence, aerospace, critical communications, transport and many more. Whatever your starting point on the RF spectrum, the growing demand for high-speed, reliable data with low latency means the direction of travel will always be upwards into higher frequencies.

Just as in other areas where limited resources are becoming depleted, the solution lies in bringing together technology specialists, innovators and people with the will to make change. When the pressure is on and there is a strong enough commercial and societal need for change, there is always a way to resolve even the greatest challenges.

If you are impacted by the need for more efficient and reliable data communications, or if you’re involved in any aspect of RF technology development, come and talk to Filtronic. The more we work together to maximise the capabilities of the RF spectrum, the brighter our prospects of meeting global demand for data, long into the future.

The post High-frequency solutions: how to manage burgeoning data traffic on a finite RF spectrum appeared first on Filtronic.

Over the past decade, Filtronic has achieved major advances in developing mmWave communications technology for challenging terrestrial applications. The core technology now employed within the latest iteration of its E-band transceiver (Morpheus II & Morpheus X2) and amplifier (Cerus) modules provide the basis for cost-effective, high-performance transceivers and amplifiers required for ultra-high-capacity satellite communications.

Core technology for LEO satellite communications

E-band transceivers and amplifiers are the essential components required by global communications businesses to support the planned development of mega satellite constellations in Low Earth Orbit (LEO). While these global organisations have considerable electronic engineering expertise and resources at their disposal, any in-house development programme cannot avoid the time, cost and pitfalls associated with complex E-band product development.

The core E-band technology developed by Filtronic over ten years of optimisation and innovation presents LEO satellite businesses with an opportunity to bypass these lengthy in-house development programmes – and potentially accelerate their satellite launch activities.

Innovations in E-band technology

This paper provides a high-level outline of some of the key innovations made by Filtronic in its E-band technology, since it produced its first E-band transceiver – Proteus – ten years ago. These advances in the core transceiver and amplifier technology have reduced development time and materials costs, increased production volumes and improved manufacturing yields, while significantly enhancing the performance of these complex components. Below details each generation of E-band product and product launch date.

Any product development programme aims to achieve improvements in size, weight and power, and this has been a key focus in the development of E-band components at Filtronic.

The graph below demonstrates the increasing terrestrial link budget for each next-generation transceiver development, arising from the increasing transmit power and linearity performance. NB: these numbers are for terrestrial links only, ground to low earth orbit is available on request.

These improvements have been achieved principally through the following innovations:

1. Integration

The original Proteus transceiver contained separate radio frequency (RF) and control boards within the module. Through the development process, these two circuit boards have been combined into a single board. This brings with it several advantages, including reducing the size and weight of the product, reducing the number of parts, simplifying product assembly, and reducing material costs. Most importantly, greater integration within the circuit board improves the overall performance of the module, with RF bandwidths increased from 500MHz to >2GHz, reductions in receiver noise figure and reduced spurious products.

2. Component rationalisation and improvement

The receiver in the Morpheus II has been simplified. The Proteus module featured a dual stage downconverter including an IF stage, with a number of associated MMICs and filters in the receive chain. In Morpheus, these have been replaced with an LNA & direct downconverter, significantly reducing the component count (and therefore the potential for component failure), reducing manufacturing costs and at the same time improving performance.

Filtronic’s continued investment in in-house MMIC design brought new capabilities in power amplifier performance. Morpheus II incorporates our latest generation E-Band GaAs HPA (High Power Amplifier), which increased the linear operating point of our transceiver from 16dBm (Orpheus) to 21dBm Morpheus II, and 24dBm (Morpheus X2 – including diplexer losses), at the same time as reducing the overall size and weight of the product.

Unlike Proteus, Morpheus II does not require numerous mechanical protective covers over key electronic components. Fitting these mechanical covers at the micro scale of a transceiver module was a complex procedure, adding time to the assembly process. Morpheus reduced the number of bespoke metalwork components from 7 (including integrated diplexer) to just 2 (also including the diplexer). Reducing the metalwork component count simplifies and accelerates the production process, enabling costs to be reduced and output volumes to be increased.

3. Cost reduction

The development of Morpheus II has been an iterative process of design, testing and refinement to deliver incremental improvements at every stage. When Proteus was first developed, it was an entirely new product at the leading edge of mmWave innovation. Creating such a novel new product demanded considerable time and resources to make the progression from initial concept through to development and prototyping. Thanks to the lessons learned along the way and the efficiencies introduced at each stage, the development time for Morpheus II was significantly less than for Proteus. In fact, development costs for Morpheus II were less than a tenth of the same costs for Proteus.

What’s more, the simplification of components and reduction in the number of parts in each module means that the build costs per unit for each transceiver today are a third of the cost per unit of the original product. 

4. Advances in manufacturing
 

Many of the advances in performance and cost are the result of design, integration and efficiency improvements. Further improvements in yields, accuracy and efficiency have been achieved thanks to investment in precision manufacturing and testing facilities, and the introduction of greater automation. As Filtronic has developed its in-house expertise in designing and manufacturing these complex components, it has been able to refine the manufacturing process and improve internal manufacturing yields.

This has enabled extremely complex components with intricate parts to be assembled with high degrees of accuracy, while improving operational efficiency and output. Ten years ago, Filtronic was producing 200 Proteus units per month, while today it can manufacture more than 3,000 Morpheus II transceivers in the same time. This considerable increase in output, combined with reductions in unit costs, equates to a significant financial saving per unit manufactured. It also enables Filtronic to meet our customers production ramp requirements successfully and consistently.

5. Accelerated testing

For such intricate and high-performance components as E-band transceivers and amplifiers, rigorous testing is required on every single unit. Batch testing is not sufficient to ensure that stringent quality standards are met in every module. This adds time to the production process. However, vast efficiency improvements have been made in testing, alongside the increases in production volumes. The time taken for testing, diagnostics and reworking for Proteus was over four times the length it takes for Morpheus II.

Versatile technology for space applications

It’s important to note that the core technology within Morpheus II and Cerus was developed for use in terrestrial applications. The terrestrial mobile communications market is highly cost-competitive, which means these are extremely lean products designed for optimum performance and efficient manufacture.

Crucially, for LEO satellite operators, these components are well suited to space applications. Filtronic mmWave products have been exhaustively tested, meaning they offer the proven reliability required. To date, we have shipped over 80k E and V-Band products.  Additionally, they have the necessary high-performance levels for satellite systems, where performance is crucial and maintenance and repair are impossible.  The compound semi-conductor (core MMIC line-up) technology used in Filtronic transceiver and amplifier modules is inherently radiation tolerant, making it fully compatible with space deployment. Other components, such as power supplies and micro-controllers, which feature silicon, are susceptible to radiation, but these can be replaced easily with readily available radiation-hardened alternatives.

The importance of design for manufacture

Key to the successful volume production of Morpheus II and Cerus is the fact that these products were specifically designed with precision manufacturing in mind. As a vertically integrated, multidisciplinary organisation, Filtronic has all the expertise in-house to enable the agile development of high-performance complex mmWave components for high-volume manufacturing.

The core skill base at Filtronic includes RF systems engineers, filter specialists, PCB layout designers, process engineers and software experts, to name a few. These specialists work collaboratively together, liaising with manufacturing planners, process management and testing specialists, to ensure the RF solutions developed are not only quality-assured and reliable, but can also be manufactured efficiently at scale.

When you’re dealing with such complex components, designing specifically for manufacture is essential. Problems often arise when the design process is divorced from the manufacturing operations. Filtronic has been called on many times to help improve components designed by clients in-house or by competitor organisations, which have proved inefficient to manufacture at scale. In one case, the client needed to improve yields for a V-band transceiver as production volumes were ramped up. Filtronic introduced a design for manufacture improvement, and took over the volume manufacturing operations, resulting in an increase in yield from 70% to more than 95%.

Pushing the boundaries

Filtronic has a long history of extending the possibilities of RF communications technology. Its track record of innovation means its expertise is frequently called upon by leading telecommunications, aerospace, defence, first-responder and space communications companies to expand the capabilities of communications systems.

As an example, one of the FAAMG technology giants challenged Filtronic to develop a transceiver for use in a new high-altitude pseudo-satellite (HAPS) application. The client wanted a transceiver that could achieve data rates of 40GB per second. At the time, the best solution available offered speeds of just 1GB per second. Such a vast improvement seemed unattainable, but Filtronic applied its ingenuity and electronic engineering skills to develop a transceiver that delivered exactly the 40GB speeds required by the client.

Opportunities to accelerate satellite communications development

In satellite communications technology, there’s no room for compromise on quality or rigour in the product development process. E-band components are required to perform reliably to extremely high standards in the harsh conditions of space – where the failure of any component comes at a high cost. There is no maintenance call-out service for orbiting satellites. 

For those communications organisations competing to deliver aggressive satellite launch programmes, time saved in product development could be the key to getting ahead of the competition. The advances in E-band technology achieved by Filtronic, combined with its practical experience and expertise, could be the solution to expediting the development of vital mmWave communications systems for LEO satellites. Contact Filtronic today to find out how we can help accelerate your market entry.

The post How to accelerate product development for complex mmWave technologies in LEO satellite communications   appeared first on Filtronic.

What is mmWave?

Millimeter wave (mmWave) is the band of electromagnetic spectrum with wavelengths between 10mm (30 GHz) and 1mm (300 GHz). It is known as the extremely high frequency (EHF) band by the International Telecommunication Union (ITU). Located between microwave and infrared waves on the spectrum, mmWave can be used for a variety of high-speed wireless communications applications, such as point-to-point backhaul links.

Macro trends accelerate data growth

As demand for data and connectivity increases globally, the frequency bands currently used for wireless communications are becoming congested, driving the need to access the higher frequency bandwidths within the mmWave spectrum. There are a number of macro trends accelerating demand for greater data capacity and speed.

1. Big data

The volume and variety of data generated and processed every day is growing exponentially. The world relies on rapid transfers of large volumes of data at high speed every second, across myriad devices. In 2020, every person generated 1.7 megabytes of data per second. (Source: IBM). At the beginning of 2020,the amount of data in the world was estimated to be 44 zettabytes (World Economic Forum). By 2025, global data creation is projected to reach more than 175 zettabytes. To put that into context, storing that volume of data would require 12.5bn of today’s largest hard drives. (International Data Corporation)

2. Urbanisation

The UN estimated that 2007 was the year when, for the first time, more people lived in urban areas than rural areas. This trend continues and by 2050 it is predicted that more than two thirds of the world population will live in urban areas. This puts increasing pressure on telecommunications and data infrastructure in these densely populated regions.

3. Multi-polarity

Global crises and instability, from the pandemic to political upheaval and conflict, mean that countries are increasingly keen to develop their sovereign capabilities – to mitigate the risks of global disruption. Governments want to reduce reliance on imports from other territories, and to support the development of products, technologies and infrastructure at home.

4. Climate change

As the world strives to cut carbon emissions, technology is opening up new opportunities to minimise carbon-hungry travel. Today, meetings and conferences are routinely hosted online. Even medical procedures can be performed remotely, without the need for surgeons to attend the operating theatre. Such precision operations are only possible with superfast, reliable, uninterrupted data flows with low latency. 

These macro factors are driving the need for ever-more data to be collected, transferred and processed globally, but also to be transferred at higher speeds and with minimal lag (latency).

What role can mmWave play?

The mmWave spectrum offers wide blocks of contiguous spectrum, allowing for much higher data transfer. The microwave frequencies currently used for most wireless communications are becoming congested and are fragmented, particularly with several bandwidths reserved for exclusive use by specific sectors, such as defence, aerospace and emergency communications.

As you move up the frequency spectrum, there are much larger portions of uninterrupted spectrum available, with fewer reserved segments. Moving up the frequency range effectively increases the size of the ‘pipes’ available to transmit data, enabling greater data flows. As the channel bandwidths are much larger at mmWave less complex modulation schemes can be used to transmit data this leads to much lower latency systems..

What are the challenges?

There are challenges associated with moving up the frequency spectrum. The components and semiconductors required to transmit and receive signals at mmWave are more difficult to manufacture – and there are fewer processes available. Manufacturing mmWave components is also more difficult because they are much smaller leading to requirements for higher tolerance assembly and careful design of interconnects and cavities to reduce loss and avoid oscillations.

Propagation is one of the major challenges for mmWave signals. At higher frequencies, signals are more easily blocked or degraded by physical objects, such as walls, trees and buildings. In built-up areas, this means mmWave receivers need to be located outside buildings, to propagate signals inside. For backhaul and satellite-to-ground communications, greater power amplification is needed to transmit signals over long distances. On the ground, point-to-point links must be located no more than 1 to 5 km apart, rather than the much larger distances possible with lower frequency networks. 

This means that in rural areas, for example, many more cell towers and antennae are required to carry mmWave signals over long distances. Installing this additional infrastructure involves more time and cost, in recent years the deployment of satellite constellations seek to solve this issue and again these employ mmWaves at the heart of their architecture.  

Where is mmWave best deployed?

The short propagation distance of mmWave makes it ideally suited for deployment in dense urban areas where there are high volumes of data traffic. The alternative to wireless is fibre-optic networks. In urban areas, digging up roads to install new fibre is extremely costly, disruptive and time-consuming. Conversely, mmWave connections can be set up cost effectively with minimal disruption in a matter of days.

The data rates achieved by mmWave signals are comparable to fibre, while offering lower latency. When you need very fast information flows, with minimal lag, wireless links are the preferred option – which is why they are used in stock exchanges where delays of milliseconds can be critical.

In rural areas, the costs of installing fibre are frequently prohibitive, due to the large distances involved. As discussed above, mmWave tower networks also require significant infrastructure investment. The solution emerging here is to use Low Earth Orbit (LEO) satellites or High-Altitude Pseudo Satellites (HAPS) to bring data connectivity to remote areas. LEO and HAPS networks mean there is no requirement to install fibre or to build short point-to-point wireless networks, while still providing excellent data rates. Satellite communications already use mmWave signals, typically at the lower end of the spectrum – Ka band (27-31GHz).There is scope for expansion into higher frequencies such as Q/V and E-band, particularly for backhaul of the data to ground stations.

The telecommunications backhaul market has led the way in the transition from microwave to mmWave frequencies. This has been driven by the proliferation of consumer devices –handheld, laptop and Internet of things (IoT) – over the past decade, which has accelerated demand for more and faster data.

Now, satellite operators are looking to follow the lead set by telecoms and expand the use of mmWave for LEO and HAPS systems. Previously, traditional Geostationary Equatorial Orbit (GEO) and Medium Earth Orbit (MEO) satellites were located too far from Earth to establish consumer communications links at mmWave frequencies. However, the expansion of LEO satellites now makes it feasible to establish mmWave links and create the high-capacity networks required worldwide.

There is huge potential for other industries to make use of mmWave technology too. In the automotive sector, driverless cars will require continuous high-speed connectivity and low latency data networks to operate safely. In the medical sector, superfast and reliable data flows will be required to enable precision medical procedures to be carried out by surgeons located remotely.

A decade of mmWave innovation

Filtronic is a leading UK specialist in mmWave communications technologies. We are one of the few companies in the UK able to design and manufacture advanced mmWave communications components at scale. We have the in-house RF engineers – including mmWave specialists – required to conceive, design and develop new mmWave technologies.

Over the past decade, we have worked with leading mobile telecoms companies to develop a range of microwave and mmWave transceivers, power amplifiers and subsystems for use in backhaul networks. Our latest products operate at E-band, this technology  offers a potential solution  for very high-capacity feeder links for satellite communications. It has been adapted and refined incrementally over the past decade, reducing its weight and cost, improving performance and perfecting the manufacturing process to increase yields. Satellite companies can now avoid many years of in-house testing and development by adopting this proven technology for deployment in space.

We work at the bleeding edge of innovation, creating the technologies in-house and co-developing in house volume manufacturing processes. We are always innovating ahead of the market, to ensure we have the technologies ready for deployment as new frequency bands are opened up by the regulators.

We are already developing W-band and D-band technologies in anticipation of congestion at E-band and significantly greater data traffic in the coming years. We work as partners with our industry clients to help them build competitive advantage through marginal gains as new frequency bands are opened up.

What next for mmWave?

Data usage rates are only going in one direction, and technologies that rely on data are continuing to advance. Augmented reality is already here and IoT devices are becoming omnipresent. Beyond domestic applications, everything from major industrial processes to oil and gas sites and nuclear plants are turning to IoT technology to enable remote monitoring and control – reducing the need for manual intervention in operating these complex facilities. The success of these and other technological advances will rely on the reliability, speed and quality of the data networks supporting them – and mmWave offers the required capacity.

mmWave does not make sub-6GHz frequencies any less important in the world of wireless communications. Instead, it is an essential complement to the frequency spectrum, enabling different applications to be delivered successfully, particularly those that require large packets of data, low-latency and greater density of connectivity.

The case for using mmWave to deliver on the expectations and opportunities of new data-reliant technologies is compelling. But there are challenges.

Regulation is one challenge. No advancement into higher mmWave bands is possible until regulators issue licences for specific applications. Nevertheless, the forecasted exponential growth in demand means that regulators are under increasing pressure to free up more parts of the frequency spectrum to avoid congestion and interference, there are also important discussions to be had around spectrum sharing between passive applications such as weather satellites and active commercial applications, this would allow even wider bands and more continuous spectrum without the need to move to sub-THz frequencies.

When it comes to capitalising on opportunities offered by new bandwidth, it’s important to have the technology in place to facilitate higher frequency communications. That’s why Filtronic is advanced in developing W-Band and D-Band technologies for the future. It’s also why we are working with universities, government and industry to drive the development of skills and knowledge in the areas required to meet future wireless technology needs. Government investment needs to be directed into the right areas of RF technology if the UK is to lead the way in developing the global data communications networks of the future.

As a partner with academia, government and industry, Filtronic plays a leading role in developing the advanced communications technologies needed to deliver new capabilities and possibilities in an increasingly data-hungry world.

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Increasing numbers of low earth orbit (LEO) satellites are being developed and deployed to address the challenge of providing ubiquitous broadband data coverage around the globe. These ‘mega constellations’ of new satellites will help to deliver the full potential of 5G and provide high-speed connectivity to remote parts of the world, including moving platforms such as aircraft and ships, as well as providing low latency connectivity for business users.

New opportunities and limitations

For the developers of satellite technologies and components, the proliferation of LEO satellite constellations presents new challenges, as well as exciting opportunities, not previously encountered with traditional Geostationary Equatorial Orbit (GEO) and Medium Earth Orbit (MEO) satellites.

Conventional geostationary satellites remain in their fixed orbits for 25 years or more. To achieve such lengthy operational lifetimes in space, all components must meet stringent requirements for reliability and radiation tolerance. The testing procedures are arduous and, where component reliability is in doubt, redundancy is achieved at the component level, by installing two or more identical sub-systems as a back-up.

Finding the right standard

For new LEO satellites used in mega constellations, redundancy is achieved at the satellite level, meaning operators launch replacement satellites to repair the constellation. These satellites have much shorter operational lives than their traditional geostationary counterparts, remaining operational for five to ten years. Nevertheless, there remains a need for the components installed on these satellites to offer high reliability, quality and performance in the high-radiation environment of space.

Using the stringent standards set for GEO and MEO satellite components would result in costly over-engineering for LEO satellite applications. So, to achieve the high quality and reliability levels required, LEO operators have tended to look to other demanding, high-performance applications – such as automotive – to set the standard for their satellite sub-systems. However, these general standards are not always fit for purpose, and there is a lack of suppliers with the necessary expertise at higher frequencies. These factors, combined with a lack of space heritage among suppliers, mean the LEO market requires a fresh approach if it is to meet growing demand for space-qualified RF components.

Meeting demand for more capacity

The volume of data being consumed worldwide is increasing apace, so there is an urgent need to increase satellite capabilities and network capacity. One example is through phased array antennas that make it possible to steer beams and target areas where extra capacity is needed, creating multiple beams at the same frequency. Care is required to avoid congestion and interference caused by overlapping beams, but in general it is possible to increase the capacity of satellites by reusing frequencies for different geographical areas.

Deploying digital processing capabilities within the satellite payload is another way to expand capacity. This enables data being brought to the satellite from users to be repackaged and consolidated on the satellite, creating extra capacity and allowing more efficient use of the frequency spectrum.

Exploring higher frequencies

However, as demand for data increases worldwide, the ultimate constraint on expansion will be RF capacity. Delivering the extra bandwidth needed will require expansion into higher frequencies, not currently widely used for earth-to-satellite communications. Ku and Ka bands offer around 2GHz of available bandwidth each, although there is some protected bandwidth within these bands. This creates additional obstacles when it comes to developing frequency plans and implementing hardware. What’s more, communications channels are becoming very congested at Ka and Ku bands, which are also shared with geostationary satellites. The orbits of any new LEO constellations therefore must be very carefully plotted to avoid interference with existing geostationary satellite transmissions.

Future satellite systems will move to Q and V bands, and indeed the International Telecommunication Union (ITU) has already approved these bands for use in forthcoming constellations. These higher frequency mmWave bands are currently little used for satellite communications and provide an important way to increase the capacity of the feeder links between satellites and the terrestrial network. Q and V bands each provide up to 5GHz of additional bandwidth, with a few excluded sub-bands. Looking further into the future, even higher frequencies will offer greater scope for expansion, with E band providing two wide-open 5GHz segments of contiguous bandwidth.

Challenges posed by mmWave

As frequency increases, so does atmospheric absorption, which, along with the difficulties in generating power in these bands, makes the links more sensitive to environmental conditions. However, the wider bandwidth available means that modulation levels can be reduced and output power increased to maintain the link, retaining data rates comparable with lower frequencies. The capacity gains thus make it an attractive option that’s worth investing in to secure long-term broadband connectivity via LEO satellites.

Currently, there are very few RF mmWave payload systems available with space heritage. That’s a limiting factor in the market, but also a huge opportunity for RF component manufacturers with the necessary expertise and track record in critical terrestrial applications. With new and well-resourced satellite operators joining the burgeoning market for LEO satellites, the demand for high-quality, space-compliant mmWave components is set to grow significantly.

UK expertise in mmWave components

High-reliability mmWave transceivers and SSPAs for communications and defence applications are already being designed and volume manufactured in the UK – and these are precisely the components needed for next-generation satellite products. Proven UK expertise in producing high reliability u-wave and mmWave modules for defence and communications systems can be applied directly to satellite applications. And because these devices have been rigorously tested and successfully deployed in terrestrial networks, satellite operators can be confident in their capabilities for non-terrestrial applications. The semiconductor processes already used in mmWave devices for terrestrial applications are inherently tolerant to radiation, so do not need further testing for space compatibility. The microprocessors and transistors used to provide power and control can be sensitive to radiation, but cost- effective radiation-tolerant alternatives are readily available.

Recently, Filtronic has designed high-capacity transceiver modules for use in high altitude pseudo-satellite (HAPS) systems, providing communications links of up to 40Gbps at E-Band. HAPS stations are unmanned aerial vehicles that provide moving 5G base stations, operating in the stratosphere at an altitude of around 20km to provide a ‘base station in the sky’. They play an important role in expanding connectivity around the globe and directly to LEO satellites at much higher altitudes where atmospheric absorption is very low. Filtronic RF technology provides solutions for both HAPS and LEO satellites, and the functionality of its terrestrial communication systems has been expanded to provide the environmental suitability for satellite applications. Filtronic is actively involved in supplying LEO demonstration hardware for both ground and payload applications.

Bold steps into new bandwidths

The solution to meeting the rapidly increasing demand for global broadband via LEO satellite constellations lies both in developing and manufacturing more commercially viable, high-performance RF components that can withstand the rigours of space, and in transitioning the bandwidths used for satellite communications into higher frequencies.

Since the u-Wave spectrum is limited and subject to many conflicting and overlapping demands, the development of feeder links operating in mmWave will be an important factor in the success of new satellite constellations.

While exploiting the possibilities of mmWave bands presents technological challenges, the experience we have in the UK of developing long-range terrestrial mmWave transceiver solutions with high data rates provides a solid foundation for further development to meet the demands of new LEO satellite systems.

Further reading:

Ground Segment Architectures for Large LEO Constellations with Feeder Links in EHF-bands, Iñigo del Portillo, Bruce Cameron, Edward Crawley. Massachusetts Institute of Technology, 2018 IEEE Aerospace Conference, March 2018.

Using E-band for Wideband SATCOM – Opportunities and Challenges. Sam Morrar Hughes Network Systems. Microwave Journal, August 2021.

Application of mmWave technology in High Altitude Pseudo Satellites (HAPS). Mike Geen, Filtronic. Microwave Journal, Feb 12th 2021.

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New TTA specification delivers greater consistency, audio quality and reliability for first-responder radio communications in North America

In 2018, one of the leading OEMs of critical communication equipment in North America changed its specification for the Tower Top Amplifiers (TTAs) installed in critical communications network base stations. This has now become their only specification of TTA available for new or replacement installations throughout the land mobile radio (LMR) network in North America. The rationale for the switch to this new specification was not widely publicised, and there remains limited understanding in the market about the benefits of the change.

Filtronic was instrumental in developing a TTA product to meet the new specification. Working closely with the OEM gave us a clear understanding of the thinking behind the new specification, the advantages it offers to radio system installers, and the improvements in LMR communications it brings to first responders.

In this paper, we outline the background to the specification change, the problems associated with the old system, the changes brought about by the new specification, and its benefits for public-safety communications in North America.

Background: Public-safety communications in North America

The current public-safety communications network in North America was established in the 1980s and early 1990s. The network of base stations aims to give 100% area coverage across North America, providing guaranteed communications connections for police and other emergency responders using land mobile radios in any location.

When the network was initially designed and implemented, it was based predominantly on analogue radio technologies, which were state-of-the-art at the time. This system proved invaluable, however, it was insecure, enabling new, easily obtainable radio scanners to pick up signals and listen in to police radio and other first-responder communications. Over the next decade or so, the radios were gradually updated to use digital modulation schemes and eventually the data was encrypted, making them secure and preventing casual eavesdropping. At the same time, channel bandwidths were reduced to enable more channels to be accommodated. More recently, the individual communication channel bandwidth is being halved again in order to double the number of channels – so the evolution continues.

However, while the radios themselves have been constantly upgraded, the radio frequency (RF) components and base stations that support the communications network have not really altered since the 1990s. This means that some components installed in base stations, such as power amplifiers, power combiners, filters, antennas and other RF conditioning products, have remained unchanged since their installation almost 30 years ago.

Technology: The role of Tower Top Amplifiers

One crucial component used in the majority of network base stations is the Tower Top Amplifier, which is used to improve receiver performance. TTAs incorporate a low noise amplifier installed at the top of the mast and a control/distribution unit installed at the base. The tower-top element incorporates a low-loss, bandpass filter to protect the receiver from out-of-band interference and a low noise amplifier to boost the received signal. The control/distribution unit at the base amplifies and splits the output signal to feed multiple different radio receivers. The tower top and base units are connected by a coaxial feeder cable running down the mast.

Over the years, many different companies have made the components for tower-top and base units, and there was some level of interoperability between them. But, over time, manufacturers opted to produce both the tower top and base elements together, meaning they had to be purchased as a pair which helped improve reliability and system performance.

An important feature of the original TTA specification was that the gain of the receive signal could be set to achieve the desired performance. That meant using attenuators to adjust the level of amplification and prevent the receiver from being overloaded. So, for example, in a dense urban environment where there is a lot of signal traffic, the gain can be reduced to prevent the receiver from picking up too many signals. This higher level of attenuation can also reduce system performance as well as restrict the range of the receiver. Conversely, for base stations in sparsely populated areas, the receiver needs to be far more sensitive so it can pick up signals from far away – so the attenuation would be reduced to achieve higher gain. At each base station, the gain would be set at the point of installation, according to the location of the site and its application.

Challenges: Complications caused by dual attenuators

The problem with the original specification for TTAs was that they featured two separate attenuators, providing two locations at which gain could be set. Both were housed in the control/distribution unit. The first ‘Reserve Gain Attenuator’ was located before the amplifier, and the second ‘Distribution Attenuator’ was located after the amplifier. As there are two locations for setting the gain, there are almost infinite possibilities for altering the ratio between them to achieve the same required level of overall gain. So, while the overall gain achieved might be the same, you would get different system performance depending on the balance between the settings of the two attenuators.  

The Reserve Gain Attenuator influences the sensitivity and noise figure of the system and its performance in the presence of high-power interfering signals. The Distribution Attenuator effects the system linearity. So, setting the first attenuator high and the second attenuator low, produces poor noise figure, poor range, but high immunity to interference. The other extreme is to have little or no attenuation at the input and all the attenuation after the distribution amplifier. In this case, you would achieve the same overall gain as the above scenario, but with very good noise figure and increased range, but greater susceptibility to interference.

Because there were multiple ways to set the two attenuators to achieve the same level of gain, different installers could set up sites differently. Each manufacturer provided guidance on how to set attenuation levels for different locations, with little constancy from one product to another, meaning it was up to individual installers to achieve the required gain levels for each site by setting the attenuators in whatever way they chose. This meant that once the base stations were operational, it was sometimes difficult to diagnose the cause of any underperformance, since the attenuators could have been set in many different ways. Any problems, such as audio drop-outs or poor call quality, were difficult to rectify without knowing how the two attenuators at each base station had been configured.

Solution: Delivering a new TTA specification

The potential problems caused by this uncertainty were one of the reasons why the leading OEM requested changes to the TTA specifications in 2018. The two significant changes made to the specification were:

1. To remove the second attenuator completely, and instead have a single adjustable attenuator located before the amplifier in the control/distribution unit. That gave installers a single way to adjust gain for the whole system.

2. To improve the low noise amplifier in the tower top by making it more linear, with better noise figure than previously required.

The new specification for Tower Top Amplifiers proved particularly challenging to achieve, and several RF suppliers attempted the task before a successful product was developed. Previously, TTAs had incorporated stand-alone filters, amplifiers and other connectorized components, which were cabled together in a waterproof housing. In the new product, all components are fully integrated into a single cast housing. As well as meeting all the performance standards stipulated by the OEM, this new product provides a lighter-weight solution in a smaller footprint, enabling better utilisation of space at the communication tower.

Benefits: Improved performance, control and reliability 

There are significant benefits of the new TTA specification for installers, end users and – ultimately – the general public. Fundamentally, each base station can now be set up very simply via a single control to optimise gain levels for the site, according to its location and the density of base stations in the region.

Having a single attenuator means there is only one point of adjustment to set the overall gain for the site. That immediately removes any ambiguity about how gain levels should be achieved. It makes setting gain levels far simpler and more consistent across the entire network. It means that if you’re in a remote rural area, you can simply set the attenuator to achieve a high system gain of 15dB, while in an urban area you set a low gain of 5dB. That eliminates idiosyncrasies in the way different installers set up gain levels at different base stations.

To compensate for the loss of an attenuator, the specification for the amplifier at the tower top has been significantly improved. This means there is no loss of performance, despite only having a single attenuator in the base unit. It gives you the best of both worlds, having the benefit of a tower-mounted amplifier with the gain effectively set to maximum, while providing the control simplicity of having a single attenuator to set the overall gain level for the site.

Outcome: Better communications for public safety

The new TTA specification supports better LMR performance for all emergency service providers. It gives radio system operators the confidence that their mission-critical networks will operate reliably with resilient connections and higher quality audio, especially in congested urban environments. Ultimately, that means greater peace of mind and security for the citizens who rely on these vital rapid-response services.

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