Combline filters

100MHz-20GHz

Combline and Interdigital Filters

Combline filters
Filter | Filtronic PLC
Microwave Filters | Filtronic PLC

Combline filters can be designed to have bandwidths of 1% to 50% of the centre frequency. Centre frequencies in the range of 100MHz to 20GHz are possible with stopbands extending to 5 times f0 . Wider stopbands are achievable with appropriate resonator loading.

Combline filters key facts

  • Combline bandwidths of 1% to 50% of the centre frequency
  • Interdigital up to 100% bandwidth
  • Contiguous and non-contiguous types available
  • Extended stop bands achievable

Combline filters features

  • Ideal as a bandpass filter
  • Can be printed or metal
  • Low cost
  • High power handling, where size is not critical
  • Can be miniaturised
  • Robust build quality, limited points of failure
  • Suitable for defence applications
  • Extensive experience of application

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    Product description

    Although very similar to cavity filters, combline filters can be designed to have bandwidths of 1% to 50% of the centre frequency. Centre frequencies in the range of 100MHz to 20GHz are possible with stopbands extending to 5 times f0 . Wider stopbands are achievable with appropriate resonator loading.

    Multiplexers can be formed by coupling band pass filters together at a common transformer junction. Both contiguous and non-contiguous types are available. Diplexers, for example, are often used in applications such as Tx/Rx communications systems, where a common antenna is shared.

    In some applications requiring wider bandwidths and where flatter group delay is important, we can use interdigital structures. The electrical and mechanical characteristics are similar to combline but the resonators are longer and are alternately inverted. The longer resonators result in a lower upper stopband frequency.

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