Filters, Diplexers and Multiplexers


RF Com, in conjunction with our technical partners, designs and manufactures a range of RF and Microwave Filters for the Wireless markets.

The filters are offered in a variety of performance characteristics including Lowpass, Highpass, Bandpass and Bandstop and are typically used for band-defining applications. In a crowded RF signal environment they are invaluable when used for blocking unwanted interfering signals. Special filters for frequency band splitting (Diplexers etc) are also available.

We utilise a range of technologies to realise the most compact and cost effective filtering solution. A large range of filter designs is currently available in:

  • Lumped Element
  • Tubular
  • Ceramic
  • Machined Combline and Interdigital
  • Waveguide
  • Microstrip and Suspended Substrate 

As there are so many infinite variations of filter types, please provide us with your specifications and we will work with you to provide the filter you need.

Tubular Filters

We can design and manufacture customised high performance Tubular Filters in Lowpass and Bandpass configurations. These filters are available over a wide frequency range and offer bandwidths of 2% to 50%. We use a low ripple Chebyshev transfer function as a standard for both types of models. These filters offer broad stopbands and high power handling capability and are ideal for harmonic rejection.

Tubular Filters are very rugged and ideal for both Military and Commercial applications. 

Lumped Element

Lumped element filter technology is commonly used in applications where small size is required and consists of discrete capacitors and inductors soldered to a substrate in various schematic configurations.

The technology lends itself to both narrowband and broadband designs and is suitable for lowpass, highpass, bandpass, bandstop and multiplexing applications. Various prototypes are used combining capacitive or inductive couplings toproduce asymmetric or symmetric responses.  The combination of excellent performance characteristics (insertion loss and out-of-band rejection) and rugged construction make lumped element technology suitable for a wide range of markets including Broadcast, Telecommunications, SATCOMS and Defence. Lumped element technology offers: 

  • Compact Size
  • Surface/PCB mount or connectorised
  • Wide range of topologies
  • Designs to 3GHz and beyond

Machine Combline and Interdigital

Machined Combline filters consist of short circuit stub resonators inductively coupled, to offer a low loss (high Q), rugged compact design. The resonators are capacitively loaded and are typically 45 degrees long at their resonant frequency giving a very broad upper stopband with high levels of attenuation.

Our combline filters use rectangular (or circular) rods machined, generally, from solid aluminium to achieve low weight and are silver plated to give the lowest possible passband loss.

  • Frequency Range: 100MHz to 18GHz
  • Bandwidth: 1% to 40%
  • Stopband: up to 6 x Fc

Interdigital filters use rectangular quarter-wave resonators, machined from solid, to offer symmetrical responses, even for very wideband filters. The electrical and mechanical characteristics are similar to combline but the resonators are longer and are alternatively inverted. The longer resonators produce a lower upper stopband frequency.

  • Frequency Range: 800MHz to 20GHz
  • Bandwidth: 1% to 50%
  • Stopband: up to 2.5 x Fc

Microstrip and Suspended Substrate

Suspended Substrate Stripline (SSS) is a printed circuit technology that can be used for both broadband and narrowband filters from 500MHz to 40GHz.

The basic configuration for SSS consists of a photo etched microwave circuit on a thin PTFE based substrate suspended in air between two silver plated ground planes. Plated through holes in the non cavity areas provide an effective means of grounding the top and bottom halves of the housing and suppress any RF leakage, this then provides high performance in terms of high-Q and low Insertion Loss, combined with a small, lightweight yet rugged construction. 

SSS allows the full range of filter structures, including lowpass, highpass, bandpass, bandstop and multiplexers to be configured.

  • Compact Design
  • High Reliability
  • Printed Technology
  • 500MHz to 40GHz
  • Repeatable


Waveguide filters can be used in the frequency range 1GHz to in excess of 100GHz. They are used in applications where high power handling and low insertion loss is required.

  • Low insertion loss
  • High Reliability
  • High power
  • Rugged construction 

Low PIM versions of these devices and other products are available, for details of these please go to our RD Microwaves page