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Cavity Filters

Resonant cavity filters are used as building blocks in duplexers, pre and post selector filters, and in receiver and transmitter multicoupling configurations. Individual cavities may also be used for a variety of interference management applications.

In addition, cavities many be cascaded to obtain a sum result of their individual characteristics, greatly expanding the configurations that can be designed and manufactured, and thereby catering for most customised requirements.

Standard individual cavity sizes on offer range from 50mm (2”) square profile, 101mm (4”) OD, 168mm (6.625”) and 254mm (10”) diameters. Traditionally we refer to the cavities in their inch sizes and for the most part each cavity type can be configured to provide pre-determined responses.

The pre-determined responses are configured using different types of coupling loop designs which are inserted and interchangeable into the respective cavities.

Band Pass

The Band Pass configured cavity passes one narrow band of frequencies at the cavities frequency of resonance and symmetrically attenuates frequencies with increasing attenuation above and below the pass frequency. The selectivity is adjustable by symmetrically rotating the loops. Higher selectivity trades off on higher insertion loss. Power handling is influenced by the insertion loss setting.


Band Pass Band Pass

Band Pass Reject


The Band Pass Reject configured loop passes a relatively narrow band of frequencies and rejects (notches ) a relatively wide frequency band either higher or lower of the pass frequency.

The Band Pass Reject achieves a greater comparative notch depth than the Series design. The notch depth is adjustable and influenced by the setting of the pass band insertion loss (0.3dB or 0.6dB typical). The Band Pass Reject is ideal for moderately close to wide pass to notch separations.


Vari-Notch Vari-Notch



The Notch configuration passes a wide band of frequencies either side of a symmetrical narrow adjustable notch. The typical notch depth varies between 15 and 25dB.

Used when the frequency requiring notching is relatively close to frequencies requiring passing.


Series-Notch Series-Notch



Series Combiner

Band Pass and Series Combiner responses are similar; however the Series Combiner is used specifically to provide two distinct and isolated signal paths. One path from a primary input / output to a common feeder line port, which exhibits a the band pass characteristic centred at the resonant frequency of the cavity and the second path from a secondary input / output port to the common feeder line port behaving as a low loss transmission line at frequencies other than the resonant frequency of the cavity. Used primarily to couple via a Series Combiner cavity any number of frequencies onto a single feeder line.


T-Pass T-Pass
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