Dual post cavity waveguide filters

A step-by-step design procedure is given for a direct coupled cavity waveguide filter. First, the amplitude response and group delay are analyzed based on the Chebyshev approximation and the realizable unloaded Q, for a given specification. After having obtained the optimal parameters, the two-post filter is realized by using two universal polynomials. One is used to calculate the post separation and the other is for the cavity length. The two polynomials are found from measured data. This design approach has been effectively used up to 20 GHz, and it can be extended to millimeter waves.<
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