Compact quasi-elliptic waveguide filters on contoured resonant diaphragms

摘要

We present a new type of waveguide bandpass quasi-elliptic filter whose resonators are implemented by thin transverse resonant diaphragms with an aperture in the form of a rectangular window with two metal L-shaped ridges. It is shown that the amplitude-frequency characteristics of such contoured diaphragms demonstrate the frequencies of parallel and series resonances simultaneously. We also construct equivalent circuits of the third and fifth-order elliptic filters and provide a computer simulation of the diaphragms satisfying the amplitude-frequency characteristics of each resonator. It is shown that for waveguide elliptic filters, some resonators can be located on one resonant diaphragm, which further reduces the length of the filter. The synthesis results of compact quasi-elliptic filters for WR137 rectangular waveguide with the central frequency of 6.5 GHz and bandwidth of 7.5% are presented. The total length of the filters is 34 mm for third order and 64 mm for fifth order, respectively.