A NEW APPROACH TO THE DESIGN OF DUAL-MODE RECTANGULAR WAVE-GUIDE FILTERS WITH DISTRIBUTED COUPLING

A synthesis procedure for a new configuration of four-pole dual-mode w aveguide filters with distributed coupling is presented, In this confi guration the dual-mode coupling is obtained by exploiting the well-kno wn fact that the diagonal polarizations are coupled in an almost squar e waveguide, The obvious advantage of this type of structure is that t he cross sections of all the discontinuities are rectangular, hence th e global prediction of the filter is more accurate, The synthesis appr oach is based on a scattering matrix formulation where the dual-mode c oupling is described in terms of a 2 x 2 propagation matrix, Universal design charts, which directly yield the scattering parameters of the various junctions, have been obtained, Comparisons with experimental r esults of a four-pole filter are also presented.