Design of high Q TE01 mode ring DR cavity filters with cross-couplings

TE₀₁ mode ring DR cavity for the design of cross-coupled filters is described. A mode matching program has been written to compute resonant frequencies. Mode charts for a ring dielectric resonator in a cylindrical enclosure are presented at about 6GHz that allows the optimum ring DR cavity geometry to be found. The practical realization of the filter is discussed in detail. The focus is on the design of filter couplings, including input/output port couplings, direct inductive couplings, inductive and capacitive cross-couplings. A cross-coupled six-pole bandpass filter is built and shows a great improvement of frequency selectivity over the conventional elliptic function filters.