Compact diplexer design using different E-plane triplets to serve contiguous passbands with high interband selectivity

An advanced compact E-plane triplet cavity arrangement is introduced to provide either the implementation of Transmission Zeros (TZs) above or below of a filter passband. The principle configuration allows the realization of inductive (TZ above passband) and capacitive (TZ below passband) irises to accommodate with the respective sign conventions for the filter couplings. This general triplet cavity structure is applied to a compact diplexer design using 6(th) order filters with asymmetric responses at 10GHz. Each filter consists of two cascaded triplets controlling independently two TZs close to one side of the passband to satisfy the high interband selectivity of the contiguous receive and transmit bands. The overall design concept has been proven by the realization of the diplexer. Good agreement of computed and measured results are obtained. Moreover, the comfortable margins regarding the requirements admit of production without the need of any tuning.