Flexible design procedure for realisation of dual-mode substrate integrated hexagonal-cavity-based diplexer

Novel symmetric and asymmetric diplexers are realised using dual-mode substrate integrated hexagonal cavity (SIHC) with the help of perturbation. Four different diplexers are designed and fabricated. The first three designs consist of single dual-mode SIHC in both Rx (lower frequency band) and Tx (higher frequency band) channels using same coupling topology and the last design consists of two dual-mode SIHC in Rx and Tx channels. Change in perturbation and feeding position provides different passband responses in terms of switching transmission zeros on both sides of the channel's passband of the diplexer's channel without changing coupling topology. As a result, the proposed diplexers provide design flexibility. Perturbation also helps in improving channel's passband selectivity and isolation between Tx and Rx channels. The input port of this proposed diplexer is a single-mode SIHC which helps in reducing diplexer size and provides greater degree of design freedom to realise symmetric and asymmetric diplexers.