Substrate integrated waveguide diplexer with dual-mode junction cavity

A compact inline K-band diplexer with dual-mode junction cavity in substrate integrated waveguide (SIW) technology is presented. The dual-mode cavity provides a transition between the input port and the two channels of the diplexer, as well as one pole for each channel filter which results in a reduced size compared to other inline diplexer topologies. The diplexer design is carried out using an efficient mode-matching technique (MMT), and its performance is validated by simulated and measured results. The diplexer channels are located at 23.7 GHz and 25.7 GHz, with 5.9 and 5.4 percent fractional bandwidths, respectively. Inband return loss measurements are better than 17.43 dB and 17.24 dB, and the insertion losses are 1.64 dB and 2.2 dB, in the lower and higher bands, respectively.