Compact Dual-Band Diplexer Based on Dual-Layer Substrate Integrated Waveguide

This letter presents a dual-layered diplexer with dual band using a type of strip-line to CPW coplanar transition structure. An example with two channel and each channel of two single-mode $(TE_{101})$ is demonstrated using substrate integrated waveguide technology. The footprint of the diplexer is reduced compared to the traditional ones since the cavity acts as a T-junction between the input port and the two channels and provides one pole for each channel filters. Furthermore, the fractional bandwidths (FBWs) of the two channel filters can be allocated flexibly based on the FBW design graph. A prototype centered at 11.6GHz and 13.6GHz with respective FBWs of 3.1% and 3.04% is designed for demonstration.