Substrate Integrated Waveguide Diplexer Design

This chapter implements the microwave diplexer circuit model established in Chapter 4, using the twenty-first substrate integrated waveguide transmission line technology. No separate junction (resonant or non-resonant) was utilised in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and lead to a bulky device. The design also featured a novel input/output coupling technique at the transmit and the receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion loss achieved on the transmit and the receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.