A rectangular waveguide to multiple microstrip lines transition for power combining application

A transition from a rectangular waveguide to multiple microstrip lines is proposed in this paper for power combining applications. First, the electromagnetic fields of shielded microstrip lines are obtained by solving a set of homogeneous simultaneous equations. The mode-matching technique is then implemented to solve the junction between a rectangular waveguide and microstrip lines. A C-band six-way power combiner is finally designed based on the transition. The 20 dB return loss bandwidth of the power combiner covers the whole operating bandwidth of the WR137 rectangular waveguide from 5.8 GHz to 8.2 GHz.