Broad-band cruciform substrate integrated waveguide couplers

This paper describes a method to broaden the bandwidth of cruciform substrate-integrated waveguide couplers. The design and the analysis of the couplers are performed using the H-plane planar circuit approach, and the frequency characteristics of the couplers designed at 24 GHz are shown. As a result, fractional bandwidths of 30% for a 3 dB coupler and 16% for a 1.7 dB coupler can be realized. The design results are verified numerically and experimentally.