A compact-size microstrip rat-race coupler with high performance

A compact slow-wave microstrip rat-race coupler is presented. The present asymmetrical T-structure slow-wave loading achieves size reduction more than that obtained using traditional symmetrical T-structure along with wide range harmonic suppression performance. Lossless transmission line model is used to derive the design equations. A compact RRC occupying only 34% of the conventional RRC at 1.0 GHz with no harmonic passband up to 6.0 GHz is demonstrated for validation using two fullwave electromagnetic simulators and the results are in good agreement.