Asymmetric coupled line directional coupler loaded with shunt inductors for directivity enhancement

摘要

A directivity enhancement technique of shunt-inductive loading is demonstrated for asymmetric coupled line backward-wave directional couplers. Through rigorous normal-mode analysis, the exact condition for isolation zero is derived. Experimental results for a 5 dB coupler at 0.9 GHz show as much as 33 dB improvements in the directivity over its conventional counterpart.