Recent Developments in Broadband Directional Couplers on Microstrip

Introduction of lumped elements in the microstrip itself proved-to be a rather simple way to overcome the difficulties encountered by achieving tight coupling (3 dB) and high directivity (>; 20 dB) for proximity couplers on plain microstrip. Three couplers were made as proof; two 3 dB proximity couplers: a distributed-lumped and an octave-flat lumped one, and a 8.34 dB decade-wide asymmetric coupler of the DuHamel & Armstrong type. It is evident that application of the new technique is not restricted to couplers.