Ka-Band Branch Line Coupler Using High-Performance Air-Buried Microstrip Lines

摘要

In this paper, a branch line coupler using airburiedmicrostrip lines (ABMSLs) has been monolithicallyfabricated for millimeter-wave applications. Because theABMSL structure employs air-dielectric medium andground conductor walls surrounding strip signal line, it isvery effective in reducing a dielectric loss, as well asparasitic coupling between close transmission lines overhigh frequency range. The fabricated branch line couplershows a coupling and transmission loss of 3.6 dB and 3.9 dB,respectively at the center frequency of 29GHz. In thefrequency range from 26GHz to 32GHz (20% bandwidth),it exhibits a return loss of better than 15 dB and isolation ofbetter than 14 dB.