A new class of nonuniform, broadband, nonsymmetrical rectangular coaxial-to-microstrip directional couplers for high power applications

An innovative class of coaxial-to-microstrip broad-band high power directional couplers is studied. The new devices overcome the drawbacks of both stripline. and coaxial couplers and allow simple and low cost mechanical construction. In this letter, we present the design, realization and characterization of a set of broad-band (900 MHz to 5.5 GHz), low coupling (-30 dB, -40 dB) directional couplers with directivity of more than 10 dB over the whole band, demonstrating good agreement between predicted and obtained performances.