A Ultra Wideband Low Loss CBCPW-to-Microstrip Transition With Multiple Via Holes

A wideband (0 to 26.5 GHz) transition from conductor backed coplanar waveguide (CBCPW) to microstrip line has been developed. Field and impedance transformation have been used in the design; also, via holes were placed on the side ground planes of the CBCPW to suppress the parallel plate resonant mode thereby reducing radiation loss. A back-to-back transition board has been fabricated and tested. The test result shows good agreement with simulation. Under test, the back-to-back design insertion loss is less than 2 dB and the return loss is less than 15 dB from 0 to 26.5 GHz.