Broadband, planar, doubly balanced star mixers

Abstract

Planar broadband star mixers comprising two CPW-CPS T-junction dual baluns are developed. The bandwidth is about 6:1 without treatment of even mode resonance. After improving of even-mode resonance, the measured relative bandwidths of the star mixers can be larger than 15:1. The planar structure of the circuit is suitable for both MIC and MMIC fabrication. Some MIC prototype circuits are fabricated with Al2O3 substrate. The measured conversion losses of the star mixers are about 6 to 10 dB typically within the bandwidth.