A New Architecture of Broadband GaAs MMIC Balanced Mixer for Very High RF/IF Isolation for 0.5-18.5 GHz Signal Analysis

This paper introduces a new architecture of balanced passive mixer aimed at providing very high bandwidth and very high isolation between RF and IF ports. The architecture is based on a double Marchand balun that allows routing the interconnection between the quad-transistors terminals such that the overlaps and misalignment between interconnections are avoided. The paper presents a mixer prototype fully integrated in 0.2 μ m GaAs p-HEMT process and is capable to convert signal in the the 0.5-18.5 GHz bandwidth into the 6-12 GHz bandwidth. Measurement reports a conversion gain between -3.5 dB and -6.5 dB and an isolation between RF (input) and IF (output) between 36 dB and 42 dB, while an LO isolation to output port in excess of 40 dB.