Systematic design of 7‐to‐40‐GHz on‐chip mixer based on optimal impedance deviation coefficient

Abstract

In this article, a 7‐GHz to 40‐GHz ultra‐wideband passive double‐balanced mixer MMIC using compact wideband Marchand balun (CWMB) is presented. The CWMB is analyzed and designed by introducing a novel optimal impedance deviation coefficient. A trade‐off between the needed bandwidth and the acceptable insertion loss in an ultra‐wideband passive‐doubly‐balanced mixer design can be made through introducing the optimal impedance deviation coefficient. Finally, to verify the proposed methodology, a compact wideband passive double‐balanced mixer monolithic microwave integrated circuit (MMIC) was designed and fabricated using a standard gallium arsenide (GaAs) pHEMT technology according to the process characteristics. Experimental results show that an ultra‐wideband mixer MMIC is realized from 7 GHz to 40 GHz (140% fractional bandwidth) with a measured conversion loss between 9.5 dB~12.5 dB (in‐band fluctuation less than 3 dB) and a LO‐to‐RF isolation larger than 34 dB. The measurement results are in good agreement with the simulation results.