Analysis and design of millimeter-wave FET-based image reject mixers

In this paper, wave analysis is applied to a field-effect transistor (FET)-based image reject mixer (IRM) in order to enhance the classical IRM theory and investigate the fundamental limitations in terms of conversion loss (LC) and image rejection ratio (IRR). Furthermore, it is also described how different FET technologies can be benchmarked versus each other regarding their suitability for use in resistive mixers. This benchmarking allows the designer to predict the performance, i.e., L-C, of resistive mixers based on dc measurements, which facilitate the use of the presented method early in the design process. Three different versions of a 60-GHz IRM is also presented. Two of the IRMs demonstrate a measured state-of-the-art IRR of 30 dB in the 60-GHz band. The IRM employs an integrated ultra-wideband IF hybrid and has been designed, fabricated, and characterized in both pseudomorphic HEMT (pHEMT) and metamorphic HEMT (mHEMT) monolithic-microwave integrated-circuit processes. The different versions were designed to investigate the influence of the selected technology (pHEMT/mHENT), but also to investigate the effect of the layout on the measured performance of the IRM.