Q-band mixers in newly released 0.15 µm GaN process

Recent advancements in communication systems have created a demand for circuits and subsystems with wide bandwidth at higher frequencies. Being one of the fundamental building blocks of transmitter and receiver chains, mixers play a major role in communication systems. Gallium-nitride (GaN) is an emerging semiconductor technology that has gained interest in realising a fully integrated transceiver chain. Therefore, it is interesting to investigate mixer designs in GaN technology which have not addressed much in literature. This thesis presents the implementation of a resistive single-ended mixer (SEM) and a single-balanced mixer (SBM) in WIN Semiconductor's newly released 0.15 m GaN process. The SEM operates over the entire Q-band and indicates a minimum conversion loss of 9 dB at midband. The SBM was realised using two SEMs connected with a Marchand balun and a Wilkinson power divider. It indicates a minimum conversion loss of 9.3 dB close to mid-band and 12.3 dB across the frequency band from 32.7 GHz to 53.6 GHz. An improved LO-RF isolation better than 47 dB was achieved using balanced LO signals. The IIP3 values of SEM and SBM are 26.6 dBm and 24.6 dBm respectively which conrm the high linearity of both mixers. The designed Marchand balun operates over a wide bandwidth from 27 GHz to 99 GHz. Furthermore, this research explores a capacitive loading technique to improve the input matching of the balun.