A High LO-to-RF Isolation 34–53GHz Cascode Mixer for ALMA Observatory Applications
This paper presents the implementation of a down-conversion single-ended mixer fabricated by 0.1-µm GaAs pHEMT process with wide IF bandwidth, high LO-to-RF isolation, and low LO power for ALMA band-1 applications. The mixer is a single-ended cascode structure using cold bias (VDS=0) mixing core for wide IF bandwidth, and LC resonators to restrict LO power coupling to the RF port. According to the measurement, the proposed mixer performs well conversion gain, good gain flatness, and wide IF bandwidth with 0 dBm LO power in 34–53 GHz RF frequency which covers ALMA band-1. The measured LO-to-RF isolation is better than 37 dB. The LC resonated technology successfully solves the main drawback of poor LO-to-RF isolation of single-ended mixers. Compared with published works, the proposed single-ended mixer shows lower LO power and competitively high LO-to-RF isolation which is better than conventional single-ended mixers and comparable to balanced mixers.