A Balanced Sub-Harmonic Cold FET Mixer for 40GHz Communication Systems

Abstract — This paper reports a novel MMIC balanced sub-harmonic cold FET mixer for MVDS applications using 0.15mm GaAs pHEMT. The mixer, which includes a LO buffer amplifier, was optimized for highly linear up-conversion performance in the 42-43.5GHz RF band, 19.5-20.5GHz LO band and 2.45-3.45 GHz IF band. A dedicated simulation method has been developed to optimize conversion loss and determine optimum matching. To achieve better (2LO-to-RF) isolation a specific balanced architecture for sub-harmonic mixing has been elaborated. The first measurements of the fabricated MMIC circuit show 13,5dB conversion losses associated to high IF input power at 1dB compression of 15dBm, and (2LO-to-RF) rejection of 20dB in reasonable agreement with simulation results. I