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

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.