Cryogenic 8–18 GHz MMIC LNA using GaAs PHEMT

An 8-18 GHz MMIC LNA is designed and fabricated using 0.15-μm GaAs pHEMT process. The peak LNA is more than 23 dB gain at room temperature and more than 27 dB gain at 17.5 K. At 18 GHz, the room temperature noise figure is 1.5 dB, and the best effective noise temperature at 17.5 K is 20 K. The measured noise data of the LNA are then fitted for the temperature dependent model. The derived equivalent drain temperature is proportional to the drain current, independent of the ambient temperature.