Microwave and millimeter-wave cryogenic wideband LNA design and characterization

This manuscript reports our progress in designing wideband LNAs for use in radio-astronomical receivers. These include two WIN-150nm and five WIN-100nm GaAs pHEMT LNAs. Following a general description of design methodology, the LNAs´ simulated and measured results at room temperature will be presented. To make these LNAs eligible for low-temperature applications, a cryogenic noise measurement system using multi-point variable-temperature-load (VTL) method is constructed where the system is computer controlled, and both the noise calibration and de-embedding concerns are properly addressed. At 14K ambient temperature, the 5-10GHz LNA has its averaged T_n equal to 8K and the 8-20GHz LNA has its T_n around 10K.