Low Noise Receivers and Their Calibration

Low noise microwave receiving systems are particularly important for deep space communications systems, radio astronomy and some sensitive laboratory measurement systems such as transmission spectroscopy. Dramatic improvements in microwave receivers have reduced noise figures from the range of 10 dB to tenths of dB´s in the last 15 to 20 years. Although cooled parametric amplifiers provide a very practical performance compromise for ultra low noise, wide bandwidth and low cost, the maser has the lowest noise temperature of any practical microwave amplifier.