Cooled GaAs-FET preamplifiers for a polarization radiometer at a wavelength of 6 cm

In connection with the desirability to increase the limiting sensitivity as much as possible, it is necessary to employ low-noise HF preliminary stages for the receiving systems of radio astronomy. Cooled GaAs-FET amplifiers provide results which are qualitywise similar to those obtained with parametric amplifiers. The design of GaAs-FET amplifiers, on the other hand, is much simpler than that of parametric amplifiers. The present investigation is concerned with the development and the design of two-stage GaAs-FET amplifiers for a two-channel polarization radiometer. The low noise characteristics of the considered amplifiers can still be improved considerably by cooling to a temperature of approximately 20 K. Attention is given to the design of the radiometer, the FET amplifier design, the implementation of the FET amplifier and the first measurements conducted with the GaAs-FET amplifier.