Ultra low noise cooled S-band amplifier

The design, fabrication and measurement of a HEMT's, ultra-low noise, microwave, cryogenically-coolable amplifier is described. The design band covers from 2.1 to 2.5 Ghz and average noise temperature under 2.5k and gain over 25 dB have been measured for a two stage amplifier when cooled under 12.5k. Microwave Design System from HP and Pospieszalski HEMT's noise model have been used to do the design and excellent agreement has been verified between theoretical model and measured parameters. The amplifier has been done to work as an RF fist stage of a radio-astronomy receiver.