Cryogenic X-Band Low Noise Amplifiers

This paper describes a number of cryogenic low noise amplifiers with very low noise for the frequency band 8.4-8.5 GHz. The amplifiers have been designed with different inputs: ostandard coaxialowaveguide ocoaxial followed by a high directivity 30 dB microstrip couplerAt 10 K ambient temperature the three-stage partly InP-based amplifiers have a gain of 33.0+/-0.5 dB and a noise temperature of 5 -7K.The InP transistors used in the amplifiers were processed at Chalmers clean room facility in our own proprietary process