We report precision measurements of the effective input noise temperature of a cryogenic (liquid helium temperature) MMIC amplifier at the amplifier reference planes within the cryostat. A method is given for characterizing and removing the effect of the transmission lines between the amplifier reference planes and the input and output connectors of the cryostat. In conjunction with careful noise measurements,this method enables us to measure amplifier noise temperatures below 5 K with an uncertainty of 0.3+- K. The particular amplifier that was measured exhibits a noise temperature below 5.5K from 1 to 11 GHz, attaining a minimum value of 2.3K+- 0.3K at 7 GHz. The measured amplifier gain is between 33.4dB+- 0.3 dB and 35.8 dB +- 0.3 dB over the 1-12 GHz range.
Citation: IEEE Transactions on Microwave Theory and Techniques
Pub Type: Journals
amplifier noise, cryogenic MMIC amplifier, noise temperature, noise measurement, thermal noise