A Cryogenic Integrated Noise Calibration and Coupler Module Using a MMIC LNA

A new cryogenic noise calibration source for radio astronomy receivers is presented. Dissipated power is only 4.2 mW, allowing it to be integrated with the cold part of the receiver. Measured long-term stability, sensitivity to bias voltages, and noise power output versus frequency are presented. The measured noise output versus frequency is compared to a warm noise diode injected into a cryogenic
K
-band receiver and shows the integrated noise module to have less frequency structure, which will result in more accurate astronomical flux calibrations. It is currently in operation on the new seven-element
K
-band focal plane array receiver on the National Radio Astronomy Observatory Robert C. Byrd Green Bank Telescope.