Avalanche diodes as transfer noise standards for microwave radiometers

Transfer calibrations of radiometers are performed by injecting noise via a directional coupler. The avalanche diode appears to have all of the physical attributes of the plasma noise tube, except for a reasonably predictable absolute noise level. Its saving in space, weight, cost and power consumption render it an attractive proposition for transfer noise calibrations. Results of measurements at three frequencies between 1 GHz and 3 GHz are given.