Measurement of absorption losses and beam efficiency in CATR by using hot and cold loads

It is shown that the absorption losses and beam efficiency of a 2 m reflector antenna can be measured in a CATR (compact antenna test range) by using hot and cold loads having a feasible size. The accuracy is better than +or-0.1 dB for loss and +or-1% for beam efficiency, assuming a low-noise receiver (T/sub R/ equivalent to 100 K), a room temperature load, and a cold load in liquid nitrogen with accuracies of +or-0.5 K and a +or-0.5% power measurement accuracy. The beam efficiency measurement is fairly simple to realize. The absorption loss measurement requires an accurate auxiliary reflector, and its beam efficiency has to be known. The results are pertinent to the qualification of millimeter-wave radiometers for future remote sensing satellites.<>