COMPARISON-TYPE RECEIVERS FOR WHITE NOISE RADIATION AT 1086 CM WAVELENGTH

摘要

In radio astronomy observations involving reception of noise radiation of large spectral width, the commutating comparison receiver introduced by Dicke has been found advantageous with respect to effective sensitivity in many cases. Two KA -band versions of the comparison receiver, together with facilities for calibration and measurement of received signal power, are described. The derivation of the output response characteristic is traced in analytical form, and it is shown to be parabolic for linear i-f detection. Optimum receiver gain stability is shown to be obtained with linear detection. Techniques used to suppress troublesome spurious emissions from the receiver input are discussed. Two methods of determining receiver noise figure are considered; the noise figure obtained with selected mixer crystals is 12 to 13 db. Expressions are derived for the absolute sensitivity of the single-detection and the comparison (double-detection) receivers, and the observed sensitivity of the subject type of receiver is found to be in reasonable agreement.