Simultaneous Measurements of Depolarization by Rain Using Linear and Circular Polarizations at 18 GHz

Limitations imposed by attenuation during heavy rain on the reliability of microwave systems are well known1 and a recent paper2 discussed observations of depolarization of circular polarization by rain at 18 GHz; it was concluded that depolarization by oblate raindrops poses a serious problem for the use of circular polarization. However, it is desirable that a direct comparison be made by simultaneous measurements of linear and circular polarizations on the same propagation path. Continuous measurements have been made during the period June 1972 through April 1973 (a total of 35 rain showers); a discussion of these follows a few remarks on the experimental system. 400 THE BELL SYSTEM TECHNICAL JOURNAL, FEBRUARY 1974 The 2.6-km propagation path used in the experiment is shown by the dashed line in Fig. 1. Two frequency-swept solid-state transmitters (with separate antennas) are located at the lower right of the path. The circularly polarized transmitter operates at a frequency of 18.65 GHz while the linear horizontally polarized transmitter is at a frequency of 18.35 GHz. The two receivers (with separate antennas) share a common building at Crawford Hill, Holmdel, New Jersey (upper left of propagation DEPOLARIZATION BY RAIN AT 18 GHz 401