Measurement of the Angle of Arrival of Microwaves

This paper describes a method of measuring the direction from which microwaves arrive at a given receiving site. Data which have been collected on two short optical paths using a wavelength of 3¼ centimeters are presented to illustrate the use of the method. Angles of arrival as large as ½ degree above the true angle of elevation have been observed in the vertical plane, while no variations greater than ±1/10 degree have been found in the horizontal plane. These results indicate that radar directions for low angles of elevation may be in error by several tenths of a degree during times when anomalous propagation conditions are present. Possible solutions to the problems introduced by variations in the angle of arrival are suggested.