High-Precision Angle Determination by Means of Radar in a Search Mode

One of the more difficult requirements to meet in the design of radars is that of accurate angular measurement. In tracking radars the azimuth and elevation of a target can be measured to a high degree of accuracy by a nulling method. Two of the most practical methods for obtaining angular accuracy in search radars are discussed in this paper. The first method is an interferometer technique employing either two receiving antennas for each dimension of angular measurement with two frequencies of transmission for the resolution of ambiguities, or three receiving antennas positioned relative to one another so that the equivalent effect is achieved with only one-frequency transmission. The second method is a combination amplitude comparison and interferometer technique in which the ambiguities are resolved by the amplitude comparison system. An analysis of each of these systems has been made using a statistical approach in which equations are developed relating the probability of error for a specified angular accuracy to SNR power in the receiver. Curves are presented which show this relationship for a 100 to 1 beam-splitting ratio.