Radio direction finding

Abstract

An automatic radio direction finding method and apparatus which employs a scanning directional wide aperture aerial system, a receiver, and a computer which effectively simulates the methods of a skilled direction finding operator in determining the direction of arrival of a radio wave using all the pattern information derived from the aerial system. A representation of the amplitude distribution of the receiver output signal as a function of the direction of maximum sensitivity of the scanning aerial system is stored, and the computer then determines the point about which this distribution is most symmetrical using an algorithm which folds the distribution, in sampled data form, in half, and computes the sum of the difference amplitudes between the overlaid samples. This procedure is repeated for each of a plurality of different fold locations, and these sums representing the asymmetry of the distribution about the associated fold point, are stored as a function of the fold point to determine the point in the distribution having the smallest sum, i.e. the greatest symmetry. This point of maximum symmetry provides an indication of the direction of arrival of the radio wave.

Dependencies are inferred from the claim text.