Range estimation from wave-front curvature

The computation of the range of a signal from its wavefront curvature has been investigated. Some success was obtained by fitting a truncated power series to phase data which was taken by a linear array of antenna. In simulated experiments the effect of noise in the data was investigated extensively. For typical data obtained with the Communications Research Centre HFDF 1.2 km array, one should be able to make useful estimates of range for distances up to about 100 kilometers. In a field experiment the ground wave was used to estimate ranges of up to 111 kilometers. The bias and the rms deviation from the mean range were low for the near transmission sites but were up to 33% and 45% respectively, for the more remote sites. An unsuccessful attempt was made to compute the range of a signal which had been reflected by the E layer of the ionosphere. In this case the range was about twice the useful limit for the present system and the received signal may well have consisted of two or more interfering rays. Because of distorted wavefronts resulting from wave interference the range cannot be computed for a resultant signal which is made up of two or more signals which come from almost the same direction.