Maximum-likelihood receiver for low-angle tracking radar. Part 2: The nonsymmetric case

In the paper, an asymmetric maximum-likelihood receiver (based on the Gram-Schmidt ortho normalisation procedure) is described for handling the low-angle tracking-radar problem where the direct and specular multipath components of the received signal impinge on the array antenna from arbitrary directions. Also, by means of a simple test based on Fisher´s F-statistic, we are able to determine the most likely number of waves incident on the array. The processor is applicable to the situation where it is desired to track multiple targets present within the radar´s scanning volume. Thus the estimator described in the paper is also applicable to the general problem of determining the frequencies of multiple sinusoids that are embedded in white Gaussian noise.