Estimating angle of arrival with non-uniformly spaced array

The present direction-finding equipment has insufficient accuracy and resol ution, so that accurate evaluation of the direction of arrival and the posi tion cannot be carried out. Although each radar signal has a narrow bandwid th, the entire bandwidth for various radars used exceeds four octaves. In o rder to search all of these, equipment for each bandwidth is used at presen t so that the entire frequency range is covered. However, it is more effect ive from the standpoint of equipment size and cost to cover the entire spec trum with a single kind of equipment. It is desirable to realize high-accur acy high-resolution direction finding over a broad bandwidth. In realizatio n, broadband antennas are used, and high-gain antennas are also needed in a low-SIN environment. Since the dimensions of high-gain and broadband anten nas are large, an array configuration with a half-wave spacing may not phys ically be possible. Thus, the array spacing becomes more than a half-wavele ngth. If the range of direction estimation is -90 to +90 degrees, the phase difference exceeds 360 degrees so that ambiguity occurs. As a method to re solve this ambiguity problem, a nonuniformly spaced array is effective. In this paper, the array conditions for a nonuniformly spaced array are determ ined in the case of one arriving wave. Next, the case of several arriving w aves is discussed and the array conditions for several arriving waves are d erived. (C) 2001 Scripta Technica.