Multiple signal direction finding with thinned linear arrays
Abstract
The evaluation of the directionfinding capabilities of nonuniform arrays is approached via algorithmindependent lower bounds on achievable angle estimation errors. Two classes of bounds are considered. The first, known was the CramerRao bound, applies only to unbiased estimates. Compact analytical expressions for these bounds are developed which are applicable to very general directionfinding problems, including an arbitrary number of emitters. It is wellknown that CramerRao bounds are overly optimistic at low signaltonoise ratios. As this ratio decreases, a point is reached at which estimation accuracy decreases abruptly. Another class of bounds, known as ZivZakai bounds, provide information about the location of this threshold point. Their study suggests that poor directionfinding performance occurs in situations where the emitter direction vectors are part of a set which is nearly linearly dependent. Such linear dependence does not occur in the case of uniformly spaced linear arrays (without getting lobes). However, it does occur when elements are removed from such arrays. A systematic test is developed to test a given array geometry for this condition.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 April 1983
 Bibcode:
 1983STIN...8334169D
 Keywords:

 Direction Finding;
 Emitters;
 Linear Arrays;
 Random Noise;
 Signal To Noise Ratios;
 Analysis (Mathematics);
 Estimates;
 Simulation;
 Thickness;
 Thresholds;
 White Noise;
 Communications and Radar