RESOLUTION THRESHOLD OF BEAMSPACE MUSIC FOR 2 CLOSELY SPACED EMITTERS

Numerous authors have advocated the use of a beamforming preprocessor to facilitate application of high-resolution directionfinding algorithms. The benefits cited include reduced computation, improved performance in environments that include spatially colored noise, and enhanced resolution. Performance benefits typically have been demonstrated via specific examples. The purpose of this paper is to provide an analysis of a beamspace version of the MUSIC algorithm applicable to two closely spaced emitters in diverse scenarios. Specifically, the analysis is applicable to uncorrelated far-field emitters of any relative power level, confined to a known plane, and observed by an arbitrary array of omnidirectional sensors. Major results include: 1) derivation of an expression for the threshold array signal-to-noise ratio at which beamspace MUSIC is able to resolve the emitters; 2) identification of the preprocessor that minimizes the resolution threshold; 3) demonstration that the resolution threshold is proportional to the dimension of the noise subspace; therefore the threshold can be reduced substantially by utilizing an appropriate beamformer to reduce the dimension of the noise subspace; 4) demonstration that MUSIC in conjunction with a suitable preprocessor can provide a resolution threshold lower than conventional (sensorspace) MinNorm. © 1990 IEEE