Analysis of Statistical Performance Measures
Abstract
When only a limited number of snapshots is available for estimating the spatial correlation matrix, a low-rank solution of the MVDR equations, obtained via a small number of iterations of Conjugate Gradients (CG), can yield a higher SINR than the full-rank MVDR beamformer. A primary issue addressed in this effort is whether the unity gain constraint in the look direction should be enforced a-priori via the use of a blocking matrix, constituting Steering Dependent Conjugate Gradients (SD-CG), or effected a-posteriori through simple scaling of the beamforming vector, constituting Steering Independent Conjugate Gradients (SI-CG). A major contribution was that the two methods yield exactly the same low-rank beamformer. This is an important result since the construction, and application to the data, of a blocking matrix for each "look" direction is computationally burdensome. A simplified expression for the power estimate obtained with the SI-CG beamformer was also developed. Extensive simulations were conducted to verify the efficacy of the theory. While it was known that the optimal number of steps of SI-CG varies with look direction, simulations presented here reveal that the optimal number of principal eigenvectors for the PCI beamformer varies substantially with look direction.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 12, 2004
- Accession Number
- ADA422819
Entities
People
- Michael D. Zoltowski
Organizations
- Purdue University