Sensitivity of two high resolution beamforming techniques to the number of line array elements and signal‐to‐noise ratio

Abstract

Two high resolution beamformers, maximum entropy method (MEM) and Wagstaff‐Berrou broadband (WB2) [R. A. Wagstaff and J. Berrou, J. Acoust. Soc. Am. 75, 1133–1141 (1984)], were compared with each other and the standard FFT beamformer to determine performance degradation when the number of line array elements and the signal‐to‐noise ratio (SNR) were decreased. Experimental data from a multi‐tonal CW source recorded on an equally spaced horizontal line array were used to investigate the main beam broadening resulting from decreased SNR for SNR values ranging from 30 dB to near zero dB. Additional CW data from an equally spaced vertical line array were used to investigate the main beam broadening which resulted when the number of array elements was decreased successively from 31 to 16, 8, 4, and finally 2. Preliminary results indicate that the main beam broadening due to the decrease in array elements for both MEM and WB2 are similar and that both of these methods offer an order of magnitude decrease in the −3 dB beamwidth with respect to the standard FTT beamformer. [Work supported by Naval Electronic Systems Command, Code 612.]