Array Gain of DIFAR-Like Sensors

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Authors
  1. Maksym, J.N.
Corporate Authors
Defence Research Establishment Atlantic, Dartmouth NS (CAN)
Abstract
This technical memorandum presents a theoretical comparison of array gains obtained with conventional and adaptive beamforming of DIFAR-like sensors. For the purposes of the memorandum, a DIFAR-like sensor is modeled by an omnidirectional element and two orthogonal horizontal dipole elements. Also considered, is an extended DIFAR-like sensor, in which the three-element sensor module is augmented by two horizontal quadrupole elements. A difficult problem in the design of beamformers is how to decide when to use an adaptive beamforming algorithm rather than a conventional beamformer. Basing the decision on data observed during sea trials can be misleading because the relative performance depends heavily on the acoustic environment. The problem can be simplified by comparisons of candidate beamforming techniques with a set of baseline acoustic noise backgrounds, namely 2D and 3D isotropic noise, with the addition of one or two discrete-bearing sources of interference. Mathematical expressions for array gain are derived, and graphical results are shown for the baseline acoustic noise backgrounds. It should be noted that the calculations in this memorandum have assumed that sensor self noise is negligible compared to background noise. This is not likely to be true in practice, especially with dipole and quadrupole sensing elements. To take self noise into account, one needs only to add the appropriate sensor self-noise powers to the diagonal of the cross spectral density matrix in

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Keywords
Adaptive Beamforming;MVDR
Report Number
DREA-TM-2001-204 — Technical Memorandum
Date of publication
01 Dec 2001
Number of Pages
62
DSTKIM No
CA024125
CANDIS No
521629
Format(s):
CD ROM

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