Design of Wideband Constant-Beamwidth Acoustic Arrays.
SACLANT ASW RESEARCH CENTRE LA SPEZIA (ITALY)
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The report considers the design of arrays of omnidirectional elements for wide frequency bands when the performance is judged in terms of beamwidth, sidelobe level, and the linear distortion when receiving off axis in the main beam pointing errors. Techniques are discussed for achieving low linear distortion by keeping the beamwidth constant over the desired frequency band. A particular method, based on suitably weighting the outputs of homothetic arrays, is treated in detail. It is shown, by means of examples, that this method often yields very good designs and essentially reduces the problem to that of designing a narrowband array. It is pointed out that the possibility of approximating independently-specified amplitude and phase characteristics by means of non-recursive digital filters makes digital techniques quite attractive for the implementation of constant beamwidth array processors. The report is intended mainly as a discussion of the general problem and a survey of available techniques, with a view to direct application in the design of underwater acoustic receiving arrays for use in experiments with explosive sound sources. Author
- Acoustic Detection and Detectors