Reverberation Envelope Statistics and Their Dependence on Sonar Beamwidth and Bandwidth
Impact of Littoral Environmental Variability of Acoustic Predictions and Sonar Performance
In order to combat high reverberation power levels in shallow water operational areas, active sonar systems have employed increased bandwidth transmissions and larger arrays. Both of these techniques have the effect of limiting the contribution of reverberation in each range-bearing resolution cell of the sonar by decreasing the cell size, which can also have an adverse effect on the probability density function (PDF) of the reverberation induced matched filter envelope. This effect is examined
... effect is examined using real data in conjunction with a recently developed model >d, 1H predicting that the shape parameter of K-distributed reverberation is proportional to the range-bearing resolution cell size. Estimation of the shape parameter of the K-distribution from real data as a function of the beamwidth of the towed-array receiver confirms this relationship. Although a similar effect may be expected for changes in the bandwidth of the transmit waveform, real data analysis indicates that, as bandwidth increases, the shape parameter estimate first decreases as expected but then increases, implying the data become more Rayleighlike at higher bandwidths. An explanation for this counterintuitive effect is proffered wherein it is hypothesized that increasing bandwidth over-resolves scatterers in range but not in angle. After accounting for the size of the scatterers with respect to the size of the range resolution cell in the model of >d, 1H, the shape parameter of an equivalent K-distribution for circular scatterers is seen to closely resemble the observed data.