ON THE ABILITY TO ESTIMATE NARROW-BAND SIGNAL PARAMETERS USING TOWED ARRAYS

Using the Cramer-Rao lower bound (CRLB) as an indicator of potential performance, we examine the limits on the estimation and resolution capabilities of a towed line array of uniformly spaced hydrophones to provide frequency and bearing information about narrow-band signals. It is assumed that a monochromatic plane wave arrives at the array from each source. Several versions of the bounds are computed using different assumptions about which parameters have known values and about the way in which samples are taken in space and in time. The CRLB values for different situations can be compared to provide information about the effective use of a moving aperture for estimation of the parameters of narrow-band signals arriving at the array. It is shown that adding at least one hydrophone occupying a fixed position in space can improve the bearing estimates of a towed array by supplying additional frequency information if both the bearings and frequencies of the sources are unknown.