Model‐based broadband towed‐array processing

Conventional broadband towed array processors operate in the frequency domain and exploit the phases of the frequency components from a DFT to extract the bearing estimate. In this process, the fact that the array is moving is not taken into consideration. In fact, to first order, the effect of the motion is negligible. However, it has been shown that, in the narrow‐band case, the effect of the motion on the variance of the bearing estimate is not negligible. This is due to the fact that the Doppler incurred by the motion itself carries bearing information. In this work, it is shown that a recursive bearing estimation scheme, based on sequential DFT’s, can produce the so‐called synthetic aperture effect, where the Cramer–Rao lower bound on the bearing estimate progressively decreases, as compared to the case where the motion is not explicitly included in the processing scheme. Examples of this effect are shown based on simulated data, and the capabilities and limitations of the technique are discussed.