Focus Improvement of Multireceiver SAS Based on Range-Doppler Algorithm

The range-Doppler (RD) technique is extensively utilized by the advanced imaging sonar that features the resolution regardless of range and frequency. Unluckily, the focusing performances are mainly limited by two factors when classical RD techniques are extended to the multireceiver synthetic aperture sonar (SAS). The primary factor lies in the developments of spectrum by using the approximation of range, which brings the range error. To design the RD algorithm, the Taylor approximation of spectrum which must be carried out brings extra phase error. Both errors would limit the focusing performance of multireceiver SAS system. To strength the performance, a new RD technique is offered with this work. In accordance with the one-by-one mapping between the sonar bearing angle and azimuth Doppler frequency, an approximated range including the monostatic equivalent range and bearing angle dependent range error is proposed. The presented model shows much higher accuracy than traditional range models. After correcting the bearing angle dependent error via the multiplication and interpolation, the datasets are viewed to be the monostatic equivalent signal. Then, an advanced RD algorithm correcting the phase error of approximated spectrum is provided. In comparison with conventional approaches, the proposed approach is efficient and owns the potential to improve the focusing performance. The computer simulations and experiments based on SAS datasets further indicate that the proposed RD technique owns the ability to achieve much more outstanding images than conventional approaches.