Abstract
The compensation of slant range motion errors needs to be carried out after range pulse compression in the signal processing of multiple-receiver synthetic aperture sonar (SAS). Whereas range pulse compression cannot be performed as the first step in multiple-receiver SAS chirp scaling (CS) algorithm, as it requires the transmitted signal to be linearly frequency modulated. For this reason, it is difficult to combine CS algorithm with motion compensation. Besides, those imaging algorithms based on interpolation, such as range-Doppler algorithm and wavenumber domain algorithm, have plenty of computation load and large phase errors. Aimed at these problems, a CZT algorithm for multiple-receiver SAS in the non-stop-hop-stop mode is proposed in this paper. The proposed algorithm can correct range cell migration utilizing chirp-z transform, which avoids interpolation. Furthermore, the algorithm is easily combined with motion compensation as it can process pulse-compressed data directly. This paper describes the algorithm in 9 key steps, including the principle of correcting range cell migration utilizing chirp-z transform in discrete domain. In the simulation and sea trial data processing, the proposed algorithm provides image quality equal to the CS algorithm, and the algorithm is slightly more efficient than CS algorithm when combined with motion compensation.
Highlights
Synthetic aperture sonar (SAS) utilizes a uniform linear motion of small physical aperture along the azimuth direction to create a large virtual aperture [1]
Due to the wave, surge and the instability of sonar platform, it is difficult for sonar platform to maintain uniform linear motion in ocean environment [2], which results in motion errors
When the imaging algorithms are combined with motion compensation procedure in the multiple-receiver SAS, decompression processing is needed if chirp scaling (CS) algorithm is adopted, while chirp-z transform (CZT) algorithm can process the signals after range pulse compression directly
Summary
Synthetic aperture sonar (SAS) utilizes a uniform linear motion of small physical aperture along the azimuth direction to create a large virtual aperture [1]. When the imaging algorithms are combined with motion compensation procedure in the multiple-receiver SAS, decompression processing is needed if CS algorithm is adopted, while CZT algorithm can process the signals after range pulse compression directly. In this case, CZT algorithm is more efficient than CS algorithm. Where RI (t; r) is the distance between the phase center and the scatterer [9], [29], [30], i.e. c2 and δR(r) represents the high-order errors of range position caused by the non-stop-hop-stop mode and separate transducers for transmission and reception, i.e. The high-order errors of range position δR(r) may impact both the phase and the envelope location of the signal impulse response (4), so the corresponding phase errors and time delay errors must be compensated in the preprocessing stage.
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