Research on Bi-Static Synthetic Aperture Sonar Resolution and Range Multipath Inhibition

摘要

Resolution including range resolution and azimuth resolution, is a key factor to evaluate the performance of synthetic aperture sonar(SAS). For bi-static SAS(bi-SAS), the physical positional separation of transmitter and receiver makes the resolution very different from mono-static SAS(mono-SAS). At first, there is little relevant research on the property of bi-SAS's two-resolution. As the existing ambiguity function method is not benefit for numerical calculation, this paper works this problem out utilizing a gradient vector method whose basis is to use the gradient of distance contour or Doppler frequency contour to calculate the two-dimensional resolution. Then this method is applied to a certain bi-static configuration and the mono-static configuration, respectively. The results prove the effectivity of the method and demonstrate the obvious space-variant property of two-dimensional resolution in bi-SAS. For a SAS system, it is a fact that there is more than one echo path with the same time-delay at any receipt time. This phenomenon can be regarded as a multipath problem, which may bring false target some times. Especially when the receiver is at a position able to receive the forward-scattering echo, multipath in range direction will occur to the system, which brings about ghost-point. This problem has hardly ever been theoretically analyzed, because it has little influence on final imaging result in practical application. This paper theoretically deduced the relationship between ghost-point position and configuration parameters of bi-SAS. Finally, we demonstrated that ghost-point position is related to height of sonar, and it basically can be inhibited by synthetic aperture processing under certain circumstances.