Fast Multi-channel Digital Stretching Technique in Shore-based ISAR for Ship Imaging

In this paper, a multi-channel digital Stretching structure applied to image multi-ships simultaneously is proposed and which is very important for the ISAR to be used in ocean environment with intensive ships. A base band width expression of ship echoes which stands for the maximum length in radial range dimension occupied by the target being imaged is deduced. Based on the fact that ISAR emission signal bandwidth is much wider than the base bandwidth of the target echoes, a fast multi-phase filtering algorithm which leads to a sharply reduction of the computation load in range information processing is introduced and a matrix method of the algorithm is presented. Finally, a formula for estimating the computation load in terms of the radio of radar signal bandwidth to target´s base band width is given, and the correctness of the equation is verified by an example from an actual ISAR system.