Design And Implementation Of An Airborne UWB-SAR Signal Processing Board

Synthetic Aperture Radar (SAR) can achieve long range, high resolution imagery in all weather conditions, day and night. So it has been used in many regions. The signal processing flow of SAR is complicated, especially for the Ultra Wide Band-SAR (UWB-SAR). A high performance signal processor for the UWB-SAR real-time imaging is very important.It mainly behaves in the processing ability, the storage memory and the transmiting rate.In this article the SAR theory is introduced at first. Then the basic parameters of the UWB-SAR real-time signal processing and the imaging algorithms are analyzed.The Modify Wavenumber Domain (MWD) algorithm and the Nonlinar Chirp Scaling (NCS) is analyzed and compared in details.Combined with the sub-zone and sub-aperture NCS algorithm, the operation and storage quantity is estimated for the UWB-SAR real-time signal processing.The framework and the core components are very critical for the UWB-SAR real-time signal processing board. The framework features of several general SAR signal processing board are analyzed and compared. According to the demand of the UWB-SAR imaging and combining with the sub-zone and sub-aperture NCS algorithm,we design a multi-DSP+FPGA framework for real-time processing.There are multi DSPs and FPGAs on the signal processing board.The DSP has advantages on the float-point radar processing for its computation precision.On the other hand,the FPGA has advantages on the operation efficiency. A 2Gbyte DDR2SDRAM is integrated on the board for the mass data transmission and thanspose. The link port transport protocols are used among All the DSPs and the FPGAs.This signal processing board has a flexible topology, so it could adapt to the changing of the algorithm flow.Finally, the implementation is discussed in this article, including the design of the sub modules and the PCB.The integrity of the high speed bus is analyzed.The debugging of signal board has gained useful results: Every DSP unit can work well; the DSP can access the DDR2 SDRAM memory successfully; and the link port interface between the DSP and the FPGA can communicate inerrably.This signal processing board has been proved to own the high calculate ability and a flexible structure.It could adapt to the UWB-SAR real-time imaging procedure.Based on it, the UWB SAR signal processor can gain more powerful performance.