A Study On Cerrecting Amplitude And Phase Errors For Multi-channel SAR Echo Signal Simulator

SAR hardware-in-loop simulation is the combination of simulation technology and SAR technology, which generate RF SAR echo containing space geometry, scene and kinds of error characteristics by combining digital simulation and SAR echo signal simulator, and have played important role in the SAR system design, hardware debugging, performance testing, systems integration and mission planning, the development and application of SAR during its life cycle.Multi-channel SAR echo signal simulator is an important ground auxiliary equipment to construct SAR hardware-in-loop simulation system on the ground for the ground‐based testing and hardware-in-loop simulation. The validation of the experiment results was main determined by the channel amplitude and the phase error of the SAR echo signal simulator. However, due to the practical constraints such as the non-ideal characteristics of analog, it's unavoidable that the amplitude and phase errors existed in multi-channel SAR echo signal simulator affect the performance evaluation of radar imaging response and InSAR. Thus it's important to correct the amplitude and phase errors of simulator in real time. The traditional pre-distortion technology cannot meet the demands of correcting of amplitude and phase errors in real-time simulation, so there is need to get a method of FIR filter with real time to correct the amplitude and phase errors of simulator in real time. As the simulator system transfer function does not have conjugate symmetry, the problem transforms to coefficient designing of complex coefficient FIR correcting filtersAt first, the multi-channel SAR echo simulator is modeled. Based on combination of theory and simulation, all the effects on the SAR image focusing performance and SAR imaging phase caused by simulator channel amplitude and phase errors is analyzed in detail, and the mismatch errors of amplitude and phase effects on the interference InSAR performance is also analyzed.Then,two methods of channel characteristics extraction are proposed:the spectral contrast method and the matching filter method, and then these two methods are compared and verified. Based on the obtained channel characteristics, the simulator channel amplitude and phase error is corrected by pre-distortion technology and FIR filters with correcting complex coefficient in real-time.Then,based on the designed FIR filter complex coefficients, utilize FPGA chip within embedded RAM configured as an asynchronous FIFO, and the FIR filter with high real-time data rate which worked in ping-pong model was constructed. As the proposed method's application, the amplitude and phase error of simulator is corrected, and the results indicate the corrected and optimized performance of simulator channel is obviously.At last,the influence of channel amplitude and phase mismatch on InSAR height measurement for the distributed SAR system by the hardware-in-loop simulation method, verified that the designed complex coefficient FIR filters can correct the amplitude and phase error of multi-channel SAR echo efficient in real-time.