Research On Time And Frequency Synchronization System Of Bistatic SAR

Compared with monostatic SAR,division of sending and receiving platform in bistatic SAR makes it have the characteristics such as good antijamming,getting rich information and strong anti-stealth capability and so on.But as a result of transceiver platform division in bistatic SAR,transmitter and receiver must use the separate clock source,leading to difficulties in keeping the consistency of the two clock sources,so timing and frequency synchronization is the key problem to be solved in bistatic SAR.In this paper,we first analyzed the mechanism of time and frequency synchronization error,and established the mode of time and frequency synchronization error.We also built a complete model of transmission from time and frequency synchronization error to the imaging results by using quadratic distance model and the RD imaging algorithm,and simulation verified the accuracy of the theoretical analysis.The simulation results provided a theoretical basis for specification of bistatic SAR.Secondly,we studied the main methods of time and frequency synchronization at present,based on which we found a system design method of time and frequency synchronization-GPS disciplines OCXO.The key technology applied in the system was studied,and we analyzed of the high precision time interval measurement technology based on FPGA,PI control algorithm based on Kalman filter and the design method of digital delay line in detail.We completed the test of performance indicators of time and frequency synchronization system-GPS disciplines OCXO,showing that the time and frequency synchronization error of the system can satisfy the specification requirement of the bistatic SAR.Finally,in order to provide each unit in the transceiver system of bistatic SAR with the clock signal,the reference signal of local oscillator,the reference signal for transmitting and so on,we designed synchronous clock with a high stability and frequency-benchmark circuits,and completed the design and realization of hardware circuit and software algorithm,and gave the test results,which showed that harmonic stray inhibition of synchronous clock with a high stability and frequency-benchmark circuits was better than 60 d Bc,and it can satisfy the clock demand of transceiver system of the bistatic SAR.