Analysis And Optimization Of Influence Factors Of Signal Amplitude And Phase Characteristics In Photonic Time Stretch Coherent Radar System

Compared with traditional microwave technology,photonics technology has unique natural advantages of low loss,large bandwidth,high resolution,anti-electromagnetic interference and so on.Therefore,the application of photonics technology in microwave signal transmission and processing provides a research idea for improving the "electronic bottleneck" of traditional radar,which is of great significance for the development of new generation of microwave photonic radar system.However,there are some defects in optical fiber,and its anti-interference ability to the external environment is poor,which makes the phase of generated microwave signal vibrate randomly.It reduces the phase stability of signal,resulting in detection results are not accurate because of the change of amplitude and time width of received signal.This thesis first introduces system architecture of the existing photonic time stretch coherent radar(PTS-CR)scheme,describes basic principles used in the process of broadband signal generation and reception,and shows the design,implementation and test results of the PTS-CR prototype.Then,the amplitude and phase characteristics of broadband signal generated in PTS-CR system are analyzed.Aiming at problem that amplitude and phase characteristics of the system are not stable enough,the effects of experimental equipment and environmental factors on signal detection performance are simulated and discussed.Finally,we study the characteristics of the detection signal in open-loop mode and closed-loop mode.The PID algorithm based on FPGA is used to carry out comparative feedback experiments in the closed-loop mode,and the possible causes of the experimental phenomena are analyzed.The main work of this thesis is as follows:(1)This thesis describes the architecture and design scheme of transmitter and receiver of PTS-CR,analyzes the basic principle of broadband signal generation and reception,and the design,implementation and test of the prototype are completed.(2)This thesis analyzes amplitude and phase characteristics of broadband signal generated in the PTS-CR,and mainly discusses the influences of experimental equipment and environmental factors on signal detection performance.The output results of pulse compression are simulated under different conditions,and compared with the performance index under ideal condition.The range of parameters to ensure the detection performance is obtained,which provides a reference for the stability of amplitude and phase characteristics of PTS-CR.(3)This thesis studies the characteristics of detection signal in the open-loop mode,and measures the length of optical fiber accurately,then measures the performance of experimental equipment based on closed-loop architecture,finally uses the PID algorithm based on FPGA to carry out the comparative feedback experiment in the closed-loop mode,and analyzes the possible causes of the experimental phenomena.