Theoretically And Experimental Evidence Of Time-delay Concealment Chaotic Signals For Radar With Enhanced Range Resolution And Anti-jamming Capability

Chaotic signal is a kind of random signal.Similar to noise signals,chaotic signals have the characteristics of randomness and wide spectrum.At the same time,it can be controlled and synchronized that the noise signal does not have.Therefore,the use of chaotic signals in radar will have more potential advantages.Due to the limitation of electronic devices,the bandwidth of electrical chaotic signal is no more than 2 GHz.Semiconductor lasers are easy to generate broadband chaotic signals because of their rich nonlinear dynamic characteristics.Therefore,laser chaotic radar has been concerned by many scholars since it was proposed.Because of the complex and changeable working environment in practice,the resolution and anti-jamming of radar system are important performance indexes of chaotic lidar.This thesis focuses on the time delay signature(TDS)of chaotic signals and the applications of TDS-concealed chaotic signals in chaotic ranging lidar.The main work is summarized as follows: 1.The reflection spectrum characteristics of fiber Bragg grating(FBG)is studied.Two new dual-path TDS-concealed chaos generation systems are proposed by using FBG feedback to replace the traditional mirror feedback.The output of dual-path TDS-concealed chaotic signals under the two schemes is realized experimentally.The advantages of FBG feedback in TDS-concealed chaos system are verified by comparing with mirror feedback system with the same structure.The influence of laser parameters on the TDS-concealment of chaotic signals in the two TDS-concealed chaos generating systems are quantitatively analyzed by means of control variables and auto-correlation function.The measurements show that,even by simply adding a single FBG path,the TDS of chaotic signals generated by both lasers in our proposed scheme can be better concealed compared to the conventional chaos generation system.Moreover,better TDS concealment can be achieved in the laser with smaller wavelength.2.Fully connected of three DFBs laser TDS-concealed chaos generating systems are proposed theoretically and experimentally.The TDS characteristics of three-channel TDS concealed chaos generating system are quantitatively analyzed by numerical simulation.The results of numerical simulation are verified experimentally,and three-channel TDSconcealed chaotic signal are obtained.3.Based on the TDS-concealed chaotic signals generated by the above experiments,the quantitative analysis of the auto-ambiguity function in distance proves that the Full Width Half Maximum of TDS-concealed chaotic signal is narrower than the original chaotic signal,and the millimeter range resolution is obtained.Using the cross-correlation function,it is proved that the TDS-concealed chaotic signals can resist the interference of other chaotic signals and sinusoidal modulated chaotic signals.Based on the above experiments,the lidar source based on the three-channel TDS-concealed chaos generating system realizes a threechannel chaotic lidar ranging system with an error of 0.15 cm and an average error rate of 0.018%.