| With the development of High Power Microwave(HPM)technology,HPM directed energy devices have emerged,which are mainly used to attack intelligent electronic devices such as drones,unmanned vehicles,and missiles,et al.The HPM is usually generated by electric vacuum or solid-state semiconductor technology,and its system is either heavy or costly,which seriously affects the promotion and application of HPM equipment.In recent years,researchers have proposed a novel time reversal(TR)pulse compression technique.This technology compresses a low-power wide pulse microwave signal through TRC and outputs a high-power narrow pulse microwave signal.These systems have the characteristics of small size and low cost.In addition,compared to other pulse compression technologies,it also has the characteristics of high gain,high repetition rate,high power capacity,simple structure,and can control the output waveform.It has good waveform agility and has potential applications in many aspects.However,the TR pulse compression technology is not mature,and there is a lack of a reliable theoretical model to study the TR performance and its influencing parameters.Therefore,based on electromagnetic reversal theory and combined with the microwave chaotic cavity(MCC)model,this dissertation conducts in-depth study on the key theories and methods of TRC pulse compression,following the approach of “theoretical model establishment →key parameter analysis → preprocessing method construction → typical application design → principle experimental verification”,and establishes a time reversal model with attenuation and crosstalk characteristics.A simple and novel time reversal pulse compression path compensation method is proposed,and several different port TRC models and their application scenarios are designed,providing a necessary theoretical basis for the application of time reversal pulse compression technology.The main work and research achievements of the thesis are as follows:1.Based on time reversal theory and multipath channel models,this dissertation establishes a time reversal model with attenuation and crosstalk characteristics through analysis of electromagnetic wave transmission attenuation,scattering,and divergence in TRC.It reasonably explains the spatiotemporal synchronous focusing of time reversal,and provides the generation mechanism and key influencing factors of time main-lobes and side-lobes.In addition,based on the assumption of random plane waves,the actual focal size and main influencing factors of spatial focusing are given,which can be used for energy extraction of reconstructed signals.These research results are consistent with the simulation calculation results,laying a theoretical foundation for the analysis of time reversal performance.2.Based on the theory of wave chaos,the ergodicity and randomness of electromagnetic wave in microwave chaotic cavities(MCC)are studied,and the basis and optimization method for using microwave chaotic cavities as TRCs are provided.Based on the time reversal model,the time main-lobe and signal-to-noise ratio are studied by the effects of path attenuation,crosstalk,stacking,and two key macroscopic parameters affecting reversal performance,cavity attenuation time constant and initial signal pulse width,are given.A detailed parameter(cavity structure)is also obtained.The basic laws and empirical formulas that affect reversal performance are summarized and provided.For these influencing factors,this dissertation designed an experimental verification system and validated the research results,which is provide technical support for the design and application of TRC.3.In order to improve the gain of TR pulse compression,based on the TR model,this paper proposes a simple and novel path compensation method(PCM)through study on time reversal theory and path characteristics.Its feasibility and compensation ability are studied from the time and frequency domains.This method compensates for path attenuation and drop characteristics,and has good compensation ability and time reversal performance.Compared to direct reversal,theoretically it can increase the compression gain by 6d B～12d B,and the experimental results are between 5d B～8.5d B.This method has higher compression gain and better compression efficiency,making it very suitable for pulse compression.4.For TRCs with different numbers of ports,this dissertation further studies the path crosstalk between their channels,establishes a channel crosstalk model,defines channel isolation degree,and analysis the impact of isolation degree on reversal performance,laying an application foundation for multi-channel time reversal of cavities.Therefore,a one-port TRC and a multi-port TRC model are designed,and their reversal characteristics and corresponding performance are studied.Their application in pulse compression,power synthesis,signal separation,and other aspects are briefly presented,and corresponding validation experiments are conducted.These research results have laid a certain technical foundation for the promotion and application of TR pulse compression technology. |
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