Research On Echo Simulation Technology Of Synthetic Aperture Radar

In recent years,SAR(Synthetic Aperture Radar)has been widely used in civilian and military fields.The echo simulation of SAR which provides targets information for SAR testing,as the foundation of SAR system simulation plays an indispensable role in the research of SAR technology.At present,the domestic SAR echo simulation is mainly based on Matlab platform and often limited to a certain efficient algorithm,which leads to a series of problems such as poor expandability and the high difficulty in improvement.Aiming at the problems existing in the field of SAR echo simulation,the time domain simulation methods and the frequency domain simulation methods are discussed in the thesis firstly.Then the advantages and disadvantages as well as the applicable conditions of different echo simulation methods are deduced.On this basis,a series of SAR simulation models with high degree of reuse and strong expansibility are established on the standardized software simulation platform.Using the models,the SAR echo simulation system with different parameters can be quickly built,and the time domain simulation method and the frequency domain simulation method are both supported.As shown below,the main work of this thesis contains:1.Based on the theory of SAR,the key points in SAR echo simulation are analyzed and the SAR raw signal and the spatial geometric models of SAR as well as the target model are established.The frequency domain and phase characteristics of the echo are analyzed meanwhile.2.Aiming at the characteristics of time domain and frequency domain of SAR echo signal,some simulation methods are proposed.The time domain simulation methods,which is represented by the time-domain pulse coherence(RTPC),focus on the simulation of signal amplitude,time delay and Doppler information.Basing on RTPC,an improved echo signal simulation method based on the relationship between the echo data of point objects in the same dimension is put forward,and the method can reduce the amount of calculation and improve the simulation efficiency.3.The frequency domain algorithms of SAR echo simulation are discussed,includingrange frequency domain pulse coherence(RFPC)and the method of two-dimensional frequency domain.The RFPC directly utilizes the frequency domain expression of the echo,and the kernel of RFPC is the simulation of the Doppler information,the coupling factor and the transmitted signal spectrum.While the two-dimensional frequency domain method is used to generating the echo data by transforming the backscattering coefficient and the impulse response function of the SAR system into the frequency domain to obtain the two-dimensional spectrum of the SAR echo,and then the spectrum is transformed into the domain via inverse Fourier transform.In the thesis,the time domain algorithms and frequency domain algorithms are compared.It is found that RTPC is better in the case of point target simulation and the simulation with high accuracy requirement,moreover,the two-dimensional frequency domain method is superior on the condition that the simulation accuracy is not strictly required or the simulation scene is very large.4.A design scheme of SAR echo simulation system based on standardized simulation software is proposed in the thesis.The software framework is designed and a set of SAR simulation model library are constructed using XML technology and Qt software.And the SAR echo simulation system is constructed for the simulation experiment of the point target and the extended target,which is used to verify the correctness of SAR echo simulation.The SAR echo simulation system does well in expansibility because the framework of the model achieves low coupling,standardization,hierarchy,visualization and portability.