Signal Processing And Characteristic Analysis Of Spaceborne Radar

Spaceborne synthetic aperture radar is an important means for obtaining information on electronic space battlefields in the future.It can perform high-resolution imaging of a large area at all times,all weathers and without restrictions on airspace.Accurate estimation of spaceborne radar transmitted waveform signal parameters is an important prerequisite to achieve performance analysis and effective interference of spaceborne synthetic aperture radar.Advanced radar systems often use more complex modulated waveform signals.Most electronic reconnaissance of non-cooperative targets belongs to the sidelobe reconnaissance model,which has a low signal to noise ratio and weak feature information.Through theoretical analysis and simulation experiments,this dissertation has carried out research on spaceborne radar signal parameter estimation,waveform synthetic aperture radar imaging analysis and classification of radar operating mode.The main work of the dissertation are as follows:(1)Parameter estimation of complex waveforms of spaceborne radar signals under low signal-to-noise ratio.For the problem of poor performance of conventional methods under low signal-to-noise ratio.A robust method is proposed in this paper for waveform parameters estimation.This method effectively improves the signal-to-noise ratio of the signal to be processed through coherent accumulation,and ensures the robustness of the parameter estimation.This dissertation designs corresponding parameter estimation algorithms based on signal waveform characteristics,and achieves accurate estimation of three waveform of Linear Frequency Modulated signal,Stepped Frequency Coded signal,and Discrete Frequency Coded signal.Simulation experiments verify the accuracy of the proposed algorithm and its robustness under different SNR conditions.In addition,in view of the large bandwidth of spaceborne radar signals,a joint processing method of multi-station data is proposed in this paper to ensure the integrity of the reconnaissance signal reception and the accuracy of the target radar signal analysis.(2)Simulation research on imaging capability of spaceborne synthetic aperture radar signal waveform.According to the characteristics of signal waveform,it can be seen that the Stepped Frequency Coded signal increases the bandwidth of Linear Frequency Modulated signal by way of frequency agility.In this paper,the bandwidth synthesis of Stepped Frequency Coded echo signals is realized in the frequency domain.During the echo simulation process,the concentric circle algorithm is used to improve the echo simulation speed for large target scenes.And the point-to-point reconstruction back-projection algorithm is used for high-resolution synthetic aperture radar imaging.Through the simulation experiments,the imaging results of Stepped Frequency Coded and Linear Frequency Modulated signals are compared to verify the high-distance resolution ability of the Stepped Frequency Coded signal after bandwidth synthesis.(3)Classification of spaceborne radar operating modes.Conventional classification methods are not suitable for the classification of a large number of sidelobe reconnaissance signals.Because the amplitude change rule of the direct wave signal corresponds to the radar operating mode.This paper uses support vector machines to train and learn this feature rule,and obtains a classifier with three working modes of strip mode,spotlight mode and sliding spotlight mode.This classifier can achieve fast and batch processing of radar operating mode classification in electronic reconnaissance work.Simulation experiments show that the classifier has more than 90% accuracy and high reliability.(4)Design of spaceborne radar signal simulation and analysis software.Aiming at the complex and tedious problems of spaceborne radar signal processing,a simulation software with high integration is designed in this paper.The software uses QT as the interface design framework and MATLAB functions as the execution library,which can meet the requirements of multi-thread processing.And it can realize the estimation of spaceborne radar signal waveform parameters,direct wave signal simulation and waveform performance analysis,classification of spaceborne radar operating modes,spaceborne synthetic aperture radar imaging simulation and interference analysis,target electromagnetic characteristic imaging processing,etc.This software is a powerful tool for analyzing and processing spaceborne radar signals.