Low Probability Of Intercept Waveform Design For Synthetic Aperture Radar

Synthetic Aperture Radar(SAR)is an active microwave remote sensing system,which is widely used in imaging reconnaissance,disaster monitoring and other fields with its full-time and all-weather imaging detection capability.However,in the face of electronic detection methods in actual combat environments,SAR transmitted signal is easy to be intercepted,which greatly restricts the robustness of imaging detection tasks.By optimizing the design of system resource elements,SAR Low Probability of Intercept(LPI)technology can reduce the probability of SAR being detected and intercepted and significantly improve the radio frequency stealth performance of the SAR system,which is practically valuable and promising in close reconnaissance,concealed penetration and other fields.LPI waveform designing for SAR is a crucial way to improve the LPI performance of SAR.This thesis focuses on the theoretical research and the simulation experiments in waveform modeling,LPI performance analysis,LPI waveform design and other issues.The main contents are divided into following three parts:1.Established a quantitative relationship model between SAR waveforms and LPI performance.Evaluated the imaging performance and LPI performance of various type of modulated waveforms with the ambiguity function of corresponding waveforms,laying a theoretical foundation for the research on LPI waveform designing.2.Researched on the hybrid modulation type design of LPI waveform for SAR.Realized the hybrid modulated waveform type design with LPI performance optimization by optimizing the modulation mode and modulation dimension and proposed reasonable parameter determination methods for the hybrid modulated waveforms,which provides a guarantee for further optimization design of the waveform.3.Proposed a SAR LPI waveform design method based on combined optimization of power LPI factor and relative entropy.Obtained different modulation types of transmitted waveforms for SAR with better LPI performance by optimizing the coding sequence,and the optimal relative entropy is achieved under the condition of guaranteeing certain detection performance.The methods mentioned above have been verified in this thesis by theoretical analysis and numerical simulation.The results show that the waveform design method proposed in this thesis can optimize the SAR LPI performance under the premise of satisfying the imaging performance.