Research On SAR Echo Data Recovery And Imaging Methods

Synthetic Aperture Radar(SAR)has many advantages and characteristics,such as all-weather,all-day,high-resolution penetrability,etc.It has attracted more and more attention and has been widely used in military and civilian fields.Synthetic aperture radar imaging is a signal processing technology that converts the scene target echo detected by it into an accurate target image for more intuitive observation of the scene.The radar echo data received by SAR system is defocused,and its basic information is hidden in the phase,so imaging algorithm is needed to process and obtain the focused image.However,the echo data is generally not ideal.In the process of electromagnetic wave propagation,it is interfered by radio frequency band and strong electric magnet,resulting in the loss of signals in a certain frequency band.The instability of the system results in large errors in recorded data.Some data need to be discarded artificially.The loss of azimuth data caused by the discontinuity of azimuth aperture will result in the loss of received echo azimuth signal data.In addition to data missing,when receiving echo signals reflected from long-distance targets,it is inevitable that they will be interfered by various noises existing in the space.At the same time,noise interference echo signals will also be generated in the transmitting and receiving electronic devices.Whether data missing or noise interference will cause the degradation of imaging quality.In this paper,the above problems are studied,and the contents are as follows:Firstly,starting from the basic system model of synthetic aperture radar and the geometric relationship of SAR data reception,the SAR signal characteristics and the principles of improving resolution in imaging process as well as the principles of traditional pulse compression imaging algorithm and phase recovery imaging algorithm are discussed.Secondly,the echo data under the condition of missing data is recovered and imaged.Combined with the sparsity of radar,the missing radar signal is restored by compressive sensing algorithm,and the restored data is imaged by RD algorithm to complete the processing range migration correction and focusing of echo data and obtain a good image.Finally,the echo data under the condition of noise interference is restored and imaged,and an algorithm is proposed to denoise the noisy two-dimensional radar echo data and then image it.The noisy signal is denoised by traditional wavelet threshold,and it is improved according to the shortcomings.Then the denoised signal is imaged by ?k algorithm.The amplitude spectrum of the signal after wavelet and consistent compression in the algorithm is used as the amplitude constraint information of phase recovery,and the imaging effect is improved by iterative imaging.