Research On Impact And Compensation Method Of Platform Vibration Error For Arc Array SAR

Arc array Synthetic Aperture Radar(SAR)is a new imaging system based on synthetic aperture radar,which has the imaging characteristics of wide-area observation scenes.In order to overcome the safety threat of the helicopter being interfered by complex terrain during take-off,landing and flight,the arc-shaped array synthetic aperture radar is mounted on the helicopter platform,and the multiple transceiver arrays arranged along the arc are used to pair the helicopter in the hovering state.The observation scene is scanned and illuminated in sequence,so as to realize the function of high-resolution and large field of view observation of the scene around the helicopter.Since the engine and rotor in the helicopter body rotate during operation,the entire arc array SAR platform will vibrate.For arc array SAR,its wavelength is in the order of millimeters,which causes the platform vibration to have a very serious impact on imaging.The quality of SAR imaging has deteriorated;and as the accuracy of Earth observation imaging is getting higher and higher,there are few studies on the analysis of vibration effects of arc-shaped array SAR at this stage,and the vibration error of the flying platform has become a constraint for highprecision ground imaging.It is a bottleneck in the development of technology,so the vibration impact analysis of arc array SAR has become an important research direction.This paper is based on the arc array SAR imaging system and imaging algorithm,through theoretical derivation and simulation experiments to analyze the influence of vibration errors in the X,Y and Z axis directions in the vibration model on the imaging quality,and then study the corresponding imaging quality.The algorithm performs phase compensation of vibration error to make it meet the requirements of focused imaging.The main contents are as follows:1.The imaging principle of arc array SAR in the new system is studied,including the layout of arc array SAR antenna elements,the imaging geometry and the establishment of echo signal model.On the basis of the arc-array SAR imaging system,the RD algorithm of arc-array SAR in ideal scenarios is studied,and the reliability and accuracy of the algorithm are verified by simulation experiments.2.Under non-ideal conditions,on the basis of the SAR imaging algorithm based on the arc array,the influence of the vibration of the arc array platform on the imaging is studied.Through the ideal scene model,establish a scene model when the X-axis,Y-axis,and Z-axis vibrate separately and when the X-axis,Y-axis,and Z-axis vibrate at the same time,and analyze the target under different vibration conditions.The distance model of the instantaneous distance from the platform and the signal model of the arc-shaped array imaging system are established to analyze the influence of the vibration direction,vibration amplitude and vibration frequency on the imaging.3.Under non-ideal conditions,the vibration of the arc-shaped array SAR platform will cause the sinusoidal frequency modulation error phase in the arc-shaped array SAR echo,resulting in serious imaging defocus.This paper further studies how to accurately eliminate the vibration phase error of the arc array SAR,and accurately compensate the vibration phase error caused by the vibration through the improved arc array SAR imaging algorithm,so as to achieve the purpose of precise focusing on the target.Two different vibration compensation algorithms are studied,including the KT algorithm and the BP algorithm,which are suitable for the arc-shaped array SAR imaging system.The inverse Radon transform principle and the Discrete Sinusoidal Frequency Modulation Transform(DSFMT)principle are used for parameter estimation respectively,the process of two vibration compensation algorithms is deduced in detail,and simulation experiments are carried out to verify the correctness and effectiveness of the algorithms.