Research On Amplitude And Phase Error Self-calibration Method For Synthetic Aperture Interferometric Radiometer

The synthetic aperture passive imaging technology has the ability of high-resolution and wide-field instantaneous imaging,and has broad application prospects in the fields of radio astronomy,earth remote sensing,safety inspection,and target detection.Synthetic Aperture Interferometric Radiometer(SAIR)is a multi-channel system based on the principle of interferometric measurement.The amplitude-frequency response is inconsistent due to the difference in physical parameters between the channels,which causes the amplitude and phase of the interferometric measurement to deviate from the ideal value,which ultimately affects the imaging quality.With the development of SAIR,the calibration of amplitude and phase error has attracted the attention of domestic and foreign researchers.The existing methods mainly include: coherent noise injection method,external source calibration method and redundant baseline self-calibration method.Among them,both the coherent noise injection method and the external source calibration method require additional hardware assistance,and the engineering implementation is relatively complex,which requires high requirements for the platform of SAIR.Therefore,in recent years,the self-calibration method has become a research hotspot because of its advantage of using measurement visibility data to achieve error data.However,the current self-calibration method based on redundant baselines has the problem of low calibration accuracy under low SNR conditions.To solve the above problems,this paper proposes a self-calibration method for the amplitude and phase errors of SAIR based on the minimum mean square error(MMSE)criterion improving the traditional redundant baseline calibration method.Different from the traditional redundant baseline calibration method model,this method analyzes the impact of the visibility function noise,considers the amplitude and phase together,directly takes the entire visibility function with errors as the research object,and establishes amplitude and phase error calibration model using measured the visibility data based on MMSE.The method in this paper also uses the SAIR redundant sampling characteristics to integrate multiple visibility data corresponding to the same frequency domain sampling point(also called the baseline),optimize the calibration model,and improve the resistance noise ability.In this calibration model,the amplitude and phase errors and the ideal visibility data are unknown,and the amplitude and phase errors can be solved iteratively using the constraint relationship between the two.Simulations and experiments show that,compared with the traditional self-correction method based on redundant baseline,this method improves the correction accuracy under the condition of low signal-to-noise ratio,and can achieve the correction effect equivalent to the external auxiliary source calibration method.