Research On System Error Calibration Algorithm For Aperture Synthesis Interferometric Radiometer

Aperture synthesis interferometric radiometer has a wide application prospect because of its fast imaging speed and high spatial resolution without error interference.In practice,due to the non-ideal characteristics of various hardware such as antenna and receiver channel,there are many kinds of errors,which seriously affect the quality of Aperture synthesis interferometric radiometer.To solve this problem,the amplitude-phase errors which have the greatest impact on inversion imaging and antenna position errors are studied in this thesis,which improves the performance of the calibration algorithm and the quality of the inversion image.The main work are as follows:(1)The relationship between visibility function and space brightness temperature of aperture synthesis interferometric radiometer is deduced and the mathematical model of system error is established.(2)A single auxiliary source calibration algorithm based on Toeplitz processing is proposed.In order to improve the performance of the single auxiliary source calibration algorithm when the auxiliary source orientation is not accurate,the amplitude error is calibrated by using the main diagonal element of the covariance matrix of onedimensional uniform linear array.By using the Toeplitz characteristic of covariance matrix,the fixed time delay between antennas is eliminated,and a special phase matrix is constructed to calibrate the phase error when the orientation of auxiliary source is unknown.Thus,the accuracy of calibration can be improved when the location of auxiliary source is unknown.(3)The amplitude-phase error calibration algorithm for low SNR based on correlation matrix eigendecomposition is proposed.Firstly,a special amplitude matrix is constructed by using the Toeplitz property of the covariance matrix of one-dimensional uniform linear array to calibrate the amplitude error and eliminate the effect of the error on noise.Based on the eigendecomposition of covariance matrix,the phase error and direction of arrival are estimated jointly,and the phase error calibration is realized.Thus,the algorithm can be applied in low SNR condition.(4)An array position error calibration algorithm based on orthogonal subspace is studied.The orthogonality of noise subspace and array manifold is used to construct the objective function,the radiation source direction of arrival and array position are estimated jointly,and the optimization is conducted iteratively.The algorithm improves the accuracy of radiometer antenna position and makes the direction estimation of radiation source more accurate.Thus,higher quality inversion images can be obtained.