Synthetic Aperture Radar System Error Correction Method

The extensive application of Synthetic Aperture Radar (SAR) demands of higher resolution, accordingly of larger system bandwidth. On account of the wide relative bandwidth, compared with the narrow-band system, large-band SAR system errors impose more severe effect on imaging quality. To the problem, this paper proposes one set of solutions applicable for large-band SAR system.Because the Quadrature Demodulator brings different errors to I and Q signals, in this paper, I , Q imbalance is separated from system amplitude & phase errors and their correction methods are given respectively.System amplitude & phase errors can be calibrated either in time domain or in frequency domain. PGA algorithm based on radar echo signal is one method of estimating and correcting phase error in time domain, and its algorithm is simple to use. The methodology based on internal calibrator signals, which is brought forward in this paper, is the one in frequency domain; it takes good advantage of the design of three-path internal calibrator, and it calls for small arithmetic computation, very suitable for huge-amount radar data processing.I , Q imbalance is corrected by integrating statistical method and instrument measurement in this paper. The statistical method estimates and corrects non-frequency-changeable I Q imbalance caused by Power Splitter and Local Oscillator, and the instrument measurement measures frequency-changeable I Q imbalance caused by two path unmatched LPFs and Video Frequency Amplifiers.In the end of the paper, the entire solution of correcting system errors is presented after combining two parts of correction schemes for system amplitude & phase errors and I, Q imbalance.