Estimation Accuracy and Cramér–Rao Lower Bounds for Errors in Multichannel HRWS SAR Systems

Multichannel synthetic aperture radar promises high-resolution and wide-swath imaging simultaneously. Channel error estimation is a critical step in signal processing before imaging. This letter mainly derives the Cramér-Rao lower bounds (CRLBs) for phase error estimates of three commonly used error estimators. Furthermore, to comprehensively evaluate the estimators, this letter compares both their accuracy and effectiveness. The accuracy is assessed by the maximum estimation deviation among channels, and the effectiveness is assessed by the proximity of the mean square errors (MSEs) to CRLB for phase error estimates. Finally, simulation is conducted to compare the maximum deviation as well as the MSE versus CRLB among the three estimators, under different clutter distributions and signal-to-noise ratios. Combined with the estimation accuracy and effectiveness, this letter aims to provide justifications for the proposed algorithms and gives recommendations for method selection in engineering applications.