Cramer-Rao Lower Bounds of Joint Delay-Doppler Estimation for an Extended Target

摘要

The problem on the Cramer-Rao Lower Bounds (CRLBs) for the joint time delayand Doppler stretch estimation of an extended target is considered in thispaper. The integral representations of the CRLBs for both the time delay andthe Doppler stretch are derived. To facilitate computation and analysis, seriesrepresentations and approximations of the CRLBs are introduced. According tothese series representations, the impact of several waveform parameters on theestimation accuracy is investigated, which reveals that the CRLB of the Dopplerstretch is inversely proportional to the effective time-bandwidth product ofthe waveform. This conclusion generalizes a previous result in the narrowbandcase. The popular wideband ambiguity function (WBAF) based delay-Dopplerestimator is evaluated and compared with the CRLBs through numericalexperiments. Our results indicate that the WBAF estimator, originally derivedfrom a single scatterer model, is not suitable for the parameter estimation ofan extended target.