High range resolution (HRR) moving target indicator (MTI) is becoming increasingly important for many military and dvilian applications such as the detection and dassification of moving targets in strong clutter background. We consider the problem of extracting the HRR features of moving targets with very dosely spaced scatterers in the presence of strong stationary clutter, where the range migration and Vopplel\"frequency are taken into account. A relaxation-based algorithm，which is robust and computationally simple, is propOsed to deal with the above problem. Numerical results have shown that the proposed algorithm exhibits super resolution and excellent estimation performance.

With conventional pulse-echo ranging approaches it is diffcult to obtain un accurate range measurement needed by a proximity ultrasonic sensor system owing to the limited bandwidth of the transducer. A continuous-wave multifreouencv ranging method is presented to accurately measure the proximity distance for an ultrasonic distance sensor system A novel time delay estimator is derived based on a nonlinear least-squares-fitting criterion for the case where the received signal amplitude is non-negative owing to the acoustically hard reflection To minimise the highly oscillatory cost function an effcient two-stage estimation algorithm is proposed Numerical results show that the estimation algorithm can approach the Cram6r-Rao bound as the signal-to-noise ratio increases.

A computationally efficient algorithm, referred to as DS-WRELAX, is proposed for the delay and Doppler scale estimation of multiple moving targets. DS-WRELAX can approach the corresponding Cramer-Rao bounds and exhibits much better convergence properties than existing algorithms.

A new algorithm, referred to as the SPAR (Semiparametric) algorithm, is presented herein for target feature extraction and complex image formation via synthetic aperture radar (SAR). The algorithm is based on a fiexible data model that models each target scatterer as a two-dimensional (2-D) complex sinusoid with arbitrary unknown amplitude and constant phase in cross-range and with constant amplitude and phase in range. By attempting to deal with one corner reflector, such as one dihedral or trihedral, at a time, the algorithm can be used to effectively mitigate the artifacts in the SAR images due to the flexible data model. Another advantage of SPAR is that it can be used to obtain initial conditions needed by other parametric target feature extraction methods to reduce the total amount of computations needed. Both numerical and experimental examples are provided to demonstrate the performance of the proposed algorithm.