Sparse-Reconstruction Time-Varying Nonlinear Compensation for Harmonic SAR Imaging

Abstract

Harmonic synthetic aperture radar (H-SAR) is inherently robust to linear interference and provides improved clutter suppression, making it well suited for radar imaging in complex environments. Experimental observations show that the harmonic responses of nonlinear targets introduce spectral distortion and partial spectral loss in some pulses, as well as high-order nonlinear phase components. Moreover, during synthetic aperture radar (SAR) imaging, the nonlinear phase exhibits significant pulse-to-pulse variations, severely degrading coherent integration and imaging performance. In this article, a sparse-reconstruction-based time-varying nonlinear compensation method is proposed, which exploits the low-dimensional sparsity of the nonlinear phase to achieve robust global reconstruction from a limited number of high-quality pulses, thereby suppressing clutter-contaminated observations and eliminating pulse-compression mismatch. The proposed nonlinear compensation method and its effectiveness in suppressing linear interference are validated through H-SAR imaging experiments.