A Resolution-Improving Method for Multiband Imaging Based on an Extrapolated RELAX Algorithm

A resolution-improving method for multiband imaging based on an extrapolated RELAX algorithm (ERA) is proposed. The proposed method improves image resolution by reconstructing a wideband signal through nonadjacent narrow subbands. The key points of this method are the coherent compensation of the subbands and the accurate extraction of target point scatters’ parameters from each subband. For coherent compensation, a two-step phase compensation (TSPC) is used to precisely compensate for the phase incoherence terms between the subbands. In order to accurately extract the parameters of point scatters (PSs), the ERA is proposed, which establishes a cost function between the extrapolated subbands and the PSs’ parameters. Furthermore, to enhance the robustness of PSs’ parameters extraction, a local band purification (LBP) process is proposed to resist the non-Gaussian clutter in the subbands. To validate the performance of the proposed method, Monte Carlo experiments using simulated data are carried out, whose results show that the proposed method can successfully improve the image resolution through the subbands under low signal-to-clutter ratio (SCR). Moreover, experiments with real measured data are conducted, using two 0.75 GHz subbands to reconstruct a 5 GHz signal, whose 2D image result is approximated to that based on the real 5 GHz signal. Image parameters are also compared, whose results demonstrate that the proposed method has satisfactory accuracy and robustness on improving image resolution.