No abstract

For inverse synthetic aperture radar (ISAR) imaging of a target with complex motions, the received signal in a range bin can be characterized by a multicomponent polynomial phase signal (PPS) after motion compensation. Due to this reason, Fourier transform (FT) based conventional range-Doppler (RD) ISAR imaging algorithm cannot handle this model well and the radar image obtained will be blurred. The synchrosqueezing transform (SST), which combines the continuous wavelet transform and frequency reassignment, is a promising tool to analyze the multicomponent PPS signal since it provides high resolution time-frequency distribution (TFD) for the multicomponent PPS, but no cross-terms. In this paper, we introduce the SST into ISAR imaging of a maneuvering target and show its potential to offer promising new possibilities for enhanced ISAR image interpretation in terms of further target recognition. Real data results and computational complexity analysis demonstrate the superior performance of the proposed method.Index Terms-Inverse synthetic aperture radar (ISAR), synchrosqueezing transform (SST), maneuvering target imaging

With an appropriate geometric configuration, a helicopter-borne rotating synthetic aperture radar (ROSAR) can break through the limitations of conventional strip-map monostatic SAR on forward-looking imaging. Owing to such a capability, ROSAR has extensive potential applications, such as selfnavigation and self-landing. Moreover, it has many advantages if combined with frequency-modulated continuous wave (FMCW) technology. In this letter, a novel geometric platform configuration and an imaging algorithm for helicopter-borne FMCW-ROSAR are proposed. First, by adopting the higher order approximation of slant range model to improve the azimuth resolution for FM-CW-ROSAR, the precise 2-D spectrum of the echo signal is derived based on series reversion. Moreover, at the same time, the Doppler offset caused by the continuous motion of the antenna is analyzed and compensated as well. Then, according to the analysis on the range-dependent velocity variation caused by ROSAR geometric configuration, an efficient inverse chirp-Z transform is utilized to remove the variant range cell migration, and a well-focused SAR image can thus be obtained. Finally, the experimental results with simulated data demonstrate the effectiveness of the proposed algorithm. IndexTerms-Frequency-modulated continuous wave (FMCW), helicopter-borne rotating synthetic aperture radar (ROSAR), inverse chirp-Z transform (ICZT), series reversion method.