Inverse synthetic aperture radar imaging based on hyperbolic frequency modulated continuous waveform

The frequency modulated continuous wave (FMCW) has been successfully applied in both synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) imaging in the recent past years, for its advantage in low cost, low powered, and compact. However, the traditional FMCW radars transmit a linear frequency modulated (LFM) waveform with a relatively long time interval. And the assumption of stop-go is no longer valid, for the target´s motion during the entire sweep must be taken into account. Therefore, more complicated parametric algorithm should be taken to estimate the phase history of noncooperative target. It is computing expensive and is not practical for some military usage where the real time imaging is required. In the present work, an ISAR imaging method based on the hyperbolic frequency modulated continuous waveform (HFMCW) is proposed. The HFMCW radar echoes are received using a “decurve” method defined in this paper. The hyperbolic frequency modulated (HFM) waveform has inherent Doppler invariant property. Therefore, the focused high resolution range profile (HRRP) can be obtained without estimation of the target´s velocity, and the traditional nonparametric motion compensation method can be directly applied in the HFMCW ISAR imaging with high computational efficiency. Finally, numerical results validate the proposed HFMCW-ISAR imaging algorithm.