A Fast High Range Resolution 3-D SAR Imaging Algorithm Based on Interarray Frequency-Hopping LFM Signal

The wide applications of 3-D synthetic aperture radar (SAR) imaging bring higher requirements for resolution and computational efficiency. The stepped frequency linear frequency-modulated signal achieves high range resolution imaging by fusing multiple subpulses (SPs). However, its wide SP bandwidth results in a large amount of echo data to be processed, which results in a significant increase in the time consumption of the bandwidth synthesis algorithm. To achieve fast high range resolution 3-D SAR imaging, we propose an interarray frequency-hopping linear frequency-modulated signal model and a 3-D variable carrier frequency back projection (BP) algorithm. The proposed signal model transmits only one narrow bandwidth SP with hopping carrier frequency in each array element, which allows the receiver to sample the echo at a lower frequency. The lower sampling frequency and the number of SPs significantly reduce the amount of echo data. The proposed algorithm not only focuses on the along-track direction and the cross-track direction of the SAR image but also fuses the low range resolution imaging results obtained by each SP into a high range resolution imaging result. Benefiting from the fusion of the bandwidth synthesis algorithm and the imaging algorithm, the computational efficiency is greatly improved. The experimental results demonstrate that the proposed algorithm achieves a comparable resolution and imaging quality as the ideal 3-D BP algorithm with a large bandwidth chirp signal. Moreover, the time consumption of the proposed algorithm has been reduced to only 2.25%–3.02% of that of the advanced high range resolution 3-D BP algorithm.