FMCW-InISAR imaging for high-speed target based on bistatic configuration

Interferometric inverse synthetic aperture radar (InISAR) imaging has been proved to be a powerful means for obtaining three-dimensional (3-D) space shape of noncooperative targets. Frequency modulated continuous wave (FMCW) InISAR (FMCW-InISAR) has unique advantages of low power, low cost, and small volume compared with traditional coherent pulsed InISAR. However, FMCW-InISAR imaging has two additional issues to consider, the one is the invalidation of the assumption of stop&go, which is caused by the relatively long sweep interval of FMCW; the other is the isolation of the transmitting and receiving antennas, which is the inherent issue of the transmitter-receiver community radar systems. To solve these two problems, a bistatic FMCW-InISAR imaging algorithm for high-speed targets is proposed in this paper. For improving the isolation of the transmitting and receiving antennas, a bistatic configuration based FMCW-InISAR system is designed. According to the characteristics of bistatic, a bistatic equivalent motion model and corresponding signal model are established. Since the assumption of stop&go is invalid in the case of FMCW, indicating that the target cannot be viewed as motionless during a sweep repetition interval (SRI), a parametric estimation based quadratic phase factor (QPF) compensation method is investigated to eliminate the range walk caused by the radial motion of the target during the SRI. In addition, considering the far-field trait of the target and combining the traditional InISAR imaging process, a combined QPF compensation technique is proposed to reduce the computational burden of the algorithm. Finally, the effectiveness and the robustness of the proposed algorithm are evaluated by some simulations.