**Ye Zhang, Qi Yang \*, Bin Deng, Yuliang Qin and Hongqiang Wang**

College of Electronic Science and Technology, National University of Defense Technology, Changsha 410073, China; zhangye10@nudt.edu.cn (Y.Z.); dengbin@nudt.edu.cn (B.D.); qinyuliang@nudt.edu.cn (Y.Q.); wanghongqiang@nudt.edu.cn (H.W.)

**\*** Correspondence: yangqi08@nudt.edu.cn; Tel.: +86-731-8457-5714

Received: 25 April 2019; Accepted: 20 May 2019; Published: 23 May 2019

**Abstract:** Translational motion of a target will lead to image misregistration in interferometric inverse synthetic aperture radar (InISAR) imaging. In this paper, a strong scattering centers fusion (SSCF) technique is proposed to estimate translational motion parameters of a maneuvering target. Compared to past InISAR image registration methods, the SSCF technique is advantageous in its high computing efficiency, excellent antinoise performance, high registration precision, and simple system structure. With a one-input three-output terahertz InISAR system, translational motion parameters in both the azimuth and height direction are precisely estimated. Firstly, the motion measurement curves are extracted from the spatial spectrums of mutually independent strong scattering centers, which avoids the unfavorable influences of noise and the "angle scintillation" phenomenon. Then, the translational motion parameters are obtained by fitting the motion measurement curves with phase unwrapping and intensity-weighted fusion processing. Finally, ISAR images are registered precisely by compensating the estimated translational motion parameters, and high-quality InISAR imaging results are achieved. Both simulation and experimental results are used to verify the validity of the proposed method.

**Keywords:** interferometric inverse synthetic aperture radar (InISAR); image registration; translational motion parameters estimation; strong scattering centers fusion; terahertz radar imaging
