Correction of Dechirp Distortion in Long-Distance Target Imaging with LFMCW-ISAR

Wen CHANG  Zenghui LI  Jian YANG  Chunmao YEH  

IEICE TRANSACTIONS on Communications   Vol.E97-B   No.11   pp.2552-2559
Publication Date: 2014/11/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.2552
Type of Manuscript: PAPER
Category: Sensing
dechirp distortion phenomenon (DDP),  inverse synthetic aperture radar (ISAR),  linear frequency modulation continuous wave (LFMCW),  long-distance target imaging,  

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The combined linear frequency modulation continuous wave (LFMCW) and inverse synthetic aperture radar (ISAR) can be used for imaging long-distance targets because of its long-distance and high resolution imaging abilities. In this paper, we find and study the dechirp distortion phenomenon (DDP) for imaging long-distance targets by a dechirp-on-receive LFMCW radar. If the targets are very far from the radar, the maximum delay-time is not much smaller than a single sweep duration, and the dechirp distortion is triggered since the distance of the target is unknown in a LFMCW-ISAR system. DDP cannot be ignored in long-distance imaging because double images of a target appear in the frequency domain, which reduces resolution and degrades image quality. A novel LFMCW-ISAR signal model is established to analyze DDP and its negative effects on long-distance target imaging. Using the proportionately distributed energy of double images, the authors propose a method to correct dechirp distortion. In addition, the applicable scope of the proposed method is also discussed. Simulation results validate the theoretical analysis and the effectiveness of the proposed method.