Analysis and Validation of 77 GHz FMCW-based GB-SAR Micro-deformation Monitoring Method

Since the development of deformation monitoring technology, various synthetic aperture radar (SAR) systems have been developed. There are two popular traditional deformation monitoring technologies including spaceborne SAR and airborne SAR. However, they both have the disadvantages such as the inability to monitor promptly, long monitoring cycles, and the micro-deformation accuracy of low. The ground-based synthetic aperture radar (GB-SAR) avoids these problems, which offers great convenience and potential for micro-deformation monitoring applications. This paper proposes a technique based on the 77 GHz frequency modulated continuous wave (FMCW) micro-deformation monitoring method for GB-SAR, which leads to a lighter, faster GB-SAR device with better monitoring accuracy. Firstly, a fusion filtering method employing wiener filtering and 2D discrete wavelet transform (2DWT) is used to remove noise in the radar echo data. Then, a GB-SAR imaging system is developed based on a back-projection (BP) algorithm, where the radar sensor scans the target scene by moving a horizontal trajectory. A modified mean filtering approach is performed for phase denoising of interferometric image. Moreover, a discrete cosine transform-based least squares (DCT-LS) method is utilized for phase unwrapping. Finally, several experiments are conducted to demonstrate effectiveness and practicability of the proposed method, and the accuracy of deformation monitoring can reach the sub-millimeter precision (1mm).