A Noncontact 3-D Back-Projection Measurement Method Based on CFAR Extraction and SFCW-GPR System

Stepped frequency continuous wave (SFCW) ground penetrating radar (GPR) is a geophysical method to detect the structure and characteristics of underground burial targets by using high-frequency electromagnetic waves. In this article, in order to reconstruct the 3-D structure of underground objects with complex structures, we design a reconfigurable multistate GPR (RM-GPR) and propose a pipelined 3-D back-projection (BP) algorithm. The system generates range profiles by using the phase of the echoes, which can effectively avoid the decline in resolution caused by the attenuation of the high-frequency part. Then, we improve the BP imaging algorithm into 3-D space and improve the computational efficiency of the algorithm by limiting the single imaging area and embedding a part of the calculation process into the signal acquisition process. Compared with the classical GPR system, the unique aspect of the RM-GPR system includes lower complexity for hardware components and lower uncertainty, higher clarity, and less calculation cost for pipelined 3-D BP imaging algorithm, which helps people have an intuitive understanding of unknown targets underground.