Research On The Techniques Of Coupling Suppression In The SFCW-GPR

Stepped frequency continuous wave ground penetrating radar (SFCW-GPR) claims our attention as it provides a safe and fast way for small targets detection, which is buried on the surface of the soil. The large leakage signal between the transmitting and receiving antennas is a severe problem encountered in SFCW-GPR, the performance of SFCW-GPR is degraded due to the existence of coupling. Efficient and innovative techniques play an important role in the realization of SFCW-GPR systems.This dissertation first analyzes the origin and properties of coupling and investigates its impacts on the keys parts of SFCW-GPR. Considering the new features of SFCW-GPR, we use a direct coupling simulation model based on the CST microwave studio, and propose a method to suppress the direct coupling by improving transmit-receive isolation. Simulation and experimental result are both satisfied.Then, the approaches to coupling suppression based on mean-subtraction are studied in detail. According to the difference of creating the cancellation signal, we propose echo domain cancellation scheme and image domain cancellation scheme. The performance of each method is satisfied if their demand is met. After character analyzing, we propose an echo and image domain mean-subtraction approach, which both has the advantages of echo domain cancellation scheme and image domain cancellation scheme and overcomes their inadequacy. In addition, the realizing procedure and the restriction of the new method are dicussed, and the suppressing result is demonstrated by experiments.In the end, an Intermediate Frequency (IF) Cancellation module has been designed that cancels the leakage signal between the transmitting and receiving antennas in a SFCW-GPR. According to the actual demand of SFCW-GPR, three main aspects are studied, which are the hardware realization scheme of cancellation method, hardware design and software logic implementation of IF Cancellation module and the impact analysis of the error between coupling and the cancellation signal. The performance of the IF cancellation module is validated by real data processing of the vehicle-mounted SFCW-GPR.This coupling suppression scheme worked well with a SFCW GPR.