Research And Realization On Receiver Of Deep Ground Penetrating Radar

Impulse ground penetrating radar(GPR) has some obvious advantages in the field survey, such as simple waveform generation, high pulse repetition, no interference in frequency domain and so on. The common GPR systems are based on the impulse radar technique and are prevalent in the commercial market. However, small dynamic range is the common problem in the GPR receiver system currently, which limits its application in the field of deep penetrating. In this thesis, the large dynamic range receiver technology of impulse GPR system is studied deeply and a physical receiver has also been developed, which has a good performance.This thesis firstly studies on the basic theory of GPR receiver system, and then analyzes the relationship between the receiver dynamic range and its penetrating depth. Several simulations and analyses to the traditional analog sampling circuit were carried out, which point out that the key factor limiting the dynamic range is the asymmetry of sampling pulse. Besides, the theoretical value of its dynamic range can be estimated through simulations. An ultra-wideband(UWB) deep GPR receiver circuit based on Analog-to-Digital Converter(ADC) and digital silicon delay chip is designed and developed finally. The highly integrated, low-cost receiver circuit has greatly improved dynamic range of receiver from 50 dB to 75 d B, satisfying the requirement for deep penetrating.Because of the characteristics of the GPR signal, this thesis then studies the dynamic range compression technology of UWB signal, and time-varying gain dynamic range compression technology is proposed for the equivalent sampling circuit. The technology can provide 20 dB dynamic range compression for the received signal.Based on the above researches, a GPR receiver system with a large dynamic range for deep penetrating has been designed and developed finally. Its dynamic range and performance has been greatly improved which was approved by tests and experiments, compared with the existing GPR system.