Impulse GPR Time-variant Gain Amplification Receiving System Design

Ground penetrating radar (GPR) is a relatively new geophysical detection method.GPR use broadband electromagnetic wave in the form of pulse to detect medium internalobjects or underground structure. It has a very wide range of applications in thegeophysical detection aspects. So it needs high resolution and efficiency. Research forGPR has very important significance. GPR receiver design directly affects the performanceof the machine. The time-varying gain circuit of receiving part can greatly increase thereceiver sensitivity and dynamic range. General literature rarely mentioned time-variantgain the gain curve get method. So obtain gain curve and research for time-varying gainGPR receiving system are of great value.The main work of this project is to design a variable gain amplifier based impulseground penetrating radar receiver system. The entire impulse ground penetrating radarreceiving system by the high-frequency part of the microwave filter, low-noise amplifiercircuit and equivalent sampling circuit, time-varying gain circuit IF part and FPGA controlmodule circuit composed. High-frequency impulse ground penetrating radar echo signalsthrough the filter and low-noise amplifier circuit is filtered and amplified, and then gothrough the equivalent sample circuit down converting, Echo signal is stretched amplifiedthrough a variable gain control module is real-time zoom and then output. The entiresystem is completed under the control of the FPGA.This topic obtains the time-varying gain curve by using the FDTD method.Completed the design and simulation of the high-frequency part. The software ofsimulation is Agilent ADS. Completed the IF equivalent sampling part of the design andsimulation. A variable gain control module is produced. Preparation of the FPGA controlprocedures for each module.This paper gets the decay curve of the electromagnetic wave propagation in lossydielectric. when medium relative dielectric constant is8and conductivity is0.04S/m andrelative permeability is1and magnetic resistance rate is0Ω/m. The excitation source is Gaussian pulse. Verify the exponential decay of electromagnetic waves in lossy media.Design microwave filter center frequency of100MHz. Meet portion20dB stop-bandattenuation requirement. Design equivalent sampling circuit simulation to achieve theeffect of high frequency echo cycle stretching1,000times. The design of time varying gaincontrol module converts the analog echo signals in real time according to the gain curve.