| Ground Penetrating Radar,as a type of geophysical detection equipment,can accurately locate the spatial location of buried objects on the surface,with high detection accuracy,non-destructive,efficient and terrain adaptability.Therefore,it plays a very important role in military,engineering,archaeological applications.Its advantages of non-destructive and high accuracy are very suitable for the application of low metal content mine detection.This thesis firstly clarifies the background and research significance of the topic,introduces the development history of ground-penetrating radar and the current situation of domestic and foreign research,explains the main research contents and the specific structure arrangement,systematically introduces the basic principles in groundpenetrating radar technology,including pulse power technology and pulse induction principle,analyzes the parameters and technical characteristics of ground-penetrating radar equipment,gives the overall system according to the typical structure of groundpenetrating radar and design requirements.The overall structure of the system is given according to the typical structure and design requirements of ground-penetrating radar,and the design and implementation of the bipolar pulse signal source and data acquisition,caching and processing modules in the ground-penetrating radar system are focused on,and finally the designed circuit modules are tested and verified using oscilloscopes and Arbitrary Waveform Generator.For ground-penetrating radar bipolar pulse signal source,the circuit scheme is based on the classic MARX generator,which basic principle of capacitor "parallel charge,series discharge" is suitable for output unipolar pulse scenario.The program of signal source is based on the classic circuit design,the unipolar output upgraded to bipolar output,the specific circuit modification: 1,choose better switching characteristics,voltage withstand capability of the power field effect tube as the circuit switching device;2,in the circuit to add 1:1 in-phase winding nanocrystal core transformer as an isolation device,the use of induction isolation principle to give the circuit bipolar output capability;3,the circuit structure adopts modular design,each level of the module contains a transformer,a set of capacitors and two switching devices,which can be flexibly increased or decreased according to demand.The circuit works through logic devices with gate drive circuit to control the on and off of different power field effect tubes to switch the circuit working state,in order to output different polarity of the pulse signal.The bipolar pulse source circuit is designed with a simple structure and flexible configuration,and can output bipolar pulse signals with high amplitude,narrow pulse width and short rise time.The STM32+FPGA+ADC circuit structure design scheme is proposed for the design of data acquisition,caching and processing.STM32 has better data processing capability and rich peripheral interface,which is suitable for data processing and expansion of peripherals.FPGA's parallel feature is more efficient than STM32 operation,which is suitable for caching data and logic control of ADC devices.The design mainly contains:1,SPI logic control of FPGA to ADC,control sampling start/stop and provide sampling clock;2,data interface FSMC(variable static storage controller)between STM32 and FPGA for communication and cache data transfer between two devices,data is first cached in FIFO,and the data is sent to STM32 for calculation and processing through FSMC.The data processing is done by software algorithms.After completing the theoretical design,the PCB is drawn using Altium Designer and the hardware circuit logic is designed using Quartus. |
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