Research And Implementation Of Ultra-wideband Pulse Technology In Ground Penetrating Radar

With the development of economy,the distribution of roads,bridges and other transportation facilities is more and more wide.In order to survey and test the safety of traffic facilities,many ground penetrating radar(GPR)systems had been widely used.Comparing with other Radar system,the ultra-wideband(UWB)GPR is more efficiency,accurate and nondestructive,and especially suited for the smart monitoring and maintenance of traffic facilities.The design idea of this thesis is: making an overall design plan of GPR,and focusing on the the key modules,including transmitting terminal and receiving terminal.An overview about the background and the characteristics of UWB is proposed,and designations of the peripheral circuit of ultra wideband ground penetrating radar are described;The UWB generator is designed for the transmitting terminal,and the equivalent sampling circuit is designed for the receiving terminal.An outstanding discusse is emphasized about the equivalent sampling of research and the realization of the circuit.The circuit of equivalent sampling verified is realizable.The detailed design contents list as follow:(1)Some concrete designs of peripheral circuit module in ground penetrating radar is discussed,including: antenna module,low noise amplifier module,the differential amplifier module,analog-todigital module,time delay module,oscillation circuit module,and power module.(2)In the peripheral circuit module part,compared with the working principle and ADS simulations of the circuits based on SRD and avalanche transistor,the circuit based on avalanche transistor is chosed to realize the design of transmitting terminal.The further research and design of the circuit are carried on.The PCB layout and production of circuit are completed which can get a pulse of 2ns pulse width and 9.5V pulse amplitude in tests.(3)In the receiving terminal part,considering the characteristic of the pulse width of UWB pulse,the method of equivalent sampling is used to sample signal.With the analyzing and ADS simulations of sampled signal circuit,sampling circuit and holding circuit in the equivalent circuit,a conclusion could be drawn that the equivalent sampling circuit can be implemented.The signal after dealing by the equivalent sampling circuit can be processed by common A/D converter,so those expensive A/D converters with high sampling frequency are no more indispensable.The whole PCB design and production of the equivalent sampling circuit are completed,which can effectively achieve the sampling circuit and holding circuit and test the realizability of equivalent sampling circuit by the experiment results.