Development Of Sub-nanosecond Pulse Source Based On Marx Circuit

In recent years,Ultra-wideband ground penetrating radar has been widely used in military and civilian fields,this is due to the advantages of ultra-wideband ground penetrating radar with wide spectrum distribution,strong penetration ability,good antijamming performance,light and simple structure,and easy operation.With the increasing requirements for the detection resolution of ultra-wideband ground penetrating radars,the signal transmitter in the radar system,namely the pulse signal source,has been continuously improved and perfected,and the design of its pulse width has developed from the nanosecond level to sub-nanosecond level.In this thesis,the following work has been done on the development of bipolar sub-nanosecond pulse source:The waveform function and its spectrum distribution of each order gaussian signal are analyzed in the first part.The first-order Gaussian signal waveform does not contain DC component,positive and negative bipolar and the circuit is simple to make,so the first-order Gaussian pulse signal is used for this thesis The launch waveform of the circuit and the pulse waveform of the Gaussian rising edge and the exponential falling edge obtained by the actual circuit test are introduced.Next,several methods of generating ultra-wideband pulse signals are introduced.After comparing the project requirements and the advantages and disadvantages of the circuit,the Marx circuit based on avalanche transistors is selected as the technical method for time-domain pulse signal generation.Subsequently,this thesis studies the avalanche multiplication effect of the avalanche transistor and its three conduction methods.After introducing the charge and discharge structure of the Marx circuit,I theoretically calculate the main device parameters of the Marx circuit based on the avalanche transistor,and analyze the series and energy storage.The influence of capacitance on the Marx circuit provides a theoretical basis for the subsequent simulation.Chapter 4 is the simulation calculation part of the Marx circuit.Before the Marx circuit simulation,I carry out the preparations for the selection of the avalanche transistor and the calculation of the spur parameters of the microstrip line.And then the Marx circuit with the microstrip line was built in the PSPICE software In the simulation model,the zero-order Gaussian signal obtained by the simulation is compressed by the sharpening capacitance method,and the distortion of the pulse waveform is improved and optimized by using a small series inductance.This paper also introduces several methods for generating first-order Gaussian pulse signals.By further adding the designed RC differential circuit to the simulation model,the zero-order Gaussian pulse signal is successfully shaped into the first-order Gaussian pulse signal,which is provided for subsequent circuit board production.A reliable basis.Finally,based on the theoretical and simulation calculation results,the pulse signal source based on the Marx circuit was actually processed and tested,and I compare the experimental test results with the simulation calculation results.The experimental test obtained the bipolar Gaussian pulse amplitude of 215 V,the pulse width is only 260 ps,the rising edge is 150 ps,the waveform is flat,and the positive and negative waveforms are more symmetrical.This paper briefly analyzes the reasons for the time jitter and trailing signal generated by the test waveform,and a solution is provided to reduce the jitter and improve the trailing signal.