Research On Step Recovery Diode Pico-second Pulse Technology Based On Different Driving Circuits

In this thesis, research work is based on ground-penetrating radar (GPR) pulse source technologywith the purpose of developing applicable GPR pico-second pulse generator using step recoverydiode(SRD). The circuits all use the special characteristics of SRD and are modeling in ADS. Aftersummarizing several different SRD rectifier circuits, a pulse generator with no driving and anotherthree with different op amps are presented. With combining simulation and experimental results,differences between these methods are comparatively analyzed.The main work and innovation of this paper are summarized as follows:(1) The basic principles of GPR and the current situation and development prospects at home andabroad are reviewed. The applicability of four kinds of frequency-domain sources as well as theunipolar Gaussian pulse and single-cycle pulse source are discussed by simulating in time domain andspectral domain. After introducing the architecture of the pulse system, the characteristics and effectsto the pulse circuit with different RC component values are explained. Various types of devices andtechniques that can be used to generate narrow pulses are simply presented.(2) The physical structure and electrical properties of SRD are discussed and three circuit modelsand six kinds of shaping circuit are summarized on the basis of the relationship between the quantityof charge and currents. The model of SRD is established in ADS using nonlinear modeling method.The junction capacitance is calculated in the way of measuring the body resistance of SRD.Discussions of differences between models and the accuracy of junction capacitance are proposed. Areasonable value of the junction capacitance is provided on the account of the measurement results.(3) Two different pulse forming circuits are analyzed and a pulse source directly driven withsignal generator is firstly fabricated. The simulation and measured results are well fitted. Then threetwo-stage load-sharing driving circuits using current feedback op amps are proposed. Theperformance and advantages of two-stage op amps are simulated. Combined with an equivalent shortline, three different driving circuits are produced and tested. The impact of several importantparameters to the waveform are discussed. The final selection using THS3091has a considerableamplitude and good waveform. A small pulse generator driven by transistors and a single powersupply is finished which can be used in high resolution short range GPR detection.