Development Of A Nanosecond Pulse Generator Based On PCB Transmission Lines And Solid-state Switches

Recently, nanosecond pulsed electric field are widelyused inbiomedical fields, which has aroused great interests of researchers home and abroad. To develop a nanosecond pulse generator, with compact, portable, excellent reliability and other good characteristics, for biomedicaluse, PCB transmission lines and solid-state switches are combianed to develop a high-voltage nanosecond pulse generator.Firstly, the working theory of the nanosecond pulse generatorbased on the PCB transmission lines and solid state switches are explained. Through the voltage wave propagation analysis of Blumlein transmission line system, the process of three kinds of outputting impedance to form square wave with related regulatory policies are interpreted. And build cascade transmission lines in series or parallel connection by using Pspice to testify the output of those systems for different uses. Furthermore, stray inductances of the load and rise time of switch have been analyzed in Pspice software to see their influence on the output characteristics of the system.Then, according to the requirements of nanosecond pulse generator, process to design Blumlein type balanced microstrip transmission lines, unbalanced multilayer microstrip transmission lines, balanced striplinesare described in detail, respectively, and distributed capacitance values of the PCB transmission linesare obtained to define operating frequency of the system under a certain DC power supply. In addition, selection of solid state switch, design of its drive circuit, and the working principle of the gate "RCD" active equalizing circuit, when applied to series connected MOSFETs for dynamic / static balancing tactics, are interpreted.Finally, on the basis of the gate "RCD" active equalizing strategy, a swith modules composed by six series connected MOSFETs has been developed to act as a single swith for the balanced Blumlein type microstrip transmission lines, unbalanced Blumlein type multilayered microstrip transmission lines, and balanced Blumlein type multilayered striplines nanosecond pulse generator to verification its output characteristics. Besides, according to the system compact requirements, balanced Blumlein type striplines have been chosed as the stacking unit with its smaller area, higher surface flashover and better shielded capability. After that, Blumlein typestriplines are parallel connected to reduce the system output impedance, series connected to increasing the pulse width of the output square wave of the system and mixed connected to approach both smaller output impedance and longer pulse width outputting, respectively. At last, we test the output of the 4 stages series connectedmicrostrip system, emphatically. The parameters of the output pulse voltage are, amplitude arranges from 0 to 3 k V continuously, width hits to several thousand ns, operating frequency goes to a few k Hz and rise time is about 20 ns, which lies the foundation for the study of biomedical effects of nanosecond pulsed electric field.