Design Of Nanosecond Pulse Source Based On Solid Switching Devices

Ultra-wideband impulse radar with wide frequency bands has many features, such as anti-interference, super-high range resolution, low power consumption, low interception rate and little interference with other systems. Therefore, it is widely used in the underground detection, biomedical science, instrumentation. Ultra wideband impulse radar system is mainly composed of transmitter, antennas, receiver. The design of impulse source used for impulse radar is discussed in this work.1. Design of high power pulse source with avalanche transistorIn this paper, several common high power pulse generating circuit are studied. The basic structure of the avalanche transistor, the avalanche breakdown voltage, charge and discharge of the avalanche and the dynamic changes of working spot are analyzed in detail. To meet the need of project, nine high power pulse source are designed to XXX radar system. Traditional Marx circuit with FMMT415 avalanche transistors as switches is used. Later, theoretical calculations, circuit simulation component selection and circuit board production and tests are carried out. The final experiment result shows that when the charging voltage is 300 V, a quasi zero-order Gaussian pulse with peak voltage of 2.3 kV, width at half maximum of 1 ns and repetition frequency of 10 kHz an be generated on the 50 ? load. The size of pulse source circuit board is 295 × 78 cm2.2. Design of bipolar pulse source with step recovery diode(SRD)The step-recovery diode working mechanism is discussed in detail, and the typical SRD pulse source circuit is introduced. In order to meet the demand of signal acquisition, a bipolar pulse sources is designed. Experimental results show that when the DC bias is 12 V, a pulse with a negative pulse and a positive pulse is made. The negative pulse has a pulse amplitude of- 4.3 V and a bottom width of 300 ps and the positive pulse has a pulse amplitude of 4.2 V, and pulse bottom width of 295 ps. The output pulse is in good symmetry and the repetition frequency is adjustable in the range of 1 kHz-5 MHz. Finally, the pulse source with simple circuit structure, low cost, small size, and superior performance characteristics is designed.