Investigation Of Ultra-Wideband Microwave Generation Based On Gaas Photoconductive Semiconductor Switches

Photoconductor Semiconductor Switches (PCSS's), as a new kind of high power ultra-wide-band electromagnetic pulse emitter, offer unique properties comparing with traditional switches. The rise time of electromagnetic pulse is on sub-nanosecond and picosecond level, the relative wide of band exceed 25%, its frequency band is range from tens MHz to several and even maybe to tens of GHz. Especially, PCSS's can be excited by lower energy laser pulse and have high-gain output, so it is possible to make the all-solid state mini-size high power ultra-wide-band electromagnetic pulse emitter system. However, when the switches are working as linear mode, the relations between the wide output electromagnetic pulse and biased dc voltage, trigging condition, and a function between the transforming efficiency and biased dc voltage, trigging condition need father research. Furthermore, the radiation at non-linear mode has not been reported, the theory of optically activated charge domain, what is used to explain the non-linear mode, need to be improved father.This article gives the research on the mechanism and application of Semi-insulating (SI) GaAs PCSS's generating ultra-wide-band electromagnetic radiation, combining with linear mode experiment, mainly analyzing the factor whichinfluencing the time characteristic of PCSS's generating ultra-fast electromagnetic pulse characteristic, and analyzing the connection between the characteristic of time and the characteristic of frequency. The article indicates the output pulse band of frequency is mainly determined by the rise time and the fall time of electromagnetic pulse. The rise time of electric pulse determine the high-frequency component of output electromagnetism pulse, the fall time determine the low-frequency component, and get the best experiment result in our nation at present. The influence factor is simulated by exciting optical pulse and the structure of switch to the time resolved electromagnetic pulse. We indicate that, to enhance the peak value of the output of electromagnetic pulse, the trigging optical pulse should be sufficiently narrow and the switch should work on the saturated mode on the condition of proper biased dc voltage; The importing of deep energy level effectively shortens the recombination time of the photo generated carriers, and the width of pulse become narrower. The narrow gap switches make the radiate relatively high efficiency of electromagnetic pulse on the premise of that there is no loss of the rise time of electric pulse. All these provide the theoretical foundation for the design and research of PCSS's in the linear mode. The article presents the hypothesis that the maintaining phase of nonlinear pulse is envelope of the narrow pulses on the base of the nonlinear radiation of pulse experiments and the theory of optically activated charge domain. In the end, preliminarily analyse the hypothesis.