Wideband microwave generation with GaAs photoconductive switches

Conference · Tue Jan 01 00:00:00 EST 1991

OSTI ID:5343092

Druce, R L; Pocha, M D; Griffin, K L ^[1]; Stein, J M ^[2]; O'Bannon, B J.J. ^[3]

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1. Lawrence Livermore National Lab., CA (United States)
2. Rockwell International Corp., Albuquerque, NM (United States)
3. Rockwell International Corp., Anaheim, CA (United States)

We are using solid state photoconductive switches to generate wideband microwave pulses with peak powers to 20 MW. A parallel-plate Blumlein transmission line is used to directly feed an exponential taper antenna to produce single pulses with rise times of 200 ps and pulse durations of 340 ps (FWHM). Voltages up to 21 kV have been generated in a 1 cm tall, 12 cm wide parallel-plate line. With the switches operated in linear mode, we have demonstrated phasing of several switches to generate a coherent wave. Generated and radiated signals agree very well with numerical calculations. Radiation efficiencies approach 30%. The Blumlein dielectric can be changed to produce a damped waveform, thereby modifying the bandwidth of the signal. We have generated damped waveforms of up to 3 cycles using this method. The parallel-plate geometry lends itself to coupling to an antenna structure to radiate efficiently. The geometry also lends itself to expanding the generator in height and width. We have stacked two generators to nearly double the output power without degrading the pulse characteristics. Applications of ultrashort microwave pulses (UWB radar, HPM weapons) require a high repetition rate and long life from the generator. Life times of >10{sup 5} shots have been seen occasionally at low to medium power densities. As the power density of a solid state photoconductive switch is increased, device life decreases. We have the capability to test devices at a repetition rate of 30 Hz and voltages to 25 kV. Preliminary data indicates that repeated pulse biasing (without switching) of large LEC grown devices in a slab geometry with fields as low as 30 kV/cm damages the switch and eventually leads to failure. 6 refs., 10 figs.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5343092
• Report Number(s): UCRL-JC-105661; CONF-910640-41; ON: DE91017544
• Resource Relation: Conference: 8. IEEE pulsed power conference, San Diego, CA (United States), 17-19 Jun 1991
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
HIGH-VOLTAGE PULSE GENERATORS
TESTING
SEMICONDUCTOR SWITCHES
USES
ANTENNAS
GALLIUM ARSENIDES
MICROWAVE EQUIPMENT
PHOTOCONDUCTORS
ARSENIC COMPOUNDS
ARSENIDES
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
EQUIPMENT
FUNCTION GENERATORS
GALLIUM COMPOUNDS
PNICTIDES
PULSE GENERATORS
SEMICONDUCTOR DEVICES
SWITCHES
426000* - Engineering- Components
Electron Devices & Circuits- (1990-)
420200 - Engineering- Facilities
Equipment
& Techniques