High-power microwave bandwidth broadening by air breakdown
Wideband, high-power microwave pulses are expected to have important applications in ultra-wideband radar. The wide bandwidth should generate increased information for target characterization and identification. The high power should result in increased target detection range for conventional targets and targets with reduced signatures. A way to generate wideband, high-power microwave pulses with relatively conventional technology is to tail erode high-power pulses by passage through a low-pressure air cell. In this process, the tails of short (3--10ns), high-amplitude (>1 MV/m) pulses are removed. This erosion shortens the pulses and generates transmitted pulses with broadened bandwidths. The pressure must be matched to several incident pulse characteristics to create enough electron density to cause strong tail erosion. The important pulse characteristics are amplitude, frequency, pulse length, and pulse shape. We have shown experimentally that tail erosion from air breakdown broadens the 3 dB bandwidths of 2.8608 GHz incident pulses in a rectangular waveguide at 3.5 torr. The incident pulse amplitude varied from 0.67--1.16 MV/m. The pulse bandwidth increased from 0.147 GHz by 0.34--1.4% relative. The incident bandwidth was 5.12% relative to the incident carrier frequency. This experimental broadening was simulated with a 2D, electromagnetic, electron fluid computer code for avalanche ionization. The simulation predicted bandwidth broadening by 0.029--0.13 GHz or 1.0--4.4% relative for a peak initial electron density of 10 electrons/cm{sup 3}. Although the measured and calculated transmitted electric field envelopes were in close agreement, the calculated bandwidths exceeded those measured by 13--47%. Because the detectors were not fast enough to resolve individual cycles we presently conclude that the simulation gives better estimates of reality than do the measurements. 8 refs.
- Research Organization:
- Lawrence Livermore National Lab., CA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6010462
- Report Number(s):
- UCRL-JC-107442; CONF-920124--5; ON: DE92005246
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
420200* -- Engineering-- Facilities
Equipment
& Techniques
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
AIR
BREAKDOWN
COMPUTERIZED SIMULATION
ELECTRIC DISCHARGES
ELECTROMAGNETIC PULSES
ELECTROMAGNETIC RADIATION
ELECTRON TUBES
ELECTRONIC CIRCUITS
ELECTRONIC EQUIPMENT
EQUIPMENT
FLUIDS
FREQUENCY ANALYSIS
FREQUENCY RANGE
GASES
GHZ RANGE
GHZ RANGE 01-100
HIGH-FREQUENCY DISCHARGES
KLYSTRONS
MEASURING INSTRUMENTS
MICROWAVE EQUIPMENT
MICROWAVE RADIATION
MICROWAVE TUBES
PULSE CIRCUITS
PULSE SHAPERS
PULSES
RADAR
RADIATIONS
RANGE FINDERS
SIGNAL CONDITIONERS
SIMULATION
TWO-DIMENSIONAL CALCULATIONS