® wang electro-opto corporation ( ) a multioctave broadband vest antenna based on smm antenna...
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Wang Electro-Opto Corporation ( )WE O ®®
A Multioctave Broadband Vest Antenna Based on SMM Antenna Technology
Johnson J. H. Wang and David J. Triplett*
Wang Electro-Opto CorporationMarietta, Georgia 30067 USA
Presented in the 2006 IEEE AP-S International Antenna SymposiumAlbuquerque, NM
July 12, 2006
This research is supported by US Army CERDEC, Ft. Monmouth, NJ.
Wang Electro-Opto Corporation ( )WE O ®®
Outline
• Motivation
• Approach
• Brassboard Models
• Measured Performance
• Concluding Remarks
Wang Electro-Opto Corporation ( )WE O ®®
Motivation
• Mobile soldiers, police, firefighters, forestry workers, etc. need “hands free” operation for their wireless equipment.
• A solution is to use antennas borne or worn on their upper torso (as vest antenna).
Wang Electro-Opto Corporation ( )WE O ®®
Prior known vest antennas have severe shortcomings
• No conductive shielding against radiation hazards to wearer– acceptable in research and test stage under the
“controlled environment” exclusion clause
– unacceptable for deployment since vest antennas are worn regularly, thus in an “uncontrolled environment”
• Poor gain pattern– low gain
– poor omnidirectional coverage
– rapid oscillatory spatial variations
Wang Electro-Opto Corporation ( )WE O ®®
Safety issues on RF radiation hazard for vest antennas — serious yet overlooked
• Vest antenna designs must be based on an “uncontrolled environment” scenario (like the cell phone), since they are worn continually, though by professionals.
• At 300-3000 MHz, PEL (Permissible Exposure Limit) for uncontrolled environment is five timesfive times lowerlower than that for controlled environment.
Wang Electro-Opto Corporation ( )WE O ®®
Radiation hazard is a critical issue for body worn antennas
• Most cell phones barely meet the 1.6 W/kg SAR (Specific Absorption Rate) limit, even at the typical 0.25 W0.25 W power.
• JTRS (Joint Tactical Radio System) mobile radios aim at 5 W5 W power.
Wang Electro-Opto Corporation ( )WE O ®®
The present approach
• Based on the SMM (spiral-mode microstrip) antenna technology– Ultrawideband (multioctave)
– has inherent ground plane to shield the wearer from radiation hazard
Wang Electro-Opto Corporation ( )WE O ®®
Design goals
• Frequency of operation– 0.225 – 1.0 GHz
• Polarization– circular polarization
• Radiation pattern– omnidirectional coverage with minimal spatial dips
• Safety requirements on RF radiation– ANSI standard for “Uncontrolled Environment”
Wang Electro-Opto Corporation ( )WE O ®®
Representative azimuth patterns on saline mannequin(pseudo-circular polarization)
5dB/divx
yVP
HP0.225 GHz 0.5 GHz 1.0 GHz
Wang Electro-Opto Corporation ( )WE O ®®
Measured peak antenna gain in the azimuth planeFFW Antenna Model #A123S01D_003on saline mannequin
-20
-15
-10
-5
0
5
0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 1.000
Frequency, GHz
Pea
k G
ain
, dB
i
HP
VP
Total
14-Jul-05
Wang Electro-Opto Corporation ( )WE O ®®
Key advantages of SMM vest antenna over whip
Instantaneous Bandwidth
Visual signature
Safety Stability of wireless connectivity
Whip
< 2:1
Visible
Easily snared, entangled, and broken
Vulnerable to multipath fading due to lack of diversity gain
SMM Vest antenna
Up to 20:1
Invisible
Safe low radiation hazard will not poke the eye
More stable due to diversity gain (>3 dB from CP and potentially more via pattern diversity).
Wang Electro-Opto Corporation ( )WE O ®®
Major disadvantages of this vest antenna
• Weight: – currently 4.4 lbs.
– reducible to 1.5 lbs.
• Disruption by other body borne gear
Wang Electro-Opto Corporation ( )WE O ®®
Concluding Remarks
• A multioctave broadband vest antenna based on the SMM antenna technology has been developed.
• The brassboard model exhibits considerably better performance than other known vest antennas.
• It has major advantages over the whip antenna: much wider bandwidth, invisible, safer, and more stable connectivity.
• It should be able to meet ANSI safety requirements on RF radiation hazard.
• It has disadvantages of weight and disruption by other body-worn gear.