® Wang Electro-Opto Corporation ( ) A Multioctave Broadband Vest Antenna Based on SMM Antenna Technology Johnson J. H. Wang and David J. Triplett* Wang.

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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.

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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

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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.

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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.

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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

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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”

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A 2-element vest array of SMM antennas

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Military gear onto which vest antenna can be installed

x

z

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Representative azimuth patterns on saline mannequin(pseudo-circular polarization)

5dB/divx

yVP

HP0.225 GHz 0.5 GHz 1.0 GHz

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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

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Measured SWR of front element antenna

2

1

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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).

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Major disadvantages of this vest antenna

• Weight: – currently 4.4 lbs.

– reducible to 1.5 lbs.

• Disruption by other body borne gear

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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.