A%20Multioctave%20Broadband%20Vest%20Antenna%20Based%20on%20SMM%20Antenna%20Technology

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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
Corporation Marietta, Georgia 30067
USA Presented in the 2006 IEEE AP-S
International Antenna Symposium Albuquerque,
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

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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).

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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 times lower
  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 W power.
• JTRS (Joint Tactical Radio System) mobile radios
  aim at 5 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
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Representative azimuth patterns on saline
mannequin(pseudo-circular polarization)
y
VP
5dB/div
x
HP
0.225 GHz 0.5 GHz 1.0 GHz
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Measured peak antenna gain in the azimuth plane

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Measured SWR of front element antenna

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Key advantages of SMM vest antenna over whip
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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.