Broadband Omnidirectional Helmet Antennas

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Broadband Omnidirectional Helmet Antennas
Johnson J. H. Wang 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 partially
supported by US Army CERDEC, Ft. Monmouth, NJ.
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Outline

• Motivation
• Approach
• Brassboard Models and Field Tests
• Fieldable Retrofittable Model and Lab Tests
• Concluding Remarks

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Motivation

• A helmet is generally worn in the field by
  soldier, police, firefighter, forest worker, and
  motorcycle rider, etc.
• The helmet-mounted antenna is the only antenna
  carried, borne, or worn by them that can possibly
  have a true and stable omnidirectional radiation
  pattern because of its
• uniquely high and unobstructed field of view
• stable orientation independent of the posture and
  movement of the wearer (since the head is
  generally held upright).

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Difficulties for helmet antennas

• Helmet antennas in the literature are in early
  stages of development, with electrical and
  physical performance grossly below the
  expectations of user community due to the
  following difficulties.
• Antenna gain-bandwidth limited by helmet size
• Safety issues on RF radiation and ballistic
  hazard
• Stringent weight and size limitation
• Competition for premium helmet location with
  other equipment

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The present approach

• Based on WEOs patented SMM (spiral-mode
  microstrip) antenna and slow-wave antenna
  technology
• ultra-wideband/multiband
• has inherent ground plane to shield the wearer
  from radiation hazard

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RF design goals

• Frequency bandwidth 1.35 2.7 GHz
• Polarization vertical
• Radiation pattern omnidirectional

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Other design goals

• Safety requirements on RF radiation
• ANSI/IEEE standard for Uncontrolled Environment
  
• Minimal ballistic effect to head of wearer
• Maximum weight 2 oz (56.7 gm)
• Retrofittable to kevlar helmets
• Producibility and low cost

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Three models developed

• Two brassboard models (Wang Ph 1 and Wang Ph
  2) were developed first
• both field tested by the US Army
• results summarized by the following two PPT
  slides prepared by Army CERDEC
• A fieldable retrofittable model recently
  developed
• meeting all design goals in WEO lab tests
• currently being field tested by Army CERDEC

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Material courtesy of U.S. Army CERDEC
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• C4ISR Demonstration Process
• Line-of-sight Range Measurements (Whips and
  Helmets)
• Evaluate Range Measurements
• Perform a Voice Communication Test With ARC Radio
  System Using the 802.11 Whip Antennas and Helmet
  Antenna
• Perform a Data Transmission Test Using the
  Commander Handheld Application for Mission
  Planning (CHAMP) Software Using the 802.11 Whip
  Antennas and Helmet Antenna
• Evaluate Performance of Helmet Antenna Based on
  Soldiers Comments

Specialist E4 Ronald D. of 104th CAV wearing the
Wang Phase II helmet

• Notable Features - Helmet Antenna
• Completely Reduces the Visual Signature - No
  Bending Required !
• Not Subjected to Body Blockage
• Isolated From Metallic Obstructions in the
  Soldier Wear
• Wide Band Operation

Better RF Range Performance than Larger,
Narrowband Whip Antenna
Material courtesy of U.S. Army CERDEC
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Annular zone on helmet clear of obstructions for
optimal performance
No obstructions allowed in the annular zone
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The latest fieldable retrofittable model

• Meeting ALL the design goals
• 2 oz (56.7 gm) in weight
• Currently being field tested by the US Army

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Measured Standing Wave Ratio (SWR)
2 1
Model A123J14
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Measured radiation patterns over 1.352.7 GHz
Azimuth
? 90
1.350 GHz
1.800 GHz
2.700 GHz
2.250 GHz
5 dB/div
Elevation
f 0
1.350 GHz
1.800 GHz
2.700 GHz
2.250 GHz
Model A123J14
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Measured peak gain over 1.35 2.7 GHz
Model A123J14
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Fieldable retrofit helmet antenna weighs only 2
oz

• Antenna assembly made of lightweight foam, thin
  copper sheet, PC board, and flexible feed cable
  in a thermochemical composite
• Conductive foil lining shielding wearers head
• Quick-snap-on connector at helmet edge

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Conclusion

• A fieldable retrofittable helmet antenna covering
  1350-2700 MHz has been developed.
• It has major advantages over other antennas
• invisible and safe
• stable and broad omnidirectional coverage
• weighs only 2 oz
• rugged (can withstand up to 70 lbs or more)
• field retrofittable
• producible at competitive cost