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Clandestine ELOS/OTH RF Communications for Unmanned Underwater Vehicles

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Final rept. 1 Jan 2001-31 Dec 2002

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This is a proposal to assess and develop critical technology for clandestine radio frequency communication systems for underwater autonomous vehicles UAVs. Under a previous ONR grant, the Applied Research Laboratories at the University of Texas at Austin developed and tested a preliminary design for a wire antenna. Assessments were made of data rates, propagation effects, and overall system impacts for a wide variety of communication methods. The long term goal of this research is to identify fundamental issues and required technological developments for small, long-range communications systems utilizing high frequency HF ground wave propagation that can be used in extended-line-of-sight and over-the-horizon ELOSOTH communications. Because ELOSOTH transmission over water requires HF frequencies, the sizes of standard antennas, such as quarter wave monopoles, are too large for UAV operation. Therefore, a major focus of this effort is on the development of electrically small antennas. This report addresses the further development of small electrical antennas that are needed for clandestine communications operating ELOSOTH. Under the previous grant, a new type of small antenna was developed the folded conical helix FLEX. Because of the initial success of the FLEX antenna, this effort focused on determining the scalability of the antenna and reducing its size. The Wheeler cap method and the relative gain method were used to measure the antennas efficiency as the size was reduced. These measurements were compared with those for a quarter wave monopole. Standing wave ratio SWR also was measured. Efficient wideband small antennas will make possible long-range 30-150 miles point-to-point communication for UAVs. And because the FLEX antenna is a wire antenna, it can be made retractable and robust in a maritime environment. 3 figures, 7 refs.

Subject Categories:

  • Electrical and Electronic Equipment
  • Submarine Engineering
  • Radio Communications

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