Surface wave-based broadband underwater radio communication and imaging

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Key Messages

  • Saltenna is engaged in several DARPA sponsored advanced research and development projects, such as DARPA MTO AMEBA and DARPA STO ARGOS programs to develop novel techniques for underwater/marine RF communication, and the Underwater Radar project sponsored by DARPA DSO
  • We have designed and demo’ed an antenna which uses surface waves for high bandwidth over long distances in seawater
  • We can breach the seawater barrier for UAV to UUV communication, since the surface wave EM field is present both above and below the seawater surface.
  • Our technology is multi-spectral, for example, using ELF over very long distances and, under software control, shifting to higher bandwidths over shorter distances
  • Applications of interest: swarming, mesh-networked UUVs, UAV to UUV communication, underwater radar, offshore oil platforms, etc.
  • Plasmonic antennas may be used to alleviate obscurations in 5G networks
  • RF communication through plasma sheath around a hypersonic vehicle

Saltenna LLC surface wave antenna technology: Transmission through ultimate obscuration – a Faraday cage

Battery-operated 2.45-GHz transmitting antenna (l=12 cm) capable of sending video signals from inside a locked 90-dB isolation Faraday cage

May be used in 5G applications and for broadband radio transmission through:

  • submarine hull
  • plasma layer around a supersonic warhead or space capsule moving through atmosphere

Communication underwater using surface waves

What Are We Trying To Do?  Communicate/image underwater and through sea surface

How Is It Done Today?  Ultrasound and visible frequencies are used

What is New in Your Approach? Use surface electromagnetic waves for communication and imaging  underwater.

Using surface wave antennas, we achieve broadband RF communications between underwater assets over distances. We propose to breach the seawater barrier for UAV to UUV communication, since the surface wave is present both above and below the seawater surface.

If you can communicate, you can image underwater

  • Unlike conventional sonars, our technique does not perturb marine life
  • Extremely sensitive to dielectric contrast
  • Spatial resolution better than 1 m

Laboratory testing: 2.45 GHz transmission through seawater

skin depth at 2.45 GHz is 3 mm

Surface wave RF technology works when laser communication fails!

Field testing at NSWC Panama City

Testing of Saltenna LLC underwater antennas at the NSWC Panama City facilities (water salinity 2.8-3.2%)

Testing results confirm our model

Compact design of a 2MHz SEW antenna

Measured/Projected Performance

Based on estimates for a flat seawater surface from K. A. Michalski and J. R. Mosig, “The Sommerfeld half-space problem revisited: From radio frequencies and Zenneck waves to visible light and Fano modes,” J. Electromagn. Waves Appl., vol. 30, pp. 1–42, 2016.


  • Surface waves are very promising for underwater communication
  • Much better theoretical understanding and experiments are needed