Surface wavebased broadband underwater radio communication and imaging

Surface wave-based broadband underwater radio communication and imaging Igor Smolyaninov Saltenna LLC 1751 Pinnacle Drive, Mc. Lean, VA 22102 www. saltenna. com igor. smolyaninov@saltenna. com

Key Messages • Saltenna LLC 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 5 G 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 -d. B isolation Faraday cage walls made of thick aluminum, lining made of LS-30 carbon-implanted foam (JRE Test LLC, model 0709) May be used in 5 G applications and for broadband radio transmission through: - submarine hull - plasma layer around a supersonic warhead or space capsule moving through atmosphere proprietary material

Communication underwater using surface waves z • 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 Zenneck surface waves: Range and depth will increase with larger free space wavelength l 0 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. Numerical simulations of surface wave excitation by underwater antenna I. Smolyaninov et al. IEEE Antennas and Wireless Propagation Letters 17, 2503 -2507 (2018)

If you can communicate, you can image underwater z - 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 transmission through clear water transmission through turbid water skin depth at 2. 45 GHz is 3 mm Surface wave RF technology works when laser communication fails! proprietary material

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 I. Smolyaninov et al. IEEE Antennas and Wireless Propagation Letters 17, 2503 -2507 (2018)

Compact design of a 2 MHz SEW antenna Measurements of the S 11 of the 2 MHz SEW antenna immersed in DI water DISTRIBUTION Assembled 2 MHz SEW antenna with radio B. Distribution Authorized to U. S. Government Agencies. Further dissemination only as directed by the DARPA Microsystems Technology Office. 9

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 wave propagation length: (operation at -90 d. B is assumed) Surface wave penetration depth: Surface wave-based RF communication scheme in seawater Frequency Wavelength (m) 2. 45 GHz 0. 12 50 MHz 6 2 MHz 150 100 KHz 3, 000 20 KHz 15, 000 1 KHz 300, 000 Skin Depth 0. 3 cm 3. 8 cm 19 cm 85 cm 2 m 8. 5 m Projected Distance 3. 8 m 190 m 900 km ∞ ∞ ∞ Measured Distance 1 m at 2 W 10 m at 5 W ~ 90 m at 30 W numbers based on Michalski @ Mosig probably unreliable Projected Depth 0. 054 m 0. 7 m 3. 5 m 15 m 36 m 150 m Measured Depth 0. 1 m at 2 W 1 m at 5 W 5. 5 m at 30 W *) diver to diver communication UUV to UUV communication - Surface waves are very promising for underwater communication -Much better theoretical understanding and experiments are needed