N222-112 TITLE: Low-profile High-Frequency Maritime Antenna

OUSD (R&E) MODERNIZATION PRIORITY: Networked C3

TECHNOLOGY AREA(S): Electronics; Sensors

OBJECTIVE: Design, construct, and test a high-gain 1.5-35 MHz transmit/receive antenna to be utilized on small, low free-board maritime craft.

DESCRIPTION: Traditional High Frequency (HF) antennas are physically large and generally instantaneously single-banded for low Voltage Standing Wave Ratios (VSWR) in order to match requisite operating frequencies. For small maritime crafts such as an unmanned surface vehicle operating at or slightly below the waterline, a large tall antenna is unfeasible due to the craft's small available footprint and a traditional monopole antenna�s high center of mass would affect the craft's stability. Vertical incidence ionospheric measurements are obtained with horizontal dipole antennas. These antennas are horizontally polarized and must be instantaneously wideband supporting VSWR below 1.5:1 from 5-20MHz and better than 2:1 from 3-35MHz. Active loop antennas can provide sufficient receive signal gain but inherently become limited in their ability to transmit energy at high power due to the tuning circuitry.

PHASE I: Design and develop a concept for a lightweight low center of mass maritime antenna that achieves the technical goals in the Description. Prepare a Phase II plan.

PHASE II: Construct a HF antenna prototype. Test the prototype for a multi-week long duration in a maritime environment across the HF spectrum to assess performance of the system.

PHASE III DUAL USE APPLICATIONS: Transition the system via a maritime platform integration of the antenna for HF communications. The commercial sector uses HF communications as a back-up for SATCOM so this antenna could support those applications in shipboard environments.

REFERENCES:

1. Ignatenko, M.; Filipovic, S.D. On the Design of Vehicular Electrically Small Antennas for NVIS Communications. IEEE Trans. Antennas Propag. 2016, 64, 2136�2145. https://ieeexplore.ieee.org/document/7442093
2. S. R. Best and J. M. McGinthy, "A comparison of electrically small HF antennas," 2005 IEEE Antennas and Propagation Society International Symposium, 2005, pp. 37-40 vol. 1B, doi: 10.1109/APS.2005.1551474.
3. R. F. M. D. Castillo, R. Ma and N. Behdad, "Platform-Based, Electrically-Small HF Antenna With Switchable Directional Radiation Patterns," in IEEE Transactions on Antennas and Propagation, vol. 69, no. 8, pp. 4370-4379, Aug. 2021, doi: 10.1109/TAP.2021.3060013.
4. N. Nikkhah and B. Zakeri, "Efficient design and implement an electrically small HF antenna," 2017 IEEE 4th International Conference on Knowledge-Based Engineering and Innovation (KBEI), 2017, pp. 0001-0004, doi: 10.1109/KBEI.2017.8324862.

KEYWORDS: antenna; high frequency; maritime

** TOPIC NOTICE **

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** TOPIC Q&A **

Questions answered 05/31/22 Q1. Can you please provide some constraints on antenna height? Perhaps threshold and goal requirements? A1. There is no constraint on antenna height - your antenna system solution needs to be able to sit at the waterline without tipping a surfboard sized platform footprint of 300cm x 81cm. Q2. Is this intended solely as an ionosonde antenna, or is the intent to use this antenna for multiple applications? A2. Please design your antenna system solution to support all HF propagation.

Questions answered 05/23/22 Q1. Are there any weight limitations or requirements for the antenna? A1. Please design your antenna system solution (antenna and any mounting or supplemental components) to be less than 75 lbs.

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