Electrically Small Antennas at High Frequency

Navy SBIR 24.1 - Topic N241-005
NAVAIR - Naval Air Systems Command
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET    [ View Q&A ]

N241-005 TITLE: Electrically Small Antennas at High Frequency


The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Design, develop, simulate and demonstrate an electrically small antenna using metamaterials that can operate at frequencies from 2–30 MHz. The antenna will be used to transmit/receive Skywave radio-wave signals to provide Beyond Line of Sight (BLOS) communications on Navy aircraft.

DESCRIPTION: In the absence of satellite communication channels, current and future missions require aircraft to communicate at High Frequencies (HF) for BLOS communications. The principle constraint on modern air platforms are size and weight which drives the need for smaller, lighter, efficient radio and antenna technologies. The innovative use of metamaterials has shown to be a promising technology to reduce size and weight while achieving effective power characteristics when compared to conventional antenna designs at other portions of the RF spectrum. Therefore, it is hypothesized that the use of metamaterials in antenna design could dramatically reduce the size of the antenna and may improve other antenna parameters such as enhancing bandwidth and increasing gain at HF. The challenge is to determine if metamaterials can significantly reduce the size and weight of an HF antenna, be affordable, and be suitable for installation on Navy platforms. Innovative solutions are being sought to develop an HF antenna that can meet the design goals shown below. In addition, there is the need for a conformal antenna to minimize drag on the aircraft and reduce risk of damage.

Antenna Design Goals:

(a) Weight—reduced in half as compared to conventional

(b) Volume—1/5 as compared to conventional

(c) VSWR—No worse than conventional, over full frequency range, 2-30 MHz

(d) Gain—3 dB improvement over conventional

Conventional HF Antenna Examples:

(a) Chelton 435 Towel Bar Antenna, appx 8 in. (20.3 cm) stand off from aircraft skin (moldline) by 10 ft long (3 m)

(b) Shunt-fed embedded HF antenna found in airplane vertical stabilizer

Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by 32 U.S.C. § 2004.20 et seq., National Industrial Security Program Executive Agent and Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence and Security Agency (DCSA) formerly Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DCSA and NAVAIR in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material during the advanced phases of this contract IAW the National Industrial Security Program Operating Manual (NISPOM), which can be found at Title 32, Part 2004.20 of the Code of Federal Regulations. Reference: National Industrial Security Program Executive Agent and Operating Manual (NISP), 32 U.S.C. § 2004.20 et seq. (1993). https://www.ecfr.gov/current/title-32/subtitle-B/chapter-XX/part-2004

PHASE I: Investigate suitable metamaterials for an antenna at HF, create a digital model, and demonstrate the feasibility of the design to meet the antenna goals defined above. Document—with detailed analysis—the predicted performance with modeling and simulation. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Using the results from Phase I, develop a prototype antenna; demonstrate in the lab, and/or chamber that the prototype can transmit and receive at HF; and measure the performance of the prototype across the frequency band. Work with NAVAIR to perform initial qualification testing on sample sections of the antenna to gain insight into suitability of the design to operate under representative conditions. Deliverables of Phase II will be the prototype array and a final report, which documents the performance of the prototype.

Work in Phase II may become classified. Please see note in Description paragraph.

PHASE III DUAL USE APPLICATIONS: Further develop the prototype produced in Phase II and work with the Navy to install on a rotorcraft. Demonstrate that the antenna can transmit and receive at HF for a military application.

This technology would be extremely useful for other airborne systems such as law enforcement, safety, and corporate transport. The technology would be helpful for situations where SATCOM is too expensive, not viable (e.g., Polar Regions or deep valleys), and if the SATCOM hardware is too large.


  1. IEEE Standards Association. (2013). 145-2013-IEEE standard for definitions of terms for antennas. IEEE, New York, NY. https://doi.org/10.1109/IEEESTD.2014.6758443
  2. Krzysztofik, W. J., & Cao, T. N. (2018). Metamaterials in application to improve antenna parameters. Metamaterials and Metasurfaces, 12(2), 63-85. https://books.google.com/books?hl=en&lr=&id=oC-RDwAAQBAJ&oi=fnd&pg=PA63&dq=Metamaterials+in+Application+to+Improve+Antenna+Parameters&ots=F_Jb40rzlu&sig=rsAi0lyahtmZ1yvHgD4FCfBvbsc#v=onepage&q=Metamaterials%20in%20Application%20to%20Improve%20Antenna%20Parameters&f=false
  3. The MIL-STD-810 Working Group. (2008, October 31). Department of Defense test method standard: Environmental engineering considerations and laboratory tests. Department of Defense. https://www.atec.army.mil/publications/Mil-Std-810G/MIL-STD-810G.pdf
  4. Kumar, P., Ali, T., & Pai, M. M. (2021). Electromagnetic metamaterials: A new paradigm of antenna design. IEEE Access, 9, 18722-18751. https://doi.org/10.1109/ACCESS.2021.3053100
  5. Chelton Limited. (n.d.). 435, 455, 465, 475 & 485 towel rail antenna arrays. Chelton. https://www.chelton.com/media/0fuhgecl/chelton-435-465-455-485-towel-rail-antenna-arrays.pdf

KEYWORDS: antenna; high frequency wavelength; electrically small antenna; ESA; metamaterials; military helicopters; Beyond Line of Sight; BLOS; Skywave HF Transmissions


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 24.1 SBIR BAA. Please see the official DoD Topic website at www.defensesbirsttr.mil/SBIR-STTR/Opportunities/#announcements for any updates.

The DoD issued its Navy 24.1 SBIR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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Topic Q & A

1/12/24  Q. 1) Is a tunable solution over the required frequency range acceptable?
2) Can the antenna be designed to work for a specific platform or is a platform-agnostic antenna required?
3) Are separate solutions that have different antenna designs for transmit and receive acceptable or is a single antenna needed for both transmit and receive operations?
   A. 1) Yes. Depending on the anticipated tuning speed, this is acceptable. Please provide the anticipated bandwidth to be achieved with your solution.
2) The antenna should be able to perform on rotary wing aircraft.
3) A transmit / receive element is preferred as we are concerned about overall antenna footprint; separate elements should have attractive footprint
1/12/24  Q. The central theme of this solicitation revolves around an antenna based on "metamaterial," which may not necessarily be the optimal choice within this frequency range and bandwidth. In light of this consideration, we have several inquiries whose answers will aid us in devising the most effective strategy.
1. Is an alternative solution that does not employ metamaterial deemed acceptable?
2. Is the required bandwidth instantaneous, meaning the antenna response should encompass the entire range from 2 to 30 MHz, or can it have a narrow bandwidth and be scalable across the frequency range of 2 to 30 MHz?
3. What are the gain and VSWR of the conventional antenna? Are these values specified for the antenna alone or for the antenna plus the matching network? (We couldn't find this information in the short data sheet of conventional antenna)
4. What is the weight of the conventional antenna?
5. Can you provide details about the aircraft platform, such as dimensions and materials?
6. Within the designated bandwidth, are there priority frequency bands where an anticipated 3 dB gain improvement would be particularly significant or relevant for mission-critical applications?
7. Could you clarify if the intended use of the antenna is for reception, transmission, or both? Additionally, if the antenna functions as a transmitter, what is the specified maximum power handling requirement?
8. What is the minimum acceptable efficiency requirement at the lower boundary of the specified bandwidth?
   A. 1. Yes, a SWAP sensitive, non-meta material solution is acceptable.
2. Instantaneous bandwidth is preferred; if not achievable, narrower bandwidth is satisfactory, but tuner implications may be prohibitive.
3. In our experience, very bad for our application >100:1 this is for the matching network, I believe.
4. Approximately 5-10lbs.
5. Not at precise details time; seeking footprints ~12”X12” that can be installed on aluminum or composite airframe.
6. The priority frequencies will be the “middle chunk”.
7. This will be Tx and Rx system. Anticipating an ERP range in the 20-75W
8. See #6 – if there are some efficiency losses at the lower bound, it may be acceptable.
1/9/24  Q. Is novel approaches such as active antenna considered ?
   A. I could maybe use a little more clarification on “active” –that antenna should be "active" in the sense that it can transmit (i.e. active and passive (or receiver)). In the sense of “active” as being a “steerable” array – no, there’s not a requirement in that sense.

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