Enhanced Radome Design

Navy SBIR 24.1 - Topic N241-051
NAVSEA - Naval Sea 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 ]

N241-051 TITLE: Enhanced Radome Design

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): FutureG; Integrated Network Systems-of-Systems

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: Develop a radome capability for providing greater filtering and aid in beam shaping.

DESCRIPTION: Radomes have been used for decades to protect an antenna from the environment and conceal the antenna. The Navy operates in harsh environments where rain, hail, salt, fog, and other natural conditions would harm sensitive electrons like an Actively Electronically Scanned Array (AESA) antenna. So, to protect those AESA antennas, the Navy uses a radome as cover to protect from environmental conditions. Because the radome covers the antenna, it must also allow it to function with minimal impacts when transmitting and receiving radio frequency signals over the frequency band of operation. Since an AESA antenna can scan over a large angle, the radome needs to minimize the distortion of the transmitting and receiving radio frequency signals over the angler range of operation. This is all typical and can be accomplished with ridge low loss dielectric materials.

More complex radomes now have Frequency Selective Surfaces (FSS) worked into the design. As the name implies, these surfaces help to filter out undesirable frequencies by allowing only selected frequencies pass through. Thus, the radome can act as a filter and aid in the reduction of electromagnetic interference.

With the advances in surfaces, the Navy is seeking to improve current radome capabilities to help beam shaping and sidelobe reduction on the edges beyond the field of view. Currently there is no commercial solution. A new capability could be designed into a radome in a passive manner by structuring the FSS or could be an active design where some sort of bias is applied that activates an adaptive surface. Also, a reactive surface could be designed to limit the amount of power that is passed through the radome, thus avoiding saturation of the electronics. This design would be non-reciprocal, in that the transmit power would be allowed to pass through the surface but the receive power would be limited. In terms of a traditional circuit approach this could be thought of as a switch or circulator with a limiter.

The material also must be capable of meeting environmental requirements, quasi planner (can allow for minor curvature,) and meet government objectives for bandwidth, one way roll-off greater than 20 dB, and low losses operating approximately 4 GHz to 6 GHz.

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 NAVSEA 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: Develop a concept for a radome capability that provides greater filtering and aid in beam shaping. Demonstrate that the concept meets the parameters in the Description. Feasibility will be demonstrated through analysis, modelling, and simulation. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II.

PHASE II: Develop and deliver a prototype radome capability that provides greater filtering and aide in beam shaping based on the results of Phase I. Demonstrate the prototype meets the parameters described in the Description through testing in a laboratory environment. The laboratory environment will be provided by the awardee. At the completion of Phase II, a minimum of six sample articles will be delivered for performance testing purposes.

It is probable that the work under this effort will be classified under Phase II (see Description section for details).

PHASE III DUAL USE APPLICATIONS: Support the Navy in transitioning the radome capability to Navy use. The enhanced radome capability will replace the existing radome on the ASEA. The company will work with the program of record prime contractor for integration onto the ASEA housing.

This technology will also benefit many other Navy and commercial antennas (industries such as telecommunication, aviation, satellite communications, etc.) by providing improved antenna performance and a means to reduce out-of-band rejection of unwanted or interfering incident RF energy increasing system sensitivity of desired signals of interest.

REFERENCES:

  1. Shavit, Reuven. "Frequency Selective Surfaces (FSS) Radomes." Radome Electromagnetic Theory and Design, IEEE, 2018, pp.39-88, doi: 10.1002/9781119410850.ch3 https://ieeexplore.ieee.org/document/8360718
  2. de Lustrac, André; Ratni, Badreddine; Piau, Gérard-Pascal; Duval, Yohann and Nawaz Burokur, Shah. "Tri-state Metasurface-Based Electromagnetic Screen with Switchable Reflection, Transmission, and Absorption Functionalities." ACS Applied Electronic Materials 3 (3), 2021, pp. 1184-1190 DOI: 10.1021/acsaelm.0c01038. https://pubs.acs.org/doi/abs/10.1021/acsaelm.0c01038
  3. Song, Xinyun; Bai, Xudong and Zhu, Weiren. "Reconfigurable Metasurface for Nearly Full-Range and Continuous Modulation of Reflection, Transmission, and Absorption." ACS Applied Electronic Materials 4 (3), 2022, pp. 1225-1231, DOI: 10.1021/acsaelm.1c01280 https://pubs.acs.org/doi/abs/10.1021/acsaelm.1c01280
  4. Özis, E.; Osipov, A.V. and Eibert, T. F. "Metamaterials for Microwave Radomes and the Concept of a Metaradome: Review of the Literature." International Journal of Antennas and Propagation, vol. 2017, Article ID 1356108, 13 pages, 2017. https://www.hindawi.com/journals/ijap/2017/1356108/

KEYWORDS: Radome; Filtering; Radio Frequency Beam Shaping; Actively Electronically Scanned Array; Dielectric Materials; Interference with radio frequencies; Reactive Surface of Radomes


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Topic Q & A

1/12/24  Q. Can you clarify the 20 dB rejection requirements? What are the frequency band edges where the 20 dB rejection is expected?
   A. The radome should have a pass band of 4 GHz to 6 GHz and in that pass band there should be low losses on the order of tenths of dB. Outside that band, the radome should reject energy by at least 20 dB. There is a transition band where the radome goes from -0.YY dB at 6 GHz to -20 dB at 6+XX GHz. That frequency delta of XX (probably in MHz) is part of the trade space wed like to understand. That is to say, we would like the roll of to be as steep as possible but that should be balanced with cost, complexity and size/weight.
1/10/24  Q. 1) Some enhanced radome approaches may be polarization dependent. What polarization(s) will be used by the intended antenna array?
2) Please clarify the 4 GHz - 6 GHz bandwidth requirement. Would larger bandwidths be desirable, or is filtering desired to limit the bandwidth to the 4 - 6 GHz range?
3) There are several objectives listed including frequency filtering, sidelobe reduction, beam-shaping, and nonreciprocal power-limiting. Are all these objectives required, or will proposals be considered that only provide a subset of these features?
4) Can you clarify what is meant by the phrase "sidelobe reduction on the edges beyond the field of view?"
5) What are the desired lateral dimensions of the radome? What is the desired standoff distance between the radome and antenna array?
   A. 1) Vertical Polarization is desired but it would be good to know if there are polarization limitations of the proposed research.
2) 4-6 GHz is the passband with frequency outside that should be attenuated to the maximum extent possible. That is to say, there should be no surprise resonant (eg 8-12 GHz) where there is much less attenuation.
3) Subsets are considered but proposals should address why they are limited. It may be cost, size/weight, or technology limit to give some examples.
4) If the array is designed to have a field of view of +/- XX degrees, then wed want to see some attempt at reducing energy beyond that. For example a radome that reduces the energy by 10dB (more than beam shaping) at XX+10 degrees.
5) 40 inches wide by 30 inches high with 0.5 inches standoff.

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