S-Band Antenna System for Littoral Combat Ship Communications Relay

Navy SBIR 21.1 - Topic N211-068
NAVSEA - Naval Sea Systems Command - Mr. Dean Putnam - dean.r.putnam@navy.mil
Opens: January 14, 2021 - Closes: February 18, 2021 (12:00pm EDT)

N211-068 TITLE: S-Band Antenna System for Littoral Combat Ship Communications Relay

RT&L FOCUS AREA(S): General Warfighting Requirements

TECHNOLOGY AREA(S): Sensors

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 section 3.5 of 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 small, affordable, lightweight, and dynamic antenna system to be mounted on a remote aerial low-altitude relay that will enable Beyond Line-of-Sight (BLOS) communications between the Littoral Combat Ship (LCS) and the Mine Countermeasures (MCM) Unmanned Surface Vehicle (USV).

DESCRIPTION: The MCM USVs execute missions for LCS MCM Mission Package (MP). The network communication services between LCS and the MCM USVs are provided by the Multiple Vehicle Communications System (MVCS), which uses direct Line-of-Sight (LOS) communications in the S-Band – more specifically, in the 2.2 to 2.4 GHz frequency band. Results of a recent analysis performed at the Naval Surface Warfare Center Panama City Division (NSWC PCD) show that the Area Coverage Rate Sustained (ACRS) scores for the MCM USVs can be maximized by increasing the current maximum achievable range by a factor of 3-5. ACRS is one Measure of Effectiveness (MOE) typically used to evaluate MCM system performance, as shown in Reference 1.

Due to the antenna heights for LCS (90 ft for Independence variant, 65 ft for Freedom variant) and the MCM USV (18 ft), a 3x-5x increase in range using direct LOS communications is unrealistic, as it is severely limited by the radio horizon from the curvature of the Earth’s surface. MCM MP data throughput requirements also effectively discard ground-wave propagation at lower frequencies as a possible solution, due to channel capacity limits. However, an intermediate relay node inserted between LCS and the MCM USV could enable a 3x-5x range increase and still meet MCM MP data throughput requirements without having to migrate to a different frequency band. This would allow having little to no change in communications equipment (i.e., radios, cables, amplifiers, and antennas) and configurations at the end nodes. Preliminary analysis and developmental test results have shown that an aerial relay at low altitudes – around 500 ft Above Sea Level (ASL) – should be sufficient to achieve the desired range increase. Not only would this be beneficial for the Navy, but also for the Marine Corps, who has shown an interest in developing a Long-Range USV (LR-USV) that can support its Expeditionary Advance Base Operations, as noted in Reference 2.

A currently existing prototype relay system uses an azimuth-plane omni antenna to establish a communications link with the MCM USV, and a gimbaled directional antenna that relies on actuators to physically steer the antenna’s main beam towards LCS in the azimuth plane only – no direction finding in the elevation plane, as it always faces the horizon. Some of the concerns with the current prototype system include the following: Azimuth-plane omni antenna limits the communications range for the relay to MCM USV link and is susceptible to jamming from any direction; the gimbaled directional antenna can only scan as fast as the actuators allow, and is not expected to have good reliability or a long life cycle due to the actuators breaking down. These concerns open up the possibility of using other solutions, such as switched array and phased array antennas, which should increase the life cycle by reducing/eliminating the need for moving parts, as well as allowing for faster scanning and/or tighter beamforming, so that directivity is maximized in any desired direction. Typical phased array antenna characteristics and design considerations are described in Reference 3.

The main objective of the technology is to produce a small, lightweight, and dynamic antenna system that can automatically beamform/beamsteer based on signal strength values reported from the radio. The antenna should be capable of handling fast beamforming/beamsteering to change beam directions between multiple end nodes. A secondary objective is for the antenna to implement null steering to avoid possible jamming sources.

There are multiple design constraints that should be observed, based on process modeling, operational experience, and optimization strategies:

antenna system – elements and switching/driving electronics

• should weigh less than 15 lbs

• should be able to achieve a gain of 15 dBi or more with a 20 dB minimum mainlobe-to-sidelobe ratio

• should have full 360-degree coverage in the azimuth plane and 40-degree coverage in the elevation plane centered at 10 degrees below the horizon

• should be able to handle 20 W average power (threshold) up to 40 W average power (objective)

• should cover the entire 2.2 to 2.4 GHz frequency band

• should not be more than 19 inches long and 15 inches in diameter

• Should have a response time of 20 microseconds or less

• should be environmentally sealed for protection against saltwater spray and continuous outdoor use

• in support of the secondary objective, the antenna should be able to create nulls at least 30 dB below the mainlobe and steer them towards jammers, while maintaining a communications link with the intended target/s.

Commercial antenna systems have been well developed for long-range communication systems in the S-Band, both for static and dynamic beam options. Switching/driving electronics for beamforming/beamsteering have also become robust. However, the challenge for this design, which necessitates innovative research & development, is being able to produce an antenna system with enough Effective Isotropic Radiated Power (EIRP) to close long-distance communications for link rates of 24 Mbps or more; minimizing Size, Weight and Power (SWaP) without exceeding cost constraints; minimizing response time for beamforming/beamsteering; and being able to survive harsh marine environments.

Any prototype antenna system developed as a result of this SBIR topic would be tested for its radiation characteristics – EIRP, directivity, beamsteering/beamforming, mainlobe-to-sidelobe ratio, mainlobe-to-null ratio – in a laboratory setup (anechoic chamber) during the Phase II effort. The optimized version of the antenna system would then go through environmental and electromagnetic interference (EMI) testing to applicable military standards (e.g., MIL-STD-810G and MIL-STD-461F). At the end of Phase III, a Seminal Transition Event (STE) will be conducted via an Over The Air (OTA) test in an operationally relevant environment onboard a relay system, with multiple active end nodes. The antenna system will be expected to not interfere with existing MVCS and endpoint certifications, and abide by established MVCS certification boundaries.

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 DOD 5220.22-M, National Industrial Security Program Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence Security Agency (DCSA). The selected contractor and/or subcontractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances, in order to perform on advanced phases of this contract 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 IAW DoD 5220.22-M during the advance phases of this contract.

PHASE I: Develop an antenna concept that can meet the design constraints listed in the Description section. Establish feasibility by developing Computer-Aided Design (CAD) models that show the antenna concept and provide estimated weight and dimensions of said antenna concept. Feasibility will also be established by computer-based simulations that show the antenna array’s beamforming/beamsteering capabilities are suitable for the project needs. 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: Based on the results of Phase I and the Phase II Statement of Work (SOW), develop and deliver a prototype antenna system for test and evaluation. Test the prototype antenna system, first in a controlled laboratory environment, then in an operationally relevant environment, to determine its capability to meet all relevant performance metrics outlined in the Phase II SOW. Demonstrate the prototype system performance in both environments to the Government and present the results in two separate test reports. Use the results to correct any performance deficiencies and refine the prototype into a pre-production design that will meet Navy requirements. Prepare a Phase III SOW to transition the technology to Navy use. Prepare a Phase III SOW that will outline how the technology will be transitioned for Navy use.

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 technology to the LCS MCM MP relay system. Work with the Navy to integrate the antenna system onto the relay platform. Support test, validation, certification, and qualification of the system through environmental qualification testing, and with an STE at the culmination of the effort.

In the military/government sector, results from Phase II and Phase III for the relay platform antenna system can be leveraged to create variants of the antenna system for use on the MCM USV and LCS platforms, as well as demonstrate the MCM USV capabilities to perform missions at extended ranges for the Marine Corps LR USV concept. In the commercial sector, antennas with beamforming/beamsteering capabilities and anti-jam protection through null-steering could have potential for use in private communication systems set in urban environments, where spectrum congestion and interference – intentional or unintentional – can be prevalent issues.

REFERENCES:

  1. Frank, David; Hogan, Kevin and Schonhoff, Shane. "Application of Model-Based Systems Engineering (MBSE) to Compare Legacy and Future Forces in Mine Warfare (MIW) Missions." Systems Engineering Capstone Project Report, SE311-132Open/Team MIW, Monterey, CA: Naval Postgraduate School, 2014, p. 359. https://calhoun.nps.edu/handle/10945/44659
  2. Eckstein, Megan. "Textron’s Common USV Ready for Production, Experimenting with Lethal Surface Warfare Payloads." USNI News, January 22, 2020 (Updated: January 23, 2020). https://news.usni.org/2020/01/22/textrons-common-usv-ready-for-production-experimenting-with-lethal-surface-warfare-payloads#more-72882
  3. Mailloux, Robert J. "Phased Array Antenna Handbook, 2nd Edition." Artech House: Norwood, MA, 2005. http://twanclik.free.fr/electricity/electronic/pdfdone11/Phased.Array.Antenna.Handbook.Artech.House.Publishers.Second.Edition.eBook-kB.pdf

KEYWORDS: LCS MCM MP; Mission Package; Littoral Combat Ships; Mine Countermeasures; MCM USV; Unmanned Surface Vehicle; Multiple Vehicle Communications Relay System; MVCRS; BLOS Communications; Beyond Line-of-Sight; ACRS; Area Coverage Rate Sustained; Phased-Array A

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