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Scalable Directional Antenna for Unmanned Aerial Vehicles (UAVs)

Description:

TECHNOLOGY AREA(S): Sensors, Electronics, Battlespace 

OBJECTIVE: Develop a scalable, directional C-Band active array antenna system suitable for Group-IV Unmanned Aerial Vehicle (UAV) platforms. 

DESCRIPTION: The Navy is seeking to develop alternative routing of data through low-cost airborne Unmanned Aerial Vehicle (UAV) nodes to enable high data bandwidth, robust connectivity, and data routing flexibility between platforms in the surface fleet. A critical component necessary for this capability is a directional antenna architecture that has the flexibility to scale in size, weight, and power (SWaP), and is suitable for airborne applications. Such an antenna architecture would enable line-of-sight networked communications utilizing Group-IV UAV platforms (for the purpose of demonstrating this capability, an MQ-8C Fire Scout will be used as the air platform). This will greatly increase data throughput, system availability, and the ability to dynamically implement alternative routing, thereby improving the fleet’s ability to successfully execute complex multi-ship missions. Currently the Navy utilizes both omnidirectional and point-to-point systems to move data between surface combatants, air platforms, and ground forces. A need exists to develop an airborne node that can provide directional data distribution enabling rapid rerouting between platforms, and achieve robustness in hostile Electro-Magnetic Interference (EMI) environments. Current directional airborne systems rely on antennas that have SWaP attributes unsuitable for installation on Group-IV UAV platforms. An active array antenna subsystem that minimizes the SWaP footprint will enable enhanced data routing utilizing a wide range of UAV platforms and provide robust alternative data paths for the fleet. Achieving these attributes requires an innovative antenna architecture that is highly directional, and supports rapid beam steering. No suitable C-Band antenna exists today in the commercial marketplace. Achieving an innovative UAV solution provides two specific benefits to the warfighter. First, it enables a greater proliferation of geographically diverse network nodes enabling data routing around EMI sources. Secondly, it can provide a relay functionality that supports sustained network connectivity between geographically diverse nodes. In both cases the system performance can be improved while avoiding deployment of high-cost tactical assets or deploying manned systems for these functions. The Navy is seeking an airborne, small SWaP, half-duplex, C-band active antenna subsystem that achieves 39dBW directional effective radiated power (EIRP) while minimizing sidelobes in transmit, and maximizing gain minus noise figure (G-F) and dynamic range in receive. This high EIRP is required in order to close links to the horizon in a variety of weather and EMI conditions while the high dynamic range is required to discern distant signals in the presence of nearby signals and noise. Rapid beam steering is necessary to support large network sizes with a highly directional array. On other platforms, this combination of requirements has resulted in antenna subsystems that have a large SWaP footprint. Accomplishing all the above on a UAV while minimizing SWaP will require utilization of modern technologies and technical innovation. The platform for this project will be the MQ-8C Fire Scout. It is critical that the architecture developed for the antenna is scalable from this design point to alternative configurations, enabling lower or higher performance based on available SWaP. For example, the primary components of the design could be scaled down to 50% of the SWaP or up to 200% based on a future design point. The driving requirements for the needed technology advances should result in a scalable, light-weight, high-efficiency, air-cooled antenna subsystem and must achieve high directivity and rapid beam steering in a small antenna, should achieve an overall transmit efficiency of no less than 25% and be capable of a transmit duty cycle of 50%. The antenna subsystem will provide interfaces that include: Radio Frequency (RF)-Transmit (Tx), RF-Receive (Rx), digital control, and power. Digital control commands to the antenna will include a trigger signal, azimuth beam-steering angle, RF frequency information, Tx power level, Tx or Rx switch control, and diagnostic queries. All antenna control functions such as power level adjustments, phase and amplitude control, and Tx and Rx switching will be processed within the antenna subsystem. Any necessary power conditioning and cooling will also be included within the antenna subsystem. The antenna subsystem is not required to perform any up or down conversion or signal processing. The antenna subsystem developed under this SBIR will also be required to interface to the MQ-8C Fire Scout for both power and physical attachment. The antenna architecture should be scalable for different levels of RF performance and SWaP so that the basic building blocks can be used across multiple applications (although each application would be expected to have a unique design). The antenna should be a steerable active phased array that operates in C-Band, and is able to rapidly form beams in any azimuth position at any frequency within the operating bandwidth (BW). Additionally, the antenna pattern must provide good coverage for all body orientations during flight with a goal of no more than 3dB of loss relative to maximum gain, in the absence of body blockage, within an elevation of ±10 degrees to the horizon. The gain roll-off for elevation angles less than -10 degrees should be proportional to gain loss with slant range. To minimize body blockage, the antenna will be housed into two pods, each with a 180° azimuthal coverage. The payload weight and volume available on UAVs is similarly constraining; therefore, a maximum weight limit of 75lbs. per pod should be assumed for the antenna subsystem. The antenna and supporting equipment housed in each pod is allocated a maximum payload dimension of 43.0” long x 10.3” high x 10.3” deep and an available power of 250W at 28VDC. Each antenna will include a self-contained cooling systems using ambient air with parameters based on worldwide operational conditions at altitudes from 1kft-15kft, and any necessary power conversion/filtering equipment. The company should identify how they plan to achieve their design and provide supporting evidence for the feasibility of its Phase II design. This should include an engineering notebook that details all calculations and assumptions used, drawings and graphics to clearly communicate the design, performance predictions and supporting model(s), and material that clearly identifies scalability and substantiates predictions. Background documents such as the interface control documents and the Phase II antenna subsystems performance specification will be provided by NAVSEA. The Phase II effort will likely require secure access. NAVSEA will process the DD254 to support the contractor for personnel and facility certification for secure access. The Phase I effort will not require access to classified information. If need be, data of the same level of complexity as secured data will be provided to support Phase I work. 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 Security Service (DSS). 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 DSS 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: Define and develop a concept for a scalable, directional C-Band active array antenna subsystem. Demonstrate the feasibility of the concept in meeting Navy needs and establish that the concept can be feasibly produced. Feasibility will be established by some combination of initial analysis or modeling. Feasibility will also be established by analysis of the proposed SWaP footprint, suitable for Group-IV UAV platforms. The Phase I Option, if awarded, will include the initial design specifications and capabilities description to build a prototype in Phase II. Develop a Phase II Plan. 

PHASE II: Based on the Phase I results and the Phase II Statement of Work (SOW), develop and deliver a prototype that will demonstrate the performance parameters outlined in the description. Testing, evaluation, and demonstration are the responsibility of the small business and should therefore be included in the proposal. Validation of the prototype will be through comparison of model predictions to measured performance. Prepare a Phase III development plan to transition the technology for Navy and potential commercial use. It is probable that the work under this effort will be classified under Phase II (see Description section for details). 

PHASE III: Support the Navy in transitioning the technology to Navy use and further refine the prototype according to the Phase III development plan to determine its readiness for system integration and qualification testing. This will be accomplished through platform integration and test events managed by PEO IWS to transition the technology into Navy Group-IV UAV systems with an initial integration onto the MQ-8C Fire Scout. The efforts of the research in scalable, high-performance antennas will have direct application to private sector industries that involve directional communications between many small nodes over large areas. These applications include transportation, air traffic control, and communication industries. 

REFERENCES: 

1: Akbar, F. and Mortazawi, A. "Design of a compact, low complexity scalable phased array antenna." 2015 IEEE MTT-S International Microwave Symposium, Phoenix, AZ, 2015, pp. 1-3. doi: 10.1109/MWSYM.2015.7167107. https://www.researchgate.net/publication/281069226_Design_of_a_compact_low_complexity_scalable_phased_array_antenna

2:  Mayo, R. and Harmer, S. "A cost-effective modular phased array." 2013 IEEE International Symposium on Phased Array Systems and Technology, Waltham, MA, 2013, pp. 93-96. doi: 10.1109/ARRAY.2013.6731807. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6731807

3:  Neumann, N., Hammerschmidt, C., Laabs, M. and Plettemeier, D. "Modular steerable active phased array antenna at 2.4 GHz." 2016 German Microwave Conference (GeMiC), Bochum, 2016, pp. 333-336. doi: 10.1109/GEMIC.2016.7461624. http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=7461624

4:  "Autonomous Vehicles in Support of Naval Operations, Chapter 4, Unmanned Aerial Vehicles: Capabilities and Potential." The National Academic Press, 2005, ISBN 0-309-09676-6

5:  https://www.nap.edu/catalog/11379/autonomous-vehicles-in-support-of-naval-operations

6:  Agrawal, A., Kopp, B., Luesse, M. and O’Haver, K. "Active Phased Array Antenna Development for Modern Shipboard Radar Systems." Johns Hopkins APL Technical Digest, 2001, Vol. 22, No. 4. http:// www.jhuapl.edu/techdigest/TD/td2204/Agrawal.pdf

KEYWORDS: Rapid Beam Steering; Directional Airborne Systems; Scalable Directional Antenna; Small SWaP; Phased Array; Group-IV Unmanned Aerial Vehicle 

CONTACT(S): 

Mrs. Onekki Montgomery 

(202) 781-1186 

onekki.montgomery@navy.mil 

Mr. David Trumpoldt 

(202) 781-0581 

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