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Antenna Design for Unmanned Aerial Vehicles

Description:

OBJECTIVE: Development of innovative antenna designs that provide UAV platforms with lightweight, low cost antenna solutions that increase their communications capacity and reliability. DESCRIPTION: The Department of Defense (DoD) is experiencing a dramatic increase in the development and use of drones across all of the armed services. This reflects what will be an even more aggressive effort in the future to expand the capabilities and role of drones. UAV usage across the military services jumped from nearly 165,000 flight hours in Fiscal Year (FY) 2006, to more than 258,000 in FY 2007. According to a 2009 Pentagon report [1], DoD plans to develop an"increasingly sophisticated force of unmanned systems"over the next 25 years. And while the use of UAVs by the DoD is growing, US law enforcement agencies and Homeland Security have recently also begun to investigate the use of UAVs as a critical resource multiplier [2]. The effort will confront some current shortfalls, including plans to improve how effectively drones rapidly and precisely locate and identify targets. As UAV technology continues to advance, innovative antenna designs, optimized for these platforms, are needed to improve communications capability, reliability, and overall mission effectiveness. UAV platforms present a number of challenges for good antenna design including significant installation impacts on antenna performance as no general purpose design philosophy exists. Typically, UAVs strive for flight endurance. Therefore minimization of payload weight and power consumption is critical. The platforms are often small, with an airframe generally fabricated using a lightweight composite material, with a significant portion of the available real estate for antennas being on, in, or near the wings. Installing antennas on or in the wing of the airframe presents challenges in that the wing has a low profile and a protruding antenna is generally undesirable. Furthermore, during flight the wing can flex, degrading or altering the antenna"s performance characteristics. Like manned airborne platforms, users strive to populate UAVs with significant electronics capabilities, therefore, minimizing the size and weight of these packages especially the antennas while maximizing mission capability is of high interest. The focus of this effort is on communication links to and from (transmit and receive) Predator-class UAVs. These UAVs are relatively inexpensive, and therefore the inventory continues to grow, but antenna designs specifically for UAV platforms have not kept pace with these trends. The goal of this work is to look more closely at UAV design trends, identify the communication (command and control) needs for UAVs, and develop innovative antenna designs to enhance or expand the capability and reliability for these systems. As an example, the Wideband Gapfiller Satellite link would require RHCP at 30-31 GHz transmit, 20.2-21.2 GHz receive, capable of 100W CW with 80 dB isolation between transmit and receive with operational antenna pattern coverage from zenith to horizon represents a significant challenge on a Predator-class UAV. There are emerging material technologies that may enable antenna designers to develop antennas that are lighter weight and more flexible and that may also enhance user maintenance in the field. PHASE I: Analyze trends in UAV design and commensurate communication system needs, and derive notional requirements for a medium data rate (~ 8 MBPS) BLOS (Ku or Ka band) comm links for Predator-class UAVs. Based on these requirements an antenna design will be developed, with emphasis on the verification of key proof of concept components. Size, weight, and cost of the concept(s) will be provided. PHASE II: Demonstrate the antenna design. A prototype unit will be developed, and the performance characterized in an antenna measurement facility (which may be, but is not required to be, a Government facility) in a suitable test platform. Measurements will be compared with predictions. The installation method for the antenna system will be developed. Pointing and tracking methodology will be provided including mechanical design. PHASE III: The antenna prototype unit will be demonstrated to TRL 6 in an environment relevant to an operational UAV platform. REFERENCES: 1. Office of the Secretary of Defense,"Unmanned Systems Roadmap (2009 - 2034),"April 2009. 2. Hadal, Chad C. and Jeremiah Gertler,"Homeland Security: Unmanned Aerial Vehicles and Border Security,"Congressional Research Service, RS21698, 8 July 2010.
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