Innovative Antennas for Wrap-around Direction Finding Arrays from 400 to 4000 MHz, 16-9331

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Principal Investigator
Keith A. Lysiak

Inclusive Dates: 07/01/02 - Current

Background - Direction finding (DF) system performance and capabilities are directly dependent on the DF antenna array. While the total system performance and capability is also dependent on other components of the system, the system as a whole can only perform as well as the antenna array permits. This generally leads to large complex antenna arrays for high-performance systems. Unfortunately, previous array approaches required major modifications to ship masts and can only be installed on large ships. The United States Navy and the United States Coast Guard are continually seeking lightweight and compact VHF/UHF antennas for smaller ships. These systems are required to provide collection and direction finding (DF) capabilities to support assigned Naval and Coast Guard missions. Traditionally, most Naval adversary forces and Coast Guard rescue communications were transmitted in the VHF and low-UHF frequency range (30-900 MHz). Recent technology advances have gradually shifted communications to include upper UHF and higher frequencies (1000-4000 MHz). Therefore, the need has arisen to extend DF frequency capabilities to these higher frequencies while maintaining DF accuracy. Current shipboard antenna configurations are not readily adapted to smaller maritime vessels or higher frequencies due to present DF array size, weight, and cost limitations.

Approach - The objective of the proposed project is to investigate the most promising approaches for an innovative maritime mast-mounted wrap-around DF antenna array. A wrap-around array describes an array that can be fastened to an existing mast structure, without removing or replacing a section of the mast. Our approach is to concentrate on the development of modular antenna components (elements or groups of a few elements) that will be used as building blocks for full arrays. This approach will allow SwRI® to satisfy our frequent customer requests to extend the upper frequency limit of operation to 4 GHz or higher, while addressing a customers' need for an array that will wrap around existing mast structure. The wrap-around antenna will benefit SwRI by advancing our DF capability and reducing design cycle time. Low cost will be achieved through the design of innovative modular components, the use of etched- printed circuit technology and modifications of commercial off-the-shelf (COTS) components wherever it is reasonable to do so. The significance of developing this technology is there are currently no manufacturers who provide a shipboard wrap-around DF array solution. SwRI is at the forefront of this technology and is a leader in this innovative approach to the industry.

Accomplishments - Significant progress has been made in numerical modeling of the antenna elements with very good agreement to measured results. Design details are currently being finalized and production will begin soon on the prototype array. Development has also been very successful in deriving MATLAB routines to calculate antenna sensitivity based on numerical model outputs. These calculations will be combined with legacy routines to estimate DF performance in order to include the impact of antenna sensitivity on DF performance estimates. These performance estimations will greatly enhance our capabilities not only for this application but also for all of our DF antenna array development.

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