Innovative Antennas for Wrap-around Direction Finding Arrays
from 400 to 4,000 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 are also dependent on other components of the system, the system as a whole can perform only 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 be only 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 to 900 MHz). Recent technology advances have gradually shifted communications to include upper UHF and higher frequencies (1,000 to 4,000 MHz). Therefore, the need has arisen to extend DF frequency capabilities to these higher frequencies while maintaining VHF performance and DF accuracy. Current shipboard antenna configurations are not readily adapted to smaller maritime vessels or higher frequencies because of 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 - Numerical modeling for this project has been successful, yielding several antenna designs with outstanding performance. Several design variations of the antenna have been built and tested. Impedance characteristics are outstanding for very broad frequency bandwidths and match numerical modeling very well. These impedance characteristics ensure a very sensitive antenna, a highly desirable design parameter for a DF antenna. DF performance for a small circular array of these antennas is also outstanding. DF performance characteristics match very well to numerically modeled results.

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