Vehicular Optically Transparent UHF Antenna for Terrestrial Communication

This paper presents the design and fabrication of a wideband, optically transparent armor embedded antenna for ground communication in military vehicles at UHF and VHF bands. This unique design allows for unidirectional radiation and helps reduce the vehicle signature and other undesirable effects, such as air drag and cosite interference, while improving the gain. As a starting point, a bow-tie-shaped monopole antenna is placed in the window and is optimized to achieve the highest bandwidth possible. Monopole architecture is chosen to minimize the antenna size and tilt the beam to the horizontal plane for a slanted windshield. The geometry of the antenna is then modified by introducing stublike extensions and bent sections to achieve an octave bandwidth starting at 275 MHz. A special mesh compatible with nonuniform surface current density on the antenna is used for minimal antenna opacity. With this method, a 40% reduction in opacity compared with a uniformly meshed antenna is achieved. A prototype armor embedded antenna with unidirectional radiation pattern is fabricated and shown to provide 5-7 dBi of gain in the desired bandwidth as well as excellent optical functionality.