Construction and Testing of Broadband High Impedance Ground Places for Surface Mount Antennas

The purpose of this research was to design and build appropriate broadband high impedance ground planes for surface mount antennas. Broadband, low-profile antennas, such as spirals, log-periodics, and bow-ties, suffer substantially in gain and bandwidth performance when they are brought close to a conducting surface. Thus, when standard broadband antenna designs are conformally placed on vehicle bodies, they can no longer achieve the high data rates required by modern communication. A simple remedy for this has been to place an absorber lined cavity behind the antenna to preserve some bandwidth, at the expense of reduced gain. However, recently introduced high impedance ground planes have novel electromagnetic features that have been shown to improve conformal antenna performance without the detrimental effects of absorber losses. In this research, first, square patch ground planes for narrowband antennas were built and analyzed. Second, a log-periodic broadband antenna was analyzed with square and circular patch ground planes. Finally, two novel triangular-patch high impedance ground plane designs as a meta-substrate for a broadband bow-tie antenna were presented. Consequently, the high impedance ground plane provided a suitable platform for the bow-tie with removing the undesired effects of a regular metallic ground plane. Results indicated that the novel designs have better gain than the bow-tie in free space, and the bow-tie over a metallic surface.

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