Research on Compact and Efficient Antennas

摘要

To investigate the limitations of electrically small tactical HF communication antennas used over ground, measurements were made on scale model UHF antennas mounted on model UHF ground. The antennas used were dipoles or monopoles with groundplanes. The model ground consisted of a carbon-loaded polyurethane elastomer, designed to simulate HF ground at UHF. Measurements on the model antennas over the model ground resulted in agreement with theory where theory existed, and allowed comparison and evaluation of arbitrary antenna configurations and ground systems. The ground modeling technique proved especially valuable in determining the groundwave attenuation rate at relatively short ranges, and in investigating a figure of merit, rather than an efficiency, for an antenna intended for groundwave communications. It was found that a relatively small ground sample could provide data useful in determining the antenna performance. Theoretical studies were carried out to determine the magnitude of the power lost in the local region of an antenna of arbitrary configuration, and to predict the field at, or near, the antenna region and at long ranges for both dipole and groundplane antennas. This report contains a recommendation that typical uniform grounds be given standardized ground constants. Tables and graphs of the reflection coefficients versus angle of incidence of representative grounds were prepared for frequencies in the HF and VHF bands. (Author)