Date of Award

Summer 1999

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)


Electrical Engineering and Computer Science


When the platform on that an antenna is mounted on is large with respect to a wavelength, the platform may be considered to be a ground plane. The effects of a ground plane on the radiation characteristics of an antenna are generally well known. When the platform is small with respect to a wavelength, the platform may no longer be considered a ground plane. The antenna will have significant interaction with the platform, and the effects of both the antenna and the platform must be considered when analyzing the radiation characteristics of a system. Because the platform is on the order of a few wavelengths, it would be beneficial to utilize the platform to enhance radiation performance. In this thesis, the performance of low profile antennas mounted to a small ground vehicle (small compared to a wavelength) were analyzed to determine the effects of the platform when the platform has a box-like shape with distinct comers, and is directly over the ground. A method of moments computer code was used to simulate different antenna types at various locations on the ground vehicle over the frequency band of 30 MHz to 90 MHz in order to understand the effects of the platform at this frequency range. Two electrically small loop antennas were used to excite currents on the platform. The radiation characteristics of the platform were analyzed across the frequency band of interest. The box-like shape of the ground vehicle was found to have a different effect on the radiation pattern of the system at different frequencies. The effects of the ground vehicle were found to be proportional to the apparent size of the vehicle with respect to wavelength. The performance of the antenna system developed in this thesis was compared to an existing antenna system on the same ground vehicle used in this work. It was found that using only loop antennas on the ground vehicle, the radiation pattern was not acceptable because it did not radiate uniformly over the bandwidth. The addition of a modified monopole antenna to the system provided low profile antenna results that were comparable to the existing antenna system.



Restricted Access Item

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