An Investigation of the Smaller-than-Normal Wire Antenna

Advisor: Prof. Anthony Martin

The student researcher working on this project will conduct a study to understand how to design certain types of antennas that are uncharacteristically small in size. Smaller-than-normal antennas are attractive for many low-frequency applications where antennas are typically very large, such as the 20-, 15- and 10-meter bands used by ham-radio operators. The decrease in size of the antenna will be accomplished by adding inductive loads to it. Antennas made small by inductive loading typically can only be used effectively over a very narrow band of frequencies. The smaller the antenna is made, the more narrow the band of usable frequencies. The main goal of this research will be to investigate whether or not it is possible to increase bandwidth enough to make small-than-normal antennas more attractive from a practical standpoint. The approach used will be to add additional loads to the antenna and explore various load circuits. For example, it might be possible to increase usable bandwidth by putting a resistive load in parallel with the inductor. The wire antennas of interest are the monopole and dipole antennas, the helical antenna, the loop antenna, and the Yagi-Uda array antenna.

The tools the student will use in this study are (1) a highly accurate computer program (that solves an integral equation via the moment method) that will be used to model the antenna and predict its behavior and (2) a genetic algorithm (patterned after Darwin's theory of evolution) that will be used for finding optimal load positions and values. The student working on this project will learn about many antenna concepts such as gain, directivity, bandwidth, impedance, and pattern. The student will become familiar with genetic-algorithm optimization. Genetic algorithms have been found to be very powerful tools in engineering design. The student will also characterize some of these antennas via experiments made using the various antenna measurement facilities available at Clemson University.