| The objective of this thesis was to develop a new technique that was flexible and accurate for analyzing the transient behavior of antennas, and to apply this technique to both the study of existing transient antennas and the design of a new, optimal transient antenna. The new technique is based on the finite-difference time-domain (FDTD) numerical method.;First, the antenna problem was formulated for solution by the FDTD numerical method, and a study of the transient radiation from perfectly conducting, cylindrical and conical monopole antennas was performed. Graphical displays of the FDTD computed behavior were shown to give valuable physical insight into the mechanisms of transient radiation. Furthermore, the accuracy of the FDTD results were verified by comparisons with published experimental measurements.;A new, efficient FDTD algorithm for modeling electrically-thick resistive material based on surface impedance concepts was developed and applied to the study of transient radiation from a simple, canonical, two-dimensional antenna: the open-ended parallel-plate waveguide with a section of resistive loading. A parametric procedure was developed for obtaining the optimal design based on three criteria: the radiated pulse should be a faithful reproduction of the excitation, the reflected signal at the input of the antenna should be small, and the amplitude of the radiated signal should be as large as possible.;A new, efficient FDTD technique for modeling electrically-thin resistive material based on a sub-cell model was developed and applied to an extensive study of transient radiation from resistively-loaded cylindrical monopole antennas. Specifically, the popular Wu-King resistive profile was analyzed and shown to be partially successful in meeting the above design criteria. Experimental models were constructed, and the measurements verified these FDTD results.;Finally, a new transient radiator was proposed, a conical monopole with a section of resistive loading whose profile was a generalization of the Wu-King profile. By adjusting the resistive loading parameter and the geometrical details, this antenna was optimized so that it met all three of the above design criteria. Again, experimental models were constructed, and the measurements verified the FDTD results. |
