The application of periodic structures to conical antenna design

The primary objective of this research has been to investigate whether periodic structures can be applied to conical antennas for the purpose of improving their performance. This has been achieved through numerical modelling, theoretical investigation and physical measurements. In this study, two dimensional rotationally symmetric periodic structures were considered. This work determined that applying modifications to the cone antenna element significantly reduced the antennas bandwidth through the creation of strong anti-resonances. However, introducing frequency dependent impedance transformations to the end-termination leads to improvements in the far field radiation patterns without significant detriment to the input characteristics. In addition, periodic structures were applied to the ground plane to reduce backward radiation through the suppression of surface wave propagation. Results from this investigation have been determined and the implications assessed. In addition a novel periodic structure designed using polar curves and mapping functions capable of operating at low frequencies and that could be applied to conformal surfaces has been designed and analysed. The results of this research demonstrate that periodic structures can improve the radiation characteristics of conical antennas without compromising the impedance bandwidth.