Abstract:
Due to the increase in modern wireless communication systems, antenna arrays with broader bandwidths, multiple bands and smaller profiles are desired. This has led to the extensive research on fractal shaped antenna designs. However, these wireless communication applications require a certain amount of allocated space on the radio frequency spectrum. The spectrum is a limited resource and requires efficient use of the frequency bands in order to meet the high demand. One possible solution for this is to apply smart antenna technology to these arrays. This thesis attempts to investigate the performance of microstrip antenna arrays in comparison to fractal antenna arrays, while applying smart antenna technology. The smart antenna technology used in this project was based on a switched beam antenna model, due to its ease to implement and cost efficiency. The antenna arrays and beam forming network (Butler matrix) were used to enable a comparison between microstrip and fractal. Two rectangular patch arrays, a triangular patch array, a Sierpinski carpet array and a Sierpinski gasket array were designed to operate at 2.4GHz. The Butler matrix combined with the antenna arrays provided four beams in different locations (+14.5, -48.6, +48.6, -14.5). Simulation results were obtained using the software package CST Microwave Studio. The S-parameters of the Butler matrix and design antennas are discussed in further detail, whilst highlighting the performance characteristics and limitations of the project. The radiation pattern measurements of the antenna arrays were obtained from the anechoic chamber. The results showed that all the antenna arrays produced 4 different beam locations (close to the ideal positions) covering a total area ranging from 110-120. The size of each Sierpinski carpet antenna element was reduced by 39.8% compared to the rectangular patch antenna elements and the Sierpinski gasket antenna elements by 82% compared to the triangular patch antenna element. The results of the antenna arrays are presented as such that they can be used as an aid for future research into the practical replacement of microstrip antennas with fractal antennas. Lastly, future work of this thesis is discussed and suggestions are made to further improve the comparisons made.