Design of compact ultra wide band antennas for wireless personal area network applications

Abstract

Modern communication systems have an increasing demand of higher data transfer rates that need to exploit wide bandwidths. Two future trends of such high speed communications are available: Ultra Wide Band and 60-GHz Wireless Personal Area Network technologies. One of the critical points in designing such systems is the antenna part. UWB antennas have many standard designs done in a variety of ways. Their design trend is heading towards a more compact size to be embedded in the new communication devices. Planar types of these antennas would be the best choice for their low profile characteristic. These antennas have been designed in too many ways with different sizes, shapes, features and performances. In WPAN adapters, portable, hand-held mobile devices and many otters, antennas are preferred to be as compact as possible, preserving the same radiation characteristics and other performance aspects as much as possible to work on the frequency band they are designed to cover. Therefore, miniaturization techniques are used in this research to enable current monopole UWB antenna designs to gain a more compact size. Two contributions were done in this research. First, a brief review was done on the most distinct and high performance UWB antennas designed so far, followed by another review on the miniaturization of some UWB antennas and its effects on the antenna performance. The best choice from the antennas reviewed was selected as a case study to be miniaturized using the techniques learned from the review again. Two ways of miniaturization techniques were studied and at different degrees. The first was rescaling the antenna size, while the second was dissecting the antenna at different levels to study the effects and optimise them for the best performance. Performances achieved were good relative to the minimized size and substrate used. Prototypes of the main and miniaturized designs were fabricated and compared with the simulation results. The final miniaturized prototypes are compact and have some different performance characteristics that make them able to be used in different situations. The types are: rescaled, horizontal-half cut, and middle-quarter cut design. The second contribution is an enhancement of a 60-GHz WPAN antenna to have a better gain and directivity since enhancing the gain is very important in 60-GHz systems. The final design had a significantly higher gain (13 dB) and a more confined radiation pattern appropriate for 60-GHz WPAN applications.