1 Wireless Systems and Printed Antennas

Wireless systems are playing an ever increasingly important role in society. Whether they are used to assist in the distribution/collection of large amounts of information or to make home entertainment systems more convenient, wireless systems are becoming more and more integrated into daily activities. The utilization of wireless technology is not currently confined to either the commercial or the military sectors. In fact, it seems that both sectors are striving for wireless solutions to enhance their resources, or simply to make their product more readily accessible and useful to the consumer. One of the important enabling technologies for wireless communications is the transducer, which converts guided energy to radiated energy (and vise versa): the antenna. Although advances in antenna engineering cannot be credited for the globalization of wireless technologies, it still plays an important role, whether it provides an aesthetically pleasing solution or helps improve the overall radio frequency (RF) link budget, or allows multiple users to utilize the single interface and thereby increase the capacity. It is undeniable that good radiator engineering allows for better wireless systems. Figure 1.1 shows a ‘snapshot’ of present and future commercial wireless systems, highlighting cellular and satellite communications, as well as the extremely popular wireless local area network (WLAN) and short-range connectivity systems such as Bluetooth. Also shown is the quandary facing next-generation systems and how they were interface with a variety of technologies including computers and small handsets. Figure 1.2 shows the frequency spectrum indicating current and next-generation wireless systems between 300 MHz and 100 GHz. As can be seen, there are a plethora of wireless systems utilizing various advantages of the different spectra. For example, systems at the