Compact multifunctional antennas for wireless systems

Chapter 1

Compact Multifunctional Antennas in Microwave Wireless Systems

1.1 Introduction

The mission of a communication system is to get messages delivered with minimum distortion. Messages such as voices, pictures, and movies are a series of natural signals over time, operating at frequencies ranging from a few to hundreds of kilohertz. Figure 1.1 shows the signal flows in a communication system. There are two types of communication systems: wired and wireless. Examples of wired systems are telephony and optical systems in which cables and fibers are deployed for transmitting signals, respectively. The telephone, patented by Alexander Graham Bell in 1876 (1), was the earliest available communication gadget that enabled the conversion of vocal messages into electronic signals. In 1966, Charles Kao (2) showed that a glass strand is able to be made into a signal-transmitting medium. Since then, tens of thousands of miles of optical fibers have been laid to carry information on land and across the oceans. The rapid advancement of optical technologies makes possible the transmission of signals in bulk using light, and it has led to a surge of internet technologies since the last century. However, the major drawback of wired communications is that it does not allow user mobility. Geographical features and human-made constructions can also pose a hindrance for laying out long wires or cables. As early as 1900, it was shown by Guglielmo Marconi that an electromagnetic wave is able to ...