Antennas have been around now for nearly 125 years. In those 125 years wireless communication has become increasingly important. Personal mobile communication applications are putting huge constraints on the antennas that need to be housed in limited spaces. Therefore the common practice of wireless engineers to consider the antenna as a black-box component is not valid anymore. The modern wireless engineer needs to have a basic understanding of antenna theory. Before we dive into the derivation of antenna characteristics, however, we will—in this chapter—present a brief overview of antenna history and the mechanisms of radiation. Thus, a solid foundation will be presented for understanding antenna characteristics and their derivations.
1.1 The Early History of Antennas
When James Clerk Maxwell, in the 1860s, united electricity and magnetism into electromagnetism, he described light as—and proved it to be—an electromagnetic phenomenon. He predicted the existence of electromagnetic waves at radio frequencies, that is at much lower frequencies than light. In 1886, Maxwell was proven right by Heinrich Rudolf Hertz who—without realizing it himself1—created the first ever radio system, consisting of a transmitter and a receiver, see Figure 1.1.
The transmitting antenna, connected to a spark gap at the secondary windings ...