Antenna Basics and Radio Wave Propagation

This chapter covers the antenna basics including: antenna fields, radiation pattern, antenna gain, beamwidth, antenna efficiency, antenna input impedance, antenna bandwidth, antenna polarization, isotropic antenna, radiation intensity, effective radiated power and antenna types. Antennas are used in wireless communication systems to radiate and receive electromagnetic (EM) waves to and from the free space. Antenna fields are typically represented in a spherical coordinate system. The radiation pattern of an antenna represents the variation of the field intensity of the antenna as a function of angles relative to a reference axis. All practical antennas are characterized with respect to a reference isotropic antenna. The transmitted EM waves spread out as they travel through the free space. Antennas can be classified in terms of their structures such as wire antennas, aperture antennas, and microstrip antennas. In a transmitter or receiver subsystem, the antenna input impedance must be matched to the ‐system to ensure maximum power transfer.