The antenna plays an essential role in sending and receiving information in
the wireless communication systems. In addition to communication systems antennas
are used in astronomy, geophysical probing, medicine and biological tissues, and radio
frequency identification systems. Based on their geometrical structure, antennas may be
classified into wire antennas; aperture type antennas; microstrip antennas; array
antennas; reflector antennas; lens antennas. This chapter introduces the basic principles
of antennas beside some topics related to antennas such as reciprocity theorem, Friis
transmission formula, and general formulations for far-field approximations. As
examples of the antenna analysis, the basic antenna parameters, and radiation
characteristics are obtained for wire antennas and simple array antennas. The topics of
the chapter are analyzed in details and supported by illustrative examples and figures in
addition to solved problems. Homework problems are included at the end of the
chapter.
Keywords: Aperture type antennas, array antennas, circular loop antenna,
directivity, dipole antenna, effective aperture, Friis transmission formula, farfield,
gain, input impedance, lens antennas, microstrip antennas, radiation pattern,
radiating near-field region, reactive near-field region, reciprocity theorem,
reflector antennas, wire antennas.
