ABSTRACT
The frequency of voltage supplied by electric companies is 50 Hz in several countries around the world. The wavelength at 50 Hz is 6000 km. At low frequencies, 50 Hz up to 1 kHz, the variation of voltage and current along electric cables may be neglected. If the length of an electric component is less than a tenth of a wavelength, then the variation of voltage and current may be neglected. If the length of the device is less than a tenth of a wavelength, then the device is called a lumped element. If the length of an electric component is longer than a tenth of a wavelength, then the variation of voltage and current cannot be neglected. In this case, the device is called a distributed element. Electric circuits that consist of a lumped element are analyzed by employing Kirchhoff’s laws and Ohm’s law. Kirchhoff’s laws and Ohm’s law assume that voltage and current do not vary along the length of a component. Circuits that consist of a distributed element cannot be analyzed by using Kirchhoff’s laws and Ohm’s law and should be analyzed by using electromagnetic theory. This chapter provides basic theory and a short introduction to electromagnetic, microwave and communication engineering. The transmitting and receiving of information in microwave frequencies is based on the propagation of electromagnetic waves.
