ABSTRACT
Data transfer from point to point in communication systems can be done by transmitting electromagnetic waves or by connecting the points via transmission lines. Time-varying currents and charges create electromagnetic waves. The electromagnetic spectrum corresponds to electromagnetic waves from the meter range to the mm wave range. The characteristic feature of these phenomena is the short wavelength involved. An antenna is used to efficiently radiate electromagnetic energy in desired directions. Antennas match radio frequency systems to space. Transmission lines are used to transfer electromagnetic energy from one point to another with minimum losses over a wide band of frequencies. Usually in communication systems the load impedance is not the same as the impedance of commercial transmission lines. A coax transmission line consists of two round conductors, one of which completely surrounds the other, with the two separated by a continuous solid dielectric.
