TABLE OF CONTENTS Through most of the 20 th Century the basic media used to transmit radio frequency (RF) energy were: wire pairs or conductors, coaxial cable, waveguides, and the atmosphere. The first two require electron flow in metallic conductors to direct the RF propagation. The last three rely on propagating electromagnetic fields, guided either by a confining structure or directive antennas. These media have provided efficient transmission capability since the early days of radio. The term media is generic, referring in general to the substance supporting the wave s propagation.
Radio is defined in the dictionary as the use of electromagnetic waves in the frequency range from 10 kilohertz (kilocycles/sec) to 300 Gigahertz to transmit electric signals without the use of wires. The upper range of modern radio frequency (RF) applications now extends beyond 40 Gigahertz, almost reaching the limit of the radio definition. Achievements in the field of electronic technology are one big reason for this progress. A growing need for mobile communications makes it difficult to know if the technology is pushing or the market is pulling. Beyond 300 Ghz, where frequencies approach the near infrared, another technology is also helping to spur growth in RF applications optical fibers. Optical fibers are small diameter cylindrical glass filaments that transmit electromagnetic (EM) waves at frequencies near the visible portion of the spectrum.
Light differs from radio because it has both the properties of particles, called photons, and the properties of EM waves. The term photonics , which is commonly applied...
