Ultrahigh Frequencies

Abstract

This chapter is meant to serve as an introduction to the various phenomena associated with ultrahigh-frequency transmission and reception of electrical energy. The differences between low-frequency and ultrahigh-frequency electric waves do not appear abruptly at any particular frequency. Although barely perceptible, they start in the low megahertz range and increase with frequency until they are quite prominent above 100 MHz. Some of the derivations required to get useful expressions concerning these phenomena require the use of differential equations and will not be included in either the text or appendix. However, the useful expressions resulting from these derivations will be used in this chapter. In the previous chapters we discussed current and voltages from dc and ac up through the rf range. The maximum frequencies that we were using were in the order of a few megahertz. Now we want to look at some of the effects when the frequencies are in the order of 100 megahertz and higher. These get into the ultrahigh frequencies and the microwave range. First, let us discuss some of the properties of dc voltages and currents and then ac as the frequencies increase from the audio range up through the rf range.