Control and Measurement of Unintentional Electromagnetic Radiation

CHAPTER 5

PERIODIC CIRCUIT CURRENTS AND THEIR MEASURED RADIATIONS

5.1 INTRODUCTION

Given the frequency-domain descriptions of periodic voltages developed in the previous chapter, it is a simple matter to similarly describe the circuit currents caused by those voltages. From those descriptions, it is then a simple matter to characterize the sinusoidal radiations of the currents. And those characterizations clearly identify the physical variables that determine the amplitudes of the sinusoidal radiations. Thus, are the physical parameters that can be adjusted to control excessive circuit current radiations clearly identified. In other words, upon reaching this point in the analysis of the problem, clear pointers to possible solutions will have been found.

It should be clear by now that the word “circuit” is used here in a very strict sense. However, a few comments may be in order, to make sure there is no misunderstanding. It is quite common among electrical engineers and technicians to use the words “circuit” and “network” to mean the same thing. That is not being done here. A circuit, as the word is used here, is a single, closed, path followed by a current. A circuit current is assumed to have essentially the same amplitude over its entire path, but not the same phase. Parts of a circuit current's path may be shared with other currents, but no two circuit currents can share the same path in its entirety.

A network, on the other hand, is a collection of circuits—at least two, and ...