Control and Measurement of Unintentional Electromagnetic Radiation

CHAPTER 7

CONTAINMENT OF UNINTENTIONAL RADIATIONS

7.1 INTRODUCTION

Containment of unintentional electromagnetic radiation is based on principles that have already been discussed, but they will now be differently applied. For example, a conducting plane in which a nearby current establishes its negative image can simply be viewed as a reflector of the radiation of that current. Based on that viewpoint then, a radiation that is fully reflected back toward its source from all directions will be fully contained. Previously it was seen that radiations can be effectively controlled by properly placing a reflector so that incident and reflected radiations cancel each other. In implementing containment, however, radiated fields are simply reflected back in the direction of their source. There is generally no attempt to cause any cancellation with the reflections.

Thus, the principles on which control and containment are based are the same and, with respect to the surrounding environment, the desired end results are the same. However, the methods of implementation are quite different from one another, and the implications of those differences are well worth examining.

7.2 FULLY CONTAINED RADIATING CURRENTS

The idea of containing circuit-current radiations is based primarily on the principle that electromagnetic fields do not exist in the interior of a perfect conductor. As discussed in Chapter 1, that makes the tangential electric field and the normal magnetic field both zero at the surface ...