TABLE OF CONTENTS Electric and magnetic force. May they live forever, and never be forgot, if only to remind us that the science of electromagnetics, in spite of the abstract nature of the theory, involving quantities whose nature is entirely unknown at present, is really and truly founded upon the observation of real Newtonian forces, electric and magnetic respectively.
Oliver Heaviside, 1900
This chapter looks at antennas from a more traditional viewpoint: as radiators and receivers of electromagnetic fields. Then as now, electromagnetics is indeed an abstract subject, as Heaviside observed [1]. Its application to antennas provides a welcomed opportunity for electromagnetic science to demonstrate its practical value. First, this chapter compares and contrasts time domain and frequency domain analysis of signals. Then, it presents time domain electromagnetics for linear antennas. Next, it introduces a variety of approximations that make a direct (if qualitative) analysis of time domain antenna problems easier and it explains the fields around an ideal dipole source. Finally, this chapter summarizes and explains the advantages and limitations of thinking of antennas as radiators and receivers of electromagnetic fields.
The time and frequency domains present two complementary and equivalent ways of looking at physical signals. Traditional electromagnetic practice has leaned heavily in the direction of frequency domain or "harmonic" signals. To be sure, the harmonic functions like sin ?t and cos ?t (or more generally, e j?t) have many attractions. They offer an excellent approximation to the...
