# 2

# CHARACTERIZATION OF PROPAGATION MEDIA

## 2.1 INTRODUCTION

It is assumed that the reader has some familiarity with electromagnetic field theory and has encountered plane waves before. Nevertheless, a brief review here seems appropriate because introductory treatments, particularly for engineers, often steer quickly toward the simplest dielectric and magnetic materials. This simplifies the equations and allows an early introduction to waveguides, antennas, and other applications. Propagation media are not necessarily simple, however, and departure from the simple model can strongly impact signal propagation.

## 2.2 MAXWELL'S EQUATIONS, BOUNDARY CONDITIONS, AND CONTINUITY

The starting point for electromagnetic theory [1–5] is the set of four equations named after James Clerk Maxwell:

In these equations, the overbars denote vectors, *t* represents time, and the usual notation of vector calculus is used. denotes the magnetic field intensity (A/m), the magnetic flux density or induction (T), ...