RF Circuit Design, 2nd Edition

Chapter 8: Equipotentiality and Current Coupling on the Ground Surface

8.1 Equipotentiality on the Ground Surface

8.1.1 Equipotentiality on the Grounded Surface of an RF Cable

Let us start our discussion of the equipotentiality on grounded surface of a regular RF cable. Simply speaking, a regular RF cable is a conductive wire encircled by a conductive cylinder (Fig. 8.1). The outer cylinder at the two ends is usually connected as the ground terminal.

Figure 8.1 Regular RF cable.

In the RF range, the following questions must be answered:

• Are the ground points on the outside cylinder G_a and G_b equipotential? Is

  8.1

• Are the ground points of an RF cable at two ends, G₁ and G₂, equipotential? Is

  8.2

In the DC or low-frequency range, these points are, approximately, equipotential.

8.3

In the RF range, they are in most cases not equipotential, that is,

8.4

8.5

unless the distances between ...