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NEOCLASSICAL THEORY OF INTERACTION 63

One of the essential mass application of resistive materials (except classical resistors
production) is the so-called “quiet” anechoic chamber. Figure 2.1.13a demonstrates the large
antenna installed in such chamber and prepared for the test.

10
An advanced anechoic test facility like shown in Figure 2.2.13b can even accommodate a
whole aircraft. The absorbing EM field blocks (see Figure 3.4.6b in Chapter 3) cover all walls,
floor, and ceiling creating the echo-free environment inside the chamber. The metal walls, floor,
and ceiling forming the closed highly conductive box (Faraday’s cage) if properly designed and
built shields the chamber interior with sensitive electronic equipment from exterior sources of
noise. A combination of both aspects means we can simulate in chambers a quiet open-space
condition, which is useful when external influences and multiple echoes inside would otherwise
disturb test results. We will come back to this issue later in Chapter 3.

2.3 BOUNDARY CONDITIONS
2.3.1 Introduction

It has been mentioned before, the world around us is full of bodies generally made of materials
with different conductivity , dielectric constant and/or

magnetic constant . Each of these parameters is a typically

smooth function of coordinates inside the bodies, but at the
boundaries between them any of these parameters or all of them
might jump from one value to other abruptly. If so, we should
expect that EM fields might leap on such boundaries, in the same
Figure 2.3.1 manner, being piecewise or “jumping” functions of coordinates.
Piecewise function Figure 2.3.1 illustrates such behavior on the example of a one-
graph example dimensional function. There is nothing wrong with that as soon as
such discontinuity is integrable. Then practically without loss of
generality, Maxwell’s equations in integral form (see Table 1.7 - 1.9) should be applied to
description EM fields elsewhere including boundaries.
That is not always correct for the differential form of
Maxwell’s equations because from a physical point of
view the derivatives do not exist in the point of field
discontinuities. The way to fix it is to apply the integral
form of Maxwell’s equations to the fields around the
interface and define the relationship between the finite
left- and right-hand limits. These limits called
boundary conditions strongly constrain the behavior of
electromagnetic fields at boundaries between two
media having different properties. Consequently, the Figure 2.3.2 Interface between
solutions of Maxwell’s equation in differential form is two materials
correct if and only if they satisfy the boundary
conditions.

10 Public Domain Images, source:
www.nasa.gov/centers/johnson/engineering/human_space_vehicle_systems/antenna_test_facility/index.
html, https://upload.wikimedia.org/wikipedia/commons/2/2a/40th_Flight_Test_Squadron_F-
16_Fighting_Falcon_sits_in_the_anechoic_chamber.jpg