Page 110 - Maxwell House

90 Chapter 2

at some fixed frequency should look like shown in Figure 2.7.4. Evidently, similar low
frequency loss splash takes place for () too. Accordingly, the ferrites have two operating
−
regions of small energy dissipation: the first bellow resonance and the second above. Although
there is no clear defining low-frequency limit, typically it lies between 100 MHz and 500 MHz
depending on ferrite type. Above the resonance operation region can be expended up to 100
GHz and higher.

2.8 METAMATERIALS
18
2.8.1 Introduction
In general, any material can be assigned to the class of “metamaterial” if it is fabricated such
way that its electromagnetic properties ( or , or both) depend on density, structure, and

lattice of such artificial tiny
inclusions as metal or
SNG Material Dielectric Material dielectric spheres, cylinders,
or printed metal strips of
different shapes embedded in
Plasmas Dielectrics a host dielectric material with
low dielectric permittivity.
DNG Material SNG Materials When the size of lattice cell
with multiple inclusions is
much shorter than the
Metamaterials Ferrites electromagnetic wavelength,
the external electromagnetic
Figure 2.8.1 Material classification fields can be considered
constant across several cells.
Based on such wide-ranging definition, we can consider as metamaterials the artificial
dielectrics described in Section 2.2.7 (see Figure 2.2.10) and most of the magnetic materials in
this chapter. Following the common classification, we denote the metamaterials as more narrow
class of unconventional mediums qualified as Single-NeGative (SNG) or Double-NeGative
(DNG). In the SNG materials, only permittivity or permeability ( or ) can achieve the

negativity at some frequencies, while DNG means that both of them negative simultaneously.
The diagram in Figure 2.8.1 illustrated such permittivity-permeability classification. According
to the American Physical Society, the metamaterials are considered one of the three most
important discoveries of the decade in the field of physics.

Why is the metamaterial so exciting? It is well-known that the speed of light c in a vacuum is
one the universal physical constant related to two SI derived units and (see Table 1.5)

0
giving us = 1 � . From above discussion surrounding the interaction electromagnetic
⁄
0
fields and materials follows that the polarization effects changes the dielectric and magnetic
material properties as → and → . Therefore, the speed of light in material

0
0
deviates accordingly
1
= = =
� 0 √

18 Greek prefix “meta” means “beyond” (imagination?).