
Artificial Electromagnetic Materials 173
where
F
a
p
=
⎛
⎝
⎜
⎞
⎠
⎟
π
2
,
(9.81)
w c
p
wa
om
/
=
(
)
3
2 8
3
π ln
.
(9.82)
In the above equations, p is the spatial period, a the inner radius of the smaller ring, w
the width of the rings, and δ the radial spacing between the rings, as marked in Figure
9.14a. From Equation 9.80, we note that μ
r
> 1, for 1 < w < w
om
, has resonance (μ
r
= ∞) at
w = w
om
, negative in the frequency domain w
om
< w < w
pm
, where
w
w
F
pm
om
=
−1
.
(9.83)
First experimental LH material based on the combination of the thin-wire structure with
the SRR was constructed by Smith etal. [13]. Kraus and Carver [11, p. 8, Figure 1.4a] show
a three-dimensional