Information Technology Reference
In-Depth Information
Intuition suggests that with decreasing
2
/
1
and hence with increasing
g
the
S
1
, the better is galvanic
coupling between the upper layer and conductive basement and the more intensive is
vertical redistribution of currents normalizing the electromagnetic field. This heuris-
tic consideration can be easily confirmed with asymptotic estimate. In the
h
-interval
−
effect attenuates. Indeed the less is
2
and the larger is
g
2
e
−
g
|
|
.
y
−
y
y
)
G
(
y
−
=
−
y
)
If the galvanic parameter
g
is sufficiently large, then the Green function
G
(
y
assumes the form of the delta-like function
˜
(
y
−
y
). Hence, with accordance to
(7.19),
v
S
1
S
1
(
y
)
h
1
S
1
(
y
)
S
1
]
Z
⊥
(
y
)
˜
Z
⊥
(
y
)
[
S
1
(
y
)
y
)
dy
=−
i
o
+
−
(
y
−
−
v
1
Z
⊥
(
y
)
S
1
S
1
(
y
)
h
S
1
S
1
(
y
)
≈−
i
o
+
−
whence
Z
⊥
(
y
)
⊥
(
y
)
=
o
h
2
≈
Z
n
(
y
)
=−
i
o
h
,
≈
n
(
y
)
.
(7
.
29)
Clearly, in the case of sufficiently large
g
the
S
−
effect vanishes. Galvanic leakage
from the upper layer may kill the
S
−
effect.
How does the
S
−
effect attenuate with distance from the inhomogeneity? Letting
|
y
|
>>
v
, we can write (7.19) as
v
fg
2
S
1
e
−
g
Re
1
f
(
|
y
|−
v
)
e
−
ig
Im
1
f
(
|
y
|−
v
)
Z
⊥
(
y
)
Z
⊥
(
y
)[
S
1
(
y
)
S
1
]
dy
.
≈
Z
N
+
−
(7
.
30)
−
v
Outside the inhomogeneity the anomalous field, characterized by the integral term,
decays exponentially as
e
−
(
|
y
|−
v
)
/
d
, where
√
S
1
R
2
Re
√
1
1
d
=
=
o
S
1
h
2
.
(7
.
31)
1
f
−
i
g
Re
effect attenuates
and the distorted transverse impedance readjusts to the normalcy. This parame-
terisreferredtoas
adjustment distance
(Ranganayaki and Madden, 1980; Singer
and Fainberg, 1985; Singer, 1992). The influence of the inhomogeneity can be
neglected if
Parameter
d
allows to estimate the distance, at which the
S
−
|
y
| −
v
>>
d
.
.
(7
32)
