Digital Signal Processing Reference
In-Depth Information
infinitely thin sheets of “virtual” conducting foil. Using the constant potential
surfaces, the capacitance per unit length of a two-dimensional system can be
found with reasonable accuracy from a careful field sketch. For example, con-
sider the cross section of a coaxial line as shown in Figure 3-24, where electric
field flux lines originate from a charge
q
distributed over a length
l
on the inner
conductor and terminate on
q
in the same length on the outer conductor. If
equal potential lines are drawn between the inner and outer conductors, the total
−
−
q
C
0
C
0
C
0
+
q
Φ
=
0
Φ
=
V
(a)
∆
C
Φ
=
0
Φ
=
V
(b)
Figure 3-24
Field map of a coaxial line showing (a) series capacitance between equal
potential surfaces and (b) capacitance per unit cell.
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