
664 Microwave Engineering
Equation 15.3 involves capacitance (C) per unit length of the stripline.
This can be obtained by solving Laplace’s equation by conformal mapping
method. This, however, involves complicated special functions. For practical
computations of the characteristic impedance, a simple relation obtained by
employing the curve-tting method is given below.
Z
b
w b
r
e
0
30
0 441
=
+
ε
.
(15.4)
• Effective width: The effective width (w
e
) of the centre conductor
involved in Equation 15.4 is related to the actual width (w) given
below:
w b w b w b
e
/ / for / 35= > 0.
(15.5a)
w b w b w b w b
e
/ / 35 / for / 35
2
=