
716 Microwave Engineering
where
ε
0
is the permittivity of free space,
ε
r
is the relative dielectric constant
of the dielectric material, w is the metal width, l is the metal length and h is
the height of the dielectric material.
16.7.3.2 Interdigitated Capacitor
As illustrated in Figure 16.6b, it consists of a single-layer structure in which the
vanes are fabricated as microstrip lines with capacitance values between 0.1
and 15 pF. The approximate value of capacitance (C in pF) can be obtained by
C
l N A A
r
=
− +
3
1 2
[( ) ]
(16.8)
where N is the number of ngers, l is the nger length, w is the nger-base
width, A
1
(= 0.089 pF/cm) is the contr ...