
523Microwave Diodes
In these gures C
j
is the junction capacitance, R
s
is series resistance and R
p
is the parallel resistance. This R
p
is the equivalent resistance of generation-
recombination current, diffusion current and surface leakage current. With
the increase in reverse bias voltage both C
j
and R
s
decrease but R
p
increases.
The efciency of a varactor diode is expressed in terms of its quality factor Q.
Its maximum value of Q is given by
Q
R
R
p
s
max
/
=
4
1 2
(13.3)
13.4.6.3 Applications
Varactor diodes are used in harmonic generation, voltage variable tuning,
mixing, detection and modulation of microwave signals, active lters and
para