
Frequency Domain
243
The impedance Z depends on frequency and its amplitude and phase are
ZR L
C
=+−
2
2
1
ω
ω
tanZ
L
C
R
=−
−
−1
1
ω
ω
which correspond respectively to the graphs in Figures 7.25 and 7.26.
Observation
The value of the Q factor is fundamental to discriminate the carrier frequency
of just one radio station, with respect to the nearest ones. Figure 7.24 repre-
sents the situation of a high vs. low Q factor, and demonstrates how a low value
lets frequencies of carriers of adjacent stations pass, so that the nal result is
to hear more than one radio station at the same time.
freq [kHz]
9.19.2 9.39.4 9.59.6 9.79.8
high Q
low Q
FIGURE 7.