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538
Performance of Communication Systems Corrupted by Noise Chap. 7
n 0 (t) = K A c
y n (t)
(7–111b)
The PSD of this output noise, n 0 (t), is obtained by the use of Eq. (6–133 l), and we get
K 2
A c 2 N 0, |f| … B T >2
n0 (f) = L
0, f otherwise
(7–112)
where the PSD of the bandpass input noise is N 0 2 over the bandpass of the IF filter and zero
outside the IF bandpass. Equation (7–112) is plotted in Fig. 7–23a, and the portion of the
spectrum that is passed by the LPF is denoted by the hatched lines.
p n0 (f)
(a) PM Detector
B T B B
2
B T
2 f
p n0 (f)
(b) FM Detector
Figure 7–23
B T B B
2
B T
2 f
PSD for noise out of detectors for receivers of angle-modulated signals.