Page 293 - Satellite Communications, Fourth Edition

Analog Signals 273

Figure 9.12 Output signal-to-noise ratio S/N versus input carrier-
to-noise ratio C/N for a modulating index of 5. The straight-line
section is a plot of Eq. (9.12).

Hence
2
G P 3 5 s5 1d 450

and
[G P ] 26.5 dB

From Eq. (9.12)
[S/N] 30 26.5 56.5 dB

9.6.5 Preemphasis and deemphasis
As shown in Fig. 9.11b, the noise voltage spectral density increases in
direct proportion to the demodulated noise frequency. As a result, the
signal-to-noise ratio is worse at the high-frequency end of the baseband,