Cisco Prisma II Platform 기술 참조
Modulation,
Continued
To find the reduction in power from the maximum, in terms of decibels, we take
10.log (0.3265), which gives 4.86 dB. The fact that the maximum modulation depth in
the PAL I standard is less than that in the PAL B/G standard results in a higher
average power of the modulated signal. We can conclude that, in PAL I systems, the
level of the digital QAM channels can be set at 5 dB below peak video envelope
power in order for them to have the same power as the analog video channels.
In practice, however, the broadband industry has generally opted for a universal
In practice, however, the broadband industry has generally opted for a universal
figure of 6 dB, rather than promote different recommendations for different TV
standards.
References
1. A. Papoulis, Probability, Random Variables and Stochastic Processes.
New York: McGraw Hill, 1965
New York: McGraw Hill, 1965
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November 2012 Printed in USA
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