Page 301 - Satellite Communications, Fourth Edition

Analog Signals 281

9.19. Explain what is meant by preemphasis and deemphasis and why these
are effective in improving signal-to-noise ratio in FM transmission. State typical
improvement levels expected for both telephony and TV transmissions.
9.20. Explain what is meant by noise weighting. State typical improvement
levels in signal-to-noise ratios which result from the introduction of noise
weighting for both telephony and TV transmissions.

9.21. Calculate the loading factor L for (a) a 12-channel, (b) a 120-channel, and
(c) an 1800-channel FDM/FM telephony signal.

9.22. Calculate the IF bandwidth required for (a) a 12-channel, (b) a 300-
channel, and (c) a 960-channel FDM/FM telephony signal. Assume that the
peak/rms factor is equal to 10 dB for parts (a) and (b) and equal to 18 dB for
part (c).

9.23. Calculate the receiver processing gain for each of the signals given in
Prob. 9.22.

9.24. A video signal has a peak deviation of 9 MHz and a video bandwidth of
4.2 MHz. Using Carson’s rule, calculate the IF bandwidth required and the
receiver processing gain.

9.25. For the video signal of Prob. 9.24, the emphasis improvement figure is
13 dB, and the noise weighting improvement figure is 11.2 dB. Calculate in
decibels (a) the signal-to-noise power ratio and (b) the video signal-to-noise
ratio as given by Eq. (9.21). The [C/N] value is 22 dB. Assume a sinusoidal video
signal.

References

Bischof, I. J., W. B. Day, R. W. Huck, W. T. Kerr, and N. G. Davies. 1981. “Anik-B Program
Delivery Pilot Project. A 12-month Performance Assessment.” CRC Report No. 1349,
Dept. of Communications, Ottawa, December.
Campanella, S. J. 1983. Companded Single Sideband (CSSB) AM/FDMA Performance.
Wiley, New York.
CCIR Recommendation 275-2. 1978. “Pre-emphasis Characteristic in Frequency
Modulation Radio Relay Systems for Telephony Using Frequency-Division Multiplex.”
14th Plenary Assembly, Vol. IX, Kyoto.
CCIR Recommendation 404-2. 1982. “Frequency Division for Analog Radio Relay Systems
for Telephony Using Frequency Division Multiplex.” 15th Plenary Assembly, Vol. IX,
part 1, Geneva.
CCIR Recommendation 405-1. 1982. “Pre-emphasis Characteristics for Frequency
Modulation Radio Relay Systems for Television.” 15th Plenary Assembly, Vol. IX, Part 1,
Geneva.
CCITT G423. 1976. “Interconnection at the Baseband Frequencies of Frequency-Division
Multiplex Radio-Relay Systems 1, 2.” International Carrier Analog Systems, Vol. III,
Part 2, Geneva.
CCITT Recommendation 567-2. 1986. “Transmission Performance of Television Circuits
Designed for Use in International Circuits.” Vol. XII, Geneva.