Page 300 - Satellite Communications, Fourth Edition

280 Chapter Nine

9.6. Explain how a 252-VF-channel group is formed for satellite transmission.

9.7. Describe the essential features of the video signal used in the NTSC color
TV scheme. How is the system made compatible with monochrome reception?

9.8. Explain how the sound information is added to the video information in
a color TV transmission.

9.9. For the matrix network M shown in Fig. 9.7, derive the equations for the
Y, Q, and I signals in terms of the input signals R, G, and B.

9.10. Explain what is meant by frequency modulation. A 70-MHz carrier is
frequency modulated by a 1-kHz tone of 5-V peak amplitude. The frequency
deviation constant is 15 kHz/V. Write down the expression for instantaneous
frequency.

9.11. An angle-modulated wave may be written as sinq(t), where the argument
q(t) is a function of the modulating signal. Given that the instantaneous angular
frequency is w i dq(t)/dt, derive the expression for the FM carrier in Prob. 9.10.
9.12. (a) Explain what is meant by phase modulation.(b) A 70-MHz carrier is
phase modulated by a 1-kHz tone of 5-V peak amplitude. The phase modulation
constant is 0.1 rad/V. Write down the expression for the argument q(t) of the
modulated wave.
9.13. Determine the equivalent peak frequency deviation for the phase-
modulated signal of Prob. 9.12.

9.14. Show that when a carrier is phase modulated with a sinusoid, the
equivalent peak frequency deviation is proportional to the modulating frequency.
Explain the significance of this on the output of an FM receiver used to receive
the PM wave.
9.15. In the early days of FM it was thought that the bandwidth could be
limited to twice the peak deviation irrespective of the modulating frequency.
Explain the fallacy behind this reasoning.

9.16. A 10-kHz tone is used to frequency modulate a carrier, the peak deviation
being 75 kHz. Use Carson’s rule to estimate the bandwidth required.

9.17. A 70-MHz carrier is frequency modulated by a 1-kHz tone of 5-V peak
amplitude. The frequency deviation constant is 15 kHz/V. Use Carson’s rule to
estimate the bandwidth required.

9.18. A 70-MHz carrier is phase modulated by a 1-kHz tone of 5-V peak
amplitude. The phase modulation constant is 0.1 rad/V. Find the equivalent peak
deviation and, hence, use Carson’s rule to estimate the bandwidth required for
the PM signal.