TUTORIAL CHAPTER 7: ANGLE MODULATION TRANSMISSION
CALCULATION QUESTIONS
1. If a frequency modulator produces 5 kHz of frequency deviation for a 10-V modulating signal, determine the deviation sensitivity. How much frequency deviation is produced for a 2-V modulating signal?
2. For an FM modulator with deviation sensitivity K1 = 4 kHz/V and a modulating signal vm(t) = 10 sin (2Ļ2000t), determine:
a. the peak frequency deviation
b. the carrier swing
c. the modulation index
3. Determine the percent modulation for a television broadcast station with a maximum frequency deviation Īf = 50 kHz when the modulating signal produces 40 kHz of frequency deviation at the antenna.
4. From the Bessel table, determine the number of side frequencies produced for the following indices: 0.25, 0.5, 1.0, 5.0, and 10.
5. For an FM modulator with modulation index m = 2, modulating signal vm(t) = Vm sin (2Ļ2000t), and an unmodulated carrier vc(t) = 8 sin (2Ļ8000t):
a. determine the number of sets of significant sidebands
b. determine their amplitudes
c. draw the frequency spectrum showing the relative amplitudes of the side frequencies
d. determine the bandwidth
6. For a given input signal, an FM broadcast-band transmitter has a frequency deviation Īf = 20 kHz. Determine the frequency deviation if the amplitude of the modulating signal increases by a factor of 2.5.
7. For an FM modulator with an unmodulated carrier amplitude Vc = 20 V, a modulation index m = 1 and a load resistance RL = 10 Ī©, determine the power in the modulated wave.