Q5 of 8 Page 530

A carrier wave of peak voltage 12V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 75%?

Amplitude of the carrier wave, Ac = 12 V

Modulation index, m = 75% = 0.75 (unitless as a ratio)


Amplitude of the modulating wave = Am


We know for modulation index:


m = Am/Ac


⇒ Am = mAc


⇒ Am = (0.75 × 12) V = 9V


More from this chapter

All 8 →
3

Digital signals

(i) do not provide a continuous set of values,


(ii) represent values as discrete steps,


(iii) can utilize binary system, and


(iv) can utilize decimal as well as binary systems.


Which of the above statements are true?

 4

Is it necessary for a transmitting antenna to be at the same height as that of the receiving antenna for line-of-sight communication? A TV transmitting antenna is 81m tall. How much service area can it cover if the receiving antenna is at the ground level?

 6

A modulating signal is a square wave, as shown in Fig. 15.14.


The carrier wave is given by c (t) = 2sin(8πt) volts.


(i) Sketch the amplitude modulated waveform


(ii) What is the modulation index?

 7

For an amplitude modulated wave, the maximum amplitude is found to be 10V while the minimum amplitude is found to be 2V. Determine the modulation index, μ. What would be the value of μ if the minimum amplitude is zero volt?