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प्रश्न
Define amplitude modulation in a communication system.
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उत्तर
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संबंधित प्रश्न
Explain any two factors that justify the need of modulating a low-frequency signal.
The frequencies of two side bands in an AM wave are 640 kHz and 660 kHz respectively. Find the frequencies of carrier and modulating signal. What is the bandwidth required for amplitude modulation?
Explain any two factors which justify the need for modulating a low frequency base-band signal.
Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.
Answer the following question.
If A and B represent the maximum and minimum amplitudes of an amplitude-modulated wave, write the expression for the modulation index in terms of A and B.
In amplitude modulation ______.
In amplitude modulation, the modulation index m, is kept less than or equal to 1 because ______.
- m > 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
- m > 1 will result in overlapping of both side bands resulting into loss of information.
- m > 1 will result in change in phase between carrier signal and message signal.
- m > 1 indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.
An amplitude modulated wave is as shown in figure. Calculate
- the percentage modulation
- peak carrier voltage and
- peak value of information voltage.
Draw the plot of amplitude versus ‘ω’ for an amplitude modulated wave whose carrier wave (ωc) is carrying two modulating signals, ω1 and ω2 (ω2 > ω1).
- Is the plot symmetrical about ωc? Comment especially about plot in region ω < ωc.
- Extrapolate and predict the problems one can expect if more waves are to be modulated.
- Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?
The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be ______.
