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प्रश्न
Explain the process of amplitude modulation.
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उत्तर
Amplitude Modulation: Amplitude modulation is produced by varying the amplitude of the carrier waves in accordance with the amplitude of the modulating wave.
Let the carrier wave be c(t) = Acsinωct and the modulating signal be m(t) = Amsinωmt where ωm = 2πfm is the angular frequency of the message signal.
Modulated signal cm(t) is
cm(t)=(Ac+Am sinωmt)sinωct
where μ = Am/Ac is the modulation index.
`c_m(t)=A_csinomega_ct+(muA_c)/2cos(omega_c-omega_m)t-(muA_c)/2cos(omega_c+omega_m)t`
ωc - ωm and ωc+ωm are the lower side and upper side frequencies, respectively.
Production of Amplitude Modulated Wave
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संबंधित प्रश्न
A modulating signal is a square wave, as shown
The carrier wave is given by `c(t) = 2 sin (8pit) "volts"`
(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?
Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.
Write two advantages of frequency modulation over 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.
Compute the LC product of a tuned amplifier circuit required to generate a carrier wave of 1 MHz for amplitude modulation.
Why is a AM signal likely to be more noisy than a FM signal upon transmission through a channel?
On radiating (sending out) an AM modulated signal, the total radiated power is due to energy carried by ωc, ωc – ωm and ωc + ωm. Suggest ways to minimise cost of radiation without compromising on information.
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?
An amplitude-modulated wave is represented by Cm(t) = 10(1 + 0.2 cos 12560t) × sin (111 × 104t) volts. The modulating frequency in kHz will be ______.
The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be ______.
