Advertisements
Advertisements
प्रश्न
Explain the process of amplitude modulation.
Advertisements
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
APPEARS IN
संबंधित प्रश्न
For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is found to be 2 V. Determine the modulation index μ. What would be the value of μ if the minimum amplitude is zero volt?
Define the term 'amplitude modulation'
Write two advantages of frequency modulation over amplitude modulation.
What is meant by term ‘modulation’? Draw a block diagram of a simple modulator for obtaining an AM signal.
Solve the following question.
A message signal of frequency 20 kHz and peak voltage 10 V is used to modulate a carrier of frequency 2 MHz and peak voltage of 15 V. Calculate the modulation index. Why the modulation index is generally kept less than one?
Define amplitude modulation in a communication system.
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.
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.
An amplitude modulated wave is as shown in figure. Calculate
- the percentage modulation
- peak carrier voltage and
- peak value of information voltage.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal are ______.
