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Assertion: AM detection is the process o...

Assertion: AM detection is the process of recovering the modulating signal from amplitude modulated waveform wich is carried out using a rectifier and an evelope detector.
Reason: Amplitude modulated waves can be produced by application of the message signal and the carrier wave to a non-linear device followed by band pass filter.

A

Superimposition

B

Amplificaiton

C

Demodulation

D

Modulation

Text Solution

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The correct Answer is:
C
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The process of recovering the audio signal from the modulated wave is known as

One of the components of frequency of amplitude modulated wave (AM) formed by the superposition of message signal of frequency omega_1 on a carrier wave of frequency omega_2 is

A: The bandwidth of a modulated signal is 2f_(m) in amplitude modulation, where f_(m) is the frequency of the modulating signal. R: In case of amplitude modulation the frequency of a modulated signal is equal to the frequency of the carrier wave.

If omega_c and omega_m are angular frequencies of carrier wave and modulating signal respectively, then Band width of amplitude modulated waves is equal to

If A_m and A_c are the amplitudes of modulating signal and carrier wave respectively, then modulation index is given by

Write three important factors which justify the need of modulating a message signal. Show diagrammatically how an amplitude modulated wave is obtained when a modulating signal is superimposed on a carrier wave.

A: If the amplitude of a message signal is half of the amplitude of the carrier wave, then the index of modulation is 50%. R: In amplitude modulation the amplitude of the carrier wave varies in accordance with the signal voltage of the message signal.

Write two basic modes of communication. Explain the process of amplitude modulation. Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing modulating signal over a sinusoidal carrier wave.

(a) Give three reasons why modulation of a message signal is necessary for long distance transmission. (b) Show graphically an audio singal, a carrier wave and an amplitude modulation wave.

The efficient transmission of signals is achieved by superimposing electrical audio signals on a high frequency carrier wave (the process is known as modulation). When the amplitude of high frequency carrier wave is changed in accordance with the intensity of modulating signal, it is called amplitude modulation. The extent to which the amplitude of carrier wave is changed by the signal is described by modulation factor. It is given as m="Amplitude change of carrier wave"/"Amplitude of unmodulated carrier wave" Let a carrier wave is represented by V_c=V_c cos omega_ct Let the modulation factor be m, the maximum change in amplitude of carrier wave is mV_c So, modulating signal can be represented as v_m=mV_c cosomega_mt So, the amplitude of modulated wave is =V_c+mV_c cosomega_m t Using this value, the instantaneous voltage of modulated wave is E=V_c cos omega_c t+ (mV_c)/2 cos (omega_c+omega_m)t + (mV_c)/2 cos (omega_c-omega_m ) t The above wave contains three frequencies namely, f_c, f_c+f_m and f_c-f_m . The frequencies f_c+f_m and f_c-f_m are called side band frequencies , USB and LSB respectively. The fraction of total power carried by side band frequencies is

AAKASH SERIES-COMMUNICATION SYSTEMS -Exercise - IA (Modulation)
  1. In amplitude modulation

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  2. Assertion: The units of some physical quantities can be expressed as c...

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  3. AM is used for broadcasting because

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  4. In amplitude modulation

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  5. The tuned circuit the Oscillator in a simple AM transmitter employs a ...

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  6. In frequency modulation

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  7. In a communication system, noise is most likely to affect the signal

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  8. The difference between phase and frequency modulation

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  9. While tuning in a certain broadcast station with a receiver, we are ac...

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  10. Digital signals (i) do not provide a continuous set of values, (ii) re...

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  11. An amino acid under certain conditions have both positive and negative...

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  12. Assertion: AM detection is the process of recovering the modulating si...

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  13. The sound waves after being converted into electrical waves are not tr...

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  14. In amplitude modulation

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  15. Modem is a device which performs

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  16. Audio signal canot be transmitted because

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  17. Of the following which is preferred modulation scheme for digital comm...

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  18. A basic communication system consists of (A) transmitter (B) informa...

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  19. Digital signals (i) do not provide a continuous set of values, (ii) re...

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  20. Identify the mathematical expression for amplitude modulated wave.

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