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प्रश्न
Draw a block diagram of a detector for AM signal and show, using necessary processes and the waveforms, how the original message signal is detected from the input AM wave.
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उत्तर
When a message is received, it gets attenuated through the channel. Therefore, receiving antenna is to be followed by an amplifier and a detector. The carrier frequency is usually changed to a lower frequency in an intermediate frequency (IF) stage. The detected signal may not be strong enough to be made use of and, hence, is required to be amplified.
In order to obtain the original message signal m(t) of angular frequency, a simple method is used which is shown below in the form of a block diagram.
When the received modulated signal is passed through a rectifier, an envelope signal is produced. This envelope signal is the message signal. In order to retrieve the message, the signal is passed through an envelope detector.
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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?
What is meant by term ‘modulation’? Draw a block diagram of a simple modulator for obtaining an AM signal.
Why is frequency modulation preferred over amplitude modulation for transmission of music?
A message signal of frequency ωm is superposed on a carrier wave of frequency ωc to get an amplitude modulated wave (AM). The frequency of the AM wave will be ______.
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.
The maximum amplitude of an A.M. wave is found to be 15 V while its minimum amplitude is found to be 3 V. What is the modulation index?
Compute the LC product of a tuned amplifier circuit required to generate a carrier wave of 1 MHz for amplitude modulation.
The maximum amplitude for an amplitude modulated wave is found to be 12V while the minimum amplitude is found to be 3V. The modulation index is 0.6x where x is ______.
A signal of 5 kHz frequency is amplitude modulated on a carrier wave of frequency 2 MHz. The frequencies of the resultant signal are ______.
