Communication System
Analog Communication
Practice questions from Analog Communication.
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IncorrectConsider a frequency-modulated (FM) signal
where and are, respectively, the amplitude and frequency (in Hz) of the carrier waveform. The frequency is in Hz, and assume that .
The peak frequency deviation of the FM signal in Hz is __________.
By comparison with standard angle modulated signal expression:
Clearly, change in frequency is given by derivative of argument of cosine with respect to time.
Here,
change in angular frequency (in rad/s)
Note in question that unit asked is Hz, thus we have to divide by to get
Max value of summation of sinusoids of different frequency is summation of amplitudes, thus peak frequency deviation
Consider a message signal which is bandlimited to , where is in Hz. Consider the following two modulation schemes for the message signal:
- Double sideband-suppressed carrier (DSB-SC):
- Amplitude modulation (AM):
Here, and are the amplitude and frequency (in Hz) of the carrier, respectively. In the case of AM, denotes the modulation index.
Consider the following statements:
(i) An envelope detector can be used for demodulation in the DSB-SC scheme if for all .
(ii) An envelope detector can be used for demodulation in the AM scheme only if for all .
Which of the following options is/are correct?
As long as , envelop detector can be used to detect and signals
mentions the word "can", this true as can at times ensure
(D) mention the word "only", it is not a must condition for , only the bound is on , thus: is wrong.
An amplitude modulator has output (in Volts)
The carrier power normalized to resistance is 50 Watts. The ratio of the total sideband power to the total power is . The value of (in Volts, rounded off to two decimal places) is_______.
Given:
Let a frequency modulated (FM) signal , where is a message signal of bandwidth . It is passed through a non-linear system with output . Let denote the FM bandwidth. The minimum value of required to recover from is
Bandwidth
Bandwidth of
To recover
Compared to FM BW, message BW is very small. So, that it can be ignored.
