Pulse Analog Modulation MCQ Quiz - Objective Question with Answer for Pulse Analog Modulation - Download Free PDF
Last updated on Jul 10, 2025
Latest Pulse Analog Modulation MCQ Objective Questions
Pulse Analog Modulation Question 1:
What is the typical maximum frequency deviation for Wide Band FM (WBFM) used in FM broadcasting?
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 1 Detailed Solution
Explanation:
Wide Band Frequency Modulation (WBFM) is a type of frequency modulation used in FM broadcasting where the frequency of the carrier wave is varied in proportion to the instantaneous amplitude of the modulating signal. WBFM is characterized by a relatively large frequency deviation, which is essential for high-quality audio transmission.
The typical maximum frequency deviation for Wide Band FM used in FM broadcasting is 75 kHz. This deviation is standardized and widely adopted in FM broadcasting systems to ensure high fidelity in audio transmission, making it the correct answer (Option 3).
Technical Details:
- In FM broadcasting, the maximum frequency deviation of 75 kHz is paired with a standard baseband bandwidth of 15 kHz (the range of frequencies in the audio signal).
- The Carson's Rule, which estimates the bandwidth required for FM signals, is given as:
B = 2 × (Δf + fm)
Where:- B: Total bandwidth
- Δf: Maximum frequency deviation (75 kHz)
- fm: Maximum modulating frequency (15 kHz)
B = 2 × (75 kHz + 15 kHz) = 180 kHz
Thus, the FM signal occupies a bandwidth of approximately 180 kHz. - The 75 kHz deviation ensures sufficient dynamic range and minimizes distortion in audio signals.
- FM broadcasting systems are designed to operate within the 88 MHz to 108 MHz frequency band, with each station allocated a bandwidth of 200 kHz. The 75 kHz deviation fits well within this allocation while leaving room for guard bands to prevent interference between adjacent channels.
Correct Option Analysis:
The correct option is:
Option 3: 75 kHz
This is the standard maximum frequency deviation used in Wide Band FM for FM broadcasting. It provides an optimal balance between audio quality and efficient use of the frequency spectrum, making it the correct answer
Pulse Analog Modulation Question 2:
Which of the following statements is/are correct regarding Frequency Modulation (FM) and Amplitude Modulation (AM)?
a) FM provides better noise immunity.
b) AM requires lower bandwidth than FM.
c) FM utilises transmitted power more efficiently.
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 2 Detailed Solution
The correct statements regarding Frequency Modulation (FM) and Amplitude Modulation (AM) are a, b, and c.
Explanation:
a) FM provides better noise immunity.
-
True. FM encodes information in frequency variations, making it less susceptible to amplitude noise (e.g., interference, static). AM, which relies on amplitude changes, is highly vulnerable to noise.
b) AM requires lower bandwidth than FM.
-
True. AM bandwidth is twice the maximum modulating frequency (e.g., 10 kHz for a 5 kHz signal).
c) FM utilizes transmitted power more efficiently.
-
True. FM maintains a constant envelope (amplitude), allowing all transmitted power to carry information. In AM, up to ⅔ of power is wasted in the carrier (non-information-bearing), reducing efficiency.
Additional Information
Property | AM | FM |
---|---|---|
Noise Immunity | Low (noise directly affects amplitude) | High (immune to amplitude noise) |
Bandwidth | Narrow (e.g., 10 kHz for audio) | Wide (e.g., 200 kHz for audio) |
Power Efficiency | Low (carrier dominates power) | High (all power carries information) |
Pulse Analog Modulation Question 3:
A carrier 1s simultaneously modulated by two sine waves with modulation indices of 0.3 and 0.4; then the total modulation index is
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 3 Detailed Solution
Calculation:
The total modulation index is the square root of the sum of the squares of the individual modulation indices. If the modulation indices for the two waves are 0.3 and 0.4, then the total modulation index is:
mtotal = √(0.3² + 0.4²)
mtotal = √(0.09 + 0.16) = √0.25 = 0.5
Therefore, the total modulation index is 0.5.
Pulse Analog Modulation Question 4:
If radiated power of AM transmitter is 10 kW, then power in the carrier for modulation index of 0.6 is nearly -
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 4 Detailed Solution
Concept
The total transmitted power for an AM system is given by:
\(P=P_c({1+{μ\over 2}^2})\)
where, Pc = Carrier Power
μ = Modulation index
Calculation
Given, Pc = 10 kW
μ = 0.6
\(10=P_c({1+{0.6\over 2}^2})\)
Pc = 8.47 kW
Pulse Analog Modulation Question 5:
PAM signals can be demodulated by using a-
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 5 Detailed Solution
Concept:
PAM (Pulse Amplitude Modulation):
- It is a technique in which the amplitude of each pulse is controlled by the instantaneous amplitude of the modulation signal.
- It is a modulation system in which the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the signal at the instant of sampling.
- The demodulation of the PAM signals is done by using a Low-pass filter as shown:
Top Pulse Analog Modulation MCQ Objective Questions
In TV, an electrical disturbance (noise) affects
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 6 Detailed Solution
Download Solution PDFIn TV transmission:
- A video is Vestigial sideband modulated, which is a type of amplitude modulated waveform
- The Video signals are thus encoded in amplitude variations of the carriers
- The Audio signal is encoded in FM waveform
- Thus, the audio signals are encoded as frequency variations of the carrier
Noise is the signal that affects amplitude majorly. Thus, the video signal is distorted from amplitude variations.
The disadvantage of FM over AM is that __________
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 7 Detailed Solution
Download Solution PDFAdvantages of FM over AM are:
- Improved signal to noise ratio.
- Smaller geographical interference between neighbouring stations.
- Less radiated power.
- Well defined service areas for given transmitter power.
Disadvantages of FM:
- Much more Bandwidth
- More complicated receiver and transmitter.
In frequency modulation
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 8 Detailed Solution
Download Solution PDFThe AM, FM and PM output waveforms are as shown:
In Frequency modulation, the frequency of the carrier is varied according to the amplitude of the message signal and the amplitude of the carrier remains constant.
The main advantage of frequency modulation over amplitude modulation is
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 9 Detailed Solution
Download Solution PDF- The Noise affects the amplitude of the modulated signal
- In the Amplitude Modulated system, the message is contained in the amplitude modulations of the carrier; hence the introduction of noise distorts the amplitude and hence the message contained in the signal
- In a frequency modulated system the message is contained in the frequency variations of the carrier, therefore, the introduction of noise does not affect the message contained in the message signal
- Since the amplitude of FM remains constant, the noise can be eliminated using an amplitude limiter at the demodulator.
Features: |
AM |
FM |
Noise immunity |
In AM, the message is stored in the form of variation in amplitude. Noise affects the amplitude of signal most so AM is less noise immune. |
In FM, the message is stored in the form of variation in frequency so it has better noise immunity. |
Bandwidth |
B.W. required in AM is = 2fm. Hence, less bandwidth is required in case of AM. |
B.W. required in FM is = 2(β+1)fm. Hence, more bandwidth is required in the case of FM. |
Transmitted power |
Power transmitted in AM is given by: \({P_T} = {P_c}\left( {1 + \frac{{{\mu ^2}}}{2}} \right)\) As the modulation index ‘μ’ increases power in AM increases. |
In FM, power transmitted is always equal to the total power of carrier before modulation. Hence, FM requires less power than AM. |
Which of the following systems is analog?
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 10 Detailed Solution
Download Solution PDF- Analog modulation is a process in which analog low-frequency baseband signals (like an audio or TV signal) are transmitted over a larger distance without getting faded away, by superimposing over a higher frequency carrier signal such as a radio frequency band.
- Different modulation techniques are explained with the help of the following block diagram:
- If the amplitude of a pulse or duration of a pulse is varied according to the instantaneous values of the baseband modulating signal, then such a technique is called as Pulse Amplitude Modulation (PAM).
In an amplitude modulated system, if the total power is 600 W and the power in the carrier is 400 W. then the modulation index is
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 11 Detailed Solution
Download Solution PDFConcept:
The total transmitted power for an AM system is given by:
\({P_t} = {P_c}\left( {1 + \frac{{{μ^2}}}{2}} \right)\)
Pc = Carrier Power
μ = Modulation Index
Calculation:
Given Pt = 600 W, Pc = 400 W
Putting these values in the total power of AM wave expression, we get:
\(600 = 400\left( {1 + \frac{{{μ^2}}}{2}} \right)\)
\(\frac{6}{4}=\left( {1 + \frac{{{μ^2}}}{2}} \right)\)
\(\frac{6}{4}=\left( {1 + \frac{{{μ^2}}}{2}} \right)\)
\(\frac{μ^2}{2}=\frac{1}{2}\)
μ = 1.00
The type of modulation used in the T.V. picture transmission is
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 12 Detailed Solution
Download Solution PDF- T.V. picture transmission uses vestigial sideband modulation which is a type of amplitude modulation
- The vestigial sideband has the advantage of reducing the bandwidth
- The T.V. audio signal uses FM modulation
Limiter circuit is not needed in the following detector:
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 13 Detailed Solution
Download Solution PDFConcept:
- Frequency Demodulators are often sensitive to amplitude variations. Therefore a limiter amplifier stage must be used before the detector, to remove amplitude variations in the signal which would be detected as noise.
- The limiter acts as a Class-A amplifier at lower amplitudes; at higher amplitudes, it becomes a saturated amplifier that clips off the peaks and limits the amplitude.
- The FM ratio detector was the more common because it offered a better level of amplitude modulation rejection of amplitude modulation.
- This enabled the circuit to provide a greater level of noise immunity as most noise is amplitude noise.
- Additional limiter circuit is not required since the output voltage is not affected by amplitude variations in the incoming signals.
It also enables the FM detector to operate more effectively even with lower levels of limiting in the preceding IF stages of the receiver.
A carrier is simultaneously amplitude modulated by two sine waves with individual modulation of 30% and 40%. The overall modulation index is
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 14 Detailed Solution
Download Solution PDFEffective modulation index will be:
\({\rm{\mu }} = \sqrt {{\rm{\mu }}_1^2 + {\rm{\mu }}_2^2}\)
Given \({{\rm{\mu }}_1} = 0.3\) and \({{\rm{\mu }}_2} = 0.4\)
The overall modulation index will be:
\({\rm{\mu }} = \sqrt {0.09 + 0.16} = \sqrt {0.25} = 0.5\)
In percentage, \({\rm{\mu }} = 50{\rm{\;\% }}\)Fidelity in a communication receiver is provided by
Answer (Detailed Solution Below)
Pulse Analog Modulation Question 15 Detailed Solution
Download Solution PDF- Fidelity in communications refers to the ability of the receiver to produce an exact replica of transmitted signal. It is provided at output stage of receiver i.e. audio stage.
- Fidelity of a receiver is its ability to reproduce the exact replica of the transmitted signals at the receiver output.
- In other words, the fidelity of a receiver is its ability to accurately reproduce, in its output, the signal that appears at its input.
- For better fidelity, the amplifier must pass high bandwidth signals to amplify the frequencies of the outermost sidebands, while for better selectivity the signal should have narrow bandwidth.
- Low frequency response of IF amplifier determines fidelity at the lower modulating frequencies while high frequency response of the IF amplifier determines fidelity at the higher modulating frequencies.