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Analog Communications Lab Viva Questions With Answers

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Q1. What is  modulation?
A: Modulation is the process of varying characteristics of a periodic waveform, called the carrier signal, with a modulating signal that typically contains information to be transmitted.

Q2. What is amplitude modulation?
A:Amplitude Modulation is the process of varying amplitude of carrier signal, with respect to amplitude of modulating signal

Q3. What are the different types of analog modulation?
A : There are three basic types of analog modulations.
1. AM or Amplitude Modulation
2. FM or Frequency Modulation
3. PM or Phase modulation

Q4. What si the need for modulation?
A : NEED FOR MODULATION
1) TO REDUCE THE ANTENNA HEIGHT
2) TO MULTIPLEX THE MORE NUMBER OF SIGNALS
3) TO REDUCE THE NOISE & DISTORTIONS
4) TO NARROW BANDING THE SIGNAL
5) TO REDUCE EQUIPMENT COMPLEXITY

Q5. What are the objectives met by modulation?
A:Length of antenna is shortened, signal loss is reduced, ease of radiation, adjustment of bandwidth, shifting signal frequency of the assigned value.

Q6. What are the advantage of PAM and PWM?
A:PAM Advantages
1)It is the base for all modulation techniques
2)Easy to modulate and demodulate
3)Transmitter and receiver circuitry is simple circuit which is easy to construct
PWM Advantages
1)less noise interference due to constant amplitude
2)Signal can be separated very easily at demodulation and noise can also be separated easily.
3)Synchronization between transmitter and receiver is not required unlike pulse position modulation.

Q7. What is Pulse position modulation?
A: In pulse position modulation, the amplitude and width of the pulses are kept constant, while the position of each pulse with reference to position of reference pulse, is changed according to the instantaneous sampled value of the modulating signal

Q8. What is the advantage of PPM over PWM and PAM?
A : Unlike PAM and PWM all the pulses in PPM have precisely the same amplitude and duration.This gives a higher degree of noise immunity than provided by PWM and especially PAM

Q9. What are the applications of pulse position modulation?
A: This method is widely used for optical communication systems such as optic fiber and IR remote controls, where efficiency is required and little or no external interference occurs.

Q10. What is the purpose of using differential pulse position modulation?
A: The Differential Pulse Position Modulation is a variation of the PPM coding, which in fact transmits data regardless of a clock. The delay between the pulses does not take reference from the rising edge of the clock. Instead, each delay takes reference from the falling edge of the previous pulse.

Q11. What are the advantage of PPM?
A:>>Due to constant amplitude of PPM pulse,the
information not contained in the
amplitude.hence noise added to PPM signal
doesnot distort the information.
>>To reconstruct PPM signal from the noise
contaminated PPM signal.

Q12. Explain the principle of PPM?
A:In pulse position modulation, the amplitude and width of the pulses are kept constant, while the position of each pulse with reference to position of reference pulse, is changed according to the instantaneous sampled value of the modulating signal

Q13. What is the purpose of PPM?
A:Pulse position modulation can be used for a number of purposes, especially in RF (Radio Frequency) communications.
-For example:
pulse position modulation is used in remote-controlled aircraft, cars, boats, and other vehicles and is responsible for conveying the controls of a transmitter to a receiver. The position of each pulse may describe the physical direction of an analogue controller while the number of pulses may describe the number of possible commands that the device may receive.

Q14. What are the analog analogies of PAM, PPM & PWM?
A:PAM is similar to AM.PPM and PWM is similar to angle modulation.

Q15. What is Frequency modulation (FM)?
A:Frequency Modulation is the process of varying frequency of a periodic waveform, called the carrier signal, with respect to the frequency of modulating signal that typically contains information to be transmitted.

Q16. What is PWM or Pulse length modulation or pulse duration modulation?
A:It is the process of modulation in which the width of the pulse train (carrier) is varied with respect to the amplitude of the message(modulating) signal.

Q17. What are the disadvantages of PWM?
A : Bandwidth is large compared to PAM

Q18. Mention the applications of PWM.
A: power delivery
volatage regulation
Audio effects and amplification

Q19.What are the advantages of PWM?
1)Unlike PAM,PWM has less noise because amplitude is held constant
2)Signal and noise separation is easy

tags: Analog Communications Lab Viva Questions With Answers,ECE Analog communications lab important viva questions, AC Lab ECE 3rd year 1st sem imp viva questions

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