Pulse Modulation (PAM, PCM, PWM) — MCQs – EE

1. Pulse modulation is a process where:
(A) The carrier wave is in the form of pulses
(B) A continuous wave is modulated in amplitude
(C) Frequency varies continuously
(D) Only phase is modulated

2. The main types of pulse modulation are:
(A) PAM, PWM, PPM, and PCM
(B) AM, FM, and PM
(C) ASK, FSK, and PSK
(D) SSB, DSB, and VSB

3. PAM stands for:
(A) Pulse Amplitude Modulation
(B) Phase Amplitude Modulation
(C) Pulse Analog Modulation
(D) Power Amplitude Method

4. In Pulse Amplitude Modulation (PAM), which parameter varies?
(A) Amplitude of the pulses
(B) Width of the pulses
(C) Position of the pulses
(D) Frequency of the pulses

5. In Pulse Width Modulation (PWM), which parameter varies?
(A) Width (duration) of the pulses
(B) Amplitude of the pulses
(C) Position of the pulses
(D) Frequency of the pulses

6. In Pulse Position Modulation (PPM), which parameter varies?
(A) Position of the pulses
(B) Width of the pulses
(C) Amplitude of the pulses
(D) Frequency of the pulses

7. PCM stands for:
(A) Pulse Code Modulation
(B) Phase Coded Method
(C) Pulse Carrier Modulation
(D) Power Control Modulation

8. Pulse Code Modulation is a type of:
(A) Digital modulation
(B) Analog modulation
(C) Frequency modulation
(D) Phase modulation

9. In PCM, the analog signal is converted into:
(A) A binary coded signal
(B) Continuous waveform
(C) Frequency-modulated wave
(D) Phase-modulated wave

10. The first step in PCM is:
(A) Sampling
(B) Quantization
(C) Encoding
(D) Regeneration

11. The process of assigning discrete values to sampled amplitudes is called:
(A) Quantization
(B) Sampling
(C) Modulation
(D) Detection

12. The process of converting quantized samples into binary code is called:
(A) Encoding
(B) Sampling
(C) Demodulation
(D) Decoding

13. The main advantage of PCM over PAM is:
(A) Better noise immunity
(B) Simpler generation
(C) Lower bandwidth requirement
(D) Easier synchronization

14. PAM signals are more susceptible to:
(A) Noise and distortion
(B) Quantization error
(C) Digital interference
(D) Binary errors

15. In PWM, all pulses have:
(A) Same amplitude but different width
(B) Same width but different amplitude
(C) Same width and amplitude
(D) Different frequency and phase

16. In PPM, all pulses have:
(A) Same amplitude and width but different positions
(B) Same position but different widths
(C) Varying amplitude and width
(D) Random positions and widths

17. The main advantage of PWM over PAM is:
(A) Better noise immunity
(B) Smaller bandwidth
(C) Simpler detection
(D) Constant power transmission

18. The main disadvantage of PAM is:
(A) High susceptibility to noise
(B) Complex circuitry
(C) Low data rate
(D) Difficult regeneration

19. In PCM, noise immunity is achieved because:
(A) The signal is transmitted in digital form
(B) The amplitude varies continuously
(C) The frequency is kept constant
(D) The phase is modulated

20. The demodulation of PCM involves:
(A) Decoding and reconstruction
(B) Filtering only
(C) Amplitude detection
(D) Frequency discrimination

21. The main disadvantage of PCM is:
(A) High bandwidth requirement
(B) Poor noise performance
(C) Low data accuracy
(D) Difficult synchronization

22. PWM is commonly used in:
(A) Motor speed control and power regulation
(B) Audio recording
(C) Television broadcasting
(D) Telephone communication

23. In PPM, information is contained in:
(A) The time position of each pulse
(B) The amplitude of each pulse
(C) The width of each pulse
(D) The frequency of each pulse

24. Which pulse modulation type can be easily converted into digital form?
(A) PCM
(B) PAM
(C) PWM
(D) PPM

25. In PCM, quantization introduces:
(A) Quantization noise or error
(B) Phase shift
(C) Frequency distortion
(D) Timing jitter

26. The regeneration of PCM signals at repeaters helps to:
(A) Eliminate accumulated noise
(B) Increase amplitude
(C) Decrease bandwidth
(D) Enhance carrier frequency

27. In analog pulse modulation, signals such as PAM, PWM, and PPM are:
(A) Continuous in amplitude
(B) Discrete in time
(C) Binary coded
(D) Digital signals

28. In digital pulse modulation (PCM), the signal is:
(A) Discrete in time and amplitude
(B) Continuous in both
(C) Continuous in amplitude only
(D) Discrete in frequency

29. The sampling process converts:
(A) A continuous signal into a discrete-time signal
(B) A digital signal into analog
(C) Frequency into amplitude
(D) Noise into data

30. The main advantage of pulse modulation techniques is:
(A) Improved noise performance and easy multiplexing
(B) Reduced transmission speed
(C) Complex detection
(D) Increased distortion