Pulse amplitude modulation is a process whereby;

Question

Pulse amplitude modulation is a process whereby;

1. A. The position of the pulse is changed as a function of the sampled value
2. B. The width of the pulse is varied as a function of time
3. C. The height of a pulse is made proportional to the sampled value (Correct answer)
4. D. None of the above

Correct Answer

Option C — The height of a pulse is made proportional to the sampled value

Detailed Solution & Explanation

The correct answer is The height of a pulse is made proportional to the sampled value.

Key Points

• In Pulse Amplitude Modulation (PAM), the amplitude (height) of each pulse is made proportional to the instantaneous value of the sampled message signal.
• The pulse width and position both remain constant; only the height varies.
• Varying the position instead gives PPM (Pulse Position Modulation), and varying the width gives PWM (Pulse Width Modulation) — the two distractors offered here.

Additional Information

• PAM is the first step in producing PCM: sampling yields PAM, which is then quantised and encoded into binary.
• Because the information rides on amplitude, PAM is more vulnerable to noise than PPM or PWM, where the information is carried by timing.