Question

Which of the following pulse modulation is analog?

• A. PCM
• B. Differential PCM
• C. PWM
• D. Delta

Hint:

Analog Pulse Modulations: PAM (Amplitude), PWM/PDM (Width/Duration), PPM (Position).
Digital Pulse Modulations: PCM, DPCM, DM, ADM.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify which of the given pulse modulation schemes is classified as an analog pulse modulation technique rather than a digital one.

Step 2: Key Formula or Approach:
Pulse modulation is divided into two major categories:
1. Analog Pulse Modulation: The carrier is a pulse train, and one of its continuous parameters (amplitude, width, or position) is varied in proportion to the message signal. No quantization is involved.
2. Digital Pulse Modulation: The message signal is sampled and quantized into discrete digital codes.

Step 3: Detailed Explanation:

• PWM (Pulse Width Modulation): The width (or duration) of each pulse is varied continuously in proportion to the amplitude of the analog message signal at that sampling instant. Since the width can take any value in a continuous range (no quantization), it is an analog pulse modulation technique.

• PCM (Pulse Code Modulation): A digital scheme where the analog signal is sampled, quantized, and encoded into binary codewords.

• Differential PCM (DPCM): A digital scheme that encodes only the difference between consecutive samples to reduce the bit rate.

• Delta Modulation (DM): A simplified 1-bit digital modulation scheme that tracks the signal steps up or down.

Step 4: Final Answer:
PWM is an analog pulse modulation technique, which corresponds to Option (C).