PCM (Pulse Code Modulation)
Definition
PCM (Pulse Code Modulation) is a method of converting analog signals into digital form by sampling, quantizing, and encoding the signal amplitude into binary values.
Detailed Explanation
Steps in PCM
-
Sampling
- Signal sampled at regular intervals
- Rate follows Nyquist theorem
- Typical rate: 8000 samples/second for voice
-
Quantization
- Samples rounded to nearest quantization level
- Usually 256 levels (8-bit) or 65536 levels (16-bit)
- Introduces quantization noise
-
Encoding
- Binary coding of quantized values
- Common formats: 8-bit, 16-bit, 24-bit
- May include error checking bits
Applications
- Digital telephony (64 kbps standard)
- Digital audio recording
- Digital video
- Voice over IP (VoIP)
Advantages
- Noise immunity
- Perfect regeneration possible
- Better quality in transmission
- Compatible with digital systems
Limitations:
- Requires more bandwidth than analog
- Quantization noise
- Complex implementation
- Higher cost for high-resolution systems