PCM Assistant
Quick Demo Modes
Try This

Set Fm = 200 Hz and Fs = 300 Hz. Observe distortion.

Tips
Pulse Code Modulation

Aim

To understand the principles of Pulse Code Modulation (PCM) and observe the effects of sampling, quantization, and encoding on analog signals.

This experiment demonstrates how continuous analog signals are converted into discrete digital representations through the PCM process, which is fundamental to modern digital communication systems.

Theory

Pulse Code Modulation (PCM) is a method used to digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony, and other digital audio applications.

The PCM process involves three main steps:

Key Parameters:

PCM Block Diagram

Analog message signal LPF Sampler Quantizer Encoder Transmitter Section PCM output given to channel Regenerative Repeater CHANNEL Regenerative Repeater Channel output Regeneration circuit Decoder Reconstruction filter Destination Receiver Section

Procedure

Follow the steps below to run the PCM simulation. Each step includes a short looping demo clip.

1 Set Input Parameters & Simulate
Configure all input parameters in the Simulation panel, then click SIMULATE:
  • Message Amplitude (V) — peak voltage of the analog input signal
  • Message Frequency — frequency of the input waveform
  • Sampling Frequency — must be 2× greater than highest frequency component of message signal
  • Quantization Levels — number of amplitude steps (4 to 256)
  • Encoding Scheme — Binary or Gray Code
  • Signal Type — Sine, Cosine, or Random
2 Observe Transmitter Signals — Channel 1
In Channel 1 – Transmitter, click each button to view the signal at every stage of PCM encoding:
  • Input — the original continuous analog waveform
  • Sampled — discrete samples taken at the sampling frequency
  • Quantized — samples rounded to the nearest quantization level
  • Encoded Signal — binary or Gray code bitstream output
3 Observe Receiver Signals — Channel 2
In Channel 2 – Receiver, switch between the two output views to analyse signal recovery:
  • Decoded Signal — DAC output showing the staircase waveform after decoding
  • Reconstructed Signal — final output overlaid with the original to visualise quantization error
▶ Full Walkthrough Tutorial
Watch the complete tutorial covering every control, all transmitter and receiver views, the Nyquist analysis panel, and how to interpret quantization error across different parameter settings.

Pre Test

Assess your prior knowledge of Pulse Code Modulation

Quiz Results

Simulation

5.0 V
50 Hz
400 Hz
Sampling Analysis

Channel 1 - TRANSMITTER

Quantization Levels

Channel 2 - RECEIVER

Post Test

Test your understanding of Pulse Code Modulation concepts

Quiz Results

Result

The principles of Pulse Code Modulation (PCM) were studied and verified through interactive simulation. The processes of sampling, quantization, and encoding were implemented and analyzed in both transmitter and receiver sections.

Observations

  • When Fs >= 2Fm, the reconstructed signal closely matches the original signal.
  • When Fs < 2Fm, aliasing occurs, causing distortion in the reconstructed waveform.
  • Increasing quantization levels reduces step size and improves amplitude resolution.
  • Higher sampling frequency increases the number of discrete samples per cycle.
  • The encoded output demonstrates digital representation of analog information.

Key Insights

  • Bit rate increases with both sampling frequency and bits per sample.
  • There is a trade-off between signal quality and bandwidth requirement.
  • Quantization error cannot be completely eliminated in practical systems.
  • PCM forms the foundation of modern digital communication systems.
  • System performance depends critically on satisfying Nyquist criterion.
Conclusion: PCM successfully converts analog signals into digital form, but reconstruction quality depends on proper sampling rate and quantization resolution.