Pulse Code Modulation Encoding

Objective

To study the Pulse Code Modulation (PCM) Encoding with respect to Ground.

 Introduction

As you know, digital transmission systems are steadily replacing analog systems in commercial communications applications. This is especially true in telecommunications. That being the case, an understanding of digital transmission systems is crucial for technical people in the communications and telecommunications industries.


PCM is a system for converting analog message signals to a serial stream of 0s and 1s. The conversion process is called encoding. At its simplest, encoding involves:

  • Sampling the analog signal's voltage at regular intervals using a sample-and-hold scheme
  • Comparing each sample to a set of reference voltages called quantisation levels.
  • Deciding which quantisation level the sampled voltage is closest to.
  • Generating the binary number for that quantisation level.
  • Outputting the binary number one bit at a time (that is, in serial form).
  • Taking the next sample and repeating the process.