Introduction to Digital Communication: Modulation

In Introduction to Digital Communication: Modulation, you'll learn ...

• The importance of timing and synchronization in digital communications
• The challenges of digital communication including distortion, attenuation, interference and multipath effects
• The goal of digital modulation
• Common digital modulation techniques

Overview

Credit: 1 PDH

Length: 15 pages

While it precedes the invention of the telegraph in the mid-19th century, digital communication has revolutionized our world in the past few decades. From the Internet and digital cable and over-the-air television broadcasts to Wi-Fi, digital cell phones, and a large number of other systems and devices, digital communication is already ubiquitous in developed countries and is becoming more pervasive worldwide.

Although some engineers specialize in development and application of these technologies, many other engineers working in a wide variety of fields may be called on to specify digital communication systems for use in factories, mines, power transmission and distribution systems including “smart grid” applications, and for network access in lab and office spaces. Also, nearly all if not all engineers are also users of these systems and could benefit from more detailed knowledge of their operation. For these two reasons it is helpful to understand underlying technologies of digital communication as well as their capabilities and limitations.

This course provides an introduction to one of many technologies that make digital communication possible. Digital modulation, and the inverse process of demodulation, transform data or digitized voice or video into a form that can be transmitted and received over the air, e.g., by radio, over copper wire, or by fiber optic cable, and then transform it back to its original form.

The course begins with a brief overview of digital communications systems, followed by a discussion of some of the challenges of digital communication such as noise and interference. Shannon’s expression for capacity of a noise-limited communication channel is presented along with a straightforward example of how to calculate this upper limit on error-free data transmission rate. Digital modulation and demodulation are discussed, starting with their goals and concepts necessary to understand the topic. Types of digital modulation are described as are important implementation issues, techniques used to achieve reliable communications, and visualization of digital modulation through constellation plots and eye diagrams. Finally, a list of common digital modulation types and their characteristics is given.