Practical Signals Theory with MATLAB Applications

Introduction to Communications

In this chapter, the reader will find examples and applications that demonstrate the pivotal role of signals theory in the world of communications systems. The chapter explores a selection of applications of signals theory to the transmission and reception of information, particularly by radio. Various approaches to modulation and demodulation are presented from a signals perspective. Practical problems associated with the design and operation of radio receivers also find elegant solutions through the theory of signals and systems that has been elaborated in earlier chapters.

LEARNING OBJECTIVES

By the end of this chapter, the reader will be able to:

• Describe the desirable properties of a carrier signal
• Identify bands in the radio spectrum by frequency and wavelength
• Explain the concepts of amplitude, frequency, or phase modulation
• List different forms of amplitude modulation (AM)
• Apply signals theory to relate message bandwidth to transmitted bandwidth
• Explain receiver sensitivity and selectivity
• Describe the operation of a superheterodyne receiver
• List different types of digital modulation methods
• Create digital modulation schemes from analog principles

10.1 Introduction

Almost every day it seems that some new communication device is enhancing our lives. In recent years, an astonishing variety of new communications services have moved from ...