Chapter Overview

Dozens of modulator circuits have been developed that cause the carrier amplitude to be varied in accordance with the modulating information signal. There are circuits to produce AM, DSB, and SSB at low or high power levels. This chapter examines some of the more common and widely used discrete-component and integrated-circuit (IC) amplitude modulators. Also covered are demodulator circuits for AM, DSB, and SSB.

Chapter Outline

4-1 Basic Principles of Amplitude
4-2 Amplitude Modulators
4-3 Amplitude Demodulators
4-4 Balanced Modulators Modulation
4-5 SSB Circuits

Chapter Objectives

• Explain the relationship of the basic equation for an AM signal to the production of amplitude modulation, mixing, and frequency conversion by a diode or other nonlinear frequency component or circuit.
• Describe the operation of diode modulator circuits and diode detector circuits.
• Compare the advantages and disadvantages of low- and high-level modulation.
• Explain how the performance of a basic diode detector is enhanced by using full wave rectifier circuits.
• Define synchronous detection and explain the role of clippers in synchronous detector circuits.
• State the function of balanced modulators and describe the differences between lattice modulators and IC modulator circuits.
• Draw the basic components of both filter-type and phase-shift-type circuits for generation of SSB signals.