Chapter Overview

A radio transmitter takes the information to be communicated and converts it to an electronic signal compatible with the communication medium. Typically this process involves carrier generation, modulation, and power amplification. The signal is then fed by wire, coaxial cable, or waveguide to an antenna that launches it into free space. This chapter covers transmitter configurations and the circuits commonly used in radio transmitters, including oscillators, amplifiers, frequency multipliers, and impedance-matching networks.

Chapter Outline

8-1 Transmitter Fundamentals
8-2 Carrier Generators
8-3 Power Amplifiers
8-4 Impedance-Matching Networks
8-5 Typical Transmitter Circuits

Chapter Objectives

• Calculate the frequency tolerance of crystal oscillators in percent and in parts per million (ppm).
• Discuss the operation of phase-locked loop (PLL) and direct digital synthesis (DDS) frequency synthesizers and explain how the output frequency is changed.
• Calculate the output frequency of a transmitter given the oscillator frequency and the number and types of multipliers.
• Explain the biasing and operation of class A, AB, and C power amplifiers using transistors.
• Define neutralization and explain how it is implemented.
• Discuss the operation and benefits of class D, E, and F switching amplifiers and explain why they are more efficient.
• Explain the basic design of L, , and T-type LC circuits and discuss how they are used for impedance matching.
• Explain the use of transformers and baluns in impedance matching.