RF Power Amplifier, 2nd Edition

Chapter 1Introduction

1.1 Radio Transmitters

Radio communication utilizes radio waves as a transmission and receiving medium. A radio transmitter consists of information source producing modulating signal, modulator, radio-frequency (RF) power amplifier, and antenna. A power amplifier is a circuit that increases the power level of a signal by using energy taken from a power supply [1–28]. Both the efficiency and distortion are critical parameters of power amplifiers. A radio receiver consists of an antenna, front end, demodulator, and audio amplifier. A transmitter and receiver combined into one electronic device is called a transceiver. A radio transmitter produces a strong RF current, which flows through an antenna. In turn, a transmitter antenna radiates electromagnetic waves (EMWs), called radio waves. Transmitters are used for communication of information over a distance, such as radio and television broadcasting, mobile phones, wireless computer networks, radio navigation, radio location, air traffic control, radars, ship communication, radio-frequency identifications (RFIDs), collision avoidance, speed measurement, weather forecasting, and so on. The information signal is the modulating signal, and it is usually in the form of audio signal from a microphone, video signal from a camera, or digital signal. Modern wireless communication systems include both amplitude-modulated (AM) and phase-modulated (PM) signals with a large peak-to-average ratio (PAR). Typically, the ...