Complete Wireless Design
If you want to climb the learning curve with grace, and start designing what you need immediately, this easy-to-understand guide will help you design an entire radio system from the ground up.
TABLE OF CONTENTS Complete Wireless Design
Chapter 2: Modulation
Different modulation schemes have been adopted for radio services, such as broadband AM and FM for broadcast, narrowband FM for line-of-site two-way voice communications, single sideband (SSB) for long-distance voice communications via the ionosphere, and digital modulation for high-speed point-to-point and multipoint microwave radio communications links.
2.1 Amplitude Modulation
2.1.1 Introduction
Amplitude modulation (AM) is the earliest modulation method for wireless voice communications. It is very simple and cheap to work with from a hardware standpoint, and it is still extensively used today for commercial and shortwave broadcast, as well as in certain citizens band and limited ham radio systems.
2.1.2 Fundamentals
Modulation is the way we insert baseband information on an RF carrier wave. The baseband information can be voice, digital data, analog video, etc. Demodulation is the procedure of extracting this baseband information, which is then sent to a speaker for voice and music, or on to digital circuits for processing or storage.
The most basic way we have of imprinting voice, data, or music on an RF carrier is by modulating the amplitude of the carrier (Fig. 2.1). The unmodulated carrier, which is produced by an oscillator, functions as the RF that will transport the baseband modulation through space to a receiver. The baseband is the intelligence always at a much lower frequency than the RF carrier and is inserted onto the carrier by nonlinear mixing of these two signals. As seen in the time domain, the amplitude of the RF carrier is modified at the rate of...
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