Frequency Modulation (FM)

Frequency modulation (FM) is a method of impressing information onto an RF carrier by means of shifting the frequency of the carrier wave proportionally to changes in the information signal. FM signals are in principle immune to sources of electrical noise that affect the amplitude of a signal, such as static electricity. Furthermore, since the amplitude of an FM modulated signal is constant, the RF amplifiers used to transmit the signal can operate at full saturated power. This operating condition allows for maximum efficiency of transferring DC power to RF power, versus dissipating power as heat. The tradeoff is that FM signals use more spectrum than other modulation formats.
See the WikiPedia article on FM.

FM Modulation Tutorial Applets


Circuit Design Inc. (Japan)

This tutorial and accompanying applet allow you to experiment with FM parameters and see the results at different stages of demodulation. Of particular interest is the applet showing the output spectrum for an adjustable modulation index, based on the values of the Bessel functions for the various sidebands.

Wireless Communications: Principles and Practice


Theodore Rappaport

Wireless Communications, Second Edition is the definitive professional's overview of wireless communications technology and system design. Building on his classic first edition, Theodore S. Rappaport reviews virtually every important new wireless standard and technological development, including W-CDMA, cdma2000, UMTS, and UMC 136/EDGE; IEEE 802.11 and HIPERLAN WLANs; Bluetooth, LMDS, and more. Includes dozens of practical new examples, solved step by step.

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