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.

Wireless Communications Resources Collection

Author

Circuit Design Inc. (Japan)

A collection calculators, such as:

Wave propagation calculation tool (for free-space and 2 wave model)
Fresnel zone calculation tool
Okumura-Hata curve calculation tool
Creating a channel plan in order to avoid third-order intermodulation interference and the near-far problem tool
Height pattern calculation tool
Mutual conversion of decibel value and true value

Web apps are utilized in the tutorials to allow you to experiment with the concepts

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FM Modulation Tutorial Applets

Author

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.

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Wireless Communications: Principles and Practice

Author

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.