Frequency Modulation ( FM ) Tutorial

Lawrence Der, Ph.D. Silicon Laboratories Inc. Introduction Edwin H. Armstrong, known as one of the founding fathers of radio technology, invented the superheterodyne radio receiver in 1918 and frequency modulation (FM) in 1933 [1]. These two concepts, along with his regenerative circuit technique developed in 1912, formed the basis of radio frequency electronics as we know it today. In the United States, FM radio stations broadcast between radio frequencies of 88 MHz to 108 MHz with a channel bandwidth of 200 kHz. FM radio was first deployed in monaural in 1940; and in 1960, FM stereo was introduced. This article presents a basic tutorial on FM with descriptions of multiplex (MPX) signaling and noise improvement techniques such as stereo-mono blending and soft mute.