Frequency modulation

Frequency modulation (FM) is the encoding of <a href="/facts/Information/3LdrzXtJ">information</a> in a <a href="/facts/Carrier_wave/ae98pBlY">carrier wave</a> by varying the <a href="/facts/Instantaneous_frequency/fJ17zuan">instantaneous frequency</a> of the wave. The technology is used in <a href="/facts/Telecommunications/vxoj1cxR">telecommunications</a>, <a href="/facts/Radio_broadcasting/FLJVq8Ec">radio broadcasting</a>, <a href="/facts/Signal_processing/Npaja6zb">signal processing</a>, and <a href="/facts/Run-length_limited/WkGWpAGR">computing</a>.
In <a href="/facts/Analog_signal/xDbb4uB5">analog</a> frequency modulation, such as radio broadcasting, of an audio signal representing voice or music, the instantaneous <a href="/facts/Frequency_deviation/922FDF7s">frequency deviation</a>, i.e. the difference between the frequency of the carrier and its center frequency, has a functional relation to the modulating signal amplitude.
<a href="/facts/Digital_data/JChckAvr">Digital data</a> can be encoded and transmitted with a type of frequency modulation known as <a href="/facts/Frequency-shift_keying/Bp1jJDPX">frequency-shift keying</a> (FSK), in which the instantaneous frequency of the carrier is shifted among a set of frequencies. The frequencies may represent digits, such as 0 and 1. FSK is widely used in computer <a href="/facts/Modem/9H0Xwtq0">modems</a> such as <a href="/facts/Fax_modem/MaodMB2Q">fax modems</a>, telephone <a href="/facts/Caller_ID/hh9DqEEj">caller ID</a> systems, garage door openers, and other low-frequency transmissions. <a href="/facts/Radioteletype/9Iv7HE0H">Radioteletype</a> also uses FSK.
Frequency modulation is widely used for <a href="/facts/FM_broadcasting/TpKl3FJv">FM radio</a> <a href="/facts/Broadcasting/AV1f3dGy">broadcasting</a>. It is also used in <a href="/facts/Telemetry/Mz9czXTl">telemetry</a>, <a href="/facts/Radar/jk9BTbFA">radar</a>, seismic prospecting, and monitoring <a href="/facts/Newborn/gaEL1QL4">newborns</a> for seizures via <a href="/facts/EEG/XGvpcBl5">EEG</a>, <a href="/facts/Two-way_radio/e6JKFtdo">two-way radio</a> systems, <a href="/facts/Frequency_modulation_synthesis/9wALwfgD">sound synthesis</a>, magnetic tape-recording systems and some video-transmission systems. In radio transmission, an advantage of frequency modulation is that it has a larger <a href="/facts/Signal-to-noise_ratio/qohClhyG">signal-to-noise ratio</a> and therefore rejects <a href="/facts/Radio_frequency_interference/gv3DlKNr">radio frequency interference</a> better than an equal power <a href="/facts/AM_broadcasting/oS0rn1lg">amplitude modulation (AM)</a> signal. For this reason, most music is broadcast over FM radio.
Frequency modulation and <a href="/facts/Phase_modulation/ws1kz7Y9">phase modulation</a> are the two complementary principal methods of <a href="/facts/Angle_modulation/TrFWfy8r">angle modulation</a>; phase modulation is often used as an intermediate step to achieve frequency modulation. These methods contrast with <a href="/facts/Amplitude_modulation/3sTxsXk6">amplitude modulation</a>, in which the <a href="/facts/Amplitude/aEckuXJM">amplitude</a> of the carrier wave varies, while the frequency and phase remain constant.

Frequency modulation open-in-new

Frequency modulation