Editing Intermediate frequency (section)

{{Short description|Frequency to which a carrier wave is shifted during transmission or reception}}
{{use dmy dates|date=July 2021|cs1-dates=y}}
[[File:19K1 IF stages.jpg|thumb|The IF stage from a Motorola 19K1 television set ''circa'' 1949]]
In communications and [[electronic engineering]], an '''intermediate frequency''' ('''IF''') is a [[frequency]] to which a [[carrier wave]] is shifted as an intermediate step in [[Transmission (telecommunications)|transmission]] or reception.<ref name="Langford-Smith_1941"/> The intermediate frequency is created by mixing the carrier signal with a [[local oscillator]] signal in a process called [[heterodyning]], resulting in a signal at the difference or [[beat frequency]]. Intermediate frequencies are used in [[Superheterodyne receiver|superheterodyne radio receivers]], in which an incoming signal is shifted to an IF for [[Amplifier|amplification]] before final [[Detector (radio)|detection]] is done.

Conversion to an intermediate frequency is useful for several reasons. When several stages of filters are used, they can all be set to a fixed frequency, which makes them easier to build and to tune. Lower frequency transistors generally have higher gains so fewer stages are required. It's easier to make sharply selective filters at lower fixed frequencies.

There may be several such stages of intermediate frequency in a superheterodyne receiver; two or three stages are called ''[[double conversion (superhet)|double]]'' (alternatively, ''dual'') or ''[[triple conversion (superhet)|triple conversion]]'', respectively.