Editing Ring modulation (section)

{{Short description|Frequency mixing function in signal processing}}
{{Use dmy dates|date=August 2019}}
{{Use American English|date=March 2020}}

[[File:Ring Modulator.PNG|thumb|right|300px|Schematic diagram of a [[ring modulator]], showing ring of [[diode]]s]]
[[File:Ring modulation two forms Multiplilcation RM.svg|thumb|upright=1.1|An example of ring modulation on sine waves of frequency <math>f</math> (top) and <math>12f</math> (middle), producing a variation in amplitude of the sine wave-like frequency on <math>12f</math> (bottom)<ref name="Roads">[[Curtis Roads]] (1996). ''[https://books.google.com/books?id=nZ-TetwzVcIC&pg=PA220 The Computer Music Tutorial]'', pp. 220-221. MIT Press. {{ISBN|9780262680820}}.</ref>]]

In [[electronics]], '''ring modulation''' is a [[signal processing]] function, an implementation of [[frequency mixing]], in which two [[signal]]s are combined to yield an output signal. One signal, called the carrier, is typically a [[sine wave]] or another simple [[waveform]]; the other signal is typically more complicated and is called the input or the [[modulator]] signal.

The '''ring modulator''' takes its name from the original implementation in which the [[analog circuit]] of [[diode]]s takes the shape of a ring, a '''diode ring'''.<ref>Richard Orton, "Ring Modulator", ''The New Grove Dictionary of Music and Musicians'', page 429, volume 21, second edition, edited by [[Stanley Sadie]] and [[John Tyrrell (professor of music)|John Tyrrell]] (London: Macmillan Publishers, 2001)</ref> The circuit is similar to a [[bridge rectifier]], except that all four diodes are polarized in the same direction.

Ring modulation is similar to [[amplitude modulation]], with the difference that in the latter the modulator is shifted to be positive before being multiplied with the carrier, while in the former the unshifted modulator signal is multiplied with the carrier. This has the effect that ring modulation of two sine waves having frequencies of 1,500 Hz and 400 Hz produce an output signal that is the sum of a sine wave with frequency 1,900 Hz and one with frequency 1,100 Hz. These two output frequencies are known as [[sideband]]s. If one of the input signals has significant [[overtones]] (which is the case for [[Square wave (waveform)|square waves]]), the output sounds quite different, since each [[harmonic]] generates its own pair of sidebands that is not harmonically-related.<ref>[[Allen Strange|Strange, Allen]] (1972). ''Electronic Music'', p. 11. Wm. C. Brown Co. Publishers. {{ISBN|0-697-03612-X}}.</ref>