Editing Crystal oscillator (section)

==History==
[[Image:Early NBS crystal oscillator frequency standards.jpg|thumb|100 kHz crystal oscillators at the US National Bureau of Standards that served as the frequency standard for the United States in 1929]]

[[File:Crystal Units Frequency Standard Oscillator XO VCXO OCXO TCXO Bell Labs AT&T Vectron.jpg|thumb|right|Very early Bell Labs crystals from Vectron International Collection]]

[[Piezoelectricity]] was discovered by [[Jacques Curie|Jacques]] and [[Pierre Curie]] in 1880. [[Paul Langevin]] first investigated quartz resonators for use in [[sonar]] during World War I. The first crystal-controlled [[electronic oscillator|oscillator]], using a crystal of [[Rochelle salt]], was built in 1917 and patented<ref name="Nicholson">Nicholson, Alexander M. ''Generating and transmitting electric currents'' {{US patent|2212845}}, filed April 10, 1918, granted August 27, 1940</ref> in 1918 by [[Alexander M. Nicholson]] at [[Bell Telephone Laboratories]], although his priority was disputed by [[Walter Guyton Cady]].<ref name="Bottom1981">{{cite conference|last=Bottom|first=Virgil E.|title=A history of the quartz crystal industry in the USA|year=1981|book-title=Proc. 35th Frequency Control Symp.|publisher=IEEE|url=http://www.ieee-uffc.org/fc_history/bottom.html|url-status=dead|archive-url=https://web.archive.org/web/20080920080605/http://www.ieee-uffc.org/fc_history/bottom.html|archive-date=2008-09-20}}</ref> Cady built the first quartz crystal oscillator in 1921.<ref name="Marrison1948">{{cite journal|last=Marrison|first=Warren|title=The Evolution of the Quartz Crystal Clock|year=1948|journal=Bell System Technical Journal|publisher=AT&T|volume=27|issue=3|pages=510–588|url=http://www.ieee-uffc.org/main/history.asp?file=marrison|doi=10.1002/j.1538-7305.1948.tb01343.x|url-status=dead|archive-url=https://web.archive.org/web/20110717061023/http://www.ieee-uffc.org/main/history.asp?file=marrison|archive-date=2011-07-17|url-access=subscription}}</ref>
Other early innovators in quartz crystal oscillators include [[G. W. Pierce]] and [[Louis Essen]].

Quartz crystal oscillators were developed for high-stability frequency references during the 1920s and 1930s.  Prior to crystals, radio stations controlled their frequency with [[tuned circuit]]s, which could easily drift off frequency by 3–4&nbsp;kHz.<ref name="Bayard">{{cite journal
  | last = Bayard
  | first = Thomas L.
  | title = The New "Crystal Pilot"
  | journal = Popular Radio
  | volume = 9
  | issue = 4
  | pages = 342–347
  | publisher = Popular Radio, Inc.
  | location = New York
  |date=April 1926
  | url = http://www.americanradiohistory.com/Archive-Popular-Radio/Popular-Radio-1926-04.pdf
  | access-date = August 24, 2014}}</ref>  Since broadcast stations were assigned frequencies only 10&nbsp;kHz (Americas) or 9&nbsp;kHz (elsewhere) apart, interference between adjacent stations due to frequency drift was a common problem.<ref name="Bayard" /> In 1925, Westinghouse installed a crystal oscillator in its flagship station KDKA,<ref name="Bayard" /> and by 1926, quartz crystals were used to control the frequency of many broadcasting stations and were popular with amateur radio operators.<ref>Virgil E. Bottom, [https://web.archive.org/web/20080920080605/http://www.ieee-uffc.org/fc_history/bottom.html A History of the Quartz Crystal Industry in the USA], Proceedings of the 35th Annual Frequency Control Symposium 1981. Ieee-uffc.org. Retrieved on 2012-06-21.</ref> In 1928, Warren Marrison of Bell Laboratories developed the first [[Quartz clock|quartz-crystal clock]]. With accuracies of up to 1 second in 30 years (30&nbsp;ms/y, or 0.95&nbsp;ns/s),<ref name="Marrison1948"/>  quartz clocks replaced precision [[pendulum clock]]s as the world's most accurate timekeepers until [[atomic clock]]s were developed in the 1950s.   Using the early work at Bell Laboratories, American Telephone and Telegraph Company (AT&T) eventually established their Frequency Control Products division, later spun off and known today as Vectron International.<ref>[http://www.mwrf.com/Articles/Index.cfm?Ad=1&ArticleID=20304 Microwaves and RF Journal. Retrieved July 17, 2011] {{Webarchive|url=https://web.archive.org/web/20110928215132/http://www.mwrf.com/Articles/Index.cfm?Ad=1&ArticleID=20304 |date=September 28, 2011 }}. Mwrf.com. Retrieved on 2012-06-21.</ref>

A number of firms started producing quartz crystals for electronic use during this time.    Using what are now considered primitive methods, about 100,000 crystal units were produced in the United States during 1939.  Through [[World War II]] crystals were made from natural quartz crystal, virtually all from [[Brazil]].  Shortages of crystals during the war caused by the demand for accurate frequency control of military and naval [[radio]]s and [[radar]]s spurred postwar research into culturing synthetic quartz, and by 1950 a [[Hydrothermal synthesis|hydrothermal]] process for growing quartz crystals on a commercial scale was developed at Bell Laboratories. By the 1970s virtually all crystals used in electronics were synthetic.

In 1968, Juergen Staudte invented a [[Photolithography|photolithographic]] process for manufacturing quartz crystal oscillators while working at [[North American Aviation]] (now [[Rockwell International|Rockwell]]) that allowed them to be made small enough for portable products like watches.<ref>[http://invention.smithsonian.org/centerpieces/Quartz/inventors/staudte.html Inventors Staudte The Quartz Watch] {{Webarchive|url=https://web.archive.org/web/20100401133600/http://invention.smithsonian.org/centerpieces/Quartz/inventors/staudte.html |date=2010-04-01 }}. Invention.smithsonian.org. Retrieved on 2012-06-21.</ref>

Although crystal oscillators still most commonly use quartz crystals, devices using other materials are becoming more common, such as [[ceramic resonator]]s.

[[File:Crystal modes multilingual.svg|thumb|right|150px|Crystal oscillation modes]]