Editing Spread spectrum (section)

==Invention of frequency hopping==
{{Further|Frequency-hopping spread spectrum}}

The idea of trying to protect and avoid interference in radio transmissions dates back to the beginning of radio wave signaling. In 1899, [[Guglielmo Marconi]] experimented with frequency-selective reception in an attempt to minimize interference.<ref name="kahn">{{Cite book|url=https://books.google.com/books?id=35ClAgAAQBAJ&dq=Marconi+1899&pg=PA158|title=How I Discovered World War II's Greatest Spy and Other Stories of Intelligence and Code|first=David|last=Kahn|authorlink=David Kahn (writer)|date=January 17, 2014|publisher=CRC Press|isbn=9781466561991 |accessdate=November 9, 2022|via=Google Books}}</ref> The concept of [[Frequency-hopping]] was adopted by the German radio company [[Telefunken]] and also described in part of a 1903 US patent by [[Nikola Tesla]].<ref>[https://www.americanscientist.org/article/random-paths-to-frequency-hopping Tony Rothman, Random Paths to Frequency Hopping, American Scientist, January–February 2019 Volume 107, Number 1, Page 46 americanscientist.org]</ref><ref>Jonathan Adolf Wilhelm Zenneck, Wireless Telegraphy, McGraw-Hill Book Company, Incorporated, 1915, page 331</ref> Radio pioneer [[Jonathan Zenneck]]'s 1908 German book ''Wireless Telegraphy'' describes the process and notes that [[Telefunken]] was using it previously.<ref name="kahn"/> It saw limited use by the German military in [[World War I]],<ref name="winter">Denis Winter, ''Haig's Command - A Reassessment''</ref> was put forward by [[Polish people|Polish]] engineer [[Leonard Danilewicz]] in 1929,<ref>Danilewicz later recalled: "In 1929, we proposed to the [[Polish General Staff|General Staff]] a device of my design for secret radio telegraphy which fortunately did not win acceptance, as it was a truly barbaric idea consisting in constant changes of transmitter frequency.  The commission did, however, see fit to grant me 5,000 [[Polish zloty|zlotys]] for executing a model and as encouragement to further work." Cited in [[Władysław Kozaczuk]], ''Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War II'', 1984, p. 27.</ref> showed up in a patent in the 1930s by Willem Broertjes ({{US Patent|1,869,659}} issued Aug. 2, 1932), and in the top-secret [[US Army Signal Corps]] [[World War II]] communications system named [[SIGSALY]].

During World War II, [[Classical Hollywood cinema|Golden Age of Hollywood]] actress [[Hedy Lamarr]] and avant-garde [[composer]] [[George Antheil]] developed an intended jamming-resistant radio guidance system for use in Allied [[torpedo]]es, patenting the device under {{US Patent|2,292,387}} "Secret Communications System" on August 11, 1942. Their approach was unique in that frequency coordination was done with paper player piano rolls, a novel approach which was never put into practice.<ref>Ari Ben-Menahem, Historical Encyclopedia of Natural and Mathematical Sciences, Volume 1, Springer Science & Business Media - 2009, pages 4527-4530</ref>