Editing Frequency-hopping spread spectrum (section)

==Origins==
In 1899, [[Guglielmo Marconi]] experimented with frequency-selective reception in an attempt to minimise interference.<ref>{{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|page=158|publisher=[[Auerbach Publications]]|date=2014|isbn=9781466561991}}</ref>

The earliest mentions of frequency hopping in open literature are in [https://patents.google.com/patent/US725605 US patent 725,605], awarded to [[Nikola Tesla]] on March 17, 1903,<ref name="American Scientist">{{cite magazine|url=https://www.americanscientist.org/article/random-paths-to-frequency-hopping|title=Random Paths to Frequency Hopping|magazine=[[American Scientist]]|author = Rothman, Tony|date=Jan–Feb 2019|volume=107|issue=1|page=46|doi=10.1511/2019.107.1.46|access-date=27 March 2024}}</ref> and in radio pioneer [[Jonathan Zenneck]]'s book ''Wireless Telegraphy'' (German, 1908, English translation McGraw Hill, 1915),<ref name="Zenneck1915">{{cite book |last= Zenneck |title= Wireless Telegraphy |first= Jonathan |date= August 1915 |orig-date=1908 |translator-last1= Seelig |translator-first1= Alfred |publisher= McGraw-Hill |location= New York |edition = 5th |chapter = Receivers |page= 331 }}</ref>{{efn |name="Zennek1915" |"Furthermore the apparatus can be so arranged that the wave-length is easily and rapidly changed and then vary the wave-length in accordance with a prearranged program, perhaps automatically. (This method was adopted by the Telefunken Co. at one time.)" Zenneck describes additional methods of security, including synchronizing receiving to only a subset of transmission.}} although Zenneck writes that [[Telefunken]] had already tried it. Nikola Tesla doesn't mention the phrase "frequency hopping" directly, but certainly alludes to it. Entitled ''Method of Signaling'', the patent describes a system that would enable radio communication ''without any danger of the signals or messages being disturbed, intercepted, interfered with in any way''.<ref name="eetimes">{{cite web| url = https://www.eetimes.com/a-short-history-of-spread-spectrum/| website = [[EE Times]]| title = A short history of spread spectrum| date = January 26, 2012}}</ref>

The German military made limited use of frequency hopping for communication between fixed command points in [[World War I]] to prevent eavesdropping by British forces, who did not have the technology to follow the sequence.<ref name="winter">{{cite book |author=Denis Winter |title=Haig's Command - A Reassessment}}</ref> Jonathan Zenneck's book ''Wireless Telegraphy'' was originally published in German in 1908, but was translated into English in 1915 as the enemy started using frequency hopping on the front line.

In 1920, Otto B. Blackwell, De Loss K. Martin, and Gilbert S. Vernam filed a patent application for a "Secrecy Communication System", granted as [https://patents.google.com/patent/US1598673A U.S. Patent 1,598,673] in 1926. This patent described a method of transmitting signals on multiple frequencies in a random manner for secrecy, anticipating key features of later frequency hopping systems.<ref name="American Scientist" />

A [[Polish people|Polish]] engineer and inventor, [[Leonard Danilewicz]], claimed to have suggested the concept of frequency hopping in 1929 to the [[Polish General Staff]], but it was rejected.<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|zloty]]s for executing a model and as encouragement to further work." Cited in {{cite book|author=Władysław Kozaczuk |author-link=Władysław Kozaczuk |title=Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War II |date=1984 |page=27}}</ref>

In 1932, {{US Patent|1,869,659}} was awarded to Willem Broertjes, named "Method of maintaining secrecy in the transmission of wireless telegraphic messages", which describes a system where "messages are transmitted by means of a group of frequencies... known to the sender and receiver alone, and alternated at will during transmission of the messages".

During [[World War II]], the [[US Army Signal Corps]] was inventing a communication system called [[SIGSALY]], which incorporated spread spectrum in a single frequency context. But SIGSALY was a top-secret communications system, so its existence was not known until the 1980s.

In 1942, actress [[Hedy Lamarr]] and composer [[George Antheil]] received {{US patent|2,292,387}} for their "Secret Communications System",<ref name="apt-news">{{cite magazine|url=https://www.aps.org/publications/apsnews/201106/physicshistory.cfm|title=June 1941: Hedy Lamarr and George Antheil submit patent for radio frequency hopping|magazine=[[APS News]]|date=June 2011|volume=20|issue=6}}</ref><ref>{{cite web|url=https://www.scientificamerican.com/article/hedy-lamarr-not-just-a-pr/|title=Hedy Lamarr: Not just a pretty face|first=Melinda|last=Wenner|date=June 3, 2008|website=[[Scientific American]]}}</ref> an early version of frequency hopping using a [[Piano roll|piano-roll]] to switch among 88 frequencies to make radio-guided [[torpedo]]es harder for enemies to detect or jam. They then donated the patent to the [[United States Navy|U.S. Navy]].<ref>{{cite web |last1=Iancu |first1=Andrei |author1-link = Andrei Iancu|title=Remarks by Director Andrei Iancu at 2018 Military Invention Day |url=https://www.uspto.gov/about-us/news-updates/remarks-director-andrei-iancu-2018-military-invention-day |website=[[United States Patent and Trademark Office]] |date=19 May 2018 |publisher=[[United States Department of Commerce]] |access-date=25 February 2024}}</ref>

Frequency-hopping ideas may have been rediscovered in the 1950s during patent searches when private companies were independently developing direct-sequence [[Code Division Multiple Access]], a non-frequency-hopping form of spread-spectrum.{{citation needed|date=July 2023}} In 1957, engineers at Sylvania Electronic Systems Division adopted a similar idea, using the recently invented transistor instead of Lamarr's and Antheil's clockwork technology.<ref name="apt-news" />{{dubious|date=October 2022}} In 1962, the US Navy utilized Sylvania Electronic Systems Division's work during the [[Cuban Missile Crisis]].<ref>{{cite magazine|url=https://physicsworld.com/a/a-tale-of-two-lives/|title=A tale of two lives|first=Tushna|last=Commissariat|date=August 1, 2018|magazine=[[Physics World]]}}</ref>

A practical application of frequency hopping was developed by [[Ray Zinn]], co-founder of Micrel Corporation. Zinn developed a method allowing radio devices to operate without the need to synchronize a receiver with a transmitter. Using frequency hopping and sweep modes, Zinn's method is primarily applied in low data rate wireless applications such as utility metering, machine and equipment monitoring and metering, and remote control. In 2006 Zinn received {{US patent| 6,996,399}} for his "Wireless device and method using frequency hopping and sweep modes."