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Sun Aug 11, 2019, 09:09 AM

77 Years Ago Today; Hedy Lamarr & George Antheil receive patent for Frequency-hopping spread spectru

https://en.wikipedia.org/wiki/Frequency-hopping_spread_spectrum





Frequency-hopping spread spectrum (FHSS) is a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. It is used as a multiple access method in the code division multiple access (CDMA) scheme frequency-hopping code division multiple access (FH-CDMA).

Each available frequency band is divided into sub-frequencies. Signals rapidly change ("hop" ) among these in a predetermined order. Interference at a specific frequency will only affect the signal during that short interval. FHSS can, however, cause interference with adjacent direct-sequence spread spectrum (DSSS) systems.

Adaptive frequency-hopping spread spectrum (AFH), a specific type of FHSS, is used in Bluetooth wireless data transfer.

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Multiple inventors
In 1899 Guglielmo Marconi experimented with frequency-selective reception in an attempt to minimise interference.

The earliest mentions of frequency hopping in the open literature are in US patent 725,605 awarded to Nikola Tesla in March 17, 1903 and in radio pioneer Jonathan Zenneck's book Wireless Telegraphy (German, 1908, English translation McGraw Hill, 1915), although Zenneck himself states 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 .

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.

A Polish engineer and inventor, Leonard Danilewicz, came up with the idea in 1929. Several other patents were taken out in the 1930s, including one by Willem Broertjes (U.S. Patent 1,869,659, issued Aug. 2, 1932).

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. However, SIGSALY was a top-secret communications system, so its existence did not become known until the 1980s.

A patent was awarded to actress Hedy Lamarr and composer George Antheil, who in 1942 received U.S. Patent 2,292,387 for their "Secret Communications System". This intended early version of frequency hopping was supposed to use a piano-roll to change among 88 frequencies, and was intended to make radio-guided torpedoes harder for enemies to detect or to jam, but there is no record of a working device ever being produced. The patent was rediscovered in the 1950s during patent searches when private companies independently developed Code Division Multiple Access, a non-frequency-hopping form of spread-spectrum, and has been cited numerous times since.

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 U.S. Patent 6,996,399 for his "Wireless device and method using frequency hopping and sweep modes."

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Oops! That's Hedy...

6 replies, 992 views

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Reply 77 Years Ago Today; Hedy Lamarr & George Antheil receive patent for Frequency-hopping spread spectru (Original post)
Dennis Donovan Aug 11 OP
oasis Aug 11 #1
colsohlibgal Aug 11 #2
pangaia Aug 11 #3
Wounded Bear Aug 11 #4
Anon-C Aug 11 #5
Sherman A1 Aug 11 #6

Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 09:17 AM

1. Hedy Lamarr, what a great life story. nt

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Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 09:38 AM

2. Read Her Bio

She was a glamour Gal for sure but also brilliant.

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Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 10:12 AM

3. BALLET MECHANIQUE

i PLAYED THIS IN ABOUT 1966-67.Fun and terribly difficult.



The other end of the Antheil spectrum--

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Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 10:14 AM

4. The Heddy Lamarr story about RF techniques has always fascinated me...

Thanks for the link!

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Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 10:50 AM

5. Wow. I had no idea!

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Response to Dennis Donovan (Original post)

Sun Aug 11, 2019, 12:12 PM

6. Watched her biography piece

on Canopy through the local library. She was certainly an interesting figure.

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