RTLS: The First Ultrawideband Wireless System

The 1942 frequency-hopping spread spectrum invention (US Patent 2,292,387) issued to H.K. Markey (Hedy Lamarr) and George Antheil exemplifies the variety of wide band signaling. Image Copyright © D. McKeown and K. Siwiak, 2003-2010. Used with permission.

Spread-spectrum and ultra-wideband (UWB) technology arose during the Second World War. Actress Hedy Kiesler Markey (better known by her screen name, Hedy Lamarr) and George Antheil invented a frequency-hopping secret communication system. [1] The  Figure below shows their frequency hopping transmitter. A record tape encodes a unique coding pattern to a network of tuning capacitors controlling a variable frequency carrier oscillator. The signal is thus virtually impossible to decode without knowledge of the frequency hopping pattern. The lack of regard for Lamarr’s invention at the time is evidenced by the fact that it was promptly allowed and published instead of being kept confidential for the duration of the conflict.

A classic example of an invention ahead of its time, spread spectrum and ultra-wideband technologies did not come into vogue until after Lamarr’s patent had already expired.

The first spread-spectrum RF system was proposed by Hedy Lamarr and George Antheil. A record tape controls which of a selection of capacitors tunes a variable oscillator.

More comprehensive histories of the development of spread spectrum and ultra-wideband technology are available elsewhere. [2], [3], [4], [5]

[1]       Hedy Kiesler Markey and George Antheil, Secret communication system, US Patent 2,292,387, August 11, 1942.

[2]      Robert Scholtz, “Notes on Spread Spectrum History,” IEEE Trans. on Communications, Vol. 31, No. 1, January 1983.

[3]      See “Spread Spectrum History” at http://www.sss-mag.com/shistory.html

[4]     See “Female Inventors – Hedy Lamarr” at http://www.inventions.org/culture/female/lamarr.html

[5]     Terence W. Barrett, “History of UltraWideBand (UWB) Radar & Communications: Pioneers and Innovators,” Progress in Electromagnetics Symposium 2000 (PIERS2000), Cambridge, MA, July 2000.

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