Early spark gap "Wireless era" transmitters actually used Spread Spectrum,
since their RF bandwidths were much wider than their information bandwidth. The first intentional
use of Spread Spectrum, however, was probably by Armstrong in the late '20's or early '30's with wideband FM.
The real impetus for Spread Spectrum came with World War II.
Both the allies and the Axis powers experimented with simple Spread Spectrum systems. Much of
what was done is still shrouded in secrecy even 60 years later. The first publically available patent on
Spread Spectrum came from Hedy Lamarr, the Hollywood movie actress, and George Antheil, an avant gard
composer. This patent was granted in 1942, but the details were a closely held military secret for many
years. The inventors never realized a dime for their invention; they simply turned it over to the US
Government for use in the war effort, and commercial use was delayed until after the patent
had expired.
Most of the work done in Spread Spectrum
throughout the '50s, '60s and '70s was heavily backed by the military and drowned in secrecy.
The GPS system is now the world's largest single Spread Spectrum system. Most of the details on
GPS are now public information (see "The Geographer's Craft Project," The University of Colorado).
Spread Spectrum was first used for commercial purposes in the 1980s when Equatorial Communications
of Mountain View, CA used Direct Sequence for multiple access communications over synchronous
satellite transponders. Later in the '80s, the US FCC opened up the ISM frequency bands for
unlicensed Spread Spectrum communications (see Spread Spectrum Technology).
There is a fair amount of historical information relative to
Spread Spectrum on the Internet these days, but much of it is duplicative. We present below
a few of the better links we have found:
"Secret Communications Technique" —
article, pictures, copies of the original patent, and other information from Chris Beaumont,
George Antheil's son. See the link on Hedy Lamar for a 1990 Forbes article that gives
details on Miss Lamar's role in the invention.
And here's a book from Amazon. Although the title is Spread Spectrum, the subtitle (illegible in
this picture) is "Hedy Lamarr and the
Mobile Phone." The author, Rob Walters, used to lecture on spread spectrum - especially UMTS, but
this book is a lighter look at the evolution of the technology and Hedy
Lamarr and George Antheil's life. For more information on the book and the author, visit the
author's site or click the link to Amazon below.
