Friday, December 18, 2020

The Genesis of Spread Spectrum Radio – Weapons, Wireless, and Hollywood

Spread-Spectrum radio communications, long a favorite wireless technology of the military, as it resists jamming and is hard for anyone trying to capture its message content. Today, spread-spectrum is also found on the commercial wireless industry.

Spread-spectrum signals are randomly coded and distributed over a wide range of frequencies, then reassembled onto their original frequency at a receiver.  Just as these signals are unlikely to be intercepted by an enemy, so are they unlikely to interfere with other signals intended for consumer wireless devices. There are two major types of spread spectrum:  direct sequence and frequency hopping.  Spread Spectrum is ubiquitous, as it is found in Satellites, Cellular, Bluetooth and Wi-Fi wireless technology.   

This technology was invented in the early 1940’s, initially the US experimented with spread spectrum for communication countermeasures, radar, and navigation beacons.

Hedy Lamarr
A 19-year-old young lady from Vienna, Austria, who in 1933 married a millionaire and a Nazi sympathizer, is responsible for this wireless technology.  Her husband, Friz Mandl and his family, were munitions manufacturers and arms dealers.  As the Mandl family was involved in arms, they had contacts with the highest levels of the people controlling Germany and Italy, both Benito Mussolini and Adolf Hitler attended Mandl's parties.

During her four-year marriage to Mandl, this young lady learned and studied weaponry by going on business trips with her husband, learning and listening to discussions regarding all kinds of weaponry and their control systems.  

Eventually, her disgust for the Nazis and a controlling and abusive husband, she disguised herself as a maid and escaped to Paris, where she got a divorce.

This young lady’s name was Hedwig Eva Maria Kiesler Mandl, she was born in 1914. Hedwig eventually met MGM’s Louis B. Mayer in London, who brought her to Hollywood and gave her a movie contract and a new name – Hedy Lamarr.  

CBS news once stated that Hedy Lamarr “possessed the kind of beauty that was haunting - an almost smoldering sensuality, with an exotic accent to match. She was once dubbed "the most beautiful woman in the world".   Hedy had a great deal of fame and fortune, as she appeared in about 30 movies over a 20-year period.
Lamarr "the most beautiful woman in the world"

After her first US movie; one viewer stated that when her face first appeared on the screen, "everyone gasped...Lamarr's beauty literally took one's breath away”

The intellectual side of Lamarr was not known or understood until later in her life.

At home, Lamarr had a comprehensive library of math and engineering reference books, a drafting table and tools where she spent time analyzing engineering problems.  What was a Hollywood star doing inventing electrical engineering circuits? 

In 1940 she met George Antheil, an American composer, pianist, author, inventor, electrical, mechanical music entrepreneur, and also an “expert” on female endocrinology where she was seeking his help on improving her upper torso.  They soon found that they had more in common - torpedoes.
George Antheil
With her knowledge of torpedoes learned while married to Mandl, she knew that a single radio controlled torpedo could easily be detected and jammed, by transmitting interference at the frequency of the signal that causes the torpedo to go off course.

With their common interest in torpedoes, Lamarr and Antheil developed the idea of using frequency hopping.  Their collaboration resulted in using a piano for coding.   A piano “roll” was used to randomly change the wireless signal sent to the torpedo by sending short bursts of 88 frequencies in the spectrum; note there are 88 black and white keys on a piano keyboard.

This scenario basically made it impossible for the enemy to find and jam all 88 frequencies. Antheil would control the frequency-hopping sequence [coding] by using a player-piano mechanism, which he had used in his “Ballet Mécanique”.       

A player-piano is a self-playing piano that uses perforated paper, where pre-programmed music is recorded – in this case the piano roll.

In 1942, after initial failure and rejection from the US Patent Office, Hedy and Antheil were granted a patent for their “secret” communication systems.  The patent was under the name of Hedy Keisler Markey, which was her married name at the time.  Hedy's idea was if you could make both the transmitter and the receiver simultaneously jump from frequency to frequency, then someone trying to jam the signal wouldn't know where the signal was – secure communications utilizing frequency hoping.
Lamarr-Antheil Spread-Spectrum Patent

Lamarr was involved in the war effort by promoting war bonds.  She stated “I’m still determined to help the war effort with or without my torpedo invention, I will be offering a kiss to anyone who donates $25,000 in war bonds - come out and support the fight against Hitler”.

Hedy quietly signed her patent over to the Navy. Like other wireless inventors, she gave the technology away, and never made a dime off of it. Others took the technology and improved on it, as well as the credit for it.  In an autobiography, Antheil gives full credit to Lamarr for the invention of spread-spectrum technology.

In 1953, Lamarr became a U.S. citizen.  In her later years, she lived a reclusive life in Orlando, FL.  It took more than 50 years for Hedy to receive credit for her invention. During her lifetime, she was given awards but never showed up to received them. 

Lamarr died on January 19, 2000, she was 86. 

In 2014, Hedy Lamarr was inducted into the National Inventors Hall of Fame.