The Communications Research Group at the University of Hull graciously invited me to speak on the subject of “Near-Field Wireless Technology.” My hosts inform me that the seminar will start with refreshments, posters and informal discussion from 2.00pm with a 2.30pm start for the main seminar. We should finish about […]
RF-Based Location
22 posts
The Providence Journal has a fascinating piece on the little known story of domestic radio surveillance during WWII. The Intelligence Division of the FCC selected several sites in the U.S. to set up monitoring stations to listen for enemy spies. A wartime short movie featured the radio surveillance effort. The […]
Writing an engaging and interesting book on a technical subject poses a significant challenge. Dive too deeply into the technical minutiae and you risk boring non-technical readers. Skim too superficially and you fail to do the subject justice. In his new book, You Are Here: From the Compass to GPS, […]
A couple of years ago, I surveyed the origins of the GPS system in a Sputnik-inspired satellite navigation system that operated using Doppler shift measurements of satellite signals. The TRANSIT or NAVSAT system yielded 100m – 400m location accuracy (accounts vary). The system included several firsts: the first nuclear powered satellite […]
The story seems an improbable fiction: a famous Hollywood actress invents a secret technology so far ahead of its time that it takes decades for the full potential of her idea to be recognized. Yet in 1941, actress Hedy Lamarr, collaborating with pianist George Anthiel, invented frequency-hopping, spread-spectrum technology. The […]
Reginald Victor Jones (or R. V. Jones) was born one hundred years ago today, on September 29, 1911. Jones was a British physicist who pioneered scientific intelligence, the art of applying scientific analysis to military intelligence. Part Richard Feynman, part Sherlock Holmes, Jones’ job was to anticipate German technical advances […]
I’ll be presenting a paper, “On the Origins of RF-Based Location,” at the 2011 IEEE Radio and Wireless Symposium this morning at 8:00 in room Cira A. The paper collects together the pre-WWII material I’ve blogged about under the History of RF-Based Location category here at ÆtherCzar. This paper will provide […]
The 2011 IEEE Radio and Wireless Symposium kicks off today in Phoenix, Arizona. ÆtherCzar will be live-blogging the proceedings. If you are in attendance, I look forward to seeing you around the conference and particularly at my three formal appearances (all on Wednesday): Paper Presentation: “On the Origins of RF-Based […]
Time for more wireless updates: Here’s a great article about the British precursor to LORAN: “GEE.” GEE was one of the first implementations of the “Time-Difference-of-Arrival (TDOA)” concept used in some modern RTLS implementations. A simple explanation of Ekahau RTLS: “The Perfect Pairing of RF and IR.” Whatever happened to […]
With the launch and tracking of Sputnik in 1957, it soon became obvious that the location of the satellite could be tracked by monitoring its Doppler shift. Frank McClure persuaded fellow researchers at Johns Hopkins Applied Physics Lab to devise a satellite navigation and positioning system based on the Doppler […]
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 […]
High Frequency Direction Finding (HF/DF or “Huff-Duff”) played a critical role in the Second World War. Shore based DF determined the location of German U-boat packs enabling convoys to be routed around them. Ship and airborne DF in conjunction with centimetric radar enabled effective antisubmarine warfare. [1, 2] One of […]
It’s been a busy week, so here is yet another RTLS/RFID update: Mark Roberti of RFID Journal has a new blog entry on the RFID Privacy Conundrum. From the Daily Californian, New Backpack Makes 3D Maps of Buildings H/T: Ericsson Labs Harris unveils firefighter location system. H/T: Stephen J. Crowley […]
Conventional RTLS typically relies on one of three general approaches: Direction Finding (DF): originated by John Stone Stone in 1902, Amplitude Ranging: originated by Lee de Forest in 1904, and Time of Flight (Time Difference of Arrival (TDOA), or Transponder Ranging are typical approaches): orignating in the 1920’s and 1930’s. […]
The Second World War spurred further innovation in RF-based navigation. The first wide-scale deployment of an RF-based location system was the Long Range Navigation or “LORAN.” LORAN was an evolution from a shorter range British system called “GEE.” Like GEE, LORAN employed synchronized impulse signal transmissions from paired transmit towers. […]
By the 1920’s direction finding was well-advanced, and DF techniques began to see everyday use in both marine and aerial navigation. [1] The Figure shows a DF array from around 1930 deployed at Croyden Aerodrome in the UK [2]. Another good example of a sophisticated and relatively simple to use […]
Under optimal conditions during daylight hours, direction finding (DF) accuracy could be as good as one to two degrees (300m at 10km range). [[1]] At night, however, the ionosphere reflects distant signals from over the horizon. The resulting “skywave” signals have a mix of vertical and horizontal polarization components that […]
In 1902, a reporter asked Guglielmo Marconi about the vulnerability of wireless signals to interception. Marconi reassured the journalist, “It isn’t possible without a special installation and without guessing the frequency.” [[1]] The First World War demonstrated the magnitude of Marconi’s error. The Russian Army began the war sending signals […]
Ettore Bellini (1876-1943) and Alessandro Tosi devised a much improved direction-finding system in 1907. [[1]] Their scheme deployed two orthogonal arrays similar to those of Stone. The key advantage of the Bellini-Tosi direction finder was a rotating transformer coupling. Rather than rotate a potentially large antenna system, the Bellini-Tosi system […]
A prolific inventor, Lee de Forest not only invented some of the first direction finding (DF) antenna systems, but also deserves the credit for having invented the first RF ranging system. Realizing that signal strength declines with distance, de Forest proposed inserting a variable resistor into the RF circuit to […]
John Stone Stone (1869-1943) patented the first effective direction finding system in 1902. [[1], [2]] Stone’s scheme involved a two element antenna with a first element (V) arranged no more than a half wavelength away from a second element (V’). The Figure below shows Stone’s invention. The two elements are […]
Communications may have been the first commercial application of wireless technology, but Real-Time Location Systems (RTLS) were close behind. In the first few years of radio, a variety of aggressive inventors recognized the problem of RTLS and leaped to offer solutions. Some of their ideas illustrated the inventors’ misunderstanding of […]