Sep. 29, 1997 A prototype RADAR flashlight that can detect a human's presence through walls and doors could one day be used by police officers, prison guards and others to make their jobs safer.
The device, for which a patent application has been filed, uses a radar and a specialized signal processor to detect movement. The RADAR flashlight discerns respiration from up to three meters away, with no physical connection between subject and radar. photo copyright information
Part of a Family of Technologies
The development is part of a family of technologies that also detects heartbeat, explained Gene Greneker, a principal research scientist at the Georgia Tech Research Institute (GTRI).
"Based on respiration signature alone, the RADAR flashlight allows us to detect a stationary individual behind a solid wooden door, or standing four feet behind an eight-inch block wall," said Greneker. "These qualities make the flashlight potentially useful to police officers in ambush situations, and to prison guards doing bed checks."
The Georgia Tech-funded project uses a rather narrow radar beam of about 15 to 20 degrees to detect body movement generated by breathing.
Additional potential applications include:
Locating people in a room during a hostage situation, based on their movement or radar respiration signature; immobilized people could be located via respiration signature alone.
Finding survivors in the rubble of earthquakes or accidents. The amount of electromagnetic radiation exposure from the flashlight is very small -- 10 times less than the voluntary exposure leakage level for microwave ovens in the United States. That's about the same amount of exposure a person receives when walking under a microwave door opener, the box over an automatic door that senses your presence and opens the door for you. For now, the signal processor is outside the flashlight-sized casing, and the respiration signature is displayed on a monitor driven by a computer-based radar signal processor. Greneker plans to make everything small enough to fit inside the flashlight housing by incorporating high-speed signal processing technology.
The RADAR flashlight has some advantages over other technologies.
"The signal from the RADAR flashlight will penetrate clothes and detect respiration through a heavy jacket," Greneker explained. "In fact, the RADAR flashlight requires a body movement of only a few millimeters to detect human presence."
Flashlight Has Origins in Battlefield Device
Research that evolved into the RADAR flashlight began in the mid-1980s, with the patenting of a frequency modulated radar for remotely checking vital signs of battlefield wounded before risking medics' lives. This early technology also was tested for its ability to monitor vital signs of soldiers clothed in chemical or biological warfare suits, without requiring them to risk contamination by removing the protective gear.
Most recently, Greneker developed a prototype vital signs monitor in hopes of displaying the heartbeats of archers and rifle competitors during television coverage of the 1996 Centennial Olympic Games. Such athletes are believed to sense their heartbeats and shoot between them to avoid the slight body movement -- and potential shooting inaccuracy -- created by each pulse.
This application ascertains heartbeat signals 30 meters from the subject. The heartbeat channel is processed by a signal processor to remove the signal created by respiration. The system also includes a sensitive, charge-coupled device camera that allows the operator to view the area on the subject's thorax that is monitored by the radar. The heartbeat monitor was never used for the Olympics, in part because the archery and rifle competitions were not broadcast during prime time television viewing hours.
Technology May Have Other Applications
The technology's potential to monitor heartbeat raises some interesting possibilities, Greneker notes.
"This version of the system might be used as a biometric identification tool," he said. "For example, if it could be shown that an individual's radar heartbeat signature is stable over long periods of time and is unique to an individual, the remotely sensed heartbeat could serve as a 'fingerprint' of sorts."
Challenge is to Reduce Clutter
Greneker also wants to explore ways to even further reduce clutter -- undesired and uncontrolled signals originating from something other than the target. Clutter may be many times stronger than the desired target's signal, requiring radar signal processing to reduce or eliminate it.
"This is a challenge," he noted. "The amount of signal returned from the chest area of a moving person due to body motion alone is approximately 1,000 to 10,000 times the heartbeat signature. We are working on clutter suppression algorithms to use in the RADAR flashlight's signal processor circuit."
Greneker has presented papers on the heartbeat monitor developed for potential Olympics use at several national and international conferences over the past year. GTRI is now seeking a partner to help commercialize this family of technologies.
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