Radar Flashlight project promises COTS-based human vital signs sensor
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   By Wilson Dizard III

   ATLANTA-It is a moonless night. Outside a friendly defended perimeter,
   a soldier in a listening post hears leaves rustle 30 meters away. The
   wind? An animal? An enemy patrol? The soldier points a slim black tube
   the size of a long police flashlight toward the noise. Within seconds,
   the Radar Flashlight has distinguished definitively between harmless
   night noises and approaching foes.

   It is the aftermath of a battle. In the rubble of a bombed-out town, a
   patrol searches buildings cautiously. Last-ditch defenders lurk in
   some crannies, while trapped civilians may survive under piles of
   rubble. Using the same Radar Flashlight technology now under
   development at Sensors and Electromagnetic Research Laboratory of the
   Georgia Institute of Technology in Atlanta, patrolling troops can
   sense the presence of the living through thick concrete walls or under
   collapsed wooden roofs.

   Gene Greneker, senior research scientist with the Georgia Tech
   Research Institute, has developed laboratory versions of a product
   that holds promise as a dual-use technology for sensing the presence
   of humans behind concrete, wood, brick walls, and steel doors. The
   system, known now as the Radar Flashlight, uses commercial
   off-the-shelf (COTS) technology throughout.

   "The Radar Flashlight system uses Doppler radar technology coupled
   with very fast signal processors," Greneker explains. Developments in
   commercially available signal processor (DSP) boards over the past
   decade are making fast Fourier transform calculations and very "sharp"
   filters necessary to distinguish human vital signs from clutter
   returns available at affordable prices, he says.

   The system uses a commercially available antenna that serves as a
   microwave lens to focus the output beam into an arc of 15 to 20
   degrees. Greneker declines to specify the exact components of the
   antenna and the signal processors that comprise the system, as it has
   commercial potential.

   The Radar Flashlight is designed to sense the movement of the human
   thorax resulting from a heartbeat or breathing. The signal it receives
   is based on a homodyne microwave antenna. Greneker`s work began with
   24.1 GHz microwaves. Now he is working with antennas that produce
   microwaves near 10.525 GHz because they penetrate walls more
   effectively than the higher-frequency microwaves.

   The system`s signal processor essentially acts as a low-pass filter
   that ignores frequencies above the highest heart rate expected. The
   first filter rejects ambient clutter signals such as those from
   fluorescent lights. The analog time domain signal feeds into an analog
   to digital converter that converts the input to a 12-bit word,
   Greneker says. DSPs then discard clutter resulting from body motion
   and sensor motion.

   "The signal from the Radar Flashlight will penetrate clothes and
   detect respiration through a heavy jacket," Greneker says. "In fact,
   the Radar Flashlight requires a body movement of only a few
   millimeters to detect human presence."

   The amount of electromagnetic radiation exposure to a target
   individual from the system is very small, about 10 times less than the
   exposure leakage level allowed from microwave ovens in the U.S.

   Research that evolved into the Radar Flashlight began in the
   mid-1980s, as a means of remotely checking the vital signs of
   battlefield wounded. The project went into abeyance until Greneker
   developed a system for the 1996 Olympic Games in Atlanta that could
   remotely sense and display how competition marksmen shoot only during
   their heart`s off-beats, to avoid the 5 milliradian motion a heartbeat
   imparts to a bow or rifle shooter`s arm.

   Greneker wants to explore ways to further reduce clutter. "This is a
   challenge," he says. "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 a
   clutter-suppression algorithm to use in the Radar Flashlight`s signal
   processor circuit."

   Greneker adds that because the system`s radar is sensitive enough to
   detect small motions of humans, it is also sensitive enough to detect
   its own motion. "When the platform [the Radar Flashlight itself] is
   moving, we have to be able to sense that and cancel that," he says.

   One approach is to generate a signal 180 degrees out of phase with the
   motion of the platform to cancel out the undesirable signal. "We have
   asked the National Institute of Justice [an arm of the U.S. Justice
   Department] to fund research we believe is necessary to achieve
   platform stabilization," Greneker says. He declined to specify the
   amount of the grant request, but says it was less than $1 million and
   that Justice Department officials are due to decide on the application
   by the end of August.

   "We have talked to the law enforcement community and they have shown
   interest in the technology," Greneker says. He notes that systems for
   sensing human presence would be of great value to police officers who
   must serve warrants to violent criminals, and sometimes arrest them in
   the process. Knowing whether a potentially armed suspect is hiding in
   a closet in a building where police are searching is one potential
   use.

   Greneker says his goal is to produce a system that would cost about as
   much as a high-end police weapon - about $300 to $500 per unit.
   "Volume production could reduce that cost," he adds. "For example, the
   signal processor could be reduced to a chip set."

   Because the Radar Flashlight is intended for marginally trained
   personnel, it may offer a simple indicator of the presence or absence
   of a human - perhaps even a red or green light indicator. "The goal is
   to have the signal processor do all the work," Greneker says, noting
   that his cost goal highly influenced the choice of COTS components.
   "Take the antenna for example. You can`t go out and design a custom
   component for a $500 target price."

   Other potential civilian uses of the technology are for prison guards
   making bed checks, rescue workers searching for persons buried by
   collapsed buildings or landslides, and for police coping with hostage
   situations. The ability of the Radar Flashlight to distinguish human
   heart rate signals may permit its use as a biometric identification
   device as well.

   In the medical field, technicians could use the technology developed
   in the Radar Flashlight project to gather and record vital signs of
   patients who are physically or mentally incapable of cooperating with
   normal heartbeat and respiration equipment. For example, it can sense
   vital signs of burn patients without touching their skin.

   In military medicine, the system could monitor the vital signs of
   soldiers wearing chemical and biological warfare gear without removing
   their protective suits.

   "We`d like to get the Pentagon involved," Greneker says. "Finding the
   right entry point has been a problem." For further information on the
   project, check the World Wide Web at: 
   http://www.gtri.gatech.edu/res-news/FLASH_SP.html