A new device detects the heartbeat and respiration of victims trapped in rubble or disaster debris, and reduces the time required to initiate a rescue. Searchers would like to distinguish live victims from those who have died recently and to distinguish humans from animals. In addition to search and rescue, there are other uses for the device that can detect multiple humans from a distance, and with material between the device and the humans.
This innovation uses continuous wave (CW) microwave radar to detect small motions due to breathing (about 1 cm) and heartbeats (about 1 mm) that can be detected amid the signal reflected from the non-moving rubble and background. The dynamic range of the receiver is improved by feeding an adjustable sample of the transmitted signal that is subtracted from the received signal, cancelling out the non-moving signals from the clutter. The cancellation signal is adjusted automatically to reduce the fixed clutter signal.
Changing the operating frequency of the radar systematically allows improving the range resolution of the measurement, allowing rejecting targets that are at distances more or less than expected. Signal processing can be used to separate multiple targets because multiple victims have different heartbeats at different rates.
Multiple radar units with multiple antennas can be used to look in different directions simultaneously, so that the position of the victim can be determined, and signals that originate from outside the rubble, and are just reflected, can be rejected. A colocated video camera is used to show the user where the antenna(s) are pointed, and to assist in selection of a suitable beamwidth, by displaying a graticule or shaded area on the image to indicate the currently selected antenna pattern. An integral GPS receiver provides time synchronization among multiple cooperating units, and provides a reliable time and position “stamp” for recording purposes. A wireless network can be used to interconnect multiple radar units, support multiple users, or connect to additional storage or signal processing computational resources.
The techniques developed here have applicability to non-life-sensing applications. The same design can serve as a high-resolution, small-form-factor radar that could probe for soft spots or holes ahead of a rover. The small, modular design lends itself to installing on an unmanned aerial vehicle (UAV), or a constellation of UAVs to scan large areas. While the present implementation is tailored to human vital sign monitoring, the basic hardware and software architecture lends itself to many high-resolution radar applications.
This work was done by James P. Lux, Vaughn P. Cable, Salman Haque, Michael R. McKee, Hirad Ghaemi, and Richard Kalantar Ohanian of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
Refer to NPO-49108.