Existing implementations of continuous wave (CW) radar are not packaged appropriately for use as part of a heartbeat detection system for disaster search and rescue. They use separately packaged microwave components and laboratory test equipment, and require substantial skill to operate properly, including setup, calibration, and interpretation of the data.
A small integrated system uses modern monolithic microwave integrated circuits (MMICs) on a printed circuit board, integrated with a microcontroller that implements control algorithms and data acquisition, providing a standard serial or USB interface. The general-purpose microwave sensor module may be used for remote sensing of heartbeat and breathing, motion detection in general, as well as other applications where small displacements of a target need to be measured.
The module integrates a microcontroller with CW radar using homodyne detection. As in all homodyne receivers, the transmitted signal is used as a reference for the demodulation of the received signal. The module includes a capability to coherently combine an amplitude and phase-adjusted sample of the transmitted signal with the received signal to improve the dynamic range of the sensor by cancelling unchanging received signals. The microcontroller provides a variety of interfaces to a host computer or larger system.
The module has the ability to change the transmitted frequency, allowing use not only as a classic CW Doppler Radar, but also for a variety of swept, stepped, or variable-fre-quency applications. The module produces a stream of data samples derived from the detected signal via a variety of interfaces. Since the data processing is programmable, the data formats and rates can be easily varied, either by loading new software into the module, or by selecting from among options provided by a single program.
The initial implementation is approximately 3×3×1 in. (≈7.6×7.6×2.5 cm) and is designed for frequencies in the low microwave (2-to-4-GHz) range, but the design is general, and different parts could be used for other frequencies with appropriate changes in the details of fabrication (e.g. choice of substrate materials for loss). A smaller package is possible, as are lower power and mass.
This work was done by James P. Lux, Luis R. Amaro, Richard Kalantar O’Hanian, Raymond Quintero, Troy M. Torrez, Keizo Ishikawa, Michael R. McKee, Salman Haque, and Carson Umsted 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 JPL
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099