Communications – electrical: acoustic wave systems and devices – Distance or direction finding – With electromagnetic wave
Reexamination Certificate
1999-10-08
2001-12-18
Pihulic, Daniel T. (Department: 3662)
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
With electromagnetic wave
Reexamination Certificate
active
06331964
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to active occupancy sensors and motion detectors, and more particularly to apparatus and methods directed to motion detection and occupancy sensing utilizing the non-Doppler shifted return signal.
BACKGROUND OF THE INVENTION
Present methods of motion and occupancy detection which utilize active microwave, infrared/optical, and acoustic/ultrasonic motion apparatus operate by transmitting an electromagnetic or acoustic wave into a region of interest, via one or more transmitters, which then reflect off of objects in the region of interest and are detected by one or more receivers. A Doppler shift of the reflected signals indicates the presence of movement within the region of interest.
Typical applications of motion and occupancy detection are described in U.S. Pat. Nos. 4,661,720, 5,189,393 and 5,640,143.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for controlling an electrical load based upon occupancy and/or motion within a monitored zone. The invention may be generally described as follows: first an interrogation signal is transmitted at a pre-determined frequency into a zone to be monitored. The interrogation signal may be transmitted either continuously or at controllable sample intervals. The return signal is then processed, either as an analog signal or digitized, to provide an indication of motion within a space. Thereafter, at a decision stage, an electrical load is either energized, de-energized, or otherwise controlled as a function of the indication of motion within the space.
The occupancy signal may be generated either actively or passively or some combination thereof. Active generation of an occupancy signal include, for example, ultrasonic, optical, acoustic, and microwave signals. Passive generation of occupancy signals include, for example, passive infrared detectors that detect moving heat sources within a monitored zone.
In the preferred embodiment of the invention, a transmitted signal is generated at a fixed frequency. An array of receivers receive a return signal from the space whereby the receivers filter out (i.e. reject) all Doppler shifted frequency components in the return signal leaving only that portion of the return signal at the original frequency of transmission. The information contained in the detected signal can either be digitized and passed to a microprocessor where a corresponding control signal will be generated to activate, deactivate or otherwise control a load. Otherwise, the analog return signal is sent directly to a driver to control an electrical load.
When the return signal is detected by a receiver array, a feature of the invention is that object displacement is detectable by virtue of the change in pathlength from the displaced object to each element of the receiver array being different thereby resulting in a different amplitude and phase characteristic at each element of the receiver array.
When the return signal is detected by a single receiver, a second novel feature of the invention is that object displacement is detectable by virtue of distinguishing amplitude and/or phase differences of the return signal at controlled time intervals.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5915332 (1999-06-01), Young et al.
Dilworth & Barrese
Pihulic Daniel T.
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