Apparatus for and method of doppler motion detection with standing wave drift compensation
US4661936A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 26, 1984 |
| Grant date | Apr 28, 1987 |
| Priority date | — |
| Expiry date | Nov 26, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S15/876
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Drift of the standing wave pattern in an acoustic doppler intrusion detection system in a confined space is compensated by adjusting the relative radiating and receiving positions of the radiator and receiver transducers, respectively, either mechanically or electrically until the signal level of the carrier wave at the receiver transducer is optimized. In the mechanical adjustment mode, either the receiver transducer or the radiating transducer is supported for movement relative to the other and is moved by a motor energized under the control of a signal level sensor circuit connected to the output of the receiver transducer. In another mode, a plurality of receiver (or alternatively radiator) transducers are connected through a switch to the signal level sensor circuit which in response to a drop in received signal level below a predetermined threshold, selectively switches the active transducer to optimize the received signal level. In still another mode, one of at least two radiator (or alternatively, receiver) transducers is connected through a variable phase shifter to the signal generator (or to the receiver circuit for the receiver transducer), the phase shifter being adjus…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.