Ultrasonic intrusion detection system
US4035798A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 26, 1976 |
| Grant date | Jul 12, 1977 |
| Priority date | — |
| Expiry date | Jan 26, 1996 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/1627
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An ultrasonic or microwave intrusion detection system uses a modulated transmitter having one or more transducers or antennas for maintaining wave fields in the area to be protected and a receiver fed by one or more transducers or antennas which detect echo reflections of the energy from within the area. The receiver employs two mixers energized to be mixed with the echo signals and a portion of the energy from the transmitter, one of the mixers receiving such transmitter energy with 90.degree. phase shift relative to the other mixer. The outputs of the two mixers thus are in quadrature phase relative to each other and define a rotating vector which contains the information relating to the echo signals. The modulation product of these quadrature signals obtained by multiplying them together is processed continuously at the modulation frequency to obtain more reliable target information in the presence of substantially larger clutter return signals and other interference.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.