Ultrasonic intrusion detection system
US4319349A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 29, 1978 |
| Grant date | Mar 9, 1982 |
| Priority date | — |
| Expiry date | Sep 29, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01S15/523
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Apparatus and method of processing in an ultrasonic alarm system to detect the doppler-shifted components which indicate the presence of an intruder. A master control applies to each of the transmitter transducers a signal which alternates between two frequencies at a modulation frequency. The output signal from the receiving transducer is synchronously detected and low pass filtered. The filtered signal is applied to electronics which respond to the presence of modulation frequency components in the filter output signal. A first embodiment utilizes a high-Q bandpass filter having a resonance frequency equal to the modulation frequency. In a second embodiment, the modulation frequency is used to effectively perform a correlation between the received signal and the modulation frequency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.