US4135185A
Expired / Lapsed
US
⏱️ 0.0 years remaining
RF loop intruder detection system
Assignee: United States Department of the Air Force
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Filing: 1977-10-07
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Granted: 1979-01-16
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Expires: 1997-10-07
Abstract
Abstract An RF intruder system utilizes two concentric loops of wire spaced apart for a predetermined magnitude, either of which can transmit and/or receive electromagnetic energy. This area within the loops are to be protected against intrusion. Without intrusion, the received signal is steady. Upon intrusion, there are signal changes which are instantly noted by signal detection and processing.
Inventors
- 👤 Walter Rotman
- 👤 J. Leon Poirier
- 👤 Nicholas V. Karas
- 👤 Peter R. Franchi
- 👤 Ronald L. Fante
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 13:31
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/26
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
99 words
An RF loop intruder detection system being comprised of two approximately concentric loops of wire surrounding a resource to be protected against human intrusion, said two concentric loops of wire spaced apart a predetermined magnitude, a transmitter feeding RF energy to one of said concentric loops of wire, indication means receiving RF energy from the other of said concentric loops of wire resulting from an electromagnetic field between said loops, and means connected to said indicating means for tripping an alarm upon predetermined change in the level of the received energy, as would be produced by said human intrusion.
Claim 2
Dependent Claim
99 words
An RF loop intruder detection system being comprised of two approximately concentric loops of wire surrounding a resource to be protected against human intrusion, said two concentric loops of wire spaced apart a predetermined magnitude, a transmitter feeding RF energy to one of said concentric loops of wire, indication means receiving RF energy from the other of said concentric loops of wire resulting from an electromagnetic field between said loops, and means connected to said indicating means for tripping an alarm upon predetermined change in the level of the received energy, as would be produced by said human intrusion.
Claim 3
Dependent Claim
20 words
An RF loop intruder detection system as defined in claim 1 wherein said indicating means is comprised of a detector.
Claim 4
Dependent Claim
65 words
An RF loop intruder detection system as defined in claim 1 wherein said indicating means is comprised of a balun, a receiver passing the output from said balun, a detector passing the receiver output, a bandpass filter receiving the detector signal, and an amplitude comparator passing the filtered signal for eventual sounding of an alarm upon exceeding a predetermined threshold voltage indicative of human intrusion.
Claim 5
Dependent Claim
34 words
An RF loop intruder detection system as described in claim 3 further including an AGC filter connected from the output of said detector to said receiver for adjusting for changes in ambient environmental conditions.
References Cited (Backward Citations)
US3696368A
Cited
US3794992A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-01-15 | 1982-07-17 | 1983-01-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-15 | 1986-07-17 | 1987-01-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-15 | 1990-07-17 | 1991-01-16 | $7700.00 | Window Closed / Lapsed |