US4213122A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Intrusion detection system
Assignee: United States Department of the Air Force
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Filing: 1978-08-23
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Granted: 1980-07-15
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Expires: 1998-08-23
Abstract
Abstract An intrusion detection system utilizes a radio frequency radiative system whose near electromagnetic field is monitored by receiving devices which respond, in a measurable way, to any disturbance of the near electromagnetic field by physical intrusion.
Inventors
- 👤 Walter Rotman
- 👤 Nicholas V. Karas
- 👤 Ronald L. Fante
- 👤 Peter R. Franchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:41
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491; G08B13/2497
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
137 words
An intrusion detection system comprising a metallic structure to be protected from intrusion, a first loop of wire surrounding said metallic structure, a second loop of wire near and approximately concentric to said first loop of wire, means to radio frequency energize said metallic structure against ground to concentrate a near electromagnetic field pattern in the vicinity of said first and second wires, said first wire being a ground wire, said second wire being a receiver wire, said ground wire effecting concentration of the near electromagnetic field and in conjunction with said receiver wire defining a detection zone, said receiver wire intercepting and being responsive to the electromagnetic field radiated by said metallic structure, and means coupled to said receiver wire to detect any changes from the quiescent, undesturbed state of the concentrated near electromagnetic field pattern.
Claim 2
Dependent Claim
137 words
An intrusion detection system comprising a metallic structure to be protected from intrusion, a first loop of wire surrounding said metallic structure, a second loop of wire near and approximately concentric to said first loop of wire, means to radio frequency energize said metallic structure against ground to concentrate a near electromagnetic field pattern in the vicinity of said first and second wires, said first wire being a ground wire, said second wire being a receiver wire, said ground wire effecting concentration of the near electromagnetic field and in conjunction with said receiver wire defining a detection zone, said receiver wire intercepting and being responsive to the electromagnetic field radiated by said metallic structure, and means coupled to said receiver wire to detect any changes from the quiescent, undesturbed state of the concentrated near electromagnetic field pattern.
Claim 3
Dependent Claim
25 words
An intrusion detection system as described in claim 1 further including support means for said metallic structure to electrically insulate said metallic structure from ground.
Claim 4
Dependent Claim
25 words
An intrusion detection system as described in claim 2 including means to transfer a first signal from said receiver wire to said means to detect.
Claim 5
Dependent Claim
29 words
An intrusion detection system as described in claim 2 including first and second means to transfer first and second signals from said receiver wire to said means to detect.
Claim 6
Dependent Claim
86 words
An intrusion detection system as described in claim 4 wherein said means to detect includes first and second radio frequency detectors, receiving said first and second signals, first and second filters having a predetermined bandpass passing the detected signals from said first and second radio frequency detectors, respectively, first and second threshold circuits, each having an associated alarm, said first and second threshold circuits receiving the first and second filtered signals, respectively, and a dual strip chart record also receiving said first and second filtered signals.
Claim 7
Dependent Claim
31 words
An intrusion detection system as described in claim 5 further including a nulling circuit interposed between said first and second transfer means and said first and second radio frequency detector means.
Claim 8
Dependent Claim
25 words
An intrusion detection system as described in claim 4 wherein said first and second means to transfer is comprised of first and second baluns, respectively.
Claim 9
Dependent Claim
17 words
An intrusion detection system as described in claim 1 wherein said metallic structure consists of a monopole.
Claim 10
Dependent Claim
17 words
An intrusion detection system as described in claim 6 wherein said metallic structure consists of a monopole.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-07-15 | 1984-01-14 | 1984-07-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-07-15 | 1988-01-14 | 1988-07-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-07-15 | 1992-01-14 | 1992-07-15 | $7700.00 | Window Closed / Lapsed |