Patent US4419659A successfully refreshed from Google Patents.
US4419659A
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Intrusion detection system using leaky transmission lines
Assignee: Senstar Corp
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Filing: 1981-07-14
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Granted: 1983-12-06
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Expires: 2001-07-14
Abstract
Abstract A sensitive intrusion detection system has an RF excited antenna located within the area to be protected and a leaky coaxial cable extending around the perimeter. The presence of an intruder alters the coupling between the antenna and the coaxial cable thereby changing the signal received by the cable. The detection system is responsive to incremental changes in the in-phase and quadrature components of the received signal. When these components are plotted against each other a cardioid-like curve is obtained in the DELTA I, DELTA Q plane. By tracking both magnitude and angle of this curve as it is generated a sensitive detection mechanism is provided. When the variations in magnitude and angle exceed a threshold an alarm is sounded. To avoid the possibility of intruders using a particular path would gives a null angle response, a second cable adjacent to the first may also be employed. A further embodiment illustrates the use of three cables together with a separate antenna which provides multiple independent sensing systems.
Inventors
- 👤 Robert K. Harman
- 👤 Ronald W. Clifton
- 👤 Russell E. Patterson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 06:42
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2491; G08B13/2497
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
100 words
An intrusion detection system comprising an antenna located within the perimeter of an area to be protectd, a leaky transmission line extending around the perimeter so that the presence of an intruder alters the electromagnetic coupling between the antenna and transmission line, an RF transmitter coupled to one of the antenna and transmission line and a receiver coupled to the other, means detecting incremental changes in the in-phase and quadrature components of signals received at said receiver and means separately measuring and accumulating magnitude and phase angle of said incremental changes to track and indicate the presence of an intruder.
Claim 2
Dependent Claim
100 words
An intrusion detection system comprising an antenna located within the perimeter of an area to be protectd, a leaky transmission line extending around the perimeter so that the presence of an intruder alters the electromagnetic coupling between the antenna and transmission line, an RF transmitter coupled to one of the antenna and transmission line and a receiver coupled to the other, means detecting incremental changes in the in-phase and quadrature components of signals received at said receiver and means separately measuring and accumulating magnitude and phase angle of said incremental changes to track and indicate the presence of an intruder.
Claim 3
Dependent Claim
44 words
A system as set out in claim 1 wherein said incremental in-phase component is ΔI and said incremental quadrature component is ΔQ and said accumulating means produces signals indicative of the phase angle and area swept out by these components in the ΔI,ΔQ plane.
Claim 4
Dependent Claim
30 words
A system as set out in claim 2 wherein the presence of an intruder is indicated when both the plane angle and area swept in the ΔI,ΔQ exceed present amounts.
Claim 5
Dependent Claim
73 words
A system as set out in claim 2 wherein said means separately measuring and accumulating includes circuitry to calculate the functions: A.sub.i =ΔI.sub.i ΔQ.sub.i-1 -ΔQ.sub.i ΔI.sub.i-1 B.sub.i =ΔI.sub.i ΔI.sub.i-1 +ΔQ.sub.i ΔQ.sub.i-1 and further includes accumulating circuits responsive to A i , representing the magnitude of swept area, and responsive to arctan B i /A i , representing angular change, to indicate when accumulate values of area magnitude and angular change exceed predetermined amounts.
Claim 6
Dependent Claim
34 words
A system as set out in claim 4 further including a circuit responsive to M=√ΔI 2 +ΔQ 2 to inhibit said means separately measuring and accumulating when M is less than a threshold value.
Claim 7
Dependent Claim
37 words
A system as set out in claim 5 wherein a series of measuring and accumulating circuits are provided controlled by a source of clock pulses and means setting separate phase angle and area thresholds for each circuit.
Claim 8
Dependent Claim
27 words
A system as set out in claim 6 wherein each measuring and accumulation circuit except the first has an integration time double that of its preceding circuit.
Claim 9
Dependent Claim
38 words
A system as set out in claim 4 further including a circuit responsive to the approximation M=max (|ΔI|, |ΔQ|)+1/2 min (|ΔI|, |ΔQ|) to inhibit said means separately measuring and accumulating when M is less than a threshold valve.
Claim 10
Dependent Claim
16 words
A system as set out in claim 1 wherein the transmission line is leaky coaxial cable.
Claim 11
Dependent Claim
26 words
A system as set out in claim 9 wherein the leaky coaxial cable has a matching termination at one end and the receiver at the other.
Claim 12
Dependent Claim
19 words
A system as set out in claim 9 wherein the leaky coaxial cable has a receiver at each end.
Claim 13
Dependent Claim
42 words
A system as set out in claim 9 further including a second transmission line adjacent the first-mentioned transmission line, a receiver connected to each transmission line whereby the received signals induced by the antenna in the transmission lines travel in opposite directions.
Claim 14
Dependent Claim
23 words
A system as set out in claim 12 wherein the first-mentioned transmission line and said second transmission line are graded leaky coaxial cables.
Claim 15
Dependent Claim
41 words
A system as set out in claim 13 and further including a third leaky cable with a transceiver connected thereto and graded in a corresponding fashion to one of the other cables to permit electromagnetic coupling thereto and to the antenna.
Claim 16
Dependent Claim
36 words
A system as set out in claim 9 further including a second transmission line adjacent the first-mentioned transmission line, transmitters operating at different frequencies coupled to each transmission line and corresponding receivers coupled to the antenna.
Claim 17
Dependent Claim
40 words
A system as set out in claim 9 further including a second transmission line adjacent the first-mentioned transmission line, a transmitter coupled to one of the transmission lines and receivers coupled to the antenna and to the other transmission line.
Claim 18
Dependent Claim
104 words
An intrusion detection system for a site where an intruder is constrained to follow a fixed path, comprising a pair of leaky transmission lines along said path, an RF transmitter coupled to one of the lines and a receiver to the other means detecting incremental changes in the in-phase and quadrature components of signals received at said receiver and providing ΔI and ΔQ signals representing said incremental changes, means producing signals indicative of the area and phase angle swept out by these components in the ΔI,ΔQ plane and means indicating the presence of an intruder when both area and phase angle exceed preset amounts.
Claim 19
Dependent Claim
104 words
An intrusion detection system for a site where an intruder is constrained to follow a fixed path, comprising a pair of leaky transmission lines along said path, an RF transmitter coupled to one of the lines and a receiver to the other means detecting incremental changes in the in-phase and quadrature components of signals received at said receiver and providing ΔI and ΔQ signals representing said incremental changes, means producing signals indicative of the area and phase angle swept out by these components in the ΔI,ΔQ plane and means indicating the presence of an intruder when both area and phase angle exceed preset amounts.
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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) | 1986-12-05 | 1987-06-06 | 1987-12-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-12-05 | 1991-06-06 | 1991-12-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-12-05 | 1995-06-06 | 1995-12-06 | $7700.00 | Window Closed / Lapsed |