US3879719A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Flat beam intruder detection device
Assignee: Shorrock Developments Ltd
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Filing: 1973-05-21
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Granted: 1975-04-22
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Expires: 1993-05-21
Abstract
Abstract A VHF transmitter transmits a flat beam of radiation from a directive aerial into an area to be protected against intruders. A receiver with a directional aerial is positioned at the opposite side of the area, and receives a constant signal from the transmitter. If an intruder enters the area, and the receiver input varies by more than a predetermined amount for not less than a given time, the receiver output operates an alarm. Small objects such as a bird present only for a short time in the area do not set off the alarm.
Inventors
- 👤 Norman Ian Buckley
- 👤 Brian Michael Mansfield
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 21:33
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/18; G08B13/181; G08B13/183; G01; G01V; G01V3/00; G01V3/12
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
182 words
An intruder detecting device comprising an ultra-high frequency transmitter and an aerial having a polar diagram producing a flat beam of radiated energy; a receiver with a receiving aerial having a polar diagram with a directive characteristic, the receiver and aerial being located remotely from the transmitter aerial so as to receive energy from said transmitter, with the polar diagrams of the transmitter and receiver aerials overlapping, and signal processing means fed from said receiver to operate an alarm when a predetermined form of received signal change occurs; said transmitter comprising an elongate strip of insulating material and an electrically conductive array printed thereon, said array including a series of parallel dipoles alternately staggered, from one end of the strip, on opposite sides of the center line of the array and increasingly spaced from such center line with respect to their location away from said one end of the strip, said array being terminated in a load resistor and said transmitter being connected to said array at said one end of the strip whereby substantially equal radiation takes place from each dipole.
Claim 2
Dependent Claim
182 words
An intruder detecting device comprising an ultra-high frequency transmitter and an aerial having a polar diagram producing a flat beam of radiated energy; a receiver with a receiving aerial having a polar diagram with a directive characteristic, the receiver and aerial being located remotely from the transmitter aerial so as to receive energy from said transmitter, with the polar diagrams of the transmitter and receiver aerials overlapping, and signal processing means fed from said receiver to operate an alarm when a predetermined form of received signal change occurs; said transmitter comprising an elongate strip of insulating material and an electrically conductive array printed thereon, said array including a series of parallel dipoles alternately staggered, from one end of the strip, on opposite sides of the center line of the array and increasingly spaced from such center line with respect to their location away from said one end of the strip, said array being terminated in a load resistor and said transmitter being connected to said array at said one end of the strip whereby substantially equal radiation takes place from each dipole.
Claim 3
Dependent Claim
182 words
An intruder detecting device comprising an ultra-high frequency transmitter and an aerial having a polar diagram producing a flat beam of radiated energy; a receiver with a receiving aerial having a polar diagram with a directive characteristic, the receiver and aerial being located remotely from the transmitter aerial so as to receive energy from said transmitter, with the polar diagrams of the transmitter and receiver aerials overlapping, and signal processing means fed from said receiver to operate an alarm when a predetermined form of received signal change occurs; said transmitter comprising an elongate strip of insulating material and an electrically conductive array printed thereon, said array including a series of parallel dipoles alternately staggered, from one end of the strip, on opposite sides of the center line of the array and increasingly spaced from such center line with respect to their location away from said one end of the strip, said array being terminated in a load resistor and said transmitter being connected to said array at said one end of the strip whereby substantially equal radiation takes place from each dipole.
Claim 4
Dependent Claim
182 words
An intruder detecting device comprising an ultra-high frequency transmitter and an aerial having a polar diagram producing a flat beam of radiated energy; a receiver with a receiving aerial having a polar diagram with a directive characteristic, the receiver and aerial being located remotely from the transmitter aerial so as to receive energy from said transmitter, with the polar diagrams of the transmitter and receiver aerials overlapping, and signal processing means fed from said receiver to operate an alarm when a predetermined form of received signal change occurs; said transmitter comprising an elongate strip of insulating material and an electrically conductive array printed thereon, said array including a series of parallel dipoles alternately staggered, from one end of the strip, on opposite sides of the center line of the array and increasingly spaced from such center line with respect to their location away from said one end of the strip, said array being terminated in a load resistor and said transmitter being connected to said array at said one end of the strip whereby substantially equal radiation takes place from each dipole.
Claim 5
Dependent Claim
24 words
An intruder detecting device as recited in claim 1 in which the constructions and polar diagrams of both transmitter and receiver aerials are similar.
Claim 6
Dependent Claim
31 words
An intruder detecting device as recited in claim 1 wherein at least said transmitting aerial is of the travelling wave type and includes a plurality of series-connected dipoles and a reflector.
Claim 7
Dependent Claim
152 words
An intruder detecting system as in claim 1 with said signal processing means including an amplifier, automatic gain control means connected in feedback relation with said amplifier for maintaining the amplitude of the amplifier output substantially constant in response to received signal strength changes having a selected slow rate, level detector means connected to the output of said amplifier for detecting changes in the amplitude thereof which are greater than a predetermined value as caused by received signal strength changes occurring at a rate greater than said selected slow rate, alarm means connected to said automatic gain control means for altering the rate of control of said automatic gain control means in response to actuation of said alarm means, and circuit means connecting said level detector means to said alarm means for actuating said alarm means only in response to changes of received signal strength indicative of the presence of an intruder.
Claim 8
Dependent Claim
31 words
A system as defined in claim 4 wherein said circuit means includes a delay circuit passing the output of said level detector means only in response to a predetermined duration thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-21 | 1978-10-21 | 1979-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-21 | 1982-10-21 | 1983-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-21 | 1986-10-21 | 1987-04-22 | $7700.00 | Window Closed / Lapsed |