Patent US3731305A successfully refreshed from Google Patents.
US3731305A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Object detection system using electro magnetic waves
Assignee: General Dynamics Corp
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Filing: 1971-12-09
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Granted: 1973-05-01
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Expires: 1991-12-09
Abstract
Abstract Objects such as personnel and vehicles are detected when they enter a sensing field produced by an antenna which is excited by oscillators operating in the VHF frequency band by producing cyclic variations in the frequency and in the amplitude of the oscillators exciting signal, which variations are in approximately quadrature phase relationship. The system responds to the correlation between the amplitude and the phase variation so as to produce an alarm indication of both the presence of an intruding object and its direction of movement, either toward or away from sensing the antenna.
Inventors
- 👤 J Gehman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:05
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101; G01V3/102; G01V3/12
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
180 words
An intrusion detection system which comprises a. an antenna for establishing a sensing field, b. electromagnetic signal generating means operative to generate signals at a given frequency, c. said generating means being coupled to said antenna for exciting said antenna with said signals to radiate said sensing field, d. means responsive to variations in the frequency of said signals to produce a first output which varies cyclically in amplitude as an object in said field approaches or retreats from said antenna, e. means responsive to variations in the amplitude of said signals to produce a second output in quadrature phase relationship with said first output and which varies cyclically when the object approaches said antenna and when the object retreats from said antenna, said second output produced when said object approaches said antenna being approximately 180* out of phase with said second output produced when said object retreats from said antenna, and f. means for correlating said first and second outputs with each other to indicate the presence and direction of movement of said object with respect to said antenna.
Claim 2
Dependent Claim
180 words
An intrusion detection system which comprises a. an antenna for establishing a sensing field, b. electromagnetic signal generating means operative to generate signals at a given frequency, c. said generating means being coupled to said antenna for exciting said antenna with said signals to radiate said sensing field, d. means responsive to variations in the frequency of said signals to produce a first output which varies cyclically in amplitude as an object in said field approaches or retreats from said antenna, e. means responsive to variations in the amplitude of said signals to produce a second output in quadrature phase relationship with said first output and which varies cyclically when the object approaches said antenna and when the object retreats from said antenna, said second output produced when said object approaches said antenna being approximately 180* out of phase with said second output produced when said object retreats from said antenna, and f. means for correlating said first and second outputs with each other to indicate the presence and direction of movement of said object with respect to said antenna.
Claim 3
Dependent Claim
33 words
The invention as set forth in claim 1 wherein said correlating means includes electromechanical phase indicator having a movable element and drive means for said element operated by said first and second outputs.
Claim 4
Dependent Claim
35 words
The invention as set forth in claim 2 wherein said indicator includes a servo motor, said movable element being the shaft of said motor, and said drive means being the stator winding of said motor.
Claim 5
Dependent Claim
48 words
The invention as set forth in claim 3 wherein said motor is a two-phase servo motor and wherein said first output is applied to the stator winding for one of said phases and said second output is applied to the stator winding for the other of said phases.
Claim 6
Dependent Claim
25 words
The invention as set forth in claim 1 wherein said generating means is an oscillator tuned to said given frequency and connected to said antenna.
Claim 7
Dependent Claim
22 words
The invention as set forth in claim 5 wherein said frequency variation responsive means is a frequency discriminator coupled to said oscillator.
Claim 8
Dependent Claim
18 words
The invention as set forth in claim 6 including a capacitor coupled to the output of said discriminator.
Claim 9
Dependent Claim
29 words
The invention as set forth in claim 1 wherein said amplitude variation responsive means comprises a directional coupler connected in a line between said generating means and said antenna.
Claim 10
Dependent Claim
48 words
The invention as set forth in claim 8 wherein said amplitude variation responsive means further comprises a detector connected to the output of said directional coupler, and means for providing an output voltage corresponding to the difference between the output voltage from said detector and a reference voltage.
Claim 11
Dependent Claim
34 words
The invention as set forth in claim 9 wherein said output voltage providing means is a differential amplifier, and a capacitor connected to the output of said differential amplifier for producing said second output.
Claim 12
Dependent Claim
39 words
The invention as set forth in claim 1 wherein said correlating means includes means for integrating the difference between said first and second outputs and for producing an alarm signal when said integrated difference exceeds a certain threshold amplitude.
Claim 13
Dependent Claim
52 words
The invention as set forth in claim 1 wherein said integrating means includes an operational amplifier having direct and inverting inputs to which said first and second outputs are applied, and an RC network connected in feedback relationship between the output of said amplifier and one of said direct and inverting inputs.
Claim 14
Dependent Claim
39 words
The invention as set forth in claim 1 wherein said correlating means comprises means for integrating the product of said first and second outputs, and means for providing an alarm output when said integrated product exceeds a certain threshold.
Claim 15
Dependent Claim
69 words
The invention as set forth in claim 13 wherein said means for integrating the product comprises means of said outputs for translating at least one of said first and second outputs into a square wave signal, means for differentiating the other of said first and second outputs, means for sampling said square wave signal with said differentiated output, and means for integrating the output of said last named means.
Claim 16
Dependent Claim
15 words
The invention as set forth in claim 14 wherein said integrating means is a counter.
Claim 17
Dependent Claim
98 words
The invention as set forth in claim 1 wherein said correlating means comprises a reversible counter having upcount and down-count input for producing an alarm output when the difference between the number of pulses applied to different ones of said inputS exceeds a certain number, and pulse generating logic means responsive to said first and second outputs having first and second output terminals connected to said up and down count inputs, respectively, for producing pulses at said first terminals when said object advances toward said antenna and at said second terminal when said object retreats from said antenna.
Claim 18
Dependent Claim
99 words
The invention as set forth in claim 16 wherein said pulse generating logic included means for translating said first and second outputs into pairs of square waves of opposite polarity, means for differentiating the pair square waves corresponding to one of said first and second outputs, means for gating said square waves corresponding to the other of said first and second outputs each with a different one of said differentiated square waves to produce two pairs of output pulses, and means for applying different pairs of said output pulses separately to said up-count input and to said down-count input.
Claim 19
Dependent Claim
171 words
An intrusion detection system which comprises a. an antenna for establishing a sensing field, b. first and second signal generating means each producing signals at different frequencies separatee by a certain difference frequency, c. means coupling said generating means to said antenna for exciting said antenna at both of said different frequencies, d. means responsive to variations in said difference frequency to produce a first output which varies cyclically in amplitude in accordance with variations in said difference frequency in response to the movement of an object in said sensing field with respect to said antenna, e. means responsive to the difference in amplitude of the signals produced by said first and second generating means to produce a second output which varies cyclically and in quadrature phase relationship with said first output as said object moves with respect to said antenna in said sensing field, and f. means for correlating said first and second outputs to indicate the presence and direction of movement of said object with respect to said antenna.
Claim 20
Dependent Claim
171 words
An intrusion detection system which comprises a. an antenna for establishing a sensing field, b. first and second signal generating means each producing signals at different frequencies separatee by a certain difference frequency, c. means coupling said generating means to said antenna for exciting said antenna at both of said different frequencies, d. means responsive to variations in said difference frequency to produce a first output which varies cyclically in amplitude in accordance with variations in said difference frequency in response to the movement of an object in said sensing field with respect to said antenna, e. means responsive to the difference in amplitude of the signals produced by said first and second generating means to produce a second output which varies cyclically and in quadrature phase relationship with said first output as said object moves with respect to said antenna in said sensing field, and f. means for correlating said first and second outputs to indicate the presence and direction of movement of said object with respect to said antenna.
Claim 21
Dependent Claim
97 words
The invention as set forth in claim 18 wherein said first and second generating means are first and second oscillators each tuned to a different frequency, a filter connected to one of said oscillators for passing said difference frequency signal, a discriminator connected to said filter to provide said first output means connected to said first and second oscillators to derive signals varying in amplitude in accordance with the variations in amplitude of the envelope of said different frequency signals, and a differential amplifier to which said last named signals are applied for providing said second output.
Claim 22
Dependent Claim
33 words
The invention as set forth in claim 18 wherein said correlating means includes electromechanical phase indicator having a movable element and drive means for said element operated by said first and second outputs.
Claim 23
Dependent Claim
33 words
The invention as set forth in claim 20 wherein said indicator includes servo motor, said movable element being the shaft of said motor, and said means being the stator winding of said motor.
Claim 24
Dependent Claim
48 words
The invention as set forth in claim 21 wherein said motor is a two-phase servo motor and wherein said first output is applied to the stator winding for one of said phases and said second output is applied to the stator winding for the other of said phases.
Claim 25
Dependent Claim
27 words
The invention as set forth in claim 18 wherein said first and second generating means are separate oscillators each to a separate one of said different frequencies.
Claim 26
Dependent Claim
22 words
The invention as set forth in claim 23 wherein said frequency variation responsive means is a frequency discriminator coupled to said oscillator.
Claim 27
Dependent Claim
18 words
The invention as set forth in claim 24 including a capacitor coupled to the output of said discriminator.
Claim 28
Dependent Claim
39 words
The invention as set forth in claim 18 wherein said correlating means includes means for integrating the difference between said first and second outputs and for producing an alarm sIgnal when said integrated difference exceeds a certain threshold amplitude.
Claim 29
Dependent Claim
52 words
The invention as set forth in claim 26 wherein said integrating means includes an operational amplifier having direct and inverting inputs to which said first and second outputs are applied, and an RC network connected in feedback relationship between the output of said amplifier and one of said direct and inverting inputs.
Claim 30
Dependent Claim
39 words
The invention as set forth in claim 18 wherein said correlating means comprises means for integrating the product of said first and second outputs, and means for providing an alarm output when said integrated product exceeds a certain threshold.
Claim 31
Dependent Claim
69 words
The invention as set forth in claim 28 wherein said means for integrating the product comprises means of said outputs for translating at least one of said first and second outputs into a square wave signal, means for differentiating the other of said first and second outputs, means for sampling said square wave signal with said differentiated output, and means for integrating the output of said last named means.
Claim 32
Dependent Claim
15 words
The invention as set forth in claim 29 wherein said integrating means is a counter.
Claim 33
Dependent Claim
98 words
The invention as set forth in claim 18 wherein said correlating means comprises a reversible counter having upcount and down-count input for producing an alarm output when the difference between the number of pulses applied to different ones of said inputs exceeds a certain number, and pulse generating logic means responsive to said first and second outputs having first and second output terminals connected to said up and down count inputs, respectively, for producing pulses at said first terminals when said object advances toward said antenna and at said second terminal when said object retreats from said antenna.
Claim 34
Dependent Claim
100 words
The invention as set forth in claim 31 wherein said pulse generating logic included means for translating said first and second outputs into pairs of square waves of opposite polarity, means for differentiating the pair of square waves corresponding to one of said first and second outputs, means for gating said square waves corresponding to the other of said first and second outputs each with a different one of said differentiated square waves to produce two pairs of output pulses, and means for applying different pairs of said output pulses separately to said up-count input and to said down-count input.
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) | 1976-04-30 | 1976-10-30 | 1977-05-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-30 | 1980-10-30 | 1981-05-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-30 | 1984-10-30 | 1985-05-01 | $7700.00 | Window Closed / Lapsed |