Patent EP0531041A1 successfully refreshed from Google Patents.
EP0100128A1
Expired / Lapsed
EP
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Absorption detection system
Assignee: Nederlandsche Apparatenfabriek NEDAP NV
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Filing: 1983-07-21
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Granted: —
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Expires: 2003-07-21
Abstract
Abstract An electromagnetic detection system is described which, in operation, in a detection zone, by means of at least one transmission antenna coil, generates a swept-frequency interrogation field capable of being at least partly absorbed by a responder comprising a tuned circuit, if such responder is present in the detection zone. Detection means are provided, coupled with the transmission antenna coil to detect such absorption. According to the invention the detection means comprises means for eliminating spurious frequencies located outside the band of the swept frequency, said means comprising a mixer including a first input to which a signal from the transmission antenna coil is supplied, and a second input to which the output signal from a sweeper feeding the transmission antenna coil is supplied, and including an output connected with a low-pass filter.
Inventors
- 👤 Tallienco Wieand Harm Fockens
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 14:06
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2414; G08B13/2465; G08B13/2468; G08B13/2471
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
131 words
An electromagnetic detection system which, in operation, in a detection zone, by means of at least one transmission antenna coil, generates a swept-frequency interrogation field capable of being at least partly absorbed by a responder comprising a tuned circuit, if such responder is present in said detection zone, there being provided detection means coupled with said transmission antenna coil for detecting such absorption, characterized in that said detection means comprises means for eliminating spurious frequencies located outside the band of the swept frequency, said means comprising a mixer including a first input, to which a signal from the transmission antenna coil is supplied, and a second input to which the output signal from a sweeper feeding said transmission antenna coil is supplied, and including an output connected with a low-pass filter.
Claim 2
Dependent Claim
131 words
An electromagnetic detection system which, in operation, in a detection zone, by means of at least one transmission antenna coil, generates a swept-frequency interrogation field capable of being at least partly absorbed by a responder comprising a tuned circuit, if such responder is present in said detection zone, there being provided detection means coupled with said transmission antenna coil for detecting such absorption, characterized in that said detection means comprises means for eliminating spurious frequencies located outside the band of the swept frequency, said means comprising a mixer including a first input, to which a signal from the transmission antenna coil is supplied, and a second input to which the output signal from a sweeper feeding said transmission antenna coil is supplied, and including an output connected with a low-pass filter.
Claim 3
Dependent Claim
57 words
An electromagnetic detection system according to claim 1, characterized by a discriminator filter means for separating signals from a responder that are passed by said low-pass filter and spurious signals that are passed by said low-pass filter and have a frequency close - to the frequency of the responder signals, by means of a second low-pass filter.
Claim 4
Dependent Claim
25 words
An electromagnetic detection system according to claim 2, characterized in that said discriminator filter means comprises a high-pass filter parallel-connected with said second low-pass filter.
Claim 5
Dependent Claim
66 words
An electromagnetic detection system according to claim 3, characterized in that said discriminator filter means comprises a first rectifier for rectifying the output signals from the second low-pass filter, and a second rectifier for rectifying the output signals from the high-pass filter, and that the output signals from the first and second rectifier are respectively supplied to a first and a second input of an integrator.
Claim 6
Dependent Claim
49 words
An electromagnetic detection system according to claim 4, characterized in that a signal at one input of the integrator effects an increase in the output signal from the integrator, and a signal at the other input of the integrator effects a decrease in the output signal from the integrator.
Claim 7
Dependent Claim
45 words
Apparatus according to claim 5, characterized in that the output from the integrator is connected via a level detector to alarm means, said level detector issuing an actuating signal for said alarm means when the output signal from the integrator has reached a pre-determined level.
References Cited (Backward Citations)
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