US5065138A
Expired / Lapsed
US
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Magnetically-coupled two-resonant-circuit, frequency divider for presence-detection-system tag
Assignee: Sensormatic Electronics LLC
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Filing: 1990-08-03
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Granted: 1991-11-12
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Expires: 2010-08-03
Abstract
Abstract A batteryless, portable, frequency divider according to the present invention includes a first resonant LC circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant LC circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency. The first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency. Each circuit includes a variable reactance element, such as a variable capacitance diode or varactor. In the variable reactance element of the first circuit, the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency. In the variable reactance element of the second circuit, the reactance varies with variations in energy transferred from the first circuit for causing the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency. Both resonant circuits include inductance coils that are disposed on a ferrite rod, for enhancing the magnetic coupling. The frequency divider may be extremely small, such as approximately one inch (2.5 cm) in length, but nevertheless has a frequency division energy transfer efficiency of the same order of magnitude as that of much larger frequency dividers. The frequency divider is included in a tag utilized in a presence detection system.
Inventors
- 👤 Ming R. Lian
- 👤 Fred W. Herman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 09:30
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/24; G08B13/2402; G08B13/2405; G08B13/2422; G08B13/2428; G08B13/2431; G08B13/2437; G08B13/2442
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
150 words
A batteryless, portable, frequency divider, comprising a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 2
Dependent Claim
150 words
A batteryless, portable, frequency divider, comprising a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 3
Dependent Claim
57 words
A frequency divider according to claim 1, wherein the second circuit includes a variable reactance element in which the reactance varies with variations in energy transferred from the first circuit for causing the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 4
Dependent Claim
31 words
A frequency divider according to claim 2, wherein each circuit includes a capacitance and an inductance coil, with the coils being disposed on magnetic circuit means for enhancing said magnetic coupling.
Claim 5
Dependent Claim
19 words
A frequency divider according to claim 3, wherein the magnetic circuit means consists of a single straight ferromagnetic rod.
Claim 6
Dependent Claim
22 words
A frequency divider according to claim 4, wherein the coils of the respective circuits are disposed about opposite ends of the rod.
Claim 7
Dependent Claim
26 words
A frequency divider according to claim 5, wherein each coil each has an inside dimension that is somewhat larger than the cross-sectional dimension of the rod.
Claim 8
Dependent Claim
16 words
A frequency divider according to claim 2, wherein the variable reactance elements include variable capacitance elements.
Claim 9
Dependent Claim
17 words
A frequency divider according to claim 1, wherein the variable reactance element is a variable capacitance element.
Claim 10
Dependent Claim
31 words
A frequency divider according to claim 1, wherein each circuit includes a capacitance and an inductance coil, with the coils being disposed on magnetic circuit means for enhancing said magnetic coupling.
Claim 11
Dependent Claim
180 words
A tag for use in a presence detection system, comprising a frequency divider; and means for fastening the frequency divider to an article to be detected by the presence detection system; wherein the frequency divider comprises a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 12
Dependent Claim
180 words
A tag for use in a presence detection system, comprising a frequency divider; and means for fastening the frequency divider to an article to be detected by the presence detection system; wherein the frequency divider comprises a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 13
Dependent Claim
56 words
A tag according to claim 10, wherein the second circuit includes a variable reactance element in which the reactance varies with variations in energy transferred from the first circuit for causing the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency.
Claim 14
Dependent Claim
30 words
A tag according to claim 11, wherein each circuit includes a capacitance and an inductance coil, with the coils being disposed on magnetic circuit means for enhancing said magnetic coupling.
Claim 15
Dependent Claim
18 words
A tag according to claim 12, wherein the magnetic circuit means consists of a single straight ferromagnetic rod.
Claim 16
Dependent Claim
21 words
A tag according to claim 13, wherein the coils of the respective circuits are disposed about opposite ends of the rod.
Claim 17
Dependent Claim
25 words
A tag according to claim 14, wherein each coil each has an inside dimension that is somewhat larger than the cross-sectional dimension of the rod.
Claim 18
Dependent Claim
15 words
A tag according to claim 11, wherein the variable reactance elements include variable capacitance elements.
Claim 19
Dependent Claim
16 words
A tag according to claim 10, wherein the variable reactance element is a variable capacitance element.
Claim 20
Dependent Claim
30 words
A tag according to claim 10, wherein each circuit includes a capacitance and an inductance coil, with the coils being disposed on magnetic circuit means for enhancing said magnetic coupling.
Claim 21
Dependent Claim
219 words
A presence detection system, comprising means for transmitting an electromagnetic radiation signal at a first frequency into a surveillance zone; a tag for attachment to an article to be detected within the surveillance zone, comprising a frequency divider and means for fastening the frequency divider to an article to be detected by the presence detection system; wherein the frequency divider comprises a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency; and means for detecting electromagnetic radiation at the second frequency in the surveillance zone.
Claim 22
Dependent Claim
219 words
A presence detection system, comprising means for transmitting an electromagnetic radiation signal at a first frequency into a surveillance zone; a tag for attachment to an article to be detected within the surveillance zone, comprising a frequency divider and means for fastening the frequency divider to an article to be detected by the presence detection system; wherein the frequency divider comprises a first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency; and a second resonant circuit that is resonant at a second frequency that is one-half the first frequency for transmitting electromagnetic radiation at the second frequency; wherein the first circuit is coupled only magnetically to the second circuit to transfer energy to the second circuit in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and wherein the first circuit includes a variable reactance element in which the reactance varies with variations in energy received by the first circuit for causing the second circuit to vary in reactance due to mutual reactive coupling to cause the second circuit to transmit electromagnetic radiation at the second frequency in response to the energy transferred from the first circuit at the first frequency; and means for detecting electromagnetic radiation at the second frequency in the surveillance zone.
Claim 23
Dependent Claim
32 words
A presence detection system according to claim 19, wherein each circuit includes a capacitance and an inductance coil, with the coils being disposed on magnetic circuit means for enhancing said magnetic coupling.
References Cited (Backward Citations)
US4481428A
Cited
US4670740A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-11-11 | 1995-05-13 | 1995-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-11-11 | 1999-05-13 | 1999-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-11-11 | 2003-05-13 | 2003-11-12 | $7700.00 | Window Closed / Lapsed |