Magnetically-coupled, two-resonant-circuit, frequency-division tag
First Claim
1. A batteryless, portable, frequency divider, comprisinga first resonant circuit that is resonant at a first frequency for receiving electromagnetic radiation at the first frequency;
- anda 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 at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and
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.
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Accused Products
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 at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency. The second circuit includes a variable reactance element, such as a variable capacitance diode or varactor, 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. 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.
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Citations
20 Claims
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1. 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 at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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 at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and 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. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. 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 comprisesa 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 at the first frequency in response to receipt by the first circuit of electromagnetic radiation at the first frequency; and 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; and means for detecting electromagnetic radiation at the second frequency in the surveillance zone. - View Dependent Claims (20)
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Specification