Frequency divider with single resonant circuit and use thereof as a transponder in a presence detection system
First Claim
1. A batteryless, portable, frequency divider, consisting ofa single resonant circuit comprisinga nonlinear inductor having a core made of amorphous magnetic material;
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Accused Products
Abstract
A batteryless, portable, frequency divider, consisting of a single resonant circuit including a nonlinear inductor having a core made of amorphous magnetic material; and a capacitance connected in series with the inductor to define a resonant circuit that detects electromagnetic radiation at a first predetermined frequency and responds to said detection by transmitting electromagnetic radiation at a second frequency that is a subharmonic of the first frequency. The resonant circuit may further include a second inductor connected in series with the nonlinear inductor and the capacitance to define the resonant circuit. The core of the nonlinear inductor includes an elongated thin flat ribbon of low coercivity amorphous magnetic material. It has been observed that the resonant circuit exhibits a bifurcated frequency-division characteristic in relation to the amplitude of the detected electromagnetic radiation at the first predetermined frequency, whereby additional frequency divisions occur as the amplitude is increased. This bifurcation characteristic is utilized in a presence detection system that uses a tag containing the frequency divider. The system transmits electromagnetic radiation at the first frequency into a surveillance zone and detects multiple subharmonic frequencies to detect the presence of the tag in the surveillance zone.
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Citations
38 Claims
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1. A batteryless, portable, frequency divider, consisting of
a single resonant circuit comprising a nonlinear inductor having a core made of amorphous magnetic material; - and
a capacitance connected in series with the inductor to define a resonant circuit that detects electromagnetic radiation at a first predetermined frequency and responds to said detection by transmitting electromagnetic radiation at a second frequency that is a sub-harmonic of the first frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A presence detection system, comprising
means for transmitting an electromagnetic radiation signal of a first predetermined frequency into a surveillance zone; -
a tag for attachment to an article to be detected within the surveillance zone, comprising a batteryless, portable, frequency divider consisting of a single resonant circuit comprising a nonlinear inductor having a coil wound around a core made of amorphous magnetic material; and
a capacitance connected in series with the inductor to define a resonant circuit that detects electromagnetic radiation at the first predetermined frequency and responds to said detection by transmitting electromagnetic radiation at a second frequency that is a sub-harmonic of the first frequency;means for providing an external magnetic bias field within the surveillance zone that is equivalent in strength to the magnetic field generated by the saturation current in the coil wound around the core of the nonlinear inductor in response to the detected electromagnetic radiation at the first predetermined frequency; and means for detecting electromagnetic radiation at the second frequency in the surveillance zone. - View Dependent Claims (15, 16)
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17. A presence detection system, comprising
means for transmitting an electromagnetic radiation signal of a first predetermined frequency into a surveillance zone; -
a tag for attachment to an article to be detected within the surveillance zone, comprising a batteryless, portable, frequency divider consisting of a resonant circuit comprising a nonlinear inductor having a core made of amorphous magnetic material; and
a capacitance connected in series with the inductor to define a resonant circuit that detects electromagnetic radiation at the first predetermined frequency and responds to said detection by transmitting electromagnetic radiation at a second frequency that is a sub-harmonic of the first frequency; andmeans for detecting electromagnetic radiation at the second frequency in the surveillance zone. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A batteryless, portable, frequency divider, consisting of
an elongated thin flat ribbon of low coercivity magnetoelastic amorphous magnetic material that has been annealed in a magnetic field that is transverse to the length of the ribbon and in the the plane of the ribbon, which has a characteristic electromagnetic resonant frequency "f", and which detects electromagnetic radiation having a given frequency nf, wherein "n" is an even integer, and responds to the detection of said radiation by transmitting electromagnetic radiation at a subharmonic of the given frequency of the detected radiation.
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27. A presence detection system, comprising
means for transmitting an electromagnetic radiation signal of a first predetermined frequency nf into a surveillance zone; -
a tag for attachment to an article to be detected within the surveillance zone, comprising a batteryless, portable, frequency divider consisting of an elongated thin flat ribbon of low coercivity magnetoelastic amorphous magnetic material that has been annealed in a magnetic field that is transverse to the length of the ribbon and in the the plane of the ribbon, which has a characteristic electromagnetic resonant frequency "f", and which detects electromagnetic radiation having the frequency nf, wherein "n" is an even integer, and responds to the detection of said radiation by transmitting electromagnetic radiation at a sub-harmonic of the frequency of the detected radiation; means for providing an external magnetic bias field within the surveillance zone of sufficient strength to cause the ribbon to frequency divide; and means for detecting electromagnetic radiation at the subharmonic frequency in the surveillance zone. - View Dependent Claims (28, 29)
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30. A batteryless, portable, frequency divider, consisting of
an elongated thin flat ribbon of low coercivity magnetoelastic amorphous magnetic material that has been annealed in a magnetic field that is transverse to the length of the ribbon and in the the plane of the ribbon, and which detects electromagnetic radiation having a given frequency and responds to the detection of said radiation by transmitting electromagnetic radiation at a subharmonic of the given frequency of the detected radiation.
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33. A presence detection system, comprising
means for transmitting an electromagnetic radiation signal of a first predetermined frequency nf into a surveillance zone; -
a tag for attachment to an article to be detected within the surveillance zone, comprising a batteryless, portable, frequency divider consisting of an elongated thin flat ribbon of low coercivity magnetoelastic amorphous magnetic material that has been annealed in a magnetic field that is transverse to the length of the ribbon and in the the plane of the ribbon, and which which detects electromagnetic radiation having the first frequency and responds to the detection of said radiation by transmitting electromagnetic radiation at a sub-harmonic of the frequency of the detected radiation; means for providing an external magnetic bias field within the surveillance zone of sufficient strength to cause the ribbon to frequency divide; and means for detecting electromagnetic radiation at the subharmonic frequency in the surveillance zone. - View Dependent Claims (34, 35)
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36. A coded tag for attachment to an article to be detected within a surveillance zone, comprising
a plurality of a batteryless, portable, frequency dividers, each of which consists of an elongated thin flat ribbon of low coercivity magnetoelastic amorphous magnetic material that has been annealed in a magnetic field that is transverse to the length of the ribbon and in the the plane of the ribbon, which has a characteristic electromagnetic resonant frequency "f", and which detects electromagnetic radiation having the frequency nf, wherein "n" is an even integer, and responds to the detection of said radiation by transmitting electromagnetic radiation at a sub-harmonic of the frequency of the detected radiation; wherein the ribbons of the respective frequency dividers are of different lengths and thereby have different characteristic electromagnetic resonant frequencies. - View Dependent Claims (37, 38)
Specification