Modulation of the resonant frequency of a circuit using an energy field
First Claim
1. A transponder comprising:
- two or more fixed electromagnetic energy storage components; and
one or more variable electromagnetic energy storage components, each of the variable electromagnetic energy storage components capable of periodically varying when excited by an external modulating energy field having, a modulating frequency, each of the variable electromagnetic energy storage components having a quiescent value when not excited by the external modulating energy field, the fixed electromagnetic energy storage components and the variable electromagnetic energy storage components electrically connected to form a resonant circuit with a circuit resonance frequency determined by the fixed electromagnetic energy storage components and the quiescent values of the variable electromagnetic energy storage components, the external modulating energy field exciting one or more of the variable electromagnetic energy storage components to continuously vary the circuit resonance about the circuit resonance frequency at the modulation frequency.
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Accused Products
Abstract
A transponder has a resonant RLC circuit with one or more electromagnetic energy storage components that vary in response to an externally applied modulating energy field. In addition to the externally modulating energy field, a base station transmits a carrier signal with a frequency essentially the same as the quiescent resonant frequency of the RLC circuit. As the component(s) vary, the resonant frequency of the RLC circuit changes, modulating the carrier signal with the external modulating energy field. Effects of the modulation are detected by the base station. Information (e.g., the presence of a tag) is obtained by receiving and demodulating the modulated signal at the base station. One or more of the circuit elements (e.g., different preferred embodiments of one or more capacitors, inductors, and resistors) can be varied (e.g. mechanically) to modulate the carrier signal. This allows the resonant circuit to modulate the carrier signal with multiple modulation frequencies to encode multiple bits of information on the carrier.
175 Citations
56 Claims
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1. A transponder comprising:
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two or more fixed electromagnetic energy storage components; and one or more variable electromagnetic energy storage components, each of the variable electromagnetic energy storage components capable of periodically varying when excited by an external modulating energy field having, a modulating frequency, each of the variable electromagnetic energy storage components having a quiescent value when not excited by the external modulating energy field, the fixed electromagnetic energy storage components and the variable electromagnetic energy storage components electrically connected to form a resonant circuit with a circuit resonance frequency determined by the fixed electromagnetic energy storage components and the quiescent values of the variable electromagnetic energy storage components, the external modulating energy field exciting one or more of the variable electromagnetic energy storage components to continuously vary the circuit resonance about the circuit resonance frequency at the modulation frequency. - View Dependent Claims (2, 3, 4, 5, 6, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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7. A transponder, as in 6, where the movement is a non-resonance response to the external modulating energy field and the external modulating energy field has a frequency not equal to any of the mechanical resonance frequencies of the constrained plate.
- 30. A transponder, as in 28, where the first plate is constrained by an elastic link that provides a restoring force giving rise to one or more mechanical resonant frequencies of the first plate.
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44. A transponder comprising:
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a resonant circuit having two or more electromagnetic energy storage components that determine a circuit resonance frequency of the resonant circuit; an external modulating energy field, having one or more modulating frequencies, one or more of the electromagnetic energy storage components being a varying component, the varying component being varied at a component frequency by the external modulating energy field, the component frequency being a mechanical resonance of the varying component, the varying component causing the circuit resonance frequency to change at the component frequency; and an electromagnetic carrier field with a carrier frequency, the carrier frequency being equal to the circuit resonance frequency and the carrier frequency being modulated with one or more component frequencies to encode information on the carrier frequency. - View Dependent Claims (45)
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46. A system for obtaining information from a transponder, comprising:
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a base station that transmits an electromagnetic carrier field with a carrier frequency and an external modulating energy field, the external modulating energy field having one or more modulating frequencies; a transponder having a resonant circuit with two or more electromagnetic energy storage components that determine a circuit resonance frequency of the resonant circuit, the circuit resonance frequency equal to the carrier frequency, one or more of the electromagnetic energy storage components being a varying component, each of the varying components being varied at a component frequency by one of the modulating frequencies, the varying component causing the circuit resonance frequency to change thereby modulating the carrier field with one or more component frequencies to encode information on the carrier field; and a receiver for receiving the modulated carrier field and detecting the information on the carrier field. - View Dependent Claims (47, 48, 49, 50, 51)
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52. A transponder comprising:
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two or more fixed electromagnetic energy storage component means; and one or more variable electromagnetic energy storage component means, each of the variable electromagnetic energy storage component means for periodically varying when excited by an external modulating energy field having a modulating frequency, each of the variable electromagnetic energy storage component means having a quiescent value when not being excited by the external modulating energy field, the fixed electromagnetic energy storage component means and the variable electromagnetic energy storage component means for being electrically connected to form a resonant circuit with a circuit resonance frequency determined by the fixed electromagnetic energy storage component means and the quiescent values of the variable electromagnetic energy storage component means, the external modulating energy field exciting one or more of the variable electromagnetic energy storage component means to continuously vary the circuit resonance about the circuit resonance frequency at the modulation frequency.
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53. A method of creating a modulated carrier field comprising the steps of:
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transmitting an electromagnetic carrier field and an external modulating energy field, the electromagnetic carrier field having a carrier frequency and the external modulating energy field having one or more modulating frequencies; and modulating the carrier field with a transponder, the transponder having a resonant circuit with two or more electromagnetic energy storage components that determine a circuit resonance frequency of the resonant circuit, the circuit resonant frequency being equal to the carrier frequency one or more of the electromagnetic energy storage components being a varying component, each of the varying components being varied at a component frequency by one of the modulating frequencies, the varying component causing the circuit resonance frequency to change thereby modulating the carrier field with one or more component frequencies. - View Dependent Claims (54, 55, 56)
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Specification