Frequency control circuit for tuning a resonant circuit of an untethered device
First Claim
1. An untethered device configured to inductively couple to a source device, the source device configured to generate a varying magnetic field having a fixed frequency, the untethered device comprising:
- a tunable resonant circuit having a resonance frequency and configured to generate a supply voltage for the untethered device in response to the varying magnetic field, the tunable resonant circuit includingan inductive coil comprising a center tap; and
a capacitive circuit coupled to the inductive coil, the capacitive circuit comprising an anti-series arrangement of varactor diodes that set a capacitance when placed in reverse bias; and
a frequency control circuit coupled to the tunable resonant circuit, the frequency control circuit comprising a control voltage source coupled to the center tap of the inductive coil, the control voltage source producing a control signal to place the varactor diodes in reverse bias and to change the capacitance of the capacitive circuit, thereby effecting a change in the resonance frequency of the tunable resonant circuit.
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Accused Products
Abstract
An untethered device, configured to inductively couple to a source device, includes a tunable resonant circuit having a resonance frequency and configured to generate a supply voltage for the untethered device in response to a varying magnetic field produced by the source device. The tunable resonant circuit includes an inductive coil comprising a center tap and a capacitive circuit coupled to the inductive coil. The capacitive circuit includes an anti-series arrangement of varactor diodes that behave as a capacitance when placed in reverse bias. A frequency control circuit is coupled to the tunable resonant circuit and includes a control voltage source coupled to the center tap of the inductive coil. The control voltage source produces a control signal to place the varactor diodes in reverse bias and to change the capacitance of the capacitive circuit, thereby effecting a change in the resonance frequency of the tunable resonant circuit.
166 Citations
17 Claims
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1. An untethered device configured to inductively couple to a source device, the source device configured to generate a varying magnetic field having a fixed frequency, the untethered device comprising:
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a tunable resonant circuit having a resonance frequency and configured to generate a supply voltage for the untethered device in response to the varying magnetic field, the tunable resonant circuit including an inductive coil comprising a center tap; and a capacitive circuit coupled to the inductive coil, the capacitive circuit comprising an anti-series arrangement of varactor diodes that set a capacitance when placed in reverse bias; and a frequency control circuit coupled to the tunable resonant circuit, the frequency control circuit comprising a control voltage source coupled to the center tap of the inductive coil, the control voltage source producing a control signal to place the varactor diodes in reverse bias and to change the capacitance of the capacitive circuit, thereby effecting a change in the resonance frequency of the tunable resonant circuit. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An untethered device configured to inductively couple to a source device, the source device configured to generate a varying magnetic field having a fixed frequency, the untethered device comprising:
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a tunable resonant circuit having a resonance frequency and configured to generate a supply voltage for the untethered device in response to the varying magnetic field, the tunable resonant circuit including; an inductive coil comprising a center tap; a capacitive circuit coupled to the inductive coil, the capacitive circuit comprising an anti-series arrangement of varactor diodes that set a capacitance when placed in reverse bias; a frequency control circuit coupled to the tunable resonant circuit, the frequency control circuit comprising a control voltage source coupled to the center tap of the inductive coil, the control voltage source producing a control signal to place the varactor diodes in reverse bias and to change the capacitance of the capacitive circuit, thereby effecting a change in the resonance frequency of the tunable resonant circuit; and
wherein the control voltage source comprises an operational amplifier having a negative input, a positive input, and an output, the output of the operational amplifier coupled to the center tap of the inductive coil. - View Dependent Claims (8, 9)
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10. A method implemented in an untethered device configured to inductively couple to a source device, the source device configured to generate a varying magnetic field having a fixed frequency, the method comprising:
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generating, by a tunable resonant circuit of the untethered device, a supply voltage for the untethered device in response to the varying magnetic field, the tunable resonant circuit comprising an inductive coil coupled to a capacitive circuit, the capacitive circuit comprising an anti-series arrangement of varactor diodes that behave as a capacitance when placed in reverse bias; and producing a control signal and applying the control signal to a center tap of the inductive coil to place the varactor diodes in reverse bias and to change the capacitance of the capacitive circuit, thereby effecting a change in the resonance frequency of the tunable resonant circuit. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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Specification