Position and movement reasonant sensor
First Claim
1. An apparatus for sensing an object including at least one of a dielectric material, a conductive material, and a magnetic material, comprising:
- a sensor including an inductor formed as a radially wound spiral flat conductor strip having a distributed inductance that produces a uniform magnetic field for sensing a proximity to the magnetic material, a relatively high distributed capacitance that produces a uniform electric field for sensing the proximity to the dielectric material, and a quality factor that varies as a function of the proximity to the conductive material, the sensor having an impedance that is a function of a frequency, the impedance having a maximum value when the frequency equals a resonant frequency of the sensor, the resonant frequency varying as a function of the proximity of the object to the sensor;
an oscillator generating a signal having an operating frequency that substantially equals or is close to the resonant frequency of the sensor;
a high-impedance element coupling the signal from the oscillator to the resonant sensor, the high-impedance element and the resonant sensor forming a voltage divider that produces from the signal a sensor voltage that is proportional to the impedance of the sensor and is, therefore, proportional to the proximity of the object to the sensor; and
a detector extracting from the sensor voltage an output signal representative of the proximity of the object to the sensor.
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Abstract
An object sensing system (10) employs a resonant sensor (20) that receives drive energy coupled from an oscillator (12) operating at a frequency equal or close to the resonant frequency of the resonant sensor. The resonant sensor preferably includes an planar winding (60) that maximizes its distributed inductive and capacitive components, which are sensitive to a proximal conductive, nonconductive, magnetic, or nonmagnetic object (22). The resonant sensor is electrically connected in one leg of a voltage divider that produces a changing output signal voltage in response to resonant frequency changes caused by the object in proximity to the resonant sensor. The signal voltage is amplified, filtered, and processed to extract relevant data indicative of the presence, distance, movement, or proximity of the object.
125 Citations
30 Claims
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1. An apparatus for sensing an object including at least one of a dielectric material, a conductive material, and a magnetic material, comprising:
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a sensor including an inductor formed as a radially wound spiral flat conductor strip having a distributed inductance that produces a uniform magnetic field for sensing a proximity to the magnetic material, a relatively high distributed capacitance that produces a uniform electric field for sensing the proximity to the dielectric material, and a quality factor that varies as a function of the proximity to the conductive material, the sensor having an impedance that is a function of a frequency, the impedance having a maximum value when the frequency equals a resonant frequency of the sensor, the resonant frequency varying as a function of the proximity of the object to the sensor; an oscillator generating a signal having an operating frequency that substantially equals or is close to the resonant frequency of the sensor; a high-impedance element coupling the signal from the oscillator to the resonant sensor, the high-impedance element and the resonant sensor forming a voltage divider that produces from the signal a sensor voltage that is proportional to the impedance of the sensor and is, therefore, proportional to the proximity of the object to the sensor; and a detector extracting from the sensor voltage an output signal representative of the proximity of the object to the sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for sensing an object including at least one of a dielectric material, a conductive material, and a magnetic material, comprising:
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providing a sensor including an inductor formed as a radially wound spiral flat conductor strip having a distributed inductance that produces a uniform magnetic field for sensing a proximity to the magnetic material, a relatively high distributed capacitance that produces a uniform electric field for sensing the proximity to the dielectric material, and a quality factor that varies as a function of the proximity to the conductive material, the sensor having an impedance that is a function of a frequency, the impedance having a maximum value when the frequency equals a resonant frequency of the sensor, the resonant frequency varying as a function of the proximity of the object to the sensor; generating a signal having an operating frequency that substantially equals or is close to the resonant frequency of the sensor; coupling the signal to the resonant sensor; forming across the sensor a sensor voltage that is proportional to the impedance of the sensor and is, therefore, proportional to the proximity of the object to the sensor; and extracting from the sensor voltage an output signal representative of the proximity of the object to the sensor. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A method for sensing an object, comprising:
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providing a sensor having an impedance that is a function of a frequency, the impedance having a maximum value when the frequency equals a resonant frequency of the sensor, the resonant frequency varying as a function of a proximity of the object to the sensor; generating with a voltage controlled oscillator a signal having an operating frequency that varies as a function of a voltage control signal; coupling the signal to the resonant sensor; forming across the sensor a sensor voltage that is proportional to the impedance of the sensor and is, therefore, related to the proximity of the object to the sensor; and deriving the voltage control signal from the sensor voltage to tune the voltage controlled oscillator to the resonant frequency of the sensor. - View Dependent Claims (28)
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29. A method for sensing an object, comprising:
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providing a sensor having an impedance that is a function of a frequency, the impedance having a maximum value when the frequency equals a resonant frequency of the sensor, the resonant frequency varying as a function of a proximity of the object to the sensor; generating a voltage-controlled oscillator signal that is tunable to an operating frequency that includes a resonant frequency of the sensor; coupling the voltage-controlled oscillator signal to the resonant sensor; forming across the sensor a sensor voltage that is proportional to the impedance of the sensor and is, therefore, proportional to the proximity of the object to the sensor; extracting from the sensor voltage an output signal representative of the proximity of the object to the sensor; deriving a voltage control signal from the output signal; and using the voltage control signal to automatically tune the voltage-controlled oscillator to the resonant frequency of the sensor. - View Dependent Claims (30)
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Specification