Device for punctual measurement of a radiofrequency magnetic field with constant amplitude and frequency
First Claim
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1. A device, comprising:
- a support, wherein the support carries;
at least one coil;
a voltage controlled oscillator having an output frequency that depends on an amplitude of a magnetic field at the at least one coil;
an absorption modulation load, wherein current through the absorption modulation load is chopped at the output frequency of the voltage controlled oscillator which results in modulating current in the at least one coil; and
an antenna coupled to the at least one coil, wherein the antenna provides an output voltage alternating at a frequency of the magnetic field and modulated in amplitude at the output frequency of the voltage controlled oscillator.
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Abstract
The invention concerns a device for measuring a radiofrequency magnetic field, characterised in that it comprises on a common support (10): a coil forming a primary reception antenna; a voltage-controlled oscillator, monitored so that its output frequency depends on the amplitude of the magnetic field received on the coil forming primary antenna; an absorption modulation load connected to the oscillator output; a secondary antenna (22) sensitive to the magnetic field influenced by the absorption modulation resulting from the power supply load by the voltage-controlled oscillator, and means (30) for operating the available signal on the secondary antenna (22).
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Citations
26 Claims
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1. A device, comprising:
a support, wherein the support carries; at least one coil; a voltage controlled oscillator having an output frequency that depends on an amplitude of a magnetic field at the at least one coil; an absorption modulation load, wherein current through the absorption modulation load is chopped at the output frequency of the voltage controlled oscillator which results in modulating current in the at least one coil; and an antenna coupled to the at least one coil, wherein the antenna provides an output voltage alternating at a frequency of the magnetic field and modulated in amplitude at the output frequency of the voltage controlled oscillator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of using a device for determining a value of a magnetic field, the method comprising:
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said device rectifying an alternating voltage output from at least one coil in an alternating magnetic field; said device controlling a voltage controlled oscillator using the rectified voltage; said device outputting a signal from the voltage controlled oscillator, wherein the signal has a frequency that depends on an amplitude of the magnetic field at the at least one coil; said device chopping current in a modulation resistance connected between the rectified voltage and a switching device that receives the signal from the voltage controlled oscillator, wherein current through a modulation resistance is chopped at the frequency of the signal from the voltage controlled oscillator which results in modulating current in the at least one coil; and said device determining a value of the magnetic field by demodulating an output voltage of an antenna coupled to the at least one coil, wherein the output voltage alternates at a frequency of the magnetic field and is modulated in amplitude at the frequency of the signal from the voltage controlled oscillator. - View Dependent Claims (16, 17, 18, 19)
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20. A device comprising:
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a sensor comprising; a coil; a voltage controlled oscillator having an output frequency that depends on an amplitude of a magnetic field at the coil; and an absorption modulation load, wherein current through the absorption modulation load is generated by a voltage induced in the coil by the magnetic field, and wherein the current is chopped at the output frequency of the voltage controlled oscillator; and an antenna, wherein the antenna comprises a plurality of turns of an electrical conductor wound around the sensor. - View Dependent Claims (21)
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22. A device made by a method comprising:
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populating a chip with at least a coil, a voltage controlled oscillator, and an absorption modulation load, wherein the voltage controlled oscillator has an output frequency that depends on an amplitude of a magnetic field at the coil, and current through the absorption modulation load is generated by a voltage induced in the coil by the magnetic field, and wherein the current is chopped at the output frequency of the voltage controlled oscillator; and forming an antenna by winding a plurality of turns of an electrical conductor around the chip. - View Dependent Claims (23, 24)
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25. A device, comprising:
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at least one coil; a voltage controlled oscillator having an output frequency that depends on an amplitude of a magnetic field at the at least one coil; an absorption modulation load, wherein current through the absorption modulation load is chopped at the output frequency of the voltage controlled oscillator which results in modulating current in the at least one coil; and an antenna coupled to the at least one coil, wherein the antenna provides an output voltage alternating at a frequency of the magnetic field and modulated in amplitude at the output frequency of the voltage controlled oscillator; wherein the magnetic field is emitted by a second coil.
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26. A device, comprising:
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at least one coil; a voltage controlled oscillator having an output frequency that depends on an amplitude of a magnetic field at the at least one coil; an absorption modulation load, wherein current through the absorption modulation load is chopped at the output frequency of the voltage controlled oscillator which results in modulating current in the at least one coil; and an antenna coupled to the at least one coil, wherein the antenna provides an output voltage alternating at a frequency of the magnetic field and modulated in amplitude at the output frequency of the voltage controlled oscillator; wherein the antenna surrounds the at least one coil, the voltage controlled oscillator and the absorption modulation load.
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Specification