Voltage current sensor with high matching directivity
First Claim
1. A method of deriving current, voltage and phase information for current and voltage components of an RF power wave that is applied at a predetermined radio frequency (RF) to an RF load, and in which a voltage/current probe having a voltage pickup of finite length and a current pickup of finite length applies a voltage pickup signal Vv and a current pickup signal Vi to a signal processor which processes said voltage and current pickup signals to produce values of voltage, current and phase appearing at said load and corrected for effects of standing wave components of voltage and current, comprising:
- computing said voltage as a complex function of the voltage pickup signal and the current pickup signal, based on coefficients precalibrated for said predetermined radio frequency, and computing said current as a complex function of the voltage and current pickup signals based on coefficients pre-calibrated for said radio frequency.
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Accused Products
Abstract
A technique for measuring the current, voltage and phase of an RF power wave to an RF load, accounts for the finite length of the voltage and current pickups, and corrects for effects of standing wave components of voltage and current. Voltage and current are computed as complex functions of the voltage pickup signal and the current pickup signal, based on coefficients precalibrated for said-predetermined radio frequency. Alternatively, a corrected current value can based on the corrected voltage value and complex load impedance. The correction coefficients can be obtained, for each of a plurality of calibrating radio frequencies within an RF range, from voltage and current pickup signals under conditions of (a) open circuit load, (b) short circuit load, (c) fixed known impedance load; and (d) one of voltage and current being applied at a precise input level to a known load from an RF calibration source. The voltage and current probe can comprise a metal housing having a cylindrical bore therethrough, and first and second recesses, a center conductor and cylindrical insulator within said bore and voltage and current sensor boards mounted in the recesses.
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Citations
12 Claims
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1. A method of deriving current, voltage and phase information for current and voltage components of an RF power wave that is applied at a predetermined radio frequency (RF) to an RF load, and in which a voltage/current probe having a voltage pickup of finite length and a current pickup of finite length applies a voltage pickup signal Vv and a current pickup signal Vi to a signal processor which processes said voltage and current pickup signals to produce values of voltage, current and phase appearing at said load and corrected for effects of standing wave components of voltage and current, comprising:
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computing said voltage as a complex function of the voltage pickup signal and the current pickup signal, based on coefficients precalibrated for said predetermined radio frequency, and computing said current as a complex function of the voltage and current pickup signals based on coefficients pre-calibrated for said radio frequency.
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2. A method of deriving current, voltage and phase information for current and voltage components of an RF power wave that is applied at a predetermined radio frequency (RF) to an RF load, and in which a voltage/current probe having a voltage pickup of finite length and a current pickup of finite length applies a voltage pickup signal Vv and a current pickup signal Vi to a signal processor which processes said voltage and current pickup signals to produce values of voltage, current and phase appearing at said load and corrected for effects of standing wave components of voltage and current, comprising:
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computing a corrected voltage value as a complex function of the voltage pickup signal and the current pickup signal, based on coefficients precalibrated for said predetermined radio frequency, computing a complex impedance of said load at said predetermined radio frequency on the basis of said voltage and current pickup signals, and computing a corrected current value based on said corrected voltage value and said complex impedance.
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3. A method of deriving current, voltage and phase information for current and voltage components of an RF power wave, at a selected operating frequency selected within a range of radio frequencies, which power wave is applied to an RF load, and in which a voltage/current probe having a voltage pickup of a finite length and a current pickup of a finite length applies a voltage pickup signal Vv and a current pickup signal Vi to a signal processor which processes said voltage and current pickup signals to produce values of voltage, current, and phase appearing at said load, and corrected for effects of standing wave components of voltage and current;
- comprising,
for each of a plurality of calibrating radio frequencies within said range, obtaining voltage and current pickup signals under conditions of (a) open circuit load, (b) short circuit load, (c) fixed known impedance load; and
(d) one of voltage and current being applied at a precise input level to a known load from an RF calibration source; and
computing and storing correction coefficients based on the voltage and current signal values obtained under said conditions (a) to (d); and
at said selected operating frequency, applying stored correction coefficients to said voltage and current pickup signals to obtain one or more of a corrected voltage value, a corrected current value, and a corrected load impedance value. - View Dependent Claims (4, 5, 6)
- comprising,
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7. Voltage and current probe for detecting voltage and current values of an RF power wave that is applied therethrough to an RF load, comprising:
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a metal housing having a cylindrical bore therethrough, and first and second recesses, the recesses each opening to said bore for an axial distance;
a center conductor extending along the axis of said bore;
a cylindrical insulator within said bore surrounding said center conductor and extending radially between said conductor and said housing;
a voltage sensor board mounted in the first recess and having a capacitive pickup plate facing radially towards the axis of the bore; and
a current sensor board mounted in the second recess and having an elongated inductive pickup conductor facing radially towards the axis of the bore and extending axially for said axial distance. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification