Digital impedance determination using peak detection of current and voltage samplers
First Claim
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1. A system to compute the parameters of a complex load impedance comprising:
- a signal source;
a load;
a transmission path for transmitting an RF signal from said signal source to said load;
quadrature current samplers for providing measures of the current in the RF signal;
a voltage sampler for providing a measure of the voltage in the RF signal;
plural peak detectors to detect the peak of the measures of current and voltage;
analog to digital converters to convert the signals output from the peak detectors to digital signals;
a digital computational unit to compute the parameters of the impedance of the load from the digital signals and from a signal indicating the frequency of said RF signal sources, wherein the digital computation unit comprises a digital look-up table.
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Abstract
A system and method for determining the complex impedance of a load, such as an antenna in an RF transmission system. The system samples both the voltage and current of the signal passing through a transmission line and directly derives digitally the impedance parameters independently of the amplitude or phase of the signal.
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Citations
16 Claims
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1. A system to compute the parameters of a complex load impedance comprising:
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a signal source; a load; a transmission path for transmitting an RF signal from said signal source to said load; quadrature current samplers for providing measures of the current in the RF signal; a voltage sampler for providing a measure of the voltage in the RF signal; plural peak detectors to detect the peak of the measures of current and voltage; analog to digital converters to convert the signals output from the peak detectors to digital signals; a digital computational unit to compute the parameters of the impedance of the load from the digital signals and from a signal indicating the frequency of said RF signal sources, wherein the digital computation unit comprises a digital look-up table.
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2. A system to compute the parameters of a complex load impedance comprising:
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a signal source; a load; a transmission path for transmitting an RF signal from said signal source to said load; quadrature current samplers for providing measures of the current in the RF signal; a voltage sampler for providing a measure of the voltage in the RF signal;
wherein the voltage sampler comprises an RC network having;a resistor and a capacitor in parallel to each other and in series with said transmission path; and
a resistor and a capacitor in parallel to each other and connected between said transmission path and a ground reference;plural peak detectors to detect the peak of the measures of current and voltage; analog to digital converters to convert the signals output from the peak detectors to digital signals; a digital computational unit to compute the parameters of the impedance of the load from the digital signals and from a signal indicating the frequency of said RF signal sources.
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3. A system to compute the parameters of a complex load impedance comprising:
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a signal source; a load; a transmission path for transmitting an RF signal from said signal source to said load; quadrature current samplers for providing measures of the current in the RF signal; a voltage sampler for providing a measure of the voltage in the RF signal; plural peak detectors to detect the peak of the measures of current and voltage; analog to digital converters to convert the signals output from the peak detectors to digital signals; a digital computational unit to compute the parameters of the impedance of the load from the digital signals and from a signal indicating the frequency of said RF signal sources, wherein a signal P is produced by adding the measure of voltage in the RF signal to a phase shifted version of one of the measures of current. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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11. A circuit for matching the impedance characteristics of a radio frequency signal to a load comprising:
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analog discriminator means for developing analog signals related to an input radio frequency (RF) signal, said discriminator comprising; a quadrature current sampler for providing a measure of the current in the RF signal; a voltage sampler for providing a measure of the voltage in the RF signal; plural peak detectors to detect the peak of the measures of current and voltage; analog to digital conversion means for converting the peak measurement current and voltage signals to digital signals; digital computational unit to compute the parameters of the load from the digital signals and produce parameter signals therefrom; coupling means between the RF signal and the load, responsive to parameter signals to selectively change inductive and capacitive elements in and out of the circuit between the RF signal and the load. - View Dependent Claims (12)
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13. A method of computing the impedance of a load in a circuit for transmitting RF signals comprising the steps of:
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a) sampling first, second and third current samples of an RF signal to be transmitted and passing from a source to a load; b) sampling a voltage sample from the RF signal; c) phase shifting the first and second current samples; d) independently summing each of the first and second current samples with the voltage sample to produce first and second sum samples, respectively; e) detecting a peak signal for each of the first and second sum samples, the third current sample, and the voltage sample to provide first, second, third and fourth peak signals, respectively; f) converting the first, second, third and fourth peak signals to related first, second, third and fourth digital signals; and g) digitally processing the first, second, third and fourth digital signals to provide at least one parameter which describes the impedance of the load. - View Dependent Claims (14, 15, 16)
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Specification