Method and apparatus for digital demodulation and further processing of signals obtained in the measurement of electrical bioimpedance or bioadmittance in an object
First Claim
1. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of a biological object, wherein the method comprises the following operations:
- placing a first current electrode and a second current electrode in contact with the biological object;
placing a first voltage sensing electrode and a second voltage sensing electrode in contact with the biological object;
applying an output of an AC current source to the first current electrode and the second current electrode, to cause an AC current to flow through the biological object between the first current electrode and the second current electrode;
measuring a voltage across the first voltage sensing electrode and the second voltage sensing electrode, wherein the measured voltage is produced due to application of the output of the AC current source to the first current electrode and the second current electrode;
digitizing the measured voltage to produce Object Voltage Samples;
obtaining a real part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with corresponding reference current samples; and
obtaining an imaginary part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with corresponding reference current samples that are shifted in phase by −
90 degrees.
1 Assignment
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Accused Products
Abstract
Methods and apparatus for digital demodulation of signals obtained in the measurement of electrical bioimpedance or bioadmittance of an object. One example comprises: generating an excitation signal of known frequency content; applying the excitation signal to the object; sensing a response signal of the object; sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase; correlating, for each frequency fAC of the excitation signal applied, digitized samples of the response signal, with discrete values representing the excitation signal; calculating, using the correlated signals for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC); providing, over time, a set of digital bioimpedance waveforms Z(fAC,t)); separating the base bioimpedance Z0(fAC), from the waveforms; and separating the changes of bioimpedance ΔZ(fAC,t), from the waveforms.
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Citations
105 Claims
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1. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of a biological object, wherein the method comprises the following operations:
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placing a first current electrode and a second current electrode in contact with the biological object;
placing a first voltage sensing electrode and a second voltage sensing electrode in contact with the biological object;
applying an output of an AC current source to the first current electrode and the second current electrode, to cause an AC current to flow through the biological object between the first current electrode and the second current electrode;
measuring a voltage across the first voltage sensing electrode and the second voltage sensing electrode, wherein the measured voltage is produced due to application of the output of the AC current source to the first current electrode and the second current electrode;
digitizing the measured voltage to produce Object Voltage Samples;
obtaining a real part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with corresponding reference current samples; and
obtaining an imaginary part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with corresponding reference current samples that are shifted in phase by −
90 degrees. - View Dependent Claims (2, 3)
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4. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of a biological object, wherein the method comprises the following operations:
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placing a first current electrode and a second current electrode in contact with the biological object;
placing a first voltage sensing electrode and a second voltage sensing electrode in contact with the biological object;
applying an output of an AC current source to the first current electrode and the second current electrode, to cause an AC current to flow through the biological object between the first current electrode and the second current electrode;
measuring a voltage between the first voltage sensing electrode and the second voltage sensing electrode, wherein the measured voltage is produced due to application of the output of the AC current source to the first current electrode and the second current electrode;
digitizing the measured voltage to produce Object Voltage Samples;
producing a voltage that is directly proportional to, and in phase with, the output of the AC current source;
digitizing the voltage that is directly proportional to, and in phase with, the output of the AC current source, to produce Object Current Samples;
obtaining a real part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with the Object Current Samples; and
obtaining an imaginary part of the bioimpedance of the biological object, by correlating the Object Voltage Samples with corresponding Object Current Samples that are shifted in phase by −
90 degrees. - View Dependent Claims (5, 6, 7)
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8. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of an object, wherein the method comprises the following operations:
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placing a first current electrode and a second current electrode in contact with the object;
placing a first voltage sensing electrode and a second voltage sensing electrode in contact with the object;
applying the output of an AC current source to the first current electrode and the second current electrode, to cause an AC current to flow through the object between the first current electrode and the second current electrode;
measuring a voltage between the first voltage sensing electrode and the second voltage sensing electrode, wherein the measured voltage is produced due to application of the output of the AC current source to the first current electrode and the second current electrode;
digitizing the measured voltage to produce Object Voltage Samples;
calculating an in-phase portion of the AC current through the object, by correlating the Object Current Samples with corresponding discrete values of a unity sine waveform; and
calculating a quadrature portion of the AC current through the object, by correlating the Object Current Samples with corresponding discrete values of a unity cosine waveform. - View Dependent Claims (9, 10, 11)
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12. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of a biological object, wherein the method comprises the following operations:
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applying the output of an AC current source to a calibration impedance, to cause an AC current to flow through the calibration impedance;
measuring a voltage across the calibration impedance, wherein the measured voltage is produced due to application of the AC current source to the calibration impedance;
digitizing the voltage measured across the calibration impedance to produce Calibration Voltage Samples;
calculating a value proportional to an in-phase portion of the calibration impedance uncorrected for measurement system phase shift, by correlating the Calibration Voltage Samples with corresponding discrete values of a unity sine waveform; and
calculating a value proportional to a quadrature portion of the calibration impedance uncorrected for measurement system phase shift, by correlating the Calibration Voltage Samples with corresponding discrete values of a unity cosine waveform. - View Dependent Claims (13, 14, 15, 16)
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17. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of a biological object, wherein the method comprises the following operations:
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applying the output of an AC current source to a calibration impedance, to cause an AC current to flow through the calibration impedance;
producing a voltage that is directly proportional to, and in phase with, the output of the AC current source;
digitizing the voltage that is directly proportional to, and in phase with, the output of the AC current source, to produce Calibration Current Samples;
measuring a voltage across the calibration impedance, wherein the measured voltage is produced due to application of the AC current source to the calibration impedance;
digitizing the voltage measured across the calibration impedance to produce Calibration Voltage Samples;
obtaining a value proportional to the real part of the calibration impedance, by correlating the Calibration Voltage Samples with the Calibration Current Samples;
obtaining a value proportional to the imaginary part of the calibration impedance, by correlating the Calibration Voltage Samples with corresponding Calibration Current Samples that are shifted in phase by −
90 degrees;
calculating a calibration impedance magnitude equivalent, by calculating the square root of the sum of the square of the real part of the calibration impedance and the square of the imaginary part of the calibration impedance; and
calculating a calibration impedance phase plus a measurement system phase shift, by calculating the arctan of the ratio of the imaginary part of the calibration impedance to the real part of the calibration impedance. - View Dependent Claims (18, 19, 20, 21)
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22. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of an object, wherein the method comprises the following operations:
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applying the output of an AC current source to a calibration impedance, to cause an AC current to flow through the calibration impedance;
producing a voltage that is directly proportional to, and in phase with, the output of the AC current source;
digitizing the voltage that is directly proportional to, and in phase with, the output of the AC current source, to produce Calibration Current Samples;
measuring a voltage across the calibration impedance, wherein the measured voltage is produced due to application of the output of the AC current source to the calibration impedance;
digitizing the voltage measured across the calibration impedance to produce Calibration Voltage Samples;
calculating a value proportional to an in-phase portion of the calibration current, by correlating the Calibration Current Samples with corresponding discrete values of a unity sine waveform; and
calculating a value proportional to a quadrature portion of the calibration current, by correlating the Calibration Current Samples with corresponding discrete values of a unity cosine waveform. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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29. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of an object, wherein the method comprises the following operations:
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generating an excitation signal of known frequency content;
applying the excitation signal to the object;
sensing a response signal of the object;
sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal, with discrete values representing the excitation signal;
calculating, using the correlated signals for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC);
providing, over time, a set of digital bioimpedance waveforms Z(fAC,t));
separating the base bioimpedance Z0(fAC) from the waveforms; and
separating the changes of bioimpedance Δ
Z(fAC,t) from the waveforms. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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52. A method for digital demodulation of signals obtained in the measurement of electrical bioadmittance of an object, wherein the method comprises the following operations:
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generating an excitation signal of known frequency content;
applying the excitation signal to the object;
sensing a response signal of the object;
sampling and digitizing the response signal to acquire a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal, with discrete values representing the excitation signal;
calculating, using the correlated signals for each frequency fAC of the excitation signal applied, complex values for the bioadmittance Y(fAC);
providing, over time, a set of digital bioadmittance waveforms Y(fAC,t);
separating the base bioadmittance Y0(fAC) from the waveforms; and
separating the changes of bioadmittance Δ
Y(fAC,t) from the waveforms. - View Dependent Claims (53, 54, 55, 56, 57, 58)
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59. A method for digital demodulation of signals obtained in the measurement of electrical bioimpedance of an object, wherein the method comprises the following operations:
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applying a calibration excitation signal to a calibration impedance;
measuring, sampling and digitizing a signal representing the calibration excitation signal to acquire calibration Excitation Signal Samples;
measuring, sampling and digitizing a calibration response signal across the calibration impedance to acquire calibration Response Signal Samples;
for each frequency fAC of the calibration excitation signal applied to the calibration impedance, correlating the calibration Excitation Signal Samples with discrete values of an ideal sine waveform in order to obtain a value proportional to an in-phase portion of the calibration excitation signal related to the ideal sine waveform as a reference sine; and
for each frequency fAC of the calibration excitation signal applied to the calibration impedance, correlating the calibration Excitation Signal Samples with discrete values of an ideal cosine waveform in order to obtain a value proportional to a quadrature portion of the calibration excitation signal wherein the AC current has a plurality of frequencies. - View Dependent Claims (60, 61, 62, 63)
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64. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioimpedance in an object, the apparatus comprising:
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a voltage controlled current source for generating an excitation signal of known frequency content;
a current monitor coupled to the voltage controlled current source;
a first electrode coupled to the current monitor;
a second electrode coupled to the current monitor, wherein the first and second electrodes are configured for applying the excitation signal to the object;
a differential amplifier;
a third electrode coupled to the differential amplifier;
a fourth electrode coupled to the differential amplifier, wherein the third and fourth electrodes are configured for sensing a response signal across the object due to application of the excitation signal;
a first analog to digital converter coupled to the differential amplifier, wherein the differential amplifier and the first analog to digital converter are configured for acquiring, sampling and digitizing the response signal, to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
a first buffer coupled to the first analog to digital converter for temporarily storing the digitized response signal;
a multiplier/accumulator coupled to the first buffer, for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal, with corresponding discrete values representing the excitation signal; and
a processing unit coupled to the multiplier/accumulator, wherein the processing unit is configured to calculate, for each frequency fAC of the excitation signal applied, complex values for the bioimpedance, from output values received from the multiplier/accumulator, and is further configured to provide, over time, a set of digital bioimpedance waveforms. - View Dependent Claims (65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78)
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79. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioadmittance in an object, the apparatus comprising:
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a voltage controlled current source for generating an excitation signal of known frequency content;
a current monitor coupled to the voltage controlled current source;
a first electrode coupled to the current monitor;
a second electrode coupled to the current monitor, the first and second electrodes for applying the excitation signal to the object;
a differential amplifier;
a third electrode coupled to the differential amplifier;
a fourth electrode coupled to the differential amplifier, the third and fourth electrodes for sensing a response signal across the object due to the application of the excitation signal;
a first analog to digital converter coupled to the differential amplifier, the differential amplifier and the first analog to digital converter for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
a first buffer coupled to the first analog to digital converter for temporarily storing the digitized response signal;
a multiplier/accumulator coupled to the first buffer, for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal, with corresponding discrete values representing the excitation signal;
a processing unit coupled to the multiplier/accumulator, for calculating, for each frequency fAC of the excitation signal applied, complex values for the bioadmittance, from output values received from the multiplier/accumulator, and for providing, over time, a set of digital bioadmittance waveforms;
a filter coupled to the processing unit; and
a monitor coupled to the filter.
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80. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioimpedance in an object, the apparatus comprising:
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signal generating means for generating an excitation signal of known frequency content;
a first pair of electrodes for applying the excitation signal to the object;
a second pair of electrodes for sensing the response signal across the object due to the application of the excitation signal;
first measuring means for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
memory means for temporarily storing the digitized response signal; and
digital demodulation means for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the response signal with corresponding discrete values of a sinusoidal reference signal to the excitation signal. - View Dependent Claims (81, 82, 83, 84, 85, 86)
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87. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioimpedance in an object, the apparatus comprising:
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signal generating means for generating an excitation signal of known frequency content;
a first pair of electrodes for applying the excitation signal to the object;
a second pair of electrodes for sensing a response signal across the object due to the application of the excitation signal;
first measuring means for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
second measuring means for acquiring, sampling and digitizing the excitation signal to obtain a digitized excitation signal representing the excitation signal with respect to frequency content, amplitude and phase;
memory means for temporarily storing the digitized response signal;
processing means for calculating for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC) from the output values of the digital demodulation means, and for providing, over time, a set of digital bioimpedance waveforms Z(fAC,t));
differentiating means for obtaining the rate of change in the bioimpedance waveforms dZ(fAC,t)/dt, and recording means for recording the rate of change in bioimpedance waveforms. - View Dependent Claims (88, 89, 90, 91)
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92. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioimpedance in an object, the apparatus comprising:
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signal generating means for generating an excitation signal of known frequency content;
a first pair of electrodes for applying the excitation signal to the object;
a second pair of electrodes for sensing a response signal across the object due to the application of the excitation signal;
first measuring means for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
second measuring means for digitizing a voltage that is directly proportional to, and in phase with, the excitation signal;
memory means for temporarily storing the digitized response signal;
digital demodulation means for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal with corresponding discrete values of a sinusoidal reference signal to the excitation signal;
processing means for calculating for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC) from the output values of the digital demodulation means, and for providing, over time, a set of digital bioimpedance waveforms Z(fAC,t));
separating means adapted to separate changes in the bioimpedance Δ
Z(fAC,t) from the waveforms;
differentiating means for obtaining a rate of change of the changes in bioimpedance d(Δ
Z(fAC,t))/dt; and
recording means for recording a temporal course of the base bioimpedance and of the changes in bioimpedance. - View Dependent Claims (93, 94, 95)
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96. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioimpedance in an object, the apparatus comprising:
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signal generating means for generating an excitation signal of known frequency content;
a first pair of electrodes for applying the excitation signal to the object;
a second pair of electrodes for sensing a response signal across the object due to the application of the excitation signal;
first measuring means for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
memory means for temporarily storing the digitized response signal;
digital demodulation means for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal with corresponding discrete values of a sinusoidal reference signal to the excitation signal;
processing means for calculating for each frequency fAC of the excitation signal applied, complex values for the bioimpedance Z(fAC) from output values of the digital demodulation means, and for providing, over time, a set of digital bioimpedance waveforms Z(fAC,t));
first separating means adapted to separate a base bioimpedance Z0(fAC) from the waveforms; and
recording means for recording a temporal course of the base bioimpedance. - View Dependent Claims (97, 98, 99, 100, 101, 102, 103, 104)
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105. An apparatus for digital demodulation and further processing of signals obtained to measure electrical bioadmittance in an object, the apparatus comprising:
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signal generating means for generating an excitation signal of known frequency content;
a first pair of electrodes for applying the excitation signal to the object;
a second pair of electrodes for sensing a response signal across the object due to application of the excitation signal;
first measuring means for acquiring, sampling and digitizing the response signal to obtain a digitized response signal representing the response signal with respect to frequency content, amplitude and phase;
memory means for temporarily storing the digitized response signal;
digital demodulation means for correlating, for each frequency fAC of the excitation signal applied, digitized samples of the digitized response signal with corresponding discrete values of a sinusoidal reference signal to the excitation signal;
processing means for calculating for each frequency fAC of the excitation signal applied, complex values for the bioadmittance Y(fAC) from output values of the digital demodulation means, and for providing, over time, a set of digital bioadmittance waveforms Y(fAC,t);
means for, for each frequency fAC of the excitation signal applied, separating the base bioadmittance Y0(fAC) from the bioadmittance waveform Y(fAC,t);
means for, for each frequency fAC of the excitation signal applied, separating the changes of bioadmittance Δ
Y(fAC,t) from the bioadmittance waveform Y(fAC,t); and
recording means for recording a temporal course of the base bioadmittance Y0(fAC).
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Specification