METHOD AND APPARATUS OF A SENSOR AMPLIFIER CONFIGURED FOR USE IN MEDICAL APPLICATIONS
First Claim
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1. A digital filter for fixed-point digital data, comprising:
- a first all-pass digital filter, wherein the first filter performs relative phase shift between constituent signal frequencies within data output from the analog-to-digital converter with a first predetermined profile of frequency-dependent relative phase shift, and wherein the first filter outputs phase-shifted data characterized by the first relative phase shift profile;
a second all-pass digital filter, wherein the second filter performs relative phase shift between constituent signal frequencies within data output from the analog-to-digital converter with a second predetermined profile of frequency-dependent relative phase shift, and wherein the second filter outputs phase-shifted data characterized by the second relative phase shift profile; and
a summer, wherein the summer accepts as inputs the outputs of the two all-pass filters, wherein the summer provides as an output the algebraic sum of the signals provided from the filters, wherein amplitude of content within at least a first predetermined frequency range reinforces through summing, and wherein amplitude of content within at least a second predetermined frequency range is canceled at least in part through summing.
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Abstract
A digital data bandpass filter process using digital signal processing processes raw digital data twice using distinct all-pass filters, wherein the two filters perform different frequency-dependent phase shifts of the digital content. The two filter output streams may be subtracted to remove out-of-band energy. The process produces lower levels of noise and conversion artifacts when used for filtering fixed-point data that may have low energy, and thus few non-zero bits, in the analog input signals, than conventional digital bandpass filters.
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20 Claims
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1. A digital filter for fixed-point digital data, comprising:
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a first all-pass digital filter, wherein the first filter performs relative phase shift between constituent signal frequencies within data output from the analog-to-digital converter with a first predetermined profile of frequency-dependent relative phase shift, and wherein the first filter outputs phase-shifted data characterized by the first relative phase shift profile; a second all-pass digital filter, wherein the second filter performs relative phase shift between constituent signal frequencies within data output from the analog-to-digital converter with a second predetermined profile of frequency-dependent relative phase shift, and wherein the second filter outputs phase-shifted data characterized by the second relative phase shift profile; and a summer, wherein the summer accepts as inputs the outputs of the two all-pass filters, wherein the summer provides as an output the algebraic sum of the signals provided from the filters, wherein amplitude of content within at least a first predetermined frequency range reinforces through summing, and wherein amplitude of content within at least a second predetermined frequency range is canceled at least in part through summing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A filter for fixed-point digital data, comprising:
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first means for all-pass filtering an input having the form of a first succession of digital words comprising data signal samples, wherein the first means for all-pass filtering provides an output having the form of a second succession of digital words, wherein the phase of frequency components of the data signal samples is shifted differentially in accordance with predetermined parameters of the first means for all-pass filtering; second means for all-pass filtering an input having the form of a first succession of digital words comprising data signal samples, wherein the second means for all-pass filtering provides an output having the form of a third succession of digital words, wherein the phase of frequency components of the data signal samples is shifted differentially in accordance with predetermined parameters of the second means for all-pass filtering, and wherein the phase shift of the second means for all-pass filtering differs from the phase shift of the first means for all-pass filtering; means for summing the outputs of the first and second means for all-pass filtering, wherein the means for summing provides an output having the form of a fourth succession of digital words, wherein the difference in phase shift between the respective means for all-pass filtering differentially reinforces and cancels frequency components of the data signal samples. - View Dependent Claims (12, 13, 14, 15)
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16. A method for filtering fixed-point digital data, comprising:
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applying a first all-pass filter function to an input having the form of a first succession of digital words comprising data signal samples, wherein the first filter provides an output having the form of a second succession of digital words, wherein the phase of frequency components of the data signal samples is shifted differentially in accordance with predetermined parameters of the first filter; applying a second all-pass filter function to an input having the form of a first succession of digital words comprising data signal samples, wherein the second filter provides an output having the form of a third succession of digital words, wherein the phase of frequency components of the data signal samples is shifted differentially in accordance with predetermined parameters of the second filter, and wherein the phase shift of the second filter differs from the phase shift of the first filter; applying a summing function to the outputs of the first and second all-pass filters, wherein the summing function provides an output having the form of a fourth succession of digital words, wherein the difference in phase shift between the respective filters differentially applies reinforcement to frequency components over at least a first frequency range and performs cancellation at least in part to frequency components over at least a second frequency range of the spectral content of the data signal samples. - View Dependent Claims (17, 18, 19, 20)
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Specification