Digitally invertible universal amplifier for recording and processing of bioelectric signals

Patent metadata

Field	Value
Publication number	US-9622672-B2
Application number	US-201414896337-A
Country	US
Kind code	B2
Filing date	Jun 6, 2014
Priority date	Jun 7, 2013
Publication date	Apr 18, 2017
Grant date	Apr 18, 2017

Abstract

A system for measuring electrical signals in a biological subject includes a variable gain amplifier with a predetermined transfer function that generates amplified signals corresponding to an input from electrical signals in the biological subject over a predetermined range of frequencies and amplification gain levels, an analog to digital converter generating digital data corresponding to the amplified signals, and a signal processing device receiving the digital data for the plurality of amplified signals. The signal processing device applies an inversion filter with another transfer function that is an inverse of the transfer function of the variable gain amplifier to remove an effect of the transfer function from the digital data, and generates an output signal corresponding to the electrical signals in the subject with reference to the filtered digital data.

First claim

The invention claimed is:

1. A system for measuring electrical signals in a biological subject comprising:
a variable gain amplifier configured to generate a plurality of amplified signals corresponding to an input from a plurality of electrical signals measured in the biological subject over a predetermined range of frequencies at a plurality of predetermined amplification gain levels, the variable gain amplifier having a predetermined transfer function;
an analog to digital converter (ADC) operatively connected to an output of the variable gain amplifier and configured to generate digital data corresponding to the plurality of amplified signals from the variable gain amplifier;
a signal processing device connected to an output of the ADC to receive the digital data corresponding to the plurality of amplified signals, the signal processing device being configured to:
apply an inversion filter to the digital data to generate filtered digital data, the inversion filter having another predetermined transfer function that is an inverse of the transfer function of the variable gain amplifier to remove an effect of the transfer function in the variable gain amplifier from the digital data; and
generate an output signal corresponding to the plurality of electrical signals in the subject with reference to the filtered digital data;

a signal generator configured to generate a predetermined signal for input to the variable gain amplifier;
a signal acquisition device configured to measure another signal from the output of the variable gain amplifier corresponding to the amplified predetermined signal; and
the signal processing device being connected to the signal acquisition device and further configured to:
identify an error between the signal from the variable gain amplifier corresponding to the amplified predetermined signal and an expected amplified signal corresponding to the predetermined input signal, the expected amplified signal being identified with reference to the predetermined transfer function of the amplifier;
modify a parameter in the predetermined transfer function of the variable gain amplifier to reduce or eliminate the identified error; and
store the modified parameter in a memory for use in the predetermined transfer function of the inversion filter to reduce an error in the output signal.

2. The system of claim 1 , the variable gain amplifier being configured to amplify each of the plurality of signals at each of the plurality of frequencies by an amount that generates the amplified signals with less than a predetermined direct current (DC) saturation level for the variable gain amplifier.

3. The system of claim 1 , the variable gain amplifier further comprising:
a high-impedance first stage operational amplifier that is configured to receive the plurality of electrical signals measured in the living subject.

4. The system of claim 3 , the variable gain amplifier further comprising:
a low-noise constant gain second stage operational amplifier configured to generate an output with a constant gain from an input signal received from the first stage operational amplifier.

5. The system of claim 4 , the variable gain amplifier further comprising:
a variable gain third stage operational amplifier configured to generate another output with reference to the output from the second stage operational amplifier.

6. The system of claim 1 wherein the transfer function of the variable gain amplifier changes an amplitude and a phase of at least one of the plurality of electrical signals.

7. The system of claim 6 wherein the inverse filter removes the change in amplitude and phase from the transfer function of the variable gain amplifier for the digital data corresponding to the at least one electrical signal.

8. The system of claim 1 wherein the variable gain amplifier is configured to amplify a signal at a first frequency with a first gain level and a signal at a second frequency with a second gain level, the first frequency being lower than the second frequency and the first gain level being lower than the second gain level.

9. The system of claim 1 , the signal processing device being further configured to:
generate data corresponding to a continuous time domain representation of the digital data from the ADC;
generate a continuous time filtered signal from the data corresponding to a continuous time representation of the digital data from the ADC using a continuous time representation of the inversion filter;
identify another error between the predetermined input signal and the continuous time filtered signal;
modify the parameter in the predetermined transfer function of the inversion filter to reduce or eliminate the other identified error; and
store the modified parameter in the memory for use in the predetermined transfer function of the inversion filter to reduce an error in the output signal.

Assignees

• Univ Indiana Res & Tech Corp

Inventors

• Yoshida Ken
• Mauser Kevin
• Stavnshoj Jan

Classifications

• A61B5/7225

  Details of analogue processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation (input circuits for detecting, measuring, or recording bioelectric or biomagnetic signals A61B5/30; specific diagnostic methods using bioelectric or biomagnetic signals A61B5/316) · CPC title

• A61B5/7203

  for noise prevention, reduction or removal · CPC title

• A61B5/0476

  Human Necessities · mapped topic

• A61B5/0402

  Human Necessities · mapped topic

• A61B5/04004 Primary

  Human Necessities · mapped topic