Apparatus and methods for removing a large-signal voltage offset from a biomedical signal

• US 10,686,715 B2
• Filed: 11/19/2018
• Issued: 06/16/2020
• Est. Priority Date: 05/09/2018
• Status: Active Grant

• Current Assignee: BioSig Technologies, Inc.
• Original Assignee: BioSig Technologies, Inc.
• Inventors: Drakulic, Budimir S., Fakhar, Sina, Foxall, Thomas G., Vlajinic, Branislav
• Primary Examiner(s): Kim, Jung
• Application Number:
  US16/195,562
• Publication Number:
  US 20190348975A1
• Time in Patent Office: 575 Days
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00577 Ablation
• CPC Class Codes: A61B 2562/18 Shielding or protection of sensors from environmental influences, e.g. protection from mechanical damage
• CPC Class Codes: A61B 2562/223 Optical cables therefor
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7217 : of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61B 5/7221 : Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7225 : Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7246 : using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/742 : using visual displays A61B5/339 takes precedence
• CPC Class Codes: A61B 5/7435 : Displaying user selection data, e.g. icons in a graphical user interface
• CPC Class Codes: G16H 40/63 : for local operation
• CPC Class Codes: H01L 2924/14335 : Digital signal processor [DSP]
• CPC Class Codes: H02H 9/04 : responsive to excess voltage lightning arrestors H01C7/12, H01C8/04, H01G9/18, H01T
• CPC Class Codes: H02H 9/045 : adapted to a particular application and not provided for elsewhere
• CPC Class Codes: H03F 2200/129 : there being a feedback over the complete amplifier
• CPC Class Codes: H03F 2200/171 : A filter circuit coupled to the output of an amplifier
• CPC Class Codes: H03F 2200/234 : the input amplifying stage being one or more operational amplifiers
• CPC Class Codes: H03F 2200/375 : Circuitry to compensate the offset being present in an amplifier
• CPC Class Codes: H03F 2200/451 : the amplifier being a radio frequency amplifier
• CPC Class Codes: H03F 2203/45116 : Feedback coupled to the input of the differential amplifier
• CPC Class Codes: H03F 2203/45528 : the FBC comprising one or more passive resistors and being coupled between the LC and the IC
• CPC Class Codes: H03F 2203/45601 : the IC comprising one or more passive resistors by feedback
• CPC Class Codes: H03F 3/45 : Differential amplifiers differential sense amplifiers G11C7/062
• CPC Class Codes: H03F 3/45475 : using IC blocks as the active amplifying circuit
• CPC Class Codes: H03F 3/68 : Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03H 2017/0298 : DSP implementation
• CPC Class Codes: H03K 5/125 : Discriminating pulses measuring characteristics of individual pulses G01R29/02; separation of synchronising signals in television systems H04N5/08
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• CPC Class Codes: H04B 1/0039 : using DSP [Digital Signal Processor] quadrature modulation and demodulation
• CPC Class Codes: H04L 43/02 : Capturing of monitoring data
• CPC Class Codes: H04L 47/50 : Queue scheduling

Abstract

Apparatus and methods remove a voltage offset from an electrical signal, specifically a biomedical signal. A signal is received at a first operational amplifier and is amplified by a gain. An amplitude of the signal is monitored, by a first pair of diode stages coupled to an output of the first operational amplifier, for the voltage offset. The amplitude of the signal is then attenuated by the first pair of diode stages and a plurality of timing banks. The attenuating includes limiting charging, by the first pair of diode stages, of the plurality of timing banks and setting a time constant based on the charging. The attenuating removes the voltage offset persisting at a threshold for a duration of at least the time constant. Saturation of the signal is limited to a saturation recovery time while the saturated signal is gradually pulled into monitoring range over the saturation recovery time.

Claims

1. A method of removing a voltage offset from a biomedical signal, comprising:

receiving the biomedical signal at a differential input of an operational amplifier;

amplifying, by the operational amplifier, the voltage offset of the biomedical signal by a gain;

monitoring an amplitude of the voltage offset of the received biomedical signal using a first pair of diode stages coupled to a differential output of the operational amplifier; and

in response to the amplitude of the voltage offset being greater than an activation threshold for a duration of at least a time period, wherein the time period is based on a plurality of timing banks coupled to the first pair of diode stages;

limiting charging, by the first pair of diode stages, of a plurality of timing banks from the biomedical signal;

producing, by the plurality of timing banks, a differential signal;

charging a resistor-capacitor network of the plurality of timing banks;

setting, by the plurality of timing banks, the duration of the time period based on the charging of the resistor-capacitor network;

limiting, by a second pair of diode stages, the differential signal from the plurality of timing banks;

limiting a saturation duration, by the second pair of diode stages, of the differential signal to less than a saturation recovery time; and

attenuating the amplitude of the voltage offset by pulling an output voltage of the second pair of diode stages toward a common mode reference voltage at a common mode node coupled to the plurality of timing banks.

2. The method of claim 1, wherein the attenuating comprises attenuating the voltage offset having the amplitude greater than the activation threshold of about 100 mV.

3. The method of claim 1, wherein the attenuating comprises attenuating the voltage offset having the amplitude greater than the activation threshold for the time period of at least about 10 milliseconds.

4. The method of claim 1, further comprising setting the time period to between and including about 2 milliseconds to about 10 milliseconds.

5. The method of claim 1, further comprising setting the activation threshold to about 100 mV and the gain to about 40.

6. The method of claim 1, further comprising:

determining the activation threshold by the gain of the operational amplifier.

7. The method of claim 1, further comprising setting the activation threshold to about 50 mV and the gain to about 80.

8. The method of claim 1, further comprising setting the activation threshold to about 200 mV and the gain to about 20.

9. The method of claim 1, further comprising:

buffering a common mode signal, by a second operational amplifier having a unity gain, at the common mode node.

10. The method of claim 1, further comprising setting the saturation recovery time to between and including about 50 milliseconds to about 100 milliseconds.

11. The method of claim 1, further comprising:

disconnecting the second pair of diode stages from the common mode node for the biomedical signal having the amplitude of the voltage offset of less than the activation threshold for less than the time period at an input to the operational amplifier, wherein the disconnecting causes an output current of the second pair of diode stages to be about zero.

12. The method of claim 1, further comprising:

pulling, by the second pair of diode stages, a positive input node voltage of the operational amplifier down toward the common mode reference voltage and a negative input node voltage of the operational amplifier up toward the common mode reference voltage.

13. The method of claim 12, further comprising:

limiting, by the second pair of diode stages, the differential signal from the plurality of timing banks, wherein the positive input node voltage and the negative input node voltage are gradually pulled into monitoring range after about the saturation recovery time.