Stimulation and recording system with multi-point artifact cancellation
A system and method for reducing or eliminating undesired effects of an artifact on a received signal is disclosed. The signal is generated from stimulating a sample. A receiver includes estimations of artifacts on the signal that are subtracted at different stages of the receiver. The estimations of the artifact may be performed via a successive approximation register scheme.
1 . A signal recorder and stimulator system comprising:
a stimulation electrode operable to be attached to a sample;
a signal generator coupled to the stimulation electrode to provide a stimulation signal to the sample;
a detection electrode operable to be attached to the sample;
a signal recorder including:
an input coupled to the detection electrode, the input receiving an input signal from the sample stimulated by the stimulation signal applied by the stimulation electrode, the input signal including an artifact;
a first artifact estimation logic circuit coupled to the input producing a first artifact estimate;
a first subtraction logic circuit subtracting the first artifact estimation from the input signal to produce a first artifact cancelled signal;
a first low noise amplifier (LNA) receiving the first artifact cancelled signal and outputting an amplified first artifact cancelled signal;
a second artifact estimation logic circuit coupled to the input signal producing a second residual artifact estimate;
a second subtraction logic circuit coupled to the first subtraction logic circuit, the second subtraction logic circuit subtracting the estimate of the second residual artifact from the amplified first artifact cancelled signal to produce a second artifact cancelled signal; and
an analog to digital converter (ADC) receiving the second artifact cancelled signal and outputting an output signal.
2 . The signal recorder and stimulator system of claim 1 , wherein the first and second estimation logic include a successive approximation register (SAR) scheme to estimate the estimation artifacts from the input signal.
3 . The signal recorder and stimulator system of claim 1 , wherein the first artifact estimation logic includes a common mode estimation logic for estimation of common mode of the artifact, and a differential mode estimation logic for estimation of differential mode of the artifact.
4 . The signal recorder and stimulator system of claim 1 , wherein the stimulation signal stimulates a selected neuron or neurons of the sample.
5 . The signal recorder and stimulator system of claim 1 , wherein the signal recorder is a system-on-chip (SoC).
6 . The signal recorder and stimulator system of claim 1 , further comprising:
an electrode coupled to the input;
a second low-noise amplifier (LNA) configured to receive the input signal from the electrode;
a gain amplifier configured to adjust a level of the electrical signals to a level appropriate for the ADC;
a filter configured to remove noise from the input signal; and
a digital signal processor (DSP) coupled to the ADC.
7 . The signal recorder and stimulator system of claim 6 , wherein the DSP is further configured to estimate and subtract a third residual stimulation artifact from the output signal from the ADC.
8 . The signal recorder and stimulator system of claim 7 , wherein the first estimation of the artifact is subtracted from the input signal by the first subtraction logic at a first point before the LNA to cancel the artifact at a first point; and wherein the second estimate of the residual artifact is subtracted from the input signal by the second subtraction logic at a second point before the gain amplifier.
9 . The signal recorder and stimulator system of claim 8 , further comprising:
a first digital-to-analog converter (DAC) configured to convert a digital representation of the first artifact estimation into an analog waveform; and
a second DAC configured to convert a digital representation of the second artifact estimation into an analog waveform.
10 . The signal recorder and stimulator system of claim 6 , further comprising:
a plurality of electrodes for receiving stimulation signals including the electrode;
a plurality of inputs including the input, each of the inputs coupled to one of the plurality of inputs;
multiple front end circuits, each having a stimulator and a low noise amplifier and defining a signal channel, wherein the low noise amplifier is part of one the multiple front end circuits, wherein each of the front end circuits are coupled to one of a plurality of inputs; and
a multiplexer sending signals selected from the plurality of front end circuit to a back end circuit including the gain amplifier.
11 . The signal recorder and stimulator system of claim 10 further comprising an offset circuit coupled to each of the channels.
12 . The signal recorder and stimulator system of claim 1 , wherein the artifact is one or more of electrical stimulation, magnetic stimulation, optical stimulation, or acoustic stimulation.
13 . The signal recorder and stimulator system of claim 1 , wherein a least-mean-square (LMS) algorithm trains the coefficients a finite-impulse-response (FIR) or infinite-impulse-response (IIR) filter to estimate the artifact.
14 . The signal recorder and stimulator system of claim 1 , further comprising a memory storing the first artifact estimation and the second artifact estimation, wherein the signal recorder includes an estimation phase to collect data from the input signal for determining the first and second artifact estimations.
15 . A method of canceling an artifact on an input signal generated from a sample by a stimulation signal, the method comprising:
attaching a stimulation electrode to the sample;
providing the stimulation signal to the sample via a signal generator coupled to the stimulation electrode;
attaching a detection electrode to the sample;
receiving the input signal from the detection electrode from the sample;
determining a first estimation of the artifact via a first estimation logic circuit;
determining a second artifact estimation of a residual of the artifact on the input signal via a second estimation logic circuit;
subtracting the first artifact estimation from the input signal to produce a first artifact canceled signal that is input to a low noise amplifier; and
subtracting the second artifact estimation from an output signal from the low noise amplifier to produce a second artifact canceled signal;
sending the second artifact canceled signal to a gain amplifier.
16 . The method of claim 15 , wherein the determination of the first and second artifact estimation is performed by a successive approximation register (SAR) scheme.
17 . The method of claim 15 , wherein the determination of the first artifact estimation includes estimating a common mode of the artifact, and estimating a differential mode of the artifact.
18 . The method of claim 15 , further comprising estimating and subtracting a third residual stimulation artifact from the input signal via a digital signal processor.
19 . The method of claim 15 , wherein the artifact is one or more of electrical stimulation, magnetic stimulation, optical stimulation, or acoustic stimulation.
20 . The method of claim 15 , further comprising:
storing the first artifact estimation and the second artifact estimation in a memory, wherein the determination of the first artifact estimation and second artifact estimation is determined in an estimation phase to collect data from the input signal; and wherein the subtraction of the first and second artifact estimations is performed in a cancelation phase; and
repeating the estimation phase in response to a changed condition.
21 . A responsive neurostimulation system comprising:
a stimulation electrode operable to be attached to a tissue;
a signal generator coupled to the electrode to provide a stimulation signal to the tissue;
a detection electrode operable to be attached to the tissue;
a signal recorder coupled to the detection electrode, the signal recorder including:
an input receiving an input signal from the detection electrode simultaneously with the signal generator providing the stimulation signal to the tissue;
a first artifact estimation logic circuit coupled to the input producing a first artifact estimate;
a first subtraction logic circuit subtracting the first artifact estimation from the input signal to produce a first artifact cancelled signal;
a first low noise amplifier (LNA) receiving the first artifact cancelled signal and outputting an amplified first artifact cancelled signal;
a second artifact estimation logic circuit coupled to the input signal producing a second residual artifact estimate;
a second subtraction logic circuit coupled to the first subtraction logic circuit, the second subtraction logic circuit subtracting the estimate of the second residual artifact from the amplified first artifact cancelled signal to produce a second artifact cancelled signal; and
an analog to digital converter (ADC) receiving the second artifact cancelled signal and outputting an output signal.