Non-contact sensing node, systems and methods of remote sensing
An example sensing system includes a non-contact sensing electrode configured to sense an electric potential and provide a sensor signal at an output of the sensing electrode based on the sensed electric potential. The output of the sensing electrode is coupled to a first input of an amplifier. The amplifier is configured to provide an amplified output signal representative of at least one measured biosignal based on the sensor signal and a feedback signal provided to the second input of the amplifier. A compensation signal generator is coupled between the output of the amplifier and the second input. The compensation signal generator is configured to estimate corresponding noise and provide the feedback signal to include a filtered signal representative of the estimated noise to the second input to the corresponding noise at the first input of the amplifier and mitigate saturation of the amplifier.
1 . A sensing system comprising:
a non-contact sensing electrode configured to sense an electric potential from an animal subject and provide a sensor signal at an output of the sensing electrode based on the sensed electric potential, wherein the animal subject is spaced a distance apart from and does not contact any part of the sensing electrode;
an amplifier having a first input, a second input, and an output, in which the output of the sensing electrode is coupled to the first input of the amplifier, the amplifier is configured to provide an amplified output signal at the output of the amplifier representative of at least one measured biosignal based on the sensor signal provided to the first input of the amplifier and a feedback signal provided to the second input of the amplifier; and
a compensation signal generator circuit having an input and an output, in which the input of the compensation signal generator circuit is coupled to the output of the amplifier and the output of compensation signal generator circuit is coupled to the second input of the amplifier, the compensation signal generator circuit is configured to estimate noise based on the amplified output signal at the output of the amplifier, the compensation signal generator circuit is configured to provide the feedback signal to the second input of the amplifier, and the feedback signal includes a filtered signal representative of the estimated noise to cancel the estimated noise and mitigate saturation of the amplifier, wherein the amplifier comprises a trans-impedance amplifier; and
a passive impedance device coupled in a feedback path between the output of the amplifier and the first input of the amplifier, in which a gain of the trans-impedance amplifier is set based on an impedance of the passive impedance device.
2 . The system of claim 1 , wherein the passive impedance device comprises a resistor, which is coupled between the output of the amplifier and the first input of the amplifier, having a resistance that is greater than or equal to 100 GΩ.
3 . The system of claim 1 , further comprising a guard electrode adjacent the sensing electrode, wherein the guard electrode includes a first planar portion that is spaced from and parallel to the sensing electrode, the first planar portion coupled to a second portion of the guard electrode that resides in the same plane as and at least partially surrounds the sensing electrode.
4 . The system of claim 1 , further comprising a filter network coupled to the output of the amplifier, the filter network configured to extract the at least one measured biosignal from the amplified output signal.
5 . The system of claim 4 , wherein the filter network further comprises:
a notch filter configured to attenuate frequencies corresponding to expected line noise and provide a first filtered signal; and
at least one biosignal filter path having an input coupled to an output of the notch filter, the biosignal filter path configured to perform multiple filtering stages on the first filtered signal and provide an output signal representative of the at least one measured biosignal.
6 . The system of claim 5 , wherein the at least one biosignal filter path includes a plurality of respective biosignal paths, each configured to provide an output representative of at least one respective biosignal.
7 . A sensing system comprising:
a single non-contact sensing electrode configured to sense an electric potential from an animal subject and provide a sensor signal at an output of the sensing electrode based on the sensed electric potential;
a passive electrical component;
an amplifier having a first input, a second input, and an output, in which the output of the sensing electrode is coupled to the first input of the amplifier, the passive electrical component is coupled between the output of the amplifier and the first input of the amplifier, a gain of the amplifier is set based on an impedance of the passive electrical component, the amplifier is configured to provide an amplified output signal at the output of the amplifier based on the sensor signal received at the first input of the amplifier and a feedback signal provided to the second input of the amplifier, and the amplified output signal is representative of at least one measured biosignal of the animal subject; and
a compensation signal generator circuit having an input and an output, in which the input of the compensation signal generator circuit is coupled to the output of the amplifier and the input of the compensation signal generator circuit is coupled to the second input of the amplifier, the compensation signal generator circuit is configured to estimate at least one of electrical environmental noise and spatial environmental noise based on the amplified output signal, the compensation signal generator circuit is further configured to provide the feedback signal to the second input of the amplifier, and the feedback signal includes a filtered signal representative of the estimated noise to remove the estimated noise and mitigate saturation of the amplifier.
8 . The system of claim 7 , wherein the amplifier comprises a trans-impedance amplifier, and the passive electrical component comprises a resistor having a resistance that is greater than or equal to 100 GΩ.
9 . The system of claim 7 , further comprising a guard electrode adjacent the sensing electrode, wherein the guard electrode includes a first planar portion that is spaced from and parallel to the sensing electrode, the first planar portion of the guard electrode is coupled to a second planar portion of the guard electrode that resides in the same plane as and at least partially surrounds the sensing electrode.
10 . The system of claim 7 , further comprising:
a filter network coupled to the output of the amplifier, wherein the filter network further comprises:
a notch filter configured to attenuate frequencies corresponding to expected line noise and provide a first filtered signal; and
at least one biosignal filter path having an input coupled to an output of the notch filter, the biosignal filter path configured to perform at least one filtering stage on the first filtered signal and provide an output signal representative of the at least one measured biosignal.
11 . The system of claim 7 , wherein the sensing electrode, the amplifier, and the compensation signal generator circuit reside on a printed circuit board, and the sensing electrode lies in a plane that is parallel with a surface of the printed circuit board.
12 . The system of claim 7 , wherein the electrical environmental noise includes power line interference,
wherein the compensation signal generator circuit comprises a power line interference estimator configured to actively estimate an indication of the power line interference in the sensor signal and provide the estimated indication of the power line interference to the second input of the amplifier, and
wherein the compensation signal generator circuit further comprises a motion noise estimator configured to estimate an indication of motion noise due to spatial motion of the animal subject relative to the sensing electrode and provide the estimated indication of motion noise to the second input of the amplifier.