Phase-Domain Electrophysiological Recording for Saturation Tolerance
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Solution Overview
Problem
Conventional electrophysiological-recording systems saturate in the presence of large, non-stationary interferers, making it difficult to record weak signals in noisy environments, such as remote locations or clinical settings, due to their limited dynamic range and inability to filter out motion artifacts and man-made interferers.
Innovation Solution
The system employs a phase-domain recording approach using a voltage-controlled-oscillator (VCO) based analog-to-digital converter with duty-cycling and harmonic-mode suppression, along with coarse and fine counting circuits, to convert electrophysiological signals into phase outputs, thereby avoiding saturation and maintaining low input-referred noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-gain amplifiers are used to amplify weak electrophysiological signals, then signal amplification is improved, but saturation occurs due to large interferers
Solution Approach 1:
The system changes the domain of signal representation from voltage to phase. The VCO converts voltage signals to phase-modulated outputs, where the phase difference between oscillator cycles encodes the input signal. This parameter transformation allows the system to handle large voltage swings without saturation while maintaining precision for small signal variations.
Solution Approach 2:
The voltage-controlled oscillator acts as an intermediary device between the input signal and the digital converter. It mediates the signal transformation by converting voltage inputs into phase outputs, which are then counted to produce digital values. This intermediary approach avoids direct voltage amplification that would cause saturation.
2Object-affected harmful factors
If conventional frequency-selective filters are used to remove interferers, then signal filtering is improved, but non-stationary interferers cannot be removed
Solution Approach 1:
The system replaces traditional voltage-domain filtering with phase-domain processing. Instead of using frequency-selective filters that struggle with non-stationary interferers, the VCO-based approach transforms the problem into phase measurement, where interferers affect the absolute phase but not the phase difference between consecutive cycles. This substitution makes the system adaptable to non-stationary conditions.
3Measurement precision
If high voltage gain is used to achieve low input-referred noise, then noise performance is improved, but dynamic range is reduced
Solution Approach 1:
The system changes from voltage gain to phase conversion gain. The VCO provides high conversion gain in the phase domain without the saturation constraints of voltage amplification. The phase difference measurement effectively amplifies small voltage variations while the oscillator's natural frequency stability provides reference for rejecting common-mode interferers, achieving both low noise and high dynamic range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for the recording of signals with saturation tolerance up to 200 mVp-p interferers, effectively recovering desired signals as low as 10 μVp, while maintaining similar power consumption and noise performance to conventional systems, supporting various invasive and non-invasive bio-signals.
Implementation Method 1
an analog to digital converter including a voltage-controlled-oscillator configured to convert the recorded analog electrophysiological input signal to a phase output
Data Source
AI summary
Signal recording sensor systems in accordance with embodiments of the invention include sensors capable of sensing and capturing electrophysiological signals in the presence of interference signals, an analog front-end including circuitry configured to record electrophysiological input signals as a voltage, and an analog to digital converter including a voltage-controlled-oscillator configured to convert the recorded analog electrophysiological input signal to a phase output. While such signal recording sensor systems can be used in the recording of biosignals and/or electrophysiological signals generated from living organisms, signal recording sensor systems in accordance with embodiments of the invention are not limited to recording biosignals and/or electrophysiological signals.