Signal Linearization for Biosignal Measurement Devices
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Solution Overview
Problem
Existing measurement devices face challenges in accurately computing differential biosignal measurements due to common-mode to differential-mode conversion (CM2DM) caused by nonlinear input channel transfer functions.
Innovation Solution
A computer-implemented method for linearizing input signals to a measurement device, which involves reading signals from multiple input channels, applying a linearization function with adjustable parameters to each channel, and using a computation algorithm to derive output measurements. The method includes a calibration operation where constant-value calibration signals are applied to determine the optimal parameters for the linearization function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear transfer functions are used in input channels, then common-mode rejection is improved, but measurement precision deteriorates when nonlinear components (diodes, thyristors, transistors, operational amplifiers, ADCs) are present in the signal path
Solution Approach 1:
The patent applies linearization functions to the input channels before the differential computation is performed. This preliminary linearization compensates for nonlinear distortions introduced by components like diodes, thyristors, transistors, operational amplifiers, and ADCs, ensuring that the subsequent differential calculation operates on linearized signals and achieves both common-mode rejection and measurement precision
Solution Approach 2:
The patent changes the parameters of the input channel transfer functions by applying linearization functions with adjustable parameters. These functions are designed to counteract the nonlinear behavior of components in the signal path, transforming the overall transfer function from nonlinear to linear, thereby resolving the contradiction between common-mode rejection and measurement precision
2Reliability
If transfer functions are made more similar to reduce CM2DM, then common-mode rejection is improved, but measurement precision deteriorates when input signals have different offsets due to nonlinearity
Solution Approach 1:
The patent applies different linearization functions to different input channels, tailored to their specific nonlinear characteristics and offset conditions. Each input channel receives a customized linearization function that accounts for its local nonlinear behavior and offset, rather than applying a uniform linearization approach. This local quality approach ensures that each channel is linearized appropriately for its specific conditions
Solution Approach 2:
The linearization functions are applied to each input channel before the differential computation, preliminarily correcting the nonlinear distortions and offset variations. This preliminary action ensures that when the differential calculation is performed, the signals have already been linearized and offset-corrected, enabling both common-mode rejection and high measurement precision
Data Source
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AI summary
A method for pre-processing electrical sensing signals for compensating for common mode to differential mode conversion caused by signal transfer function nonlinearities. Linearization functions are applied to the input signals to counter the nonlinearities. The method includes a calibration process in which a plurality of sets of standardized test signals are applied to the input channels of the measurement operation, and corresponding test outputs measured for each test signal set. The parameters of the linearization functions are set based on the obtained dataset of test outputs.