ICG Peak Detection Circuit for Low-Power Wearable Measurement
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Solution Overview
Problem
Existing impedance cardiography (ICG) devices face challenges in achieving small size, low power consumption, and high accuracy due to the use of high-resolution ADCs and complex signal processing, leading to noise and reduced measurement precision, especially when used in wearable devices.
Innovation Solution
The proposed ICG device integrates a positive and negative peak value detection unit with hold functionality, allowing for the use of slower ADCs and simpler hardware, which accurately determines ICG characteristic points by using peak value detection and hold units to stabilize signal values for precise calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution and high-sampling frequency ADC is used, then measurement precision is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary action by detecting and holding peak values of the ICG signal before ADC conversion. The peak detection circuit identifies characteristic points (B, C, X points) and holds their voltage values, allowing the ADC to convert only these pre-selected peak values rather than continuously sampling at high frequency. This preliminary peak detection and holding action enables accurate ICG parameter measurement while significantly reducing ADC energy consumption and sampling frequency requirements.
2Measurement precision
If cascaded differentiators are used to determine characteristic points, then measurement precision is improved, but noise increases
Solution Approach 1:
The patent extracts only the essential characteristic information from the ICG signal by directly detecting peak values using a dedicated peak detection circuit, rather than applying cascaded differentiators that amplify noise. The peak detection circuit identifies B, C, and X points by detecting voltage extrema and their corresponding time points, extracting the necessary characteristic information without the noise-amplifying differentiation process. This extraction approach maintains measurement precision while eliminating the harmful noise effect.
3Measurement precision
If complex signal analysis is performed in local processor, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary peak detection and hold circuit between the ICG signal source and the ADC/processor. This intermediary circuit pre-processes the signal by detecting peak values and holding them until conversion, transforming the complex continuous signal analysis task into simple ADC conversion of pre-identified peak points. The intermediary peak detection circuit performs the sophisticated analysis function hardware-wise, allowing the microcontroller to simply read held voltage values and calculate parameters, thereby reducing processor complexity while maintaining measurement precision.
4Measurement precision
If high-sampling frequency is used, then measurement precision is improved, but device size increases
Solution Approach 1:
The patent applies preliminary action by using a peak detection circuit that identifies and holds characteristic points (B, C, X points) in the ICG signal before ADC conversion. This preliminary detection ensures accurate time domain measurement of characteristic points without requiring high sampling frequency, as the peak detection circuit continuously monitors and captures peak moments regardless of ADC sampling rate. Consequently, the device can use a lower sampling frequency ADC, reducing overall device complexity and size while maintaining time domain measurement precision.
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 approach enhances measurement accuracy and reduces power consumption, enabling the development of compact, low-power ICG devices suitable for wearables by stabilizing signal peaks for precise determination of ICG parameters.
Implementation Method 1
the electrical bioimpedance signal (acquired, for example, from the patient's chest or wrist)
Data Source
AI summary
The impedance cardiography device comprises an impedance measuring unit, connected to the human body to be measured, a differentiator, a comparator and a microcontroller integrated with an analog-to-digital converter, characterized by that the device further comprises two peak voltage detection units with different polarities (positive and negative), the strobing outputs of them being connected to the digital (binary) inputs of the microcontroller and the analog hold outputs to the inputs of the analog-to-digital converter.