Bio-impedance Spectroscopy System with Broadband Signal Generator
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Solution Overview
Problem
Current bio-impedance spectroscopy systems face challenges in achieving a high signal-to-noise ratio over a wide frequency range while being power-efficient, especially when simultaneously measuring bio-impedance and ECG, due to the need for wideband amplifiers and high-speed ADCs, which increase power consumption and system complexity.
Innovation Solution
An impedance spectroscopy system with a signal generator producing a broadband frequency spectrum and an analog injection current with a high pass frequency characteristic, allowing for simultaneous multi-parameter measurements using a single voltage readout channel, and incorporating a pseudo-random binary sequence and digital differentiation to adapt to bio-impedance behavior and amplifier characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wideband amplifiers and high-speed ADCs are used to achieve high signal-to-noise ratio over wide frequency range, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The patent employs periodic square wave stimulation signals at multiple frequencies to excite the bio-impedance network. By using periodic actions at different frequencies and combining the responses through correlation analysis, the system achieves high signal-to-noise ratio measurements across a wide frequency range without requiring wideband amplifiers or high-speed ADCs, thus reducing power consumption.
Solution Approach 2:
The patent replaces the conventional mechanical/electronic approach of using wideband amplifiers and high-speed ADCs with a signal processing approach. By using correlation analysis between the stimulation signal and the measured response, the system extracts impedance information across a wide frequency range from a narrowband measurement, substituting hardware complexity with algorithmic processing.
2Adaptability or versatility
If multiple separate readout circuits are used for simultaneous bio-impedance and ECG measurement, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent uses a single readout circuit that can measure both bio-impedance and ECG signals by utilizing the same hardware for different measurement purposes. The system distinguishes between bio-impedance and ECG measurements through the frequency characteristics of the stimulation signal and correlation analysis, allowing one circuit to serve multiple functions and reducing overall system complexity.
Solution Approach 2:
The patent creates a virtual copy of the ECG signal processing path within the bio-impedance measurement system. By using correlation analysis with the known stimulation signal pattern, the system extracts ECG information from the same measurement channel that is used for bio-impedance measurement, effectively copying the ECG analysis capability without requiring separate hardware.
3Measurement precision
If analog signal processing is used for multi-frequency bio-impedance measurement, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent uses periodic square wave stimulation signals at multiple frequencies simultaneously and processes the responses using correlation analysis. By applying periodic actions across different frequencies and using the time-domain correlation method, the system achieves accurate bio-impedance measurements across a wide frequency range without requiring sequential measurement at each frequency, thus reducing acquisition time.
Solution Approach 2:
The patent replaces sequential analog signal processing at each frequency with a simultaneous time-domain correlation analysis approach. By measuring the response to multi-frequency square wave stimulation and using correlation analysis to extract impedance information across all frequencies simultaneously, the system achieves both high measurement precision and reduced acquisition time.
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 enables efficient bio-impedance measurement with a more constant signal-to-noise ratio across frequencies, reduced power consumption, and the ability to measure dynamic impedance variations over a wide range, while also allowing for simultaneous ECG and respiration tracking.
Implementation Method 1
the analog injection signal has a high pass frequency characteristic
Implementation Method 2
measuring a voltage signal in response to the analog injection current
Implementation Method 3
analyzing the voltage signal to derive a bio-impedance spectrum
Data Source
AI summary
The present disclosure is directed to an impedance spectroscopy system for bio-impedance measurement. The impedance spectroscopy system includes a signal generator configured to generate a signal with a broadband frequency spectrum and to generate an analog injection current from the signal with the broadband frequency spectrum. The analog injection current has a high pass frequency characteristic. The impedance spectroscopy system also includes an amplifier configured to measure a voltage signal in response to the analog injection current and to simultaneously measure a biopotential signal. Further, the impedance spectroscopy system includes a processor configured to analyze the voltage signal to derive a bio-impedance spectrum as well to derive further information from the biopotential signal.