Bioimpedance Analysis Circuit Using Digital Signal Processing
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Solution Overview
Problem
Existing body composition analysis systems face challenges in miniaturization and variability of characteristics when implemented as integrated circuits, particularly in extracting specific frequency components of biological signals for bioimpedance analysis, due to the need for complex band pass filters with many passive elements.
Innovation Solution
A body composition analysis system incorporating a sinusoidal signal generator, synchronous detector, and bioimpedance analyzer, which uses digital-to-analog conversion and low-pass filtering to extract target frequency components with high selectivity, reducing the number of passive elements and area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a band pass filter is used to extract specific frequency components, then frequency selectivity is improved, but device complexity and area increase due to requiring multiple passive elements
Solution Approach 1:
The patent replaces the traditional analog band pass filter (mechanical/electrical system with passive elements) with a digital signal processing approach. A digital band pass filter is implemented using digital signal processing techniques, where the frequency selection is achieved through digital algorithms rather than physical passive components. This substitution dramatically reduces the number of passive elements required while maintaining frequency selectivity, directly resolving the technical contradiction between measurement precision and device complexity.
Solution Approach 2:
The patent changes the operating parameters of the system by moving from analog frequency filtering to digital frequency filtering. The frequency selection parameter is controlled through digital signal processing parameters (such as sampling frequency, filter coefficients, and digital filter order) rather than through physical component values. This parameter change allows flexible frequency selection without requiring changes to physical passive elements, reducing both device complexity and area while maintaining measurement precision.
2Measurement precision
If a band pass filter with multiple passive elements is implemented, then frequency selectivity is improved, but manufacturing precision and characteristic variation worsen
Solution Approach 1:
The patent substitutes the analog band pass filter system with multiple passive elements (resistors, capacitors, inductors) with a digital signal processing system. Digital filters are implemented using active components and digital logic, eliminating the need for precise passive element matching. This substitution removes the source of manufacturing precision problems and characteristic variation, as digital filter performance is determined by software algorithms rather than physical component tolerances.
Solution Approach 2:
The patent uses digital copying of filter characteristics through software implementation. Instead of relying on physical passive elements with inherent tolerances, the filter response is copied and replicated through digital signal processing algorithms. This digital copying ensures consistent frequency selectivity across all devices, eliminating characteristic variation caused by manufacturing tolerances of passive elements.
3Area of moving object
If the body composition analysis system is miniaturized for mobile devices, then portability is improved, but signal processing capability and area for passive elements are reduced
Solution Approach 1:
The patent replaces area-intensive passive filtering components with compact digital signal processing circuits. The digital band pass filter requires minimal physical space compared to analog filters with multiple passive elements, enabling significant miniaturization of the device. This substitution maintains signal processing capability through efficient digital algorithms while dramatically reducing the area required, thus resolving the contradiction between device area and measurement precision.
Solution Approach 2:
The patent segments the signal processing function into discrete digital processing stages that can be efficiently implemented in integrated circuit form. The frequency filtering operation is divided into digital sampling, digital filtering, and signal analysis stages, each requiring minimal area. This segmentation allows the system to maintain full signal processing capability while occupying minimal device area, enabling miniaturization for mobile applications.
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 minimizes area and variation in characteristics while improving selectivity for extracting target frequency components, enhancing the accuracy and portability of bioimpedance analysis in integrated circuits.
Implementation Method 1
a digital-to-analog converter that converts the digital sinusoidal signal to an analog sinusoidal signal
Implementation Method 2
The synchronous detector extracts a target frequency component of a bioelectrical signal generated in response to an analog sinusoidal signal based on a digital sinusoidal signal
Implementation Method 3
The low-pass filter may filter components below the reference frequency of the mixed signal. In this case, the low-pass filter may extract the DC (Direct Current) component of the mixed signal
Implementation Method 4
The body composition analysis system using the bioelectrical impedance analysis (BIA) method is attracting attention in that it may analyze the body composition by calculating the impedance inside the body
Data Source
AI summary
The inventive concept relates to a body composition analysis system. A body composition analysis system according to an embodiment of the inventive concept includes a sinusoidal signal generator, a synchronous detector, and a bioimpedance analyzer. The sinusoidal signal generator converts a digital sinusoidal signal having a target frequency into an analog sinusoidal signal. The synchronous detector extracts a target frequency component of a bioelectrical signal generated in response to an analog sinusoidal signal based on the digital sinusoidal signal. The bioimpedance analyzer calculates the bioimpedance based on the target frequency component of the bioelectrical signal. According to the inventive concept, it is possible to improve the selectivity for extracting the target frequency component of the bioelectrical signal and to reduce the area and variations of characteristics for the implementation of the integrated circuit.