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CN-121995113-A - Integrated impedance measurement system adapting to biological signal acquisition front end

CN121995113ACN 121995113 ACN121995113 ACN 121995113ACN-121995113-A

Abstract

The invention discloses an integrated impedance measurement system adapting to a biological signal acquisition front end, which comprises a sine wave current generator, a band-pass filter, an amplifier module BPFA, a multiplexer and an analog-to-digital converter ADC which are sequentially communicated, wherein the sine wave current generator is used for generating low-amplitude alternating current for measuring tissue-electrode impedance, the alternating current acts on an electrode to be measured to generate corresponding alternating voltage, the band-pass filter and the amplifier module BPFA are used for amplifying and filtering the alternating voltage, the analog-to-digital converter ADC receives the amplified and filtered alternating voltage through the multiplexer to conduct digital signal conversion, and tissue-electrode impedance measurement of the electrode to be measured acting on tissue is completed.

Inventors

  • JIN GANG
  • TANG HUALIAN
  • HAN JINGJING
  • LIU WEIFENG

Assignees

  • 西安电子科技大学

Dates

Publication Date
20260508
Application Date
20260210

Claims (8)

  1. 1. An integrated impedance measurement system adapted to a biological signal acquisition front end is characterized by comprising a sine wave current generator, a band-pass filter, an amplifier module BPFA, a multiplexer and an analog-to-digital converter ADC which are sequentially communicated; The sine wave current generator is used for generating low-amplitude alternating current for measuring tissue-electrode impedance, and the alternating current acts on the electrode to be measured to generate corresponding alternating voltage; The band-pass filter and amplifier module BPFA is used for amplifying and filtering the alternating voltage; the analog-to-digital converter ADC receives the amplified and filtered alternating voltage through the multiplexer to perform digital signal conversion, and the tissue-electrode impedance measurement of the measured electrode acting on the tissue is completed.
  2. 2. The integrated impedance measurement system for adapting a biological signal acquisition front end according to claim 1, wherein the sine wave current generator comprises a digital-to-analog converter DAC, a low pass filter LPF, and a conversion capacitor C S ; The input end of the digital-to-analog converter 8-bit DAC is connected with a band gap reference BG and is used for converting a digital excitation signal into a stepped sine wave voltage signal, and the voltage signal is filtered by a low pass filter LPF and then converted into alternating current through a series conversion capacitor C S to act on a tested electrode.
  3. 3. An integrated impedance measurement system adapted to a biological signal acquisition front end according to claim 2, wherein the capacitance value of the conversion capacitor C S is selectively adjustable by a register.
  4. 4. An integrated impedance measurement system adapted to a biological signal acquisition front end according to claim 2, wherein the sine wave voltage generated by the digital-to-analog converter DAC and having an amplitude V A and a dc offset V off is specifically expressed as follows: (1) where f is the frequency of the sine wave signal and t is time.
  5. 5. The integrated impedance measurement system of claim 4 wherein the ac current injected into the electrode under test is a cosine wave current of zero offset and amplitude, of the formula: (2)。
  6. 6. an integrated impedance measurement system adapted to a biological signal acquisition front end according to claim 1, wherein the digital-to-analog converter DAC is an 8-bit digital-to-analog converter.
  7. 7. An integrated impedance measurement system adapted to a biological signal acquisition front end according to claim 1, wherein the multiplexer is a multiplexer 16:1mux.
  8. 8. An integrated impedance measurement system adapted to a biological signal acquisition front end according to claim 1, wherein the analog-to-digital converter ADC is a 16-bit digital-to-analog converter.

Description

Integrated impedance measurement system adapting to biological signal acquisition front end Technical Field The invention relates to the technical field of tissue-electrode impedance measurement, in particular to an integrated impedance measurement system adapting to a biological signal acquisition front end. Background The stimulation acquisition chip is a core integrated circuit of the biomedical electronic equipment, is mainly applied to implantable medical equipment, integrates two core functions of electric stimulation output and bioelectric signal acquisition, and realizes bidirectional electric interaction between the equipment and biological tissues. At the stimulation level, the chip can output accurate electric stimulation signals according to preset frequency, amplitude and pulse width, and the electric stimulation signals act on target biological tissues such as nerves, muscles and cardiac muscles through electrodes, so that physiological function regulation or treatment is realized, for example, arrhythmia is corrected by outputting electric stimulation to cardiac muscles, and the stimulation is output to specific areas of the brain to relieve the symptoms of Parkinson's disease. On the acquisition level, the chip can capture weak bioelectricity signals with the amplitude of the electrocardio, the electroencephalogram and the myoelectricity generally in the mu V-mV level, process the signals through the built-in amplifying, filtering and analog-to-digital conversion module, output digital signals for analysis and monitor the physiological state of the organism in real time. The chip has the core value of realizing closed-loop control of 'stimulus-acquisition-feedback', has high integration level, small volume and low power consumption compared with the traditional separated stimulus equipment and acquisition equipment, can effectively reduce hardware redundancy, reduces the design difficulty of implanted and portable equipment, and improves the stability and clinical applicability of the equipment. In the stimulation link, the interface impedance of the electrode and the tissue is a key parameter for the transmission of the stimulation signal, and can dynamically change along with the electrode material, the tissue type and the implantation time. The real-time impedance measurement can dynamically adjust the parameters such as the stimulus amplitude, the pulse width and the like. In the acquisition link, bioelectric signals are weak and easy to interfere, the matching degree of electrode impedance and input impedance of the acquisition front end directly determines signal quality, signal partial pressure attenuation and reflection interference can be generated when the impedance is not matched, and weak signals are extremely easy to be submerged after link noise is overlapped, so that acquired data is distorted. The real-time impedance measurement can optimize and adjust the input impedance of the acquisition front end according to the impedance value, maximize the signal receiving efficiency and improve the signal-to-noise ratio. The prior art is as follows: CN 109363674B discloses a multimode bioimpedance measurement system and method, which takes multimode bioimpedance accurate measurement of medical health monitoring scenes as a core target, adopts a full-link architecture of excitation generation, signal conversion, acquisition processing and data output, an excitation module consists of a DDS (direct digital frequency synthesizer) and a pseudorandom sequence generator, can flexibly output single-frequency sine waves, sweep signals and multi-frequency pseudorandom signals under the control of an FPGA (field programmable gate array), supports dynamic adjustment of key parameters such as frequency, amplitude and the like, adapts to impedance measurement requirements of different biological tissues, is designed based on a Howland current source principle, forms a closed-loop feedback network through an operational amplifier and 5 precision resistors, stably converts alternating voltage signals output by the excitation module into constant current signals, ensures that current injected into the biological tissues is not influenced by load impedance change, adopts a time division multiplexing front-end architecture, realizes switching control of a plurality of groups of electrode channels by means of high-performance analog switches, acquires a low-noise amplifier and a low-pass filter which are specially used for acquiring links, performs noise suppression and amplification processing on voltage signals generated at two ends of the electrodes, effectively improves signal quality, and controls and processes the control and the amplitude to provide a time sequence data to be used for the FPGA to support the characteristics of a clinical data, such as a human body, and the clinical tissue monitoring function. CN204600474U discloses a bioimpedance measurement circuit, which is oriented to portable