Method and system for eliminating direct current offset between electrodes based on chopping technology

Abstract

The invention discloses a method and a system for eliminating direct current offset between electrodes based on a chopping technology. The method comprises the following steps: step S1, outputting an electroencephalogram signal after chopping modulation and a direct current offset signal between the electrodes; s2, outputting direct current offset current between the electrodes; s3, extracting an integral direct current offset signal; s5, the electroencephalogram signals enter a chip amplification module to be amplified and demodulated, the electroencephalogram signals are returned to an original electroencephalogram signal frequency band, and original electroencephalogram signals are obtained; s6, filtering the original electroencephalogram signals through a low-pass filter to obtain noise-filtered electroencephalogram signals; and S7, transmitting the noise-filtered electroencephalogram signal into a digital-to-analog converter, and converting the noise-filtered electroencephalogram signal into a digital signal. The direct-current servo circuit effectively suppresses direct-current offset between the electrodes, compared with a traditional direct-current servo circuit, the process delay is reduced, meanwhile, the capacitance value of the input capacitor in the circuit is the same as that of the feed-forward capacitor, an ABBA type layout arrangement mode can be adopted, and process errors in the chip manufacturing process are effectively avoided.

Description

technical field [0001] The invention relates to the technical field of integrated circuit design, in particular to a method for eliminating direct current offset between electrodes based on chopper technology. Background technique [0002] With the continuous development of contemporary technology, the research on the brain, the most complex organ in the human body, has become the focus of scholars. Brain-computer interface technology restores the operation mechanism of the brain and controls external devices through several parts such as EEG signal acquisition, feature extraction, feature classification and external control. At present, with the rapid development of smart wearable technology, smart wearable devices worn on the body or integrated into clothing and accessories can collect EEG signals in real time to realize intelligent control. [0003] The quality of the EEG signals collected by the wearable EEG acquisition device directly determines the quality of the data...

AI Technical Summary

Problems solved by technology

In a conventional AC-coupled amplifier, this large DC voltage offset (usually 10mV to 500mV) caused by the acquisition electrode will be directly filtered by the input capacitor without affecting the normal operation of the amplifying unit of the acquisition module, but The use of conventional AC-coupled amplifiers has the disadvantage of high input noise. Therefore, in the acquisition process of weak signals (such as EEG signals, etc.), the input signal is usually modulated by a chopper amplifier to avoid flicker noise at the input end, and then The output terminal demodulates the amplified signal and eliminates the noise in the amplification process through filtering, but amplifying the signal through chopping modulation will cause the acquisition mode of the amplifier to change from AC coupling to DC coupling, which cannot be used for DC voltage offset Filtering, and when the DC offset voltage between the acquisition electrodes enters the amplifier through chopping modulation, it will cause the output voltage of the amplifier to saturate, and the normal amplification work for the target EEG signal cannot be performed, and the subsequent modulus The converter as well as the entire receiver function fails

[0004] Aiming at the problem that the chopper amplifier cannot filter out the DC voltage offset between the electrodes, a common practice is to filter the DC voltage offset by adding a decoupling capacitor before the chopper modulation unit, but this solution requires a relatively large capacitor value. Large (usually on the order of 100nF) decoupling capacitors, which are bulky and not suitable for wearable devices, and will greatly reduce the input impedance of the system

Another way is to extract the DC component at the output of the amplifier through a DC servo loop, and then feedback it at the input of the amplifier to eliminate the DC voltage offset. However, this solution is not suitable due to the slow feedback speed and the introduction of noise. Designed to work with large DC voltage excursions

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