高共模抑制比心电信号采集模拟前端电路设计_毕业设计_论文.pdf
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2023-10-26
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ABSTRACT
II
ABSTRACT
With the development of economy and society, peoples attention to their own health
has gradually increased, which has also led to the flourishing development of wearable
biomedical sensors. Wearable biomedical sensors enable real-time monitoring of human
health and timely warning of possible abnormalities in the body, thereby reducing the
prevalence, severity and mortality of users. A bioelectric signal acquisition and sensing
system with excellent performance needs an analog front-end circuit with low power
consumption, low size, low noise and high interference suppression capability.
Bioelectric signal has the characteristics of low frequency and low amplitude, and is
very vulnerable to external environmental interference and the noise of its own circuit.
For two-electrode ECG signal acquisition system, the peak value of common mode
interference signal coupled to human body by surrounding power lines can be as high as
tens of volts, leading to the saturation of the front-end circuit. There is a large impedance
mismatch between the dry electrode models, which will affect the common mode
rejection ratio (CMRR) of the front-end circuit system, and will introduce the error of
common mode slip mode. The electrodes react with human skin by introducing a larger
DC electrode offset (DEO) voltage. In addition, the presence of an impedance voltage
component in the signal pathway can cause signal attenuation. Finally, the noise in the
front-end circuit will affect the accuracy of signal collection.
To solve the above problems, this thesis presents a front-end circuit for two-electrode
ECG acquisition, which is mainly composed of common-mode interference suppression
module and signal amplification module. The signal amplification module is composed
of instrument amplifier module and programmable gain amplifier (PGA) module
combined with input impedance lifting technology. In this design, a common mode
interference suppression module circuit is proposed to suppress the common mode
interference signal. The integrated common mode replication technology can greatly
increase the common mode input impedance to weaken the influence of electrode
mismatch on the common mode rejection ratio. An adaptive input impedance lifting loop
is presented to reduce the influence of input capacitance and input parasitic capacitance
on the input differential mode impedance of the signal amplifier module. A capacitive
coupled instrumentation amplifier is used to reduce the system mismatch caused by poor
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