针对微弱表面肌电信号的采集电路设计

表面肌电信号频率低、极易受干扰，针对此设计基于高阶滤波的信号采集电路。为避免噪声被过度放大而造成信号淹没，电路采用两级放大方案。带通滤波部分采用两组5阶Sallen-Key，以奇次在前、偶次在后的顺序级联，避免输出信号中混入高频泄露信号，且阻带下降速度达-100 dB/dec。此外，陷波器部分设置可调电位器，灵活调整品质因数（Q值），以获得最佳采集效果。结果表明，该电路可实现高达60 dB的放大增益，可有效提取20~500 Hz之间的有用信号，同时很好地抑制50 Hz工频干扰，具有良好的抗噪声性能。

Design of acquisition circuit for weak surface electromyography signals

Abstract: Considering that surface electromyography signals (sEMG) has low frequency and is extremely vulnerable to interference, a signal acquisition circuit based on high-order filtering is designed. A two-stage amplification scheme is adopted in circuit for preventing the noise from being over-amplified. Two sets of 5th-order Sallen-Key is used in band-pass filtering, and the cascaded follows the order of odd first and even second, thereby avoiding mixing high-frequency leakage signals in the output signal and the stop-band descent speed reaches -100 dB/dec. In addition, the notch filter is equipped with an adjustable potentiometer to flexibly adjust the quality factor (Q value) in order to obtain the optimal signal acquisition. The results show that the circuit can not only achieve an amplification gain up to 60 dB, effectively extracting useful signals between 20 Hz and 500 Hz, but also effectively suppresses 50 Hz power-line interference, with a good anti-noise performance.