基于开关电容技术的磁通门选频放大电路研究

Study on Frequency-Selective Amplifier for Fluxgate Based on Switched-Capacitor

传统磁通门信号处理电路中的选频放大电路由运放和电阻电容网络构成的多环反馈型带通滤波器组成,具有电路结构简单、可靠性高、成本低等特点。但电路中电阻、电容的值较大,不易集成。基于将磁通门传感器微型化的目的,在已有Hspice磁通门探头信号产生模型的基础上,提出一种由双2阶模块级联的开关电容带通滤波器实现选频放大功能的方法,运用互补开关技术和动态范围定标技术,提高了滤波器的精度。在3V供电电压下,利用Hspice进行仿真验证,结果表明:设计的开关电容带通滤波器,其中心频率约为2.2kHz,增益约为15dB,能较好地对磁通门传感器中的2次谐波进行选择并放大。

Frequency-selective amplifier in signal processing circuit for conventional fluxgate is composed of multiple-loop feedback band-pass filter consisting of one operational amplifier,resistors and capacitors,which features simple structure,high reliability and low cost.However,the value of resistors and capacitors in the circuit is too large for integration.To miniaturize fluxgate sensors,a switched-capacitor band-pass filter cascaded by biquad modules to realize frequency selection and amplification was proposed based on the existing Hspice model of cell signal generation for fluxgate.In this circuit,complementary switching and dynamic range scaling were used to improve accuracy of the filter.Hspice simulation showed that the proposed switched-capacitor bandpass filter had a center frequency of about 2.2 kHz and a gain of about 15 dB,and it could properly select and amplify the secondary harmonic in the fluxgate sensor.