中心频率可调节的低频带通滤波器设计与实现

Design and Realization on the Low Frequency Band Pass Filter with Center Frequency Adjustment

在地磁弱信号检测处理过程中,接收端需要放大非常微弱频率很低的信号,因此要求放大器具有低噪声、高增益,滤波器应满足带宽窄中心频率可调节的功能。开关电容滤波器可实现低通、高通、带通和带阻滤波功能,而且中心频率可调节,本文采用了MF10开关电容滤波器集成模块进行电路设计,时钟频率由CD4046锁相环控制。实验结果表明本文设计的滤波器通带宽度达到20Hz,中心频率从1kHz到3kHz可调节,满足实际需要。

In the process of geomagnetic weak signal examination and disposal, the amplifier must possess high gain according to the amplified low frequency and small amplitude（nV） signal in the receiver. The amplifier must possess low noise, high gain as well as the center frequency of filter can be adjusted and the bandwidth is narrow because of the low frequency and small amplitude of received signal. The function of either low pass, high pass, band pass or a notch can be achieved by the Switched Capacitor Filter. The MF10 Switched Capacitor Filter can be adopted and the clock frequency can also be adopted by CD4046 phase-lock loop in this design. The results of the test showed that the bandwidth of filter is 20Hz and the center frequency of the filter can be changed from 1KHz to 3 KHz, the demand of practice is satisfied.