开关电容梳状滤波器幅频特性的深入分析

Analysis of Switched-capacitor Comb Filter′s Frequency Characteristic

分别从时域和频域对一种开关电容滤波器的特性进行了全面深入分析,首次给出了解析形式频谱函数和相应频率特性曲线,结果表明,电路特性依赖于参数τ=RC与开关切换时间T的比值α=τ/T。当电子开关的切换时间T相对较短(即α较大)时,该电路是一个梳齿幅度衰减型梳状滤波器,通带中心频率等于开关频率的奇数倍,开关频率的偶数倍则为其阻带频率。随着开关频率降低(T增,α减),电路过渡为幅频特性有起伏的低通滤波器。分析结论与实验结果很好地吻合。

Frequency characteristics of a switched- capacitor filter are analyzed in the time and frequency domain. The analytical function and the corresponding frequency characteristic curve are given. The results show that characteristics dependent on（parameter τ=RC and the switching time T,α= τ/T）. When the switching time T is relatively short,this circuit is a comb filter,and the passband center frequency is equal to the odd times of switching frequency fr ,and the band elimination frequency is equal to the even times of fτ. With the fτ lower, this SCF circuit change into a low- pass filter. The analysis results correspond with the experiment.