说明：  介绍了数字滤波器的种类和设计方法,在MATLAB环境下对满足有源滤波器性能要求 的低通数字式滤波器进行了实例设计,并分析了其滤波特性,最后结合有源滤波器中所使用的DSP 控制器,完成了该低通数字滤波器的实现。
(Describes the type and design of digital filter method, under the MATLAB environment to meet the performance requirements of active filter low-pass digital filter design example was carried out, and analyzes its filtering properties, the final combination in the active filter DSP controller is used to complete the low-pass digital filter implementation.)