为了从模拟滤波器出发设计IIR数字滤波器，必须先设计一个满足技术指标的模拟滤波器，亦即要把数字滤波器的指标转换成模拟滤波器的指标，因此必须先设计对应的模拟原型滤波器。-Starting from the design of analog filters to IIR digital filter, you must first design an analog filter to meet the technical indicators, which indicators should convert the digital filter and analog filter indicators, so must the corresponding simulation of the prototype filter design device.