IIR 数字滤波器设计：模拟低通巴特沃思滤波器、模拟低通切比雪夫1型滤波器、模拟低通切比雪夫2型滤波器、模拟椭圆低通滤波器-IIR Digital Filter Design: Analog low-pass Butterworth filter, analog low-pass Chebyshev Type 1 filter, analog low-pass Chebyshev type 2 filter, analog elliptical low-pass filter