数字滤波器的设计源代码和不同数字滤波器之间的过渡代码，包括数字低通滤波器到数字带通滤波器、数字低通滤波器到数字带阻滤波器、数字低通滤波器到数字高通滤波器、数字低通滤波器到数字低通滤波器-Digital filter design source code to code and transition between different digital filters, including a digital low-pass filter to the digital band-pass filt