Butterworth Filter in Fortran, which is very popular in high-accuracy applications of numerical filter.

fortran 编写的巴特沃斯滤波程序，可以实现低通滤波，高通滤波，带通滤波，作者是李建平。-fortran program written Butterworth filter, can achieve low-pass filtering, high pass filter, band-pass filter, the author is Li Jianping.

desiir.for 利用双线性Z变换设计巴特沃斯和切比雪夫I型IIR数字滤波器，包括低通、高通、带通、带阻四种形式。使用者只需指定通带、阻带的边缘实际频率及相应的衰减，便可输出数字滤波器 的级联形式的各子系统分子、分母的系数，并输出其幅频和相频响应。 -bilinear Z transform desiir.for design using Butterworth and Chebyshev IIR digital filter-I, including the low-pass, h

二阶Butterworth带通滤波器:求序列x(n)(n是资料长度)的二阶Butterworth带通滤波序列y(n)-Second Order Butterworth Band-Pass Filter