说明：  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, high pass, band-pass, band-stop four forms. Users can specify passband, stopband edge of the actual frequency and the corresponding attenuation, will be able to output digital filter cascade of molecular forms of the various subsystems, the denominator of the coefficient, and output of its amplitude-frequency and phase frequency response.)