帮我设计一个用matlab实现的双线性滤波器的代码

好的，以下是一个用MATLAB实现的双线性滤波器的代码示例：

function [b,a] = bilinearFilter(fs,fc,Q,filterType)
% BILINEARFILTER Design a digital filter using bilinear transformation
%
% Inputs:
%   - fs: sampling frequency
%   - fc: cutoff frequency
%   - Q: filter quality factor
%   - filterType: type of filter ('lowpass', 'highpass', 'bandpass', or 'bandstop')
% Output:
%   - b: numerator coefficients of the filter transfer function
%   - a: denominator coefficients of the filter transfer function

% Calculate analog filter coefficients
wc = 2*pi*fc; % cutoff frequency in radians
if strcmp(filterType,'lowpass')
    [num,den] = butter(1,wc,'s'); % 1st order lowpass Butterworth filter
elseif strcmp(filterType,'highpass')
    [num,den] = butter(1,wc,'high','s'); % 1st order highpass Butterworth filter
elseif strcmp(filterType,'bandpass')
    f1 = fc/sqrt(Q); % lower cutoff frequency
    f2 = fc*sqrt(Q); % upper cutoff frequency
    [num,den] = butter(1,[f1 f2],'s'); % 1st order bandpass Butterworth filter
elseif strcmp(filterType,'bandstop')
    f1 = fc/sqrt(Q); % lower cutoff frequency
    f2 = fc*sqrt(Q); % upper cutoff frequency
    [num,den] = butter(1,[f1 f2],'stop','s'); % 1st order bandstop Butterworth filter
else
    error('Invalid filter type');
end

% Convert analog filter to digital filter using bilinear transformation
[numd,dend] = bilinear(num,den,fs);

b = numd;
a = dend;
end

此函数使用了MATLAB的`butter`函数来设计一个一阶Butterworth模拟滤波器，并使用双线性变换将其转换为数字滤波器。`fs`是采样率，`fc`是截止频率，`Q`是质量因数，`filterType`是滤波器类型（低通、高通、带通或带阻）。函数的输出是数字滤波器的分子和分母系数。

你可以根据自己的需求修改此代码。