matlab 带通滤波,MATLAB窗函数实现带通滤波器
%本函数利用窗函数法设计带通滤波器，主要用来滤出单一频率，即中心频率
%data是输入的数据, centerFre是带通的中心频率, offsetFre是频偏,最终带通为centerFre +- offsetFre/2
%,sampFre是采样率
function y = BPassFilter(data, centerFre, offsetFre, sampFre)
%设计I型带通滤波器
M = 0 ; %滤波器阶数(必须是偶数)
Ap = 0.82; %通带衰减
As = 45; %阻带衰减
Wp1 = 2pi(centerFre - offsetFre)/sampFre; %算出下边频
Wp2 = 2pi(centerFre + offsetFre)/sampFre; %算出上边频
% (1)矩形窗
N = ceil(3.6*sampFre/offsetFre); %计算滤波器阶数,采用矩形窗，3dB截频在中心频率到上下边频的中点
M = N - 1;
M = mod(M,2) + M ; %使滤波器为I型(偶数)
%单位脉冲响应的下脚标
h = zeros(1,M+1); %单位冲击响应变量赋初值
for k = 1:(M+1);
if (( k -1 - 0.5*M)==0)
h(k) = Wp2/pi - Wp1/pi;
else
h(k) = Wp2sin(Wp2.(k - 1 - 0.5M))/(pi(Wp2*(k -1 - 0.5*M))) -
Wp1sin(Wp1(k - 1 - 0.5M))/(pi(Wp1*(k -1 - 0.5*M)));
end
end
% (2) Hann Window
% N = ceil(12.4*sampFre/offsetFre); %计算滤波器阶数,采用矩形窗，3dB截频在中心频率到上下边频的中点
% M = N - 1;
% M = mod(M,2) + M ; %使滤波器为I型(偶数)
% h = zeros(1,M+1); %单位冲击响应变量赋初值
% for k = 1:(M+1);
% if (( k -1 - 0.5*M)==0)
% h(k) = Wp2/pi - Wp1/pi;
% else
%
h(k) = Wp2sin(Wp2.(k - 1 - 0.5M))/(pi(Wp2*(k -1 - 0.5*M))) -
Wp1sin(Wp1(k - 1 - 0.5M))/(pi(Wp1*(k -1 - 0.5*M)));
% end
% end
% K = 0:M;
% w = 0.5 - 0.5cos(2pi*K/M);
% h = h.*w;
% (3)Hamming Window
% N = ceil(14*sampFre/offsetFre); %计算滤波器阶数,采用矩形窗，3dB截频在中心频率到上下边频的中点
% M = N - 1;
% M = mod(M,2) + M ; %使滤波器为I型(偶数)
% h = zeros(1,M+1); %单位冲击响应变量赋初值
% for k = 1:(M+1);
% if (( k -1 - 0.5*M)==0)
% h(k) = Wp2/pi - Wp1/pi;
% else
%
h(k) = Wp2sin(Wp2.(k - 1 - 0.5M))/(pi(Wp2*(k -1 - 0.5*M))) -
Wp1sin(Wp1(k - 1 - 0.5M))/(pi(Wp1*(k -1 - 0.5*M)));
% end
% end
% K = 0:M;
% w = 0.54 - 0.46cos(2pi*k/M);
% h = h.*w;
% (4)Blackman window
% N = ceil(22.8*sampFre/offsetFre); %计算滤波器阶数,采用矩形窗，3dB截频在中心频率到上下边频的中点
% M = N - 1;
% M = mod(M,2) + M ; %使滤波器为I型(偶数)
% h = zeros(1,M+1); %单位冲击响应变量赋初值
% for k = 1:(M+1);
% if (( k -1 - 0.5*M)==0)
% h(k) = Wp2/pi - Wp1/pi;
% else
%
h(k) = Wp2sin(Wp2.(k - 1 - 0.5M))/(pi(Wp2*(k -1 - 0.5*M))) -
Wp1sin(Wp1(k - 1 - 0.5M))/(pi(Wp1*(k -1 - 0.5*M)));
% end
% end
% K = 0:M;
% w = 0.42 - 0.5cos(2piK/M) + 0.08cos(4piK/M);
% h = h.*w;
y = filter(h,[1],data);