基于Matlab的FIR数字滤波器的设计与仿真源程序

自己写的线性相位的FIR低通和带通的数字滤波器程序，绝对没有错误，注释非常详细。用的是窗函数法，画了单位冲击响应和幅频响应的图。

% 设计线性相位的FIR带通滤波器
% 2014.03.12 
clcclear all;
wls=0.2*pi;                            % 阻带最小频率 
wlp=0.35*pi;                           % 通带最小频率
whp=0.65*pi;                           % 通带最大频率
whs=0.8*pi;                            % 阻带最大频率 
wc=[wlp/piwhp/pi];                    % 带通滤波器的归一化截止频率
B=wlp-wls;                             % 过渡带宽=低端通带截止频率-低端阻带截止频率 
N=ceil（6.2*pi/B）;                      % hanning窗阶数N，由过渡带宽B=8*pi/N算出Nceil为取整函数
window=hanning（N）;                     % 窗选择hanning窗，为N*1的矩阵/向量
n=0:1:N-1; 
[h1w]=freqz（window1）;                % window是N*1矩阵，h1是hannning窗的频率响应
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
subplot（221）;                        % 将多个图画在一个平面上
stem（window）;                          % 绘制离散序列图
axis（[0 45 0 1.2]）;                    % 定义xy轴范围 
grid;                                  % 显示网格线
xlabel（‘n‘）;                           % x轴命名
title（‘Hanning窗函数‘）;               
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
subplot（222）;
plot（w/pi20*log（abs（h1）/abs（h1（1））））; % w来自freqz函数，为N个频率等分点的值（N*1矩阵），后面计算的是幅度值
axis（[0 1 -350 0]）;
grid;
xlabel（‘w/pi‘）;
ylabel（‘幅度（dB）‘）;
title（‘Hanning 窗函数的频谱‘）;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
hn=fir1（N-1wchanning（N））;            % 设计filter。函数fir1返回的是filter的系数h（n）即冲激相应
[h2w]=freqz（hn1512）;                % filter的频率响应h2
subplot（223）;
stem（nhn）;
axis（[0 45 -0.25 0.25]）;
grid;
xlabel（‘n‘）;
ylabel（‘h（n）‘）;
title（‘Hanning 窗函数的单位脉冲响应‘）;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
subplot（224）;
plot（w/pi20*log（abs（h2）/abs（h2（1））））;  % w来自freqz（与h2对应）
grid;
xlabel（‘w/pi‘）;
ylabel（‘幅度（dB）‘）;
title（‘Hanning 窗设计带通滤波器的幅频响应‘）;

 属性            大小     日期    时间   名称
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     文件       2034  2014-03-13 21:33  FIR_BPF.m

     文件       1892  2014-03-13 21:34  FIR_LPF.m

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