matlab 数字信号实验三.doc

1、N=45，计算并画出矩形窗、汉明窗、布莱克曼窗的归一化幅度谱，并比较各自的主要特点。clear;N=45;%矩形窗window1=boxcar(N);%W = RECTWIN(N) returns the N-point rectangular window.same aswvtool(window1);%Window Visualization Tool.% WVTOOL is a Graphical User Interface (GUI) that allows you to analyze windows. clear;N=45;%汉明窗window2=hamming(N);wvtool(window2);clear;N=45;%布莱克曼窗window3=blackman(N);wvtool(window3)Sec way:clear;N=45;b=boxcar(N);H,w=freqz(b,1);subplot(2,1,1);plot(w/pi,20*log10(abs(H);xlabel(f w/pi);ylabel(fudu/db);title(rect win f domain);grid onsubplot(2,1,2);stem(b);xlabel(N);ylabel(phase);title(rect win t domain);grid onclear;N=45;b=hamming(N);H,w=freqz(b,1);subplot(2,1,1);plot(w/pi,20*log10(abs(H);xlabel(f w/pi);ylabel(fudu/db);title(hamming win f domain);grid onsubplot(2,1,2);stem(b);xlabel(N);ylabel(phase);title(hamming win t domain);grid onclear;N=45;b=blackman(N);H,w=freqz(b,1);subplot(2,1,1);plot(w/pi,20*log10(abs(H);xlabel(f w/pi);ylabel(fudu/db);title(blackman win f domain);grid onsubplot(2,1,2);stem(b);xlabel(N);ylabel(phase);title(blackman win t domain);grid on2、（1）：N=15，带通滤波器的两个通带边界分别是：。用汉宁窗设计线性相位带通滤波器，观察它的实际3dB和20dB带宽。（2）：N=45重复这一设计，观察幅频和相位特性的变化，注意长度N变化的影响。clear;N=15;wn=0.3,0.5;window=hanning(N+1); %return N+1 lenb=fir1(N,wn,window);freqz(b);title(hanning N=15);clear;N=45;wn=0.3,0.5;window=hanning(N+1); %return N+1 lenb=fir1(N,wn,window);freqz(b);title(hanning N=45);3、分别改用布莱克曼窗，设计2题中的带通滤波器，比较三种窗的特点。clear;N=15;wn=0.3,0.5;window=blackman(N+1); %return N+1 lenb=fir1(N,wn,window);freqz(b);title(blackman N=15);clear;N=45;wn=0.3,0.5;window=