信號與系統(tǒng)第2版- MATLAB仿真程序代碼 嚴國志

第2章抽出的MATLAB代碼%ch2j23.m%ch2j23.mt=-10:0.01:10;xt=sinc(t); %MATLAB中sinc(t)函數(shù)表示的是plot(t,xt)xlabel('t/s')ylabel('x(t)')title('抽樣函數(shù)信號')%ch2j24.m%ch2j24.mt=-10:0.01:10;ut=(t>=0);%t>=0為關系運算,t>=0成立時輸出結果為1,不成立時輸出結果為0plot(t,ut);xlabel('t/s')ylabel('u(t)')title('單位階躍信號');axis([-10,10,-0.2,1.2])%指定橫、縱坐標的范圍%ch2j26.m%ch2j26.mt=-10:0.01:10;ut1=(-1).*(t<0);ut2=(t>=0);ut=ut1+ut2;plot(t,ut);xlabel('t/s')ylabel('u(t)')title('符號函數(shù)信號');axis([-10,10,-1.2,1.2])%cp2liti4.m%cp2liti4.mt=-4:0.001:4;xt1=(0.5*t+2).*((t<0)&(t>=-4));xt2=((t>=0)&(t<2)).*2;xt3=(-t+4).*((t>=2)&(t<=4));xt=xt1+xt2+xt3; %原信號figuresubplot(221) %subplot為繪制子圖,subplot(221)表示在一張畫布上畫2行

2列共4張圖,第3位數(shù)表示第幾張圖plot(t,xt) %繪制原信號gridon %繪制網格xlabel('t/s');title('x(t)');subplot(222)plot(-t,xt) %繪制原信號的反折信號gridonxlabel('t/s');title('x(-t)');subplot(223)plot(-t+4,xt) %繪制反折信號的時移信號,波形沿時間軸向右平移4個單位gridonxlabel('t/s');title('x(-t+4)');subplot(224)plot(0.5*(-t+4),xt) %信號沿時間軸壓縮到原來的1/2gridonxlabel('t/s');title('x(-2t+4)');%cp2liti215.m%cp2liti215.mdt=0.01;k1=0:dt:1; %生成信號x1(t)x1=ones(1,length(k1));k2=0:dt:2; %生成信號x2(t)x2=ones(1,length(k2));y=dt*conv(x1,x2); %計算卷積x1(t)*x2(t),conv函數(shù)為計算卷積的函數(shù)，要注意用conv求連續(xù)信號（離散序列）的卷積的不同k0=k1(1)+k2(1);k3=length(k1)+length(k2)-2;k=k0:dt:(k0+k3)*dt; %確定卷積x1(t)*x2(t)的非零樣值的時間向量plot(k,y)xlabel(‘t/s’);title(‘卷積結果’)第3章抽出的MATLAB代碼例3-7%cp3liti7.mA=1;T=2;tao=1;t=-2:0.001:2;N=input('Number

of

harmonic=')X0=A*tao/T;w0=2*pi/T;X=X0*ones(1,length(t));for

k=1:1:N

X=X+2*X0*sinc(k*w0*tao/2/pi)*cos(k*w0*t);endplot(t,X)例3-9%cp3liti9.msymsxtx=exp(-2*t)*sin(2*pi*t)*heaviside(t)subplot(311)ezplot(x)title('衰減正弦信號')X=fourier(x);X=simplify(X)subplot(312)ezplot(abs(X))title('幅度譜')subplot(313)ezplot(angle(X))title('相位譜')例3-20%cp3liti20.m%cp3liti20.mw=0:0.01:5;b=[1];a=[1221];h=freqs(b,a,w);%subplot(2,1,1);plot(w,abs(h));xlabel('\omega(rad/s)');ylabel('|H(j\omega)|')gridon;%subplot(2,1,2);plot(w,angle(h));xlabel('\omega(rad/s)');ylabel('\phi(\omega)|')gridon;第4章抽出的MATLAB代碼MATLAB實現(xiàn)的代碼見cp4liti5.m，%cp4liti5.mxt1=exp(-2*t);xt2=exp(-5*t);xt=2*xt1+5*xt2;Xs=laplace(xt);運行結果為Xs=2/(s+2)+5/(s+5)MATLAB實現(xiàn)的代碼見cp4liti6.m，%cp4liti6.msymstkTpositivext=dirac(t-k*T);Xs=laplace(xt)運行結果為Xs=exp(-T*k*s)%cp4liti20.mnum=[1]; %分子系數(shù),按降冪排列den1=conv([15],[15]);den2=conv([15],[13]);den=conv(den1,den2) %分母系數(shù),按降冪排列[r,p,k]=residue(num,den)運行結果為r=-0.1250-0.2500-0.50000.1250p=-5.0000-5.0000-5.0000-3.0000k=[]%cp4liti20a.mnum=[24];den=[1040];[r,p,k]=residue(num,den)運行結果為r=-0.5000-0.5000i-0.5000+0.5000i1.0000p=0+2.0000i0-2.0000i0k=[]%cp4liti22b.msymss;Xs=(2*s+4)./(s^3+4*s)xt=ilaplace(Xs) %拉普拉斯反變換運行結果為xt=sin(2*t)-cos(2*t)+1%cp4liti23a.msymssX=(s-4)/s/(s+1)^3x=ilaplace(X)%cp4liti23b.mnum=[1-4];a=conv([10],[11]);b=conv([11],[11]);den=conv(a,b);[r,p,k]=residue(num,den)運行結果為r=4.00004.00005.0000-4.0000p=-1.0000-1.0000-1.00000k=[]%cp4liti26.msymsst;Xs=laplace(exp(-2*t)) %拉普拉斯變換Hs=laplace(exp(-5*t)) %拉普拉斯變換Ys=Xs*Hsyt=ilaplace(Ys) %拉普拉斯反變換運行結果為Xs=1/(s+2)Hs=1/(s+5)Ys=1/((s+2)*(s+5))yt=exp(-2*t)/3-exp(-5*t)/3%cp4liti29.mnum=[26] %分子多項式系數(shù)den=[132] %分母多項式系數(shù)z=roots(num) %求零點p=roots(den) %求極點運行結果為z=-3p=-2-1%cp4liti34.mk=3;w=-k*pi:0.01:k*pi;num=[14];den=[134];H=freqresp(num,den,sqrt(-1)*w);subplot(2,1,1);plot(w/pi,abs(H));xlabel('\omega/\pi');ylabel('|H(j\omega)|');title('幅頻特性曲線');gridon;subplot(2,1,2);plot(w/pi,angle(H)/pi);xlabel('\omega/\pi');ylabel('\phi(\omega)/\pi');title('相頻特性曲線');gridon;%cp4liti35b.mnum6=[1];p=0; %極點den61=conv([1-p],[1]) %1階極點den62=conv([1-p],den61) %2階極點den63=conv([1-p],den62) %3階極點den64=conv([1-p],den63) %4階極點impulse(num6,den63); %畫3階極點的的波形%cp4liti36a.mb=[14];a=[1320][r,p,k]=residue(b,a)運行結果為r=[1-32]p=[-2-10]k=[]%cp4liti36b.m%畫單位沖激響應的時域波形num=[14]; %分子多項式系數(shù)den=[1320]; %分母多項式系數(shù)sys=tf(num,den)impulse(sys);%cp4liti36c.m%畫系統(tǒng)的零、極點圖num=[14];den=[1320];sys=tf(num,den);pzmap(sys);第5章MATLAB代碼%cp5j21.m%cp5j21.mn=-5:1:5;x=0*(n>=-5&n<0)+1*(n==0)+0*(n>0&n<=5);stem(n,x,'filled');%stem為繪制火柴棒圖,這里主要用來繪制離散時間圖形axis([-6,6,-0.2,1.2])%cp5j22.m%cp5j22.mn=-5:1:5;x=0*(n<0)+1*(n>=0);stem(n,x,'filled');axis([-6,6,-0.2,1.2])第6章MATLAB代碼%cp6j23.m%MATLAB代碼：周期矩形序列的DFSN=20; %周期N1=2; %半脈寬M=N1*2+1;n=-2*N+(M+1)/2:1:2*N-(M+1)/2;f0=zeros(1,N-M);f1=ones(1,M);x=[f0,f1,f0,f1,f0,f1,f0]; %產生xN(n)subplot(2,1,1);stem(n,x); %繪制xN(n)圖xlabel('n');title('xN(n)');n=-2*N+(M+1)/2:1:2*N-(M+1)/2;k=-2*N+(M+1)/2:1:2*N-(M+1)/2;WN=exp(-j*2*pi/N);nk=n'*k;Xk=x*WN.^nk/N; %依定義式計算DFS系數(shù)XN(k)subplot(2,1,2);stem(k,Xk,'b'); %繪制XN(k)圖xlabel('k');title('XN(k)');holdon;plot(k,Xk,'r');holdoff; %繪制XN(k)包絡圖%cp6liti10.m%MATLAB代碼：DFT的頻率分辨率N1=50;fs=200;Ts=1/fs;n1=0:1:N1-1;x1=cos(49*2*pi*n1*Ts)+cos(51*2*pi*n1*Ts);X1=fft(x1,N1)/N1; %用fft()計算DFTk1=0:1:N1-1;w1=2*pi/N1*k1; %Ω=k*2π/Nsubplot(331);stem(n1,x1,'.'); %畫x1(n)xlabel('n');title('x1(n)');axis([0,200,-2.5,2.5]);subplot(332);stem(w1/pi*100,abs(X1),'.');%f=Ω/π*100,Hz為單位畫|X1(k)|xlabel('f/Hz');title('|X1(k)|');axis([0,200,0,0.55]);subplot(333);stem(w1/pi*100,abs(X1),'.');%畫|X1(k)|局部放大xlabel('f/Hz');title('|X1(k)|局部放大');axis([43,57,0,0.55]);%%%%%%%%%%%%%%%%%%%N2=200;n2=0:1:N2-1;x2=[x1(1:1:50)zeros(1,150)];X2=fft(x2,N2)/N2;k2=0:1:N2-1;w2=2*pi/N2*k2; %Ω=k*2π/Nsubplot(334);stem(n2,x2,'.');xlabel('n');title('x2(n)');axis([0,200,-2.5,2.5]);subplot(335);stem(w2/pi*100,abs(X2),'.'); %f=Ω/π*100(Hz)xlabel('f/Hz');title('|X2(k)|');axis([0,200,0,0.55]);subplot(336);stem(w2/pi*100,abs(X2),'.');xlabel('f/Hz');title('|X2(k)|局部放大');axis([43,57,0,0.55]);%%%%%%%%%%%%%%%%%%%N3=200;n3=0:1:N3-1;x3=cos(49*2*pi*n3/200)+cos(51*2*pi*n3/200);X3=fft(x3,N3)/N3;k3=0:1:N3-1;w3=2*pi/N3*k3; %Ω=k*2π/Nsubplot(337);stem(n3,x3,'.');xlabel('n');title('x3(n)');axis([0,200,-2.5,2.5]);subplot(338);stem(w3/pi*100,abs(X3),'.'); %f=Ω/π*100(Hz)xlabel('f/Hz');title('|X3(k)|');axis([0,200,0,0.55]);subplot(339);stem(w3/pi*100,abs(X3),'.');xlabel('f/Hz');title('|X3(k)|局部放大');axis([43,57,0,0.55]);%%%%%%%%%%%%%%%%%%%%cp6j101.m%MATLAB代碼：信號的表示w0=2*pi*50; %基波頻率w0t=0:0.00001:0.04;xt1=10*sin(w0*t+0.1*pi);xt2=5*sin(w0*t*5+0.2*pi);xt3=3*sin(w0*t*9+0.3*pi);xt4=sin(w0*t*13+0.4*pi);xt=xt1+xt2+xt3+xt4; %設置x(t)plot(t,xt); %畫x(t)波形xlabel('t/s');title('x(t)');gridon;%cp6j102.m%MATLAB代碼：信號的抽樣w0=2*pi*50; %基波頻率w0Ts=1./(50*13*5); %抽樣周期TsN=2*pi/Ts/w0; %抽樣點數(shù)Nn=0:1:N-1;xn1=10*sin(w0*n*Ts+0.1*pi);xn2=5*sin(w0*n*Ts*5+0.2*pi);xn3=3*sin(w0*n*Ts*9+0.3*pi);xn4=sin(w0*n*Ts*13+0.4*pi);xn=xn1+xn2+xn3+xn4; %建立x(n)stem(n,xn); %畫x(n)波形xlabel('n');title('x(n)');gridon;%cp6j103.m%MATLAB代碼：DFT變換%Xk=fft(xn,N); %用fft()函數(shù)求N點DFT變換k=0:1:N-1;Xk=xn*exp(-j*2*pi/N*n'*k); %按定義求N點DFT變換stem(k,abs(Xk)); %畫幅頻特性圖xlabel('k');ylabel('|X(k)|');%cp6j104.m%MATLAB代碼：檢查DFT頻譜的幅值及相位k=[1,5,9,13];fori=1:length(k)ki=k(i)Ak=abs(Xk(ki+1))*2/Npk=angle(Xk(ki+1))/piend%cp6j1051.m%MATLAB代碼：改變抽樣頻率%cp6j1051.mw0=2*pi*50;mi=[5,3,2,1];%m=5,3,2,1;改變抽樣頻率倍數(shù)fori=1:length(mi)m=mi(i);Ts=1./(50*13*m); %m=5,3,2,1;改變抽樣頻率N=2*pi/Ts/w0;%N=65,39,26,13;抽樣點數(shù)n=0:1:N-1;xn1=10*sin(w0*n*Ts+0.1*pi);xn2=5*sin(w0*n*Ts*5+0.2*pi);xn3=3*sin(w0*n*Ts*9+0.3*pi);xn4=sin(w0*n*Ts*13+0.4*pi);xn=xn1+xn2+xn3+xn4;%建立x(n)I=(i-1)*2;subplot(4,3,I+i);stem(n,xn); %x(n)時域波形xlabel('n');ylabel('x(n)');title(['N=',num2str(N)]);%X=fft(x,N);k=0:1:N-1;Xk=xn*exp(-j*2*pi/N*n'*k);%按定義計算N點DFTf=k/Ts/N; %取式(6-123b)subplot(4,3,I+i+1);stem(f,abs(Xk)/N);%幅值頻譜圖形xlabel('f/Hz');ylabel('|X(k)|/N');title(['fs=',num2str(m),'*650Hz']);subplot(4,3,I+i+2);stem(f,abs(Xk)/N); %幅值頻譜局部放大圖title('|X(k)|局部放大圖');xlabel('f/Hz');ylabel('|X(k)|/N');axis([0,800,0,6]);end%%%%%%%%%%%%%%%%%%%%%%%%%%%%cp6j1052.m%MATLAB代碼：改變抽樣時長%cp6j1052.mw0=2*pi*50;m=5;Ni=[65,33,17]; %改變抽樣時長fori=1:length(Ni)Ts=1./(50*13*m);N=Ni(i);n=0:1:N-1;xn1=10*sin(w0*n*Ts+0.1*pi);xn2=5*sin(w0*n*Ts*5+0.2*pi);xn3=3*sin(w0*n*Ts*9+0.3*pi);xn4=sin(w0*n*Ts*13+0.4*pi);xn=xn1+xn2+xn3+xn4;%建立x(n)I=(i-1)*1;subplot(3,2,I+i);stem(n*Ts*1000,xn);%x(n)時域波形xlabel('nT/ms');ylabel('x(n)');%title(['N=',num2str(N)]);axis([0,20,-20,20]);%X=fft(x,N); %按fft()計算N點DFTk=0:1:N-1;Xk=xn*exp(-j*2*pi/N*n'*k);%按定義計算N點DFTf=k/Ts/N; %取式（6-123b）subplot(3,2,I+i+1);stem(f,abs(Xk)/N);%幅值頻譜圖形xlabel('f/Hz');ylabel('|X(k)|/N');%r=2^(i-1);%title(['T0=T50/',num2str(r)]);axis([0,1/Ts,0,10]);end%%%%%%%%%%%%%%%%%%%%%%%%%%%%cp6j1053.m%MATLAB代碼：抽樣信號補0%cp6j1053.mw0=2*pi*50;Ts=1./(50*13*5);N=2*pi/Ts/w0; %抽樣點數(shù)n=0:1:N;xn1=10*sin(w0*n*Ts+0.1*pi);xn2=5*sin(w0*n*Ts*5+0.2*pi);xn3=3*sin(w0*n*T