信號與線性系統(tǒng)分析(根據(jù)MATLAB的方法與實(shí)現(xiàn))第九章

MATLAB比較，觀察周期信號的分解與合成過程。%dm09101%觀察周期方波信號的分解與合成%m：傅里葉級數(shù)展開的項(xiàng)數(shù)display('Pleaseinputthevalueofm(傅里葉級數(shù)展開的項(xiàng)數(shù))');%在命令窗口顯示提示信息m=input('m); %鍵盤輸入傅里葉級數(shù)展開的項(xiàng)數(shù)t-2*pi:0.01:2*pi; %時(shí)域波形的時(shí)間范圍-2π~2π，0.01nround(length(t)/4); 1/2數(shù)fcos(t).*(t<(-3*pi/2))+cos(t).*((t>(-pi/2))&(t<(pi/2)))+cos(t).*(t>3*pi/2); yzeros(m+1,max(size(t)));y(m+1,:)=f';figure(1);plot(t/pi,y(m+1,:),'LineWidth',2); %繪制方波信grid; %在圖形中加入柵格axis([-22-0.51.5]); %指定圖形顯示的橫坐標(biāo)范圍和縱坐標(biāo)范圍title('周期信號'); %給顯示的圖形加上標(biāo)題xlabel('單位pi','Fontsize',8); %顯示橫坐標(biāo)單x=zeros(size(t));kk='直流分量';pause;k=1;x=x+1/pi;y(1,:x; %計(jì)算各次諧波疊加和plot(t/pi,y(m+1,:),'LineWidth',2);holdon;plot(t/pi,y(1,:),'r','LineWidth',3);holdoff;grid;axis([-22-0.51.5]);title(strcat(kk));xlabel('單位pi','Fontsize',8);kk=strcat(kk,'和第',num2str(k));pause;k=k+1;x=x+0.5.*cos(t);y(2,:)=x;plot(t/pi,y(m+1,:),'LineWidth',2);holdon;plot(t/pi,y(2,:),'r','LineWidth',3);holdoff;grid;axis([-22-0.51.5]);title(strcat(kk,'次諧波疊加'));

%繪制諧波疊加信號%計(jì)算各次諧波疊加和%繪制諧波疊加信號xlabel('單位pi','Fontsize',8);kk=strcat(kk,'、',num2str(k));pause;x=x+2/(3.*pi).*cos(2.*t);y(3,:x; %計(jì)算各次諧波疊加和plot(t/pi,y(m+1,:),'LineWidth',2);holdon;plot(t/pi,y(3,:),'r','LineWidth',3);holdoff;grid;axis([-22-0.51.5]);title(strcat(kk,'次諧波疊加'));xlabel('單位pi','Fontsize',8);kk=strcat(kk,'、',num2str(k+2));pause;x=x-2/(15.*pi).*cos(4.*t);y(4,:)=x;plot(t/pi,y(m+1,:),'LineWidth',2);holdon;plot(t/pi,y(4,:),'r','LineWidth',3);holdoff;grid;axis([-22-0.51.5]);

%繪制諧波疊加信號%計(jì)算各次諧波疊加和%繪制諧波疊加信號title(strcat(kk,'次諧波疊加'));xlabel('單位pi','Fontsize',8);pause;plot(t/pi,y(1:m+1,:),'LineWidth',3);grid;axis([-22-0.51.5]);title('各次諧波疊加波形');xlabel('單位pi','Fontsize',8);%End1.510.50-0.5-2 -1.5 -1

周期信號0 0.5 1 1.5 2單位pi1.510.50-0.5-2 -1.5 -1

直流分量0 0.5 1 1.5 2單位pi1.510.50

直流分量和第次諧波疊加-0.5-2 -1.5 -1

0 0.5 1 1.5 2單位pi1.510.50

直流分量和第次諧波疊加-0.5-2 -1.5 -1

0 0.5 1 1.5 2單位pi1.510.50

直流分量和第次諧波疊加-0.5-2 -1.5 -1

0 0.5 1 1.5 2單位pi1.510.50

各次諧波疊加波形-0.5-2 -1.5 -1

0 0.5 1 1.5 2單位pi%dm09201%繪制周期信號的頻譜特function CTFS_RP% 以周期矩形脈沖信號為例，計(jì)算其頻譜特性% Nf：級數(shù)分解的諧波次數(shù)，由鍵盤輸入% Nn：輸出數(shù)據(jù)的準(zhǔn)確位數(shù)% a0：直流項(xiàng)系數(shù)% an：1,2,3,...次諧波余弦項(xiàng)展開系數(shù)% bn：1,2,3,...次諧波正弦項(xiàng)展開系數(shù)% tao：周期矩形脈沖信號脈寬，由鍵盤輸入% T：周期矩形脈沖信號周期，由鍵盤輸入display('PleaseinputthevalueofT,taoandNf'); T=input('Ttao=input('tao=');Nf=input('Nf=');symstnkx %定義符號變量Nn32; 32anzeros(Nf+1,1); anbnzeros(Nf+1,1); bnx=(heaviside(t+tao/2)-heaviside(t-tao/2))*cos((pi/tao)*t); u(t+tao/2)-u(t-tao/2)A0=2*int(x,t,-T/2,T/2)/T; %求出直流項(xiàng)a0As=2*int(x*cos(2*pi*n*t/T),t,-T/2,T/2)/T; %求出余弦項(xiàng)系數(shù)Bs=2*int(x*sin(2*pi*n*t/T),t,-T/2,T/2)/T; %求出正弦項(xiàng)系數(shù)bnan(1double(vpa(A0,Nn)); A0ASCIIfork=1:Nfan(k+1)=double(vpa(subs(As,n,k),Nn)); %獲取參數(shù)組As所對應(yīng)的ASCII碼數(shù)值數(shù)組bn(k+1)=double(vpa(subs(Bs,n,k),Nn)); %獲取參數(shù)組Bs所對應(yīng)的ASCII碼數(shù)值數(shù)組endcnsqrt(an.*an+bn.*bn); %計(jì)算幅度譜t=-T*2:0.001:T*2;xx=(heaviside(t+tao/2)-heaviside(t-tao/2)).*cos((pi/tao).*t);forkk=1:2side(t-tao/2-kk*T)).*cos((pi/tao).*(t-kk*T)); pulstranendsubplot(211);clearsubplot;plot(t,xx);axis([-T*2T*201.1]);%title('周期矩形脈沖信號','Fontsize',8);s1=strcat('周期矩形脈沖信號 xlabel(s1,'Fontsize',8);subplot(212);k=0:Nf;stem(k,cn);holdon;plot(k,cn);xlabel('幅度譜 \omega','Fontsize',8);%EndPleaseinputthevalueofT,taoandNfT=2*pitao=pi

%將顯示窗口分為3個(gè)子窗口，并指向第1個(gè)子窗口%繪制周期矩形脈沖信號%指定坐標(biāo)系范圍%標(biāo)注標(biāo)題Tao=',num2str(tao),'t');%x軸標(biāo)簽%指向第2個(gè)子窗口%繪制幅度譜%繪制幅度譜包絡(luò)線Nf=3010.80.60.40.20

-10 -5 0 5 10周期矩形脈沖信號T=6.2832Tao=3.1416t0.80.60.40.200 5 10 15幅度譜

20 25 30PleaseinputthevalueofT,taoandNfT=2*pitao=2*piNf=3010.80.60.40.20

-10 -5 0 5 10周期矩形脈沖信號T=6.2832Tao=6.2832t1.510.500 5 10 15幅度譜

20 25 30PleaseinputthevalueofT,taoandNfT=20*pitao=piNf=3010.80.60.40.20

-100 -50 0 50 100周期矩形脈沖信號T=62.8319Tao=3.1416t0.080.060.040.0200 5 10 15幅度譜

20 25 30PleaseinputthevalueofT,taoandNfT=20*pitao=4*piNf=3010.80.60.40.20

-100 -50 0 50 100周期矩形脈沖信號T=62.8319