% Transmission Line Animation. Animates the lossless transmission line
% 
% Input data includes the characteristic impedance Z0, the load impedance 
% ZL, the source impedance Zg, the line length L in meters, the phasor 
% source voltage Vs in rectangular form, the propagation velocity up, and 
% the frequency of operation f in hertz.
% This m-file was written at the University of Wyoming in the Electrical
% and Computer Engineering Department and is to be distributed without
% cost.
clear all
set(0,'DefaultAxesFontSize',12);
set(0,'DefaultTextFontSize',12);
L=5500;%Line length in meters, input data
Vg=1;%Source voltage in phasor form (rectangular form), input data
up=2e8;%1.897e8;%3e8;%Propagation velocity on the line, input data
Z0=300;%Line characteristic impedance (real), input data
Zg=300;%Source impedance (rectangular form), input data
f=1e5;%Frequency of driving source in Hz., input data
%Calculate these from input data
clc
disp(['    The Line Length L = ' num2str(L) ' meters']);
disp(['    The Source Voltage Amplitude Vg = ' num2str(Vg) ' volts']);
disp(['    The Source Impedance Zg = ' num2str(Zg) 'ohms']);
disp(['    The Propagation Velocity up = ' num2str(up) ' m/s']);
disp(['    The Line Characteristic Impedance = ' num2str(Z0) ' ohms']);
disp(['    The Frequency of Operation = ' num2str(f) ' Hz']);
disp('  ')
betaL=2*pi*L*f/up;
zoverL=[-1:.01:0];
lambda=up/f;
ZL=input('    The load impedandce ZL = ');
Zin=Z0*((ZL+j*Z0*tan(betaL))/(Z0+j*ZL*tan(betaL)));
gamma=(ZL-Z0)/(ZL+Z0);
disp('  ')
disp(['    The Reflection Coefficient = ',num2str(gamma)]);
if abs(gamma)==1
    VSWR=Inf;
else
    VSWR=(1+abs(gamma))/(1-abs(gamma));
end
Strg2=['    The Voltage Standing Wave Ratio = ',num2str(VSWR)];
Strg1=['    The Reflection Coefficient = ',num2str(gamma)];
disp(['    The Input Impedance to the Line = ', num2str(Zin) ' ohms']);
disp(['    The Wavelength on the Line = ' num2str(lambda) ' meters']);
Fact=(Vg*Zin/(Zg+Zin))/(exp(j*betaL)+gamma*exp(-j*betaL));
Vofz=Fact*(exp(-j*betaL*zoverL)+gamma*exp(j*betaL*zoverL));
lim=max(abs(Vofz));

figure(1);clf;%Plot the so-called standing wave pattern
axis([-1 0 0 1.2*lim]) 
hold on
box on
plot(zoverL,abs(Vofz));
lim=max(abs(Vofz));
xlabel('Dimensionless Distance, z/L')
ylabel('Standing Wave Amplitude')
text(-.9,.1*lim,Strg1)
text(-.9,.2*lim,Strg2)
hold off
text(-.9,1.1*lim,'Press Enter to Continue')
pause
mag=abs(Vofz);
angl=angle(Vofz);
omegat2=linspace(0,4*pi,101);
Vin=Vg*Zin/(Zin+Zg);
VL=Vin*((1+gamma)/(exp(j*betaL)+gamma*exp(-j*betaL)));
Vint=abs(Vin)*cos(omegat2+angle(Vin)*ones(1,101));
VLt=abs(VL)*cos(omegat2+angle(VL)*ones(1,101));
Vgt=abs(Vg)*cos(omegat2+angle(Vg)*ones(1,101));
lim2=max(abs([Vg VL Vin]));


figure(2);clf;%Plot vg(t), vin(t) and vL(t)
axis([0 4*pi -1.1*lim2 1.1*lim2])
hold on
box on
plot([0 omegat2(1,101)], [0 0])
hold on
plot(omegat2,Vint,'--',omegat2,VLt,'-.',omegat2,Vgt,'.')
xlabel('Dimensionless Time, \omega t')
ylabel('v_g(t), v_i_n(t), v_L(t), volts')
text(5,-.6*abs(Vg),'v_i_n  - - - -','FontSize',12)
text(5,-.8*abs(Vg),'v_g . . . .','FontSize',12)
text(5,-abs(Vg),'v_L . - . - . -','FontSize',12)
text(.4*pi,abs(Vg),'Press Enter to Continue')
hold off
pause

% calculate the animation data
omegat=linspace(0,8*pi,801);
framedata=zeros(801,101);
for i=1:801
    framedata(i,:)=mag.*cos(omegat(1,i)*ones(1,101)+angl);
end


figure(3);clf;%Plot v(z) for various times
axis([-1.2 .2 -1.2*lim 1.2*lim])
hold on
box on
xlabel('Dimensionless Distance on the Line, z/L')
ylabel('Line Voltage, v(z,t)')
thnd1=text(-.9,1.1*lim,'Press Enter to Animate');
text(-1,1.1*lim,'                      ')
set(thnd1,'String','                               ')
for i=1:20:201%121
    plot(zoverL,framedata(i,:),'k');
    hold on
    pause(.4)
    
end
text(-.9,-1.1*lim,'\omega\Deltat = \pi/5')
text(-.9,1.1*lim,'Press Enter to Animate')
pause

figure(4);clf;% Animate v(z,t)
axis([-1.2 .2 -1.2*lim 1.2*lim])
hold on
box on
L=plot(zoverL,framedata(1,:),'k','EraseMode','xor');
hold on
plot([-1 -1],[-1.2*lim 1.2*lim])
hold on
plot([0 0],[-1.2*lim 1.2*lim])
hold on
M=plot([-1 0],[framedata(1,1) framedata(1,101)],'o','EraseMode','xor');
xlabel('Dimensionless Distance on the Line, z/L')
ylabel('Line Voltage, v(z,t)')
thnd1=text(-.9,1.1*lim,'Press Enter to Animate');
pause
text(-1,1.1*lim,'                      ')
set(thnd1,'String','                               ')
for i=1:801
    set(L,'Ydata',framedata(i,:))
    set(M,'Ydata',[framedata(i,1),framedata(i,101)])
    pause(.01)
end
text(-.9,1.1*lim,'Press Enter to Continue')
hold off
pause
tdata=linspace(0,8*pi,801);
[Y,X]=meshgrid(omegat,zoverL);

figure(5);clf; %3-d plotof v(z,t)
axis([-1 0  0 8*pi -1.1*lim 1.1*lim])
hold on
mesh(X,Y,framedata')
view(45,30)
text( -.8,0,-1.5*lim,'Distance, z/L','Rotation', -18)
text(0, 8,-1.5*lim,'Dimensionless Time,  \omegat','Rotation',20)
zlabel('Line Voltage, v(z,t)')
grid on
text(-1,30,lim,'Press Enter to Continue', 'Rotation',-18)
pause