% Animates the propagation of a pulse on a lossless transmission line
% with resistive source and load. The pulse at ther source is 
% Vg volts high and has a duration of f*L/up sec. where f is a decimal
% fraction. The source resistance is Rg and the load resistance is RL.
% The source is attached to the line at z=-L and the load at z=0. 
% 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);
clc
f=-.5;Vg=-2;Rg=-100;Z0=-100;RL=-100;
disp('The temporal duration of the pulse is to be a fraction')
disp('of the transit time, L/up, where L is the line length')
disp('and up is the propagation velocity')
disp('Tpulse = f*L/up where f is a positive decimal fraction')
disp('Author suggests 0.1<=f<=0.8')
while f<=0
    f=input('           f = ');
end
while Vg<=0
    Vg=input('           The height of the pulse at the source in volts Vg = ');
end

while Rg<0
    Rg=input('           The source resistance Rg = ');
end

while Z0<=0
    Z0=input('           The line characteristic impedance Z0 is real and Z0 = ');
end
while RL<0
    RL=input('           The load resistance RL = ');
end
n1=fix(200*f);
V0=Vg*Z0/(Z0+Rg);
gammaL=(RL-Z0)/(RL+Z0);
disp('    ');
disp(['           The load reflection coefficient GammaL = ' num2str(gammaL)]);
gammag= (Rg-Z0)/(Rg+Z0);
disp(['           The source reflection coefficient Gammag = ' num2str(gammag)]);
a0=V0;a1=gammaL*a0;a2=gammag*a1;a3=gammaL*a2;a4=gammag*a3;
%set upper and lower limits for plots
if gammaL>=0&gammag>=0
    lim1=1.1*(1+gammaL)*V0;
    lim2=-.5*V0;
    ztextloc=1.2*lim2;
end
if gammaL<=0&gammag>=0
    lim1=1.2*V0;
    lim2=-1.2*V0;
    ztextloc=1.4*lim2;
end
if gammaL>=0&gammag<=0
    lim1=1.2*(1+gammaL)*V0;
    lim2=-lim1;
    ztextloc=1.4*lim2;
end
if gammaL<=0&gammag<=0
    lim1=1.2*V0;
    lim2=-lim1;
    ztextloc=1.4*lim2;
end
z=linspace(-1,0,201);
vwave=zeros(1,1821);
pulse=ones(1,n1+1);
vwave(1,401-n1:401)=a2*pulse;
vwave(1,801-n1:801)=a0*pulse;
vwave(1,1201:1201+n1)=a1*pulse;
vwave(1,1601:1601+n1)=a3*pulse;
u=vwave(1,801:1001);
W=[u];
for i=1:30:571
    W=[W;vwave(1,801+i:1001+i)+vwave(1,801-i:1001-i)];
end

figure(1);clf;
axis([-1.1 .1 lim2 lim1])
hold on
box on
T1=text(-.95,.9*lim1,'Press Return to Continue');
pause
xlabel('Dimensionless Distance Down the Line, z/L')
hold on;
ylabel('Voltage on the Line, volts')
hold on
for i=1:9
    plot(z,W(i,:))
    hold on
end
text(-.9,.6*lim2,['Pulse Duration = ' num2str(f) '*L/u_p sec.'])
text(-.9, .8*lim2,'\Deltat = 3*L/(20u_p)')
set(T1,'String','Press Return to Continue');
hold off
pause

figure(2);clf;
axis([-1.1 .1 lim2 lim1])
hold on
lim=2.2*V0;
plot([0 0],[lim2 lim1])
hold on
plot([-1 -1],[lim2 lim1])
hold on
text(-.9,.6*lim2,['Pulse Duration = ' num2str(f) '*L/u_p sec.'])
hold on;
xlabel('Dimensionless Position Down the Line, z/L')
hold on;
ylabel('Voltage on the Line, volts')
hold on;
U=[u];
P=plot(z,u,'EraseMode','xor');
box on
VL=[u(1,201)];
V1=[u(1,195)];
T=text(-.9,.9*lim1,'Press Enter to Continue');
pause
set(T,'String','                  ');
%pulse is n1 spatial steps wide(n1+1 samples)
for i=1:800
    u=vwave(1,801+i:1001+i)+vwave(1,801-i:1001-i);  
    set(P,'Ydata',u);
    VL=[VL u(1,201)];
    V1=[V1 u(1,195)];
    pause(.01) 
    if fix(i/2)~=i/2
        U=[U;u];
    end
end
box on
set(T,'String','Press Enter to Continue');
pause
%hold off
t=linspace(0,4,801);

figure(3);clf;
axis([0 t(1,801) lim2 lim1])
hold on
box on
plot(t,VL,'k--',t,V1,'k-')
xlabel('Dimensionless Time, u_pt/L');
ylabel('Voltage on the Line, volts,v(z_i,t)');
text(1.7,.95*lim1,'dashes = v(0,t)');
text(1.7,.8*lim1,['line = v(-0.03*L,t)']);
text(1.5,.6*lim2,['Pulse Duration = ' num2str(f) '*L/u_p sec.']);
text(1.5,.95*lim2,'Press Enter to Continue');
pause
%hold off

figure(4);clf;%3-D Plot
axis([-1 0  0 3 lim2 lim1])
hold on
t1=linspace(0,3,51);
z1=linspace(-1,0,51);
UU=[];
for i=0:50
    UU(i+1,:)=U(5*i+1,1:4:201);
end
[Z,T]=meshgrid(z1,t1);
mesh(Z,T,UU,'Edgecolor',[0 0 0]);
newmapdata=colormap;
newmapdata=ones(size(newmapdata));
colormap=newmapdata;
%ztextloc=-.75*(lim1-lim2);
text(-.9,0,1.3*ztextloc,'Distance, z/L','Rotation',-15);
text(0,1.5,1.5*ztextloc,'Time, u_pt/L','Rotation',43);
zlabel('Line Voltage, v(z,t)');
text(-.8,3,lim1, 'Press Return to Continue','Rotation',-15);
view(30,50);