%Roh-Maximum Characteristic Impedance that can be achieved using CPW filter
%Rol-Minimum Characteristic Impedance that can be achieved using CPW filter
%Ro-Impedance of filter
%fc-Cut-off frequency of lowpass filter
%g[n]-Filter coefficients
%Actual[n]-Actual L,C,R values
%L=g[k]*Ro/2*pi*fc
%C=g[k]/Ro*2*pi*fc
%n-No. of filter coefficients
%l[k]-Lengths of elements
%A[k]-Angles-beta*l
%epso-Dielectric constant of air
%muo-Permeablility of air
%epsr-Dielectric constant of the material
%epseff-Effective Dielectric constant
%lambdag-Wavelength in the dielectric
%ratiol-b/a for Rol
%ratioh-b/a for Roh
%L-Insertion loss in dB at frequency f
%Lm-Ripple magnitude in dB
%W[k]-Width of Tx. line
%D-Distance between two ground planes
repeat='y';
while repeat=='y'
clc
clear
%Constants
epso=8.854*power(10,-12);
muo=4*pi*power(10,-7);
Rol=100;
Roh=750;
Ro=300;
choice=menu('Click on your choice','Chebychev filter','Butterworth filter','Plot between Characteristic impedance and b/a','Plot between Insertion loss and n');
if isequal(choice,1)
choice1=1;
elseif isequal(choice,2)
choice1=1;
elseif isequal(choice,3)
choice1=2;
elseif isequal(choice,4)
choice1=3;
end
switch (choice1)
%Normalized values for Butterworth filter
case 1
if isequal(choice,2)
fc=input('Enter the Cut-off frequency in Giga Hertz(GHz) :');
L=input('Required Insertion loss in dB :');
f=input('At frequency in Giga Hertz(GHz) :');
n=0.5*(log(power(10,L/10)-1)/log(f/fc));
n=ceil(n);
if isequal(rem(n,2),0)
n=n+1;
end
g(1)=1;
for i=2:n+1
g(i)=2*sin((2*(i-1)-1)*pi/(2*n));
end
g(n+2)=1;
%Normalized values for Chebychev filter
%Temporary variables-a(i),b(i),gamma,beta
else
fc=input('Enter the Cut-off frequency in Giga Hertz(GHz) :');
L=input('Required Insertion loss in dB :');
f=input('At frequency in Giga Hertz(GHz) :');
Lm=input('Ripple magnitude in dB :');
if (f/fc)<1
n=acos(sqrt((power(10,L/10)-1)/(power(10,Lm/10)-1)))/acos(f/fc);
else
n=acosh(sqrt((power(10,L/10)-1)/(power(10,Lm/10)-1)))/acosh(f/fc);
end
n=ceil(n);
if isequal(rem(n,2),0)
n=n+1;
end
g(1)=1;
g(n+2)=1;
beta=log(coth(Lm/17.37));
gamma=sinh(beta/(2*n));
for i=2:1:n+1
a(i)=sin((2*i-3)*pi/(2*n));
b(i)=power(gamma,2)+power(sin((i-1)*pi/n),2);
end
g(2)=2*a(2)/gamma;
for i=3:1:n+1
g(i)=4*a(i-1)*a(i)/(b(i-1)*g(i-1));
end
end
epsr=input('Enter the di-electric constant of the material :');
%Calculation for normalized values is over
epseff=(epsr+1)/2;
lambdag=3*power(10,8)/(fc*sqrt(epseff)*power(10,9));
Actual(1)=g(1)*Ro;
Actual(n+2)=g(n+2)*Ro;
for i=2:2:n+1
Actual(i)=g(i)*power(10,12)/(Ro*2*pi*fc); % in pico farad
l(i)=asin(g(i)*Rol/Ro)*lambdag*1000/(2*pi); % in mm
A(i)=asin(g(i)*Rol/Ro)*180/pi;
end
for i=3:2:n+1
Actual(i)=g(i)*Ro*power(10,9)/(2*pi*fc); % in nano henry
l(i)=asin(g(i)*Ro/Roh)*lambdag*1000/(2*pi); % in mm
A(i)=asin(g(i)*Ro/Roh)*180/pi;
end
ratiol=power(power(0.25*(exp(pi*Rol*sqrt(2*epso*(epsr+1)/muo))-(1+pi*Rol*sqrt(2*epso*(epsr+1)/muo))),-0.0068*Rol+2.5986)+power(1+8*exp(-1*pi*sqrt(muo/(8*epso*(epsr+1)))/Rol),-0.0068*Rol+2.5986),1/(-0.0068*Rol+2.5986));
ratioh=power(power(0.25*(exp(pi*Roh*sqrt(2*epso*(epsr+1)/muo))-(1+pi*Roh*sqrt(2*epso*(epsr+1)/muo))),-0.0068*Roh+2.5986)+power(1+8*exp(-1*pi*sqrt(muo/(8*epso*(epsr+1)))/Roh),-0.0068*Roh+2.5986),1/(-0.0068*Roh+2.5986));
%Distance between two ground planes is constant
D=lambdag;
Tlength=0;
for i=2:n+1
if rem(i,2)==0
W(i)=D/ratiol;
else
W(i)=D/ratioh;
end
Tlength=Tlength+l(i);
end
if Tlength>100
hscale=150;
vscale=3;
end
hscale=100;
vscale=2;
display('Vertical Scale');display(vscale);
display('Horizantal Scale');display(hscale);
%Drawing the layout-Scaling widths by vscale,lengths by hscale
temp=0.1;
handle=annotation('rectangle',[0.1 0.5+vscale*D/2 Tlength/hscale 0.2]);
set(handle,'Facecolor',[0 0 0]);
handle=annotation('rectangle',[0.1 0.3-vscale*D/2 Tlength/hscale 0.2]);
set(handle,'Facecolor',[0 0 0]);
for i=2:n+1
handle=annotation('rectangle',[temp 0.5-vscale*W(i)/2 l(i)/hscale vscale*W(i)]);
if rem(i,2)==0
set(handle,'FaceColor',[1 0 1]);
else
set(handle,'FaceColor',[0 1 1]);
end
temp=temp+l(i)/hscale;
end
%Plotting the graph between Z0 and b/a
case 2
epsr1=input('Enter the di-electric constant of the material(epsr1) :');
epsr2=input('Enter the di-electric constant of the material(epsr2) :');
figure;
hold on;
Z0=50:10:350;
for i=1:31
epsr=epsr1;
ratio(i)=power(power(0.25*(exp(pi*Z0(i)*sqrt(2*epso*(epsr+1)/muo))-(1+pi*Z0(i)*sqrt(2*epso*(epsr+1)/muo))),-0.0068*Z0(i)+2.5986)+power(1+8*exp(-1*pi*sqrt(muo/(8*epso*(epsr+1)))/Z0(i)),-0.0068*Z0(i)+2.5986),1/(-0.0068*Z0(i)+2.5986));
ratio(i)=1/ratio(i);
epsr=epsr2;
ration(i)=power(power(0.25*(exp(pi*Z0(i)*sqrt(2*epso*(epsr+1)/muo))-(1+pi*Z0(i)*sqrt(2*epso*(epsr+1)/muo))),-0.0068*Z0(i)+2.5986)+power(1+8*exp(-1*pi*sqrt(muo/(8*epso*(epsr+1)))/Z0(i)),-0.0068*Z0(i)+2.5986),1/(-0.0068*Z0(i)+2.5986));
ration(i)=1/ration(i);
end
plot(Z0,ratio,'r',Z0,ration,'m');
legend('epsr1','epsr2');
xlabel('Characteristic Impedance');
ylabel('a/b');
case 3
option=input('Enter the filter type-Chebychev(C)/Butterworth(B)','s');
figure;
hold on;
relf=logspace(-1,0.25,31);
if option=='B'
for i=1:31
Loss1(i)=10*log10(1+power(relf(i),2*3));
Loss2(i)=10*log10(1+power(relf(i),2*5));
Loss3(i)=10*log10(1+power(relf(i),2*7));
Loss4(i)=10*log10(1+power(relf(i),2*9));
end
else
for i=1:31
if relf<1
Loss1(i)=10*log10(1+(power(10,0.05)-1)*power(cos(3*acos(relf(i))),2));
else
Loss1(i)=10*log10(1+(power(10,0.05)-1)*power(cosh(3*acosh(relf(i))),2));
end
if relf<1
Loss2(i)=10*log10(1+(power(10,0.05)-1)*power(cos(5*acos(relf(i))),2));
else
Loss2(i)=10*log10(1+(power(10,0.05)-1)*power(cosh(5*acosh(relf(i))),2));
end
if relf<1
Loss3(i)=10*log10(1+(power(10,0.05)-1)*power(cos(7*acos(relf(i))),2));
else
Loss3(i)=10*log10(1+(power(10,0.05)-1)*power(cosh(7*acosh(relf(i))),2));
end
if relf<1
Loss4(i)=10*log10(1+(power(10,0.05)-1)*power(cos(9*acos(relf(i))),2));
else
Loss4(i)=10*log10(1+(power(10,0.05)-1)*power(cosh(9*acosh(relf(i))),2));
end
end
end
semilogx (relf,Loss1,'r',relf,Loss2,'m',relf,Loss3,'b',relf,Loss4,'g');
xlabel('Relative frequecy');ylabel('Attenuation in dB');
legend('n=3','n=5','n=7','n=9');
end
repeat=input('Do you want to repeat the calculation(y/n) :','s');
end
