Example.m

%EXAMPLE:
%  This function implements a simple RF circuit.  It cascades a 200 source
%  impedance, 2:1 source matching transformer, 50ohm transmission line,
%  load matching network, and 30pF + 100ohm load.  As a function of
%  frequency, the following parameters are plotted:
%      Voltage transfer function, H(s) = Vout/Vin
%      Input Impedance
%      Output Impedance
%      Impedance looking into load matching network



f=linspace(170e6,220e6,1e3);   %Setup a frequency space from 170Mhz to 220Mhz
w=f.*2.*pi;   %This is the omega vector
clear ABCD    %Clean things up from a prior simulation
n=1;
%Transformer source impedance
  ABCD{n} = ser_r(f,200);  n=n+1;                     %1  Series resistor = 200ohms (Source Impedance)
  ABCD{n} = tform(f,2); n=n+1;                        %2  Transformer to turn 200ohms into 50ohms 
%50ohm, transmission line length of 1m
  ABCD{n} = tline(f,50,0.1,62e-12,1) ;n=n+1;          %3  Transmission Line, 50ohms not very lossy
%Network to transform load into 50ohms at 200Mhz:
  ABCD{n} = ser_c(f,14.92e-12);  n=n+1;               %4  Series capacitor
  ABCD{n} = par_l(f,63.73e-9);  n=n+1;                %5  Parallel inductor
%Load = 100ohms + 30pF (series representation)
  ABCD{n} = par_r(f,100 + 1./(w.*30e-12.*1i)) ;n=n+1; %6  Load input directly as a vector

%Combine all ABCD matrices in a cascade
ABCD_C=cascade_combine(ABCD);

%Find the voltage transfer function, = H(s) = Vout/Vin.
%  This is equal to 1/A in the ABCD matrix
OutputVoltage = 1./(ABCD_C(:,1));

%Find the input impedance = A/C
InputImpedance = ABCD_C(:,1)./ABCD_C(:,3);

%Flip the matrix to find the output impedance
ABCD_Flip = flip_ABCD(ABCD_C);
%Output impedance = A/C on flipped ABCD matrix
OutputImpedance = ABCD_Flip(:,1)./ABCD_Flip(:,3);

%Find the impedance looking into the load, = impedance looking into cell 4
ImpedanceLookingIntoLoad = ImpedanceIntoCell(ABCD,4);


%Now do a bunch of plots.  For impedances, real part in top plot, imaginary
%part in bottom plot
figure(1)
clf;
plot(f,abs(OutputVoltage));
title('Voltage transfer function from input to output (Vout/Vin)');

figure(2)
clf;
subplot(2,1,1)
plot(f,real(InputImpedance))
title('Input Impedance')
subplot(2,1,2)
plot(f,imag(InputImpedance))

figure(3)
clf;
subplot(2,1,1)
plot(f,real(OutputImpedance))
title('Output Impedance')
subplot(2,1,2)
plot(f,imag(OutputImpedance))


figure(4)
clf;
subplot(2,1,1)
plot(f,real(ImpedanceLookingIntoLoad))
title('Impedance looking into transformed load')
subplot(2,1,2)
plot(f,imag(ImpedanceLookingIntoLoad))