s_plus_match_2.asv

spread spectrum communication will be helpful to you!

% This script takes the transistor s parameters that were measured with the HP 8505a 
% and adds the two LC matching networks where the values were previously
% computed and saved to a file. 
% To check the design, the voltage transfer function will be computed. 

% There are several ways to solve this, but here we will start by 
% transforming the s parameter two port network description to an ABCD two port (chain matrix) description. 
% Then, the LC matching netorks will be added to ech end of the transistor
% two port networks in ABCD form.  
% The advantage of using the chain matrix approach is that matrix
% multiplication gives the desired solution. The alternative would be to
% stay in s paramter form and solve the overall signal flowgraph. 

clc
clear

% define some symbolic variables: 
syms Zo s11 s12 s21 s22 
% Unable to locate an accurate s to ABCD transform, so transform from 
% s to z parameters as a first step. 
z11 = Zo*((1+s11)*(1-s22)+s12*s21)/((1-s11)*(1-s22)-s12*s21);
z22 = Zo*((1+s22)*(1-s11)+s12*s21)/((1-s22)*(1-s11)-s12*s21);
z12 = Zo*2*s12/((1-s11)*(1-s22)-s12*s21);
z21 = Zo*2*s21/((1-s11)*(1-s22)-s12*s21);

% then transform from z to  ABCD ... call it the F 
Dz      = simple(z11*z22-z12*z21);
Fa(1,1) = simple(z11/z21);    % A 
Fa(1,2) = simple(Dz/z21);     % B
Fa(2,1) = simple(1/z21);      % C
Fa(2,2) = simple(z22/z21);    % D

Fa         % there is nothing "simple" about this,  it is a mess !  
           % no wonder text books do not cover S <-> ABCD
           
% With that out of the way, define input output matching network            
syms  x y Z Y s   L1 L2 C1 C2  Rl w
Z(1,1) = 1; Z(1,2) = x; Z(2,1) = 0; Z(2,2)=1;    % series impedance chain matrix 
Y(1,1) = 1; Y(1,2) = 0; Y(2,1) = y; Y(2,2)=1;    % shunt admittance chain matrix

% Build a network , same matching network topology just *happens* to be used on transistor input and output 
 Z(1,2) = L2*s;            % series L2
 Y(2,1) = C2*s;            % shunt C2
 N      = Z*Y;             % combine (series 1st)
 Z(1,2) = L1*s + 1/(C1*s); % series lC
 N      = N*Z;             % series L2, shunt C2, followed by series L1 C1
% N is now the symbolic matching network.  

load amp_data;     % pick up LC values for matching networks

     % start at load end of circuit and terminate with a shunt conductance 
     Y(2,1)  = 1/50;                % termination  
     Nout = Y;     
     % add output matching network 
     Nout = subs(N, {L1 L2 C1 C2}, {L1o L2o C1o C2o})*Nout;
     Y(2,1)  = Coo*s; % then a capacitor 
     Nout  = simple(Y*Nout);
     
    %  input match network 
     Ninput = subs(N, {L1 L2 C1 C2}, {(L1i+Loi) L2i C1i C2i});
     % input resistor ... 
     Z(1,2) = 50; 
     Ninput = Z*Ninput;
     
     

 % load transistor s parameter data over a range of frequencies 
 fmin = 15;    % MHz
 fmax = 1000;  %  "
 df   = 10;    %  "
 [stx,f] = s_extract('mrf904_10_10a.rfa',fmin,fmax,df);  % get measured s parameter data for mrf904

 k=1; 
 
 for k=1:length(f)
     jw=j*2*pi*f(k)*1e6;
     % Transform the S parameter transistor data to a chain m
     Ntr = double(subs(Fa, {s11 s12 s21 s22 Zo}, {stx(1,1).s(k), stx(1,2).s(k), stx(2,1).s(k), stx(2,2).s(k) 50} ));
    
     Nall = double(subs(Ninput,s,jw))*Ntr*double(subs(Nout,s,jw));
     H(k) =  2/Nall(1,1);       % the inverse of the  "A" term is the overall voltage xfer function, 
                                % need 2 for the -6dB loss (a 0 dB gain amp has a 2:1 loss)
 end;    
 figure
 plot(f,20*log10(abs(H))); grid on;