Matlab_射频上常用的转换以及分析_S矩阵转化成Z矩阵_放大器稳定性分析

function [Z,fig_num]=rf_imp_transform(freq, fig_num_in) % % this function computes an inpute impedance and plot all % impedance transformations in the network which is stored % in the global variable rf_Network. % Network is analyzed at given frequency specified by % the input parameter freq. % Outputs of this routine are input impedance and a figure % number which contains the Smith Chart with impedance transformations % if the Smith Chart was specified by fig_num_in, then fig_num=fig_num_in % global Z0; global rf_Network; % initialize a reference to the global variable % % Global variable rf_Network contain a description of the network. % The description of each element in the network contains the following % five fields stored in rf_Network: % % field# | field name | meaning % --------+--------------+--------------- % 1 | element | describes what element is connected % | | this field can have the following values % | | 0 - constant impedance (e.g. resistor) % | | 1 - inductance % | | 2 - capacitance % | | 3 - transmission line % | | 4 - short-circuit stub % | | 5 - open-circuit stub % --------+--------------+--------------- % 2 | value | value of the element % --------+--------------+--------------- % 3 | shunt/series | 1=shunt or 0=series connection % --------+--------------+--------------- % 4 | frequency | frequency at which electrical length of the line is specified % --------+--------------+--------------- % 5 | Z0 | characteristic line impedance % --------+--------------+--------------- % NN=size(rf_Network); Nodes=NN(2); % find out how many elements are in the network fig_num=-1; % indication that network is empty Z=inf; if Nodes==0 % if there are no elements, then just return. return; end; f=freq; w=2*pi*f; % find out which element is the first % it can be either capacitor, or inductor, or impedance, or stub % there is no check performed for illegal combinations, so it is % left up to user to worry about the correctness of the description element=rf_Network(1,1); value=rf_Network(2,1); line_Z0=rf_Network(5,1); shunt=rf_Network(3,1); frequency=rf_Network(4,1); if element==0 % constant impedance if shunt==1 % shunt connection Z=value; end; elseif element==1 % inductor value=j*w*value; if shunt==1 % shunt connection Z=value; end; elseif element==2 % capacitor value=1/(j*w*value); if shunt==1 % shunt connection Z=value; end; elseif element==4 % sc stub theta=value*f/frequency*pi/180; Z_stub=j*line_Z0*tan(theta); if shunt==1 % shunt connection Z=Z_stub; end; elseif element==5 % oc stub theta=value*f/frequency*pi/180; Z_stub=-j*line_Z0/tan(theta); if shunt==1 % shunt connection Z=Z_stub; end; end; if nargin>1 fig_num=figure(fig_num_in); else fig_num=smith_chart; end; hold on; s_Point(Z); if Z~=inf % check that the first element was correct, % i.e., Z was recomputed for n=2:Nodes % run through all remaining elements in the network % read in the description of the next component element=rf_Network(1,n); value=rf_Network(2,n); line_Z0=rf_Network(5,n); shunt=rf_Network(3,n); frequency=rf_Network(4,n); if element==0 % constant impedance % (here it is considered to be just a resistor) if shunt==1 % shunt connection G1=real(1/Z); B=imag(1/Z); Z=1/(1/Z+1/value); G2=real(1/Z); s_ArcB(B,G1,G2); s_Point(Z); else % series connection R1=real(1/Z); X=imag(1/Z); Z=Z+value; R2=real(1/Z); s_ArcX(X,R1,R2); s_Point(Z); end; elseif element==1 % inductor value=j*w*value; if shunt==1 % shunt connection B1=imag(1/Z); G=real(1/Z); Z=1/(1/Z+1/value); B2=imag(1/Z); s_ArcG(G,B1,B2); s_Point(Z); else % series connection X1=imag(Z); RR=real(Z); Z=Z+value; X2=imag(Z); s_ArcR(RR,X1,X2); s_Point(Z); end; elseif element==2 % capacitor value=1/(j*w*value); if shunt==1 % shunt connection B1=imag(1/Z); G=real(1/Z); Z=Z*value/(Z+value); B2=imag(1/Z); s_ArcG(G,B1,B2); s_Point(Z); else % series connection X1=imag(Z); RR=real(Z); Z=Z+value; X2=imag(Z); s_ArcR(RR,X1,X2); s_Point(Z); end; elseif element==3 % line % here we have to take into account that characteristic % line impedance may be different from Z0 for which % the Smith Chart is plotted Gamma0=(Z-line_Z0)/(Z+line_Z0); Gamma1=(line_Z0-Z0)/(line_Z0+Z0); theta=value*f/frequency*pi/180; aa=(0:100)/100*theta; GG=(Gamma1+Gamma0*exp(-2*j*aa))./(1+Gamma1*Gamma0*exp(-2*j*aa)); hold on; plot(real(GG), imag(GG), 'b', 'linewidth', 2); hold off; Gamma=Gamma0*exp(-2*j*theta); Z=line_Z0*(1+Gamma)/(1-Gamma); s_Point(Z); elseif element==4 % sc stub theta=value*f/frequency*pi/180; Z_stub=j*line_Z0*tan(theta); if shunt==1 % shunt connection B1=imag(1/Z); G=real(1/Z); Z=1/(1/Z+1/Z_stub); B2=imag(1/Z); s_ArcG(G,B1,B2); s_Point(Z); else % series connection X1=imag(Z); RR=real(Z); Z=Z+Z_stub; X2=imag(Z); s_ArcR(RR,X1,X2); s_Point(Z); end; elseif element==5 % oc stub theta=value*f/frequency*pi/180; Z_stub=-j*line_Z0/tan(theta); if shunt==1 % shunt connection B1=imag(1/Z); G=real(1/Z); Z=1/(1/Z+1/Z_stub); B2=imag(1/Z); s_ArcG(G,B1,B2); s_Point(Z); else % series connection X1=imag(Z); RR=real(Z); Z=Z+Z_stub; X2=imag(Z); s_ArcR(RR,X1,X2); s_Point(Z); end; end; end end; hold off;