pll_mod_param.m

课程设计做的PLL

% Lab #3 - integer-N PLL parameters
%
% note: this matlab m-file is used to compute the PLL parameters
%       for the simulink model. you have to design the loop filters
%       such that the PLL is stable (i.e. choose a suitable damping factor
%       zeta)
%
% Author: Walt Bax
% Date: November 25, 1998
%
%-----------------------------------------------------------
echo off;

if ~exist('gc')
  gc='b';
end
str=sprintf('graph colour <%s>: ',gc);
buff=input(str,'s');
if ~isempty(buff)
  gc=buff;
end

if ~exist('samples')
  samples=5000;		% set initial # samples for time domain
end

npts=800;

if ~exist('fr')
  fr=10e6;
end

str=sprintf('Reference frequency <%4.1fMHz>: ',fr/1e6);    
buff=input(str);
if ~isempty(buff)
  fr=buff;
end
T=1/fr;

if ~exist('gmode')
  gmode='log';
end
str=sprintf('x-axis (lin|log) <%s>: ',gmode);
buff=input(str,'s');
if ~isempty(buff)
  clf;				% clear figure for new graph mode
  gmode=buff;
end

f=logspace(1,log10(fr-1),npts);

%-----------------------------------------------------------
% given PLL loop parameters

BW=;

Kphi=2;
Kv=50e6;
N=;
K=Kphi*Kv/N;

%-----------------------------------------------------------
% PFD [rad] --> [V]

Bpfd=Kphi*[1];
Apfd=[1];

Hpfd=freqs(Bpfd,Apfd,2*pi*f);

%-----------------------------------------------------------
% loop filter 1 - analog integrator with compensating zero
%
%          B(s)    (Tau2)s + 1	
%   H(s) = ---- = ------------
%          A(s)    (Tau1)s

if (1)

zeta=;                          % zeta specified for this filter
Tau2=;
Tau1=;

Bloop=[Tau2 1];
Aloop=[Tau1 0];
Hloop1=freqs(Bloop,Aloop,2*pi*f);
end

%-----------------------------------------------------------
% VCO [V] --> [rad]

Bvco=2*pi*Kv*[1];
Avco=[1 0];

Hvco=freqs(Bvco,Avco,2*pi*f);

%-----------------------------------------------------------
% PLL frequency response

Hloop=Hloop1;                          % choose a loop filter

Hopen=Hpfd.*Hloop.*Hvco/N;             % PLL open-loop response

Hclose=Hpfd.*Hloop.*Hvco./(1 + Hopen); % PLL closed-loop response

%-----------------------------------------------------------
% plot routine

tf=input('transfer function: ');

fprintf(1,'  fr = %2.0fMHz\n',fr/1e6);
fprintf(1,'  BW = %2.1fKHz\n',BW/1e3);
%fprintf(1,'  Wn = %2.1fKHz\n',wn/(2*pi)/1e3);
%fprintf(1,'zeta = %3.1f\n',zeta);
fprintf(1,'   K = %3.0f\n',K);

if ~isempty(tf)
  mag=abs(tf);				% magnitude response
  phase=360/(2*pi)*unwrap(angle(tf));	% phase response [deg]

  %clf;
  subplot(2,1,1);
  semilogx(f,20*log10(mag),gc);
  grid on
  hold on;
  plot([min(f) max(f)],[0 0],'r');
  plot(2*pi*BW,0,'ro');
  title('Transfer function');
  xlabel('Frequency   (Hz)');
  ylabel('Gain   (dB)');

  subplot(2,1,2);
  semilogx(f,phase,gc);
  grid on
  hold on;
  plot([min(f) max(f)],[-180 -180],'r');
  xlabel('Frequency   (Hz)');
  ylabel('Phase   (deg)');
end