% File: pllpre.m
% Software given here is to accompany the textbook: W.H. Tranter, 
% K.S. Shanmugan, T.S. Rappaport, and K.S. Kosbar, Principles of 
% Communication Systems Simulation with Wireless Applications, 
% Prentice Hall PTR, 2004.
%
clear all						% be safe
disp(' ')                       % insert blank line 
fdel = input('Enter the size of the frequency step in Hertz > ');
fn = input('Enter the loop natural frequency in Hertz > ');
lambda = input('Enter lambda, the relative pole offset > ');
disp(' ')
disp('Accept default values:')
disp(' zeta = 1/sqrt(2) = 0.707,')
disp(' fs = 200*fn, and')
disp(' tstop = 1')
dtype = input('Enter y for yes or n for no  > ','s');
if dtype == 'y'
   zeta = 1/sqrt(2);
   fs = 200*fn;
   tstop = 1;
else           
zeta = input('Enter zeta, the loop damping factor > ');
fs = input('Enter the sampling frequency in Hertz > ');
tstop = input('Enter tstop, the simulation runtime > ');
end
%
npts = fs*tstop+1;              % number of simulation points
t = (0:(npts-1))/fs;            % default time vector
nsettle = fix(npts/10);         % set nsettle time as 0.1*npts
tsettle = nsettle/fs;           % set tsettle
%
% The next two lines establish the loop input frequency and phase 
% deviations.
%
fin = [zeros(1,nsettle),fdel*ones(1,npts-nsettle)];
phin = [zeros(1,nsettle),2*pi*fdel*t(1:(npts-nsettle))];
% 
disp(' ')                       % insert blank line
%       end of script file pllpre.m