ISU EE 573 SPRING 2002 Quizes
%Program Name: quiz.m
% PURPOSE: To investigate the influence of delt on the psd
% of a 2nd order underdamped system excited by white noise
% =======================================================
% SPECIFY 2ND ORDER SYSTEM PARAMETERS
zeta=0.01; %analog system damping ratio
wn=10; %analog system undamped natural frequency
Sxx=[];
delt=[];
% COMPUTE DIGITAL SYSTEM PSD FOR Wsamp = 10, 100 & 1000 times Wn
for m=1:3
ws=wn*10^m; %sampling frequency
vn=wn/ws;
deltm=2*pi/ws;
delt=[delt deltm];
alpha=exp(-2*pi*zeta*vn);
beta=2*pi*vn*(1-zeta^2)^0.5;
a1=alpha*sin(beta);
b1=-2*alpha*cos(beta);
b2=alpha^2;
% COMPUTE PSD
A=(deltm*abs(fft([0 a1],4096))).^2;
A=A(1:2048);
B=(abs(fft([1 b1 b2],4096))).^2;
B=B(1:2048);
Sxx=[Sxx ; 10*log10(A./B)];
end
fvec=0:1/4096:0.5-1/4096;
plot(fvec,Sxx)
xlabel('Normalized Frequency (Hz)')
ylabel('Sampled System PSD (dB')
title('PSDs for ws=10, 100 and 1000 times wn')