% ex6_1.m exemplifying FIR design
%
% I. we specify the poles and zeros. we begin with a simple design of an FIR
% filter with one zero at z=a and hence a single pole at z=0:
% THEREFORE, SIMPLE LOWPASS AND HIGHPASS FILTERS CAN BE DESIGNED
% the user inputs the value of a
% The column vector of zeros is q=a
% The column vector of poles is p=0
clear, clc, clf
a=input('enter zero location, a real number a ')
% a=-1;
q=a;
p=0;
% II. we make a pole-zero plot
figure(1)
zplane(q,p)
title('pole-zero plot')
disp('press any key to proceed')
pause
% III. we find the transfer function form
b=poly(q);
a=poly(p);
disp('the numerator polynomial (in 1/z) coeficients b are ')
b
disp('the denominator polynomial (in 1/z) coeficients a are ')
a
disp('press any key to proceed')
pause
% IV. we can now plot the frequency response
figure(2)
freqz(b,a,512,'whole')
title('FIR Frequency Response')
disp('press any key to proceed')
pause
% the impulse response is, for an fir, simply b: plot it
figure(3)
plot(b,'x')
axis([1 2 -max(b) max(b)])
title('FIR Impulse Response')
%
% V. QUESTIONS
% - where is a located for a lowpass filter?
% - where is a located for a highpass filter?
% - when a is replaced by 1/a,
% what is the difference in FR magnitude?
% what is the differenc in FR phase?
% - is a bandpass filter possible? with real IR?