Subversion Repositories fir_filter

clear all;

format long g;

%XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

%                       filtro_FIR.vhd

%XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

% http://t-filter.appspot.com/fir/index.html

fs=64e6

order=31

fc=2e6

input_size=8

%%%%%%%%%%%%%%%%%%%% h[n] %%%%%%%%%%%%%%%%%%%%%%%%%

fnyquist=fs/2;

%normalized cut-off frequency

wn=fc/fnyquist;

h= fir1(order,wn,'low')

figure(1);

stem(h);

title('h(n)');grid on;

%%%%%%%%%%%%%%%%%%%% H[z] %%%%%%%%%%%%%%%%%%%%%%%%%

figure(2);

freqz(h);

%%%%%%%%%%%%%%%%%%%% x[n] %%%%%%%%%%%%%%%%%%%%%%%%%

num_cycles=16;

amplitude=2^input_size-1;

freq=fc/4;

num_samples=num_cycles*(fs/freq);

n=0:1/(fs/freq):num_cycles;

sin=amplitude*sin(2*pi*n);

x=sin+(amplitude/20)*randn(size(n));

figure(3);

subplot(2,2,1);

str=sprintf('x[n]:  f=%g Hz  max=%g+noise',freq,max(sin));

stem(x); title(str); grid on;

%%%%%%%%%%%%%%%%%%%% x[z] %%%%%%%%%%%%%%%%%%%%%%%%%

% NFFT = 2^nextpow2(num_samples);

% f = (1:NFFT/2+1)*(fs/NFFT);          % wn=1 <> fs/2

% X = fft(x,NFFT);

% peakpowerX = max(X).*conj(max(X))/NFFT;

subplot(2,2,2);

% stem(f,2*abs(X(1:NFFT/2+1)));

% str=sprintf('x[z]  peak power=%g',peakpowerX);

% title(str); grid on;

% xlabel('f[Hz]')

% ylabel('|x[z]|')

periodogram(x,rectwin(length(x)),length(x),fs);

% %%%%%%%%%%%%%%%%%%%% y[n] %%%%%%%%%%%%%%%%%%%%%%%

y=filter(h,1,x);

subplot(2,2,3);

str=sprintf('y[n]:  fc=%g Hz  peak=%g',fc,max(y(length(h):num_samples)));

stem(y); title(str); grid on;

%%%%%%%%%%%%%%%%%%%% y[z] %%%%%%%%%%%%%%%%%%%%%%%%%

subplot(2,2,4);

periodogram(y,rectwin(length(y)),length(y),fs);

format;