Adaptive Filters and Applications - Digital Signal Processing: Fundamentals and Applications - page 472

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FIGURE 10.14

Spectrum for the input signal, unknown system output, and the adaptive filter output.

sum ¼ sum þ w(i)*x(m-i);
end
y(m) ¼ sum;

e(m) ¼ d(m)-y(m);

for i ¼ 1:1:21

w(i) ¼ w(i) þ 2*mu*e(m)*x(m-i);

end
end
% Calculate the single-sided amplitude spectrum for the input
X ¼ 2*abs(fft(x))/length(x);X(1) ¼ X(1)/2;
% Calculate the single-sided amplitude spectrum for the unknown system output
D ¼ 2*abs(fft(d))/length(d);D(1) ¼ D(1)/2;
% Calculate the single-sided amplitude spectrum for the adaptive filter output
Y ¼ 2*abs(fft(y))/length(y);Y(1) ¼ Y(1)/2;
% Map the frequency index to its frequency in Hz
f ¼ [0:1:length(x)/2]*fs/length(x);
% Plot signals and spectra
subplot(4,1,1), plot(x);grid; axis([0 length(x) -3 3]);
ylabel( ' System input ' );
subplot(4,1,2), plot(d);grid; axis([0 length(x) -1.5 1.5]);
ylabel( ' System output ' );
subplot(4,1,3),plot(y);grid; axis([0 length(y) -1.5 1.5]);