exa4_21.m

新版Matlab 7辅助信号处理技术与应用

% exa4-21_lpc.m , for example 4-21
% Design lpc DF

clear all;
randn('state',0);
noise = randn(50000,1);  % Normalized white Gaussian noise
x = filter(1,[1 1/2 1/3 1/4],noise);
x = x(45904:50000);
a = lpc(x,3);
est_x = filter([0 -a(2:end)],1,x);    % Estimated signal
e = x - est_x;                        % Prediction error
[acs,lags] = xcorr(e,'coeff');        % ACS of prediction error
plot(1:97,x(4001:4097),1:97,est_x(4001:4097),'--');
title('Original Signal vs. LPC Estimate');
xlabel('Sample Number');
ylabel('Amplitude'); 
grid;
legend('Original Signal','LPC Estimate')
figure(2)
plot(lags,acs); 
title('Autocorrelation of the Prediction Error');
xlabel('Lags'); 
ylabel('Normalized Value'); 
grid;