fft_causal.m

用于模拟时变非平稳的ARMA过程

function y= fft_causal(x)
% function y= fft_causal(x)
%   This file is part of the TFPM toolbox v0.5 (c)
%   [e-mail] and underlies the GPL.
% 
% Augments the signal vector x of length N1 to a causal signal y of
% length N (power of 2), which is causal, i.e., y[n]= 0 for
% N/2<n<N. 

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if(0)% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST
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clear;tfpm;
N1= 34;
x= randn(N1, 1);
figure(97);plot(x);
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end;% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST
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% Dimensions
N1= length(x);
n= ceil(log2(N1));
if(2^(n-1)+1==N1)
   N= 2^n;
else
   N= 2^(n+1);
end;
y= zeros(N, 1);
y(1:length(x))= x;

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if(0)% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
figure(98);plot(y);
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end;% TEST TEST TEST TEST TEST TEST TEST TEST TEST TEST
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