Отправлено aLexiy 16 сентября 2004 г. 14:16 В ответ на: Помогите начинающему разобраться. Есть два сигнала ... отправлено aLexiy 16 сентября 2004 г. 12:40

к сожалению не силен я в МАТЛАБЕ и в математике чтобы понять все это.

function val = myfshift(x1,x2)

%fshift
%
% out = fshift(x1,x2) returns the maximum shift between
% two signals of the same size. out is the value of the
% maximum shift between the two signals.
%
% See also: maxt, gowave2, go2, twomicplot, blargh3.

%Check if the two vectors are of the same size
if size(x1) ~= size(x2),
'Matrix dimensions must agree.'
out = NaN,
return,
end

%Take the middle half "chunk" of one of the vectors (x2 in this case)
%middlex2 is the middle half chunk of x2
N = max(size(x1));
startindex = N/4+1;
middlex2 = x2(startindex:startindex + N/2 - 1);

%create a vector of same length as x1, x2 with middle chunk
%of x2 called newx2
newx2a = [zeros(1,startindex), middlex2];
newx2 = [newx2a, zeros(1,N-max(size(newx2a)))];

%flip newx2 around for convolution
newx2 = fliplr(newx2);

%%nn=0:N-1;

filt = [ones(1,N/8), zeros(1,3*N/4),ones(1,N/8)];

%convolute newx2 with x1 to compare where they are very close
%(i.e. where the inner product is very, very big)

val = real(ifft( fft(x1).*fft(newx2).*filt));

val = fftshift(val);
%val=val(1:(max(size(val))) -3); %3 is centering factor. Need signals of large enough length

%EXPERIMENTAL, TRIMMING THE SHIFT VECTOR:
%p=max(size(val));
%q = (p-1)/4;
%val=val((q+1):(p-q));

%figure
%L = (max(size(val)) - 1)/2
%L2 = 128
%t = -L2:L2;
%L+1-L2
%L+1+L2
%stem(t,val(L+1-L2:L+1+L2));

%calculate maximum shift
%out=maxt(val);

clear newx2a newx2 middlex2

%---------------------------------------------------------
function T = maxt(x);

%maxt
%
% T = maxt(x) returns the maximum shift between two signals
% which have been convoluted using fshift and assigned to x.
% maxt takes the first shift (left or right) which matches
% the signal peak.
%
% See also: fshift, gowave2, go2, twomicplot, blargh3.

N = max(size(x)); % Note N is odd since it is the
% result of the convolution of
% two even length vectors.

maxval = max(x); % Maximum value in x

mid = (N+1)/2; % middle value for vector
% note mid is an integer since N
% is always odd

% compare the value at each x point to the max value, returns the index that cooresponds to the max value

for i = 0:mid-1

if x(mid - i) == maxval
T=-i;,return
end

if x(mid + i) == maxval
T=i;,return
end
end

• Кажется тут не фазовый сдвиг определяется, а задержка между двумя последовательностями. То есть некая последовательность и из нее две выборки х1 и х2 взятые с задержкой одна относительно другой — alostap   (16.09.2004 16:48, пустое)