function [naf,tau,xi]=ambifunb(x,tau,N,trace);%AMBIFUNB Narrow-band ambiguity function.%	[NAF,TAU,XI]=AMBIFUNB(X,TAU,N,TRACE) computes the narrow-band %	ambiguity function of a signal X, or the cross-ambiguity %	function between two signals.%	%	X     : signal if auto-AF, or [X1,X2] if cross-AF (length(X)=Nx).%	TAU   : vector of lag values     (default : -Nx/2:Nx/2).%	N     : number of frequency bins (default : length(X)).%	TRACE : if nonzero,              (default : 0)%	        the progression of the algorithm is shown.%	NAF   : doppler-lag representation, with the doppler bins stored %	        in the rows and the time-lags stored in the columns.%	        When called without output arguments, AMBIFUNB displays%	        the squared modulus of the ambiguity function by means of%	        contour.%	XI    : vector of doppler values.%%	Example :%	 sig=anabpsk(256,8);%	 ambifunb(sig); %%	See also AMBIFUWB.%	O. Lemoine, F. Auger - August 1995.%	Copyright (c) 1996 by CNRS (France).%%	------------------- CONFIDENTIAL PROGRAM -------------------- %	This program can not be used without the authorization of its%	author(s). For any comment or bug report, please send e-mail to %	f.auger@ieee.org if (nargin == 0), error('At least one parameter required');end;[xrow,xcol] = size(x);if (xcol==0)|(xcol>2), error('X must have one or two columns');end;if (nargin == 1), if rem(xrow,2)==0, tau=(-xrow/2+1):(xrow/2-1);  else tau=(-(xrow-1)/2):((xrow+1)/2-1); end N=xrow; trace=0;elseif (nargin == 2), N=xrow ; trace=0;elseif (nargin == 3), trace=0;end;[taurow,taucol] = size(tau);if (taurow~=1), error('TAU must only have one row'); elseif (N<0), error('N must be greater than zero');end;naf=zeros(N,taucol); if trace, disp('Narrow-band ambiguity function'); end;for icol=1:taucol, if trace, disprog(icol,taucol,10); end; taui=tau(icol); t=(1+abs(taui)):(xrow-abs(taui)); naf(t,icol)=x(t+taui,1).* conj(x(t-taui,xcol));end;naf=fft(naf);naf=naf([(N+rem(N,2))/2+1:N 1:(N+rem(N,2))/2],:);xi=(-(N-rem(N,2))/2:(N+rem(N,2))/2-1)/N;if (nargout==0), contour(2*tau,xi,abs(naf).^2,16);  grid xlabel('Delay'); ylabel('Doppler'); shading interp title('Narrow-band ambiguity function');end;