function x=altes(N,fmin,fmax,alpha) ;%ALTES	Altes signal in time domain.%	X=ALTES(N,FMIN,FMAX,ALPHA) generates the Altes signal in%	the time domain.%%	N     : number of points in time   %	FMIN  : lower frequency bound (value of the hyperbolic%	        instantaneous frequency law at the sample N), %	        in normalized frequency             (default : .05) %	FMAX  : upper frequency bound (value of the hyperbolic%	        instantaneous frequency law at the first sample), %	        in normalized frequency             (default : 0.5)%	ALPHA : attenuation factor of the envelope (default : 300)%	X     : time row vector containing the Altes signal samples.%%	Example: %	 x=altes(128,0.1,0.45); plot(x);%%	See also KLAUDER, ANASING, ANAPULSE, ANASTEP, DOPPLER.%	P. Goncalves - September 1995.%	Copyright (c) 1995 Rice University%%	------------------- 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 ( 'The number of parameters must be at least 1.' );elseif (nargin == 1), fmin=0.05; fmax=0.5; alpha=300;elseif (nargin == 2), fmax=0.5; alpha=300;elseif (nargin == 3), alpha=300 ;end;if (N <= 0), error ('The signal length N must be strictly positive' );elseif (fmin > 0.5) | (fmin < 0), error ( 'FMIN must be in ]0 , 0.5]' ) ;elseif (fmax > 0.5) | (fmax < 0), error ( 'FMAX must be between 0 and 0.5' ) ;elseif (alpha <= 1), error ( 'ALPHA must be > 1' ) ;else g = exp((log(fmax/fmin))^2/(8*log(alpha))) ; nu0 = sqrt(fmin*fmax) ; beta=sqrt(2*log(g)*log(alpha)); t0 = N/(exp(beta)-exp(-beta)) ; t1 = t0*exp(-beta); t2 = t0*exp(beta) ; b = -t0*nu0*g*log(g) ; t = linspace(t1,t2,N+1) ; t = t(1:N) ; x = (exp(-(log(t./t0).^2)/(2*log(g)))).*cos(2*pi*b*log(t./t0)/log(g)) ; x = x.'/norm(x) ;end