
From:  Eric ChassandeMottin 
Subject:  Re: [Tftbhelp] question about instfreq.m 
Date:  Tue, 25 May 2010 15:18:45 +0200 (CEST) 
Useragent:  Alpine 2.00 (DEB 1167 20080823) 
hi John,
fnormhat=0.5*(angle(x(t+1).*conj(x(t1)))+pi)/(2*pi); I agree that the output that I receive from this seems to be correct, but I cannot find the relationship between these two. Could someone please explain to me what I am missing, or point me in the right direction for a reference to this calculation.
I think what this expression does is simply the finite difference of the phase of the analytic signal.
if x(t) is the complexvalue analytic signal of the data, denoting its modulus and phase by x(t)=rho(t) exp(i phi(t)) f(t) = 1/2pi dphi(t)/dt ~ (phi(t+delta t)  phi(tdelta t))/(2 delta t)/2 pi. which is what the above expression says. cheers, eric PS: +pi term is prob. because of phase unwrapping.
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