Comments on "On amplitude and frequency demodulation using energy operators"

The authors comment that while testing some of the results obtained by Maragos, Kaiser and Quatieri (see ibid., vol.41, no.4, p.1532-50, 1993) with a discrete FM signal of the form x(n)=Acos(/spl phi/(n)) where /spl phi/(n)=/spl Omega//sub c/n+/spl Omega//sub m///spl Omega//sub f/sin(/spl Omega//sub f/n)+/spl theta/ they noticed that the error in the instantaneous frequency increased as /spl Omega//sub f/ increased. One would hope that frequency tracking of a constant frequency sinusoidal signal would be very accurate. However, this does not agree with one of their proposition as there is an error in its proof.