[eagle] Re: TeamSpeak conference for Tuesday 16 Jan
Frank Brickle
brickle at pobox.com
Tue Jan 9 19:34:14 PST 2007
Phil Karn wrote:
> I was going to model phase noise as 1/f^2, but Bob pointed out that the
> integral of that expression bounded at zero (DC) is undefined. So we
> need another, more realistic model of oscillator phase noise if we're
> going to compute its effect on digital demodulation.
Hmm. Is there more to it than simply doubling the spectral density?
Suppose you constrain the noise to be zero-mean. The spectral
density will be 0 at f = 0. Then the noise has spectral density
W(f) which is a real, even function of the bandwidth, so W(f) =
W(-f). By convention only the spectral density at f >= 0 is
considered, so you need to double the spectral density at f to
account for the contribution at -f.
The zero-mean constraint is unrealistic, maybe.
Frank
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