[eagle] Re: TeamSpeak conference for Tuesday 16 Jan

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