From: [EMAIL PROTECTED] Subject: Re: [time-nuts] Ultra low phase noise floor measurement system for RF devices. Date: Fri, 30 Mar 2007 22:04:05 EDT Message-ID: <[EMAIL PROTECTED]>
> > In a message dated 3/30/2007 12:26:46 Pacific Daylight Time, > [EMAIL PROTECTED] writes: > > Until I've actually read the paper, ask yourself how our GPS receivers is > able > to track signals below their internal noise. > > There are a number of tricky aspects involved in doing that and I beleive the > paper goes into those. I have it in print here and will read it as I come > back > home. > > Cheers, > Magnus > > > > Weekend reading for me too :) > > But GPS uses highly correlated 'noise' which allows the payload data to be > below the noise floor through simple correlation since the noise is expected > to be random. This was my point. Correlation. That gets you below the noisefloor since you can average out the noise. > Just wondering about the numbers, -200dBc/Hz is 10 Billion times smaller > than the carrier, and that's in terms of voltage leves - power is that number > > squared... 10 Miljard times below the carrier you mean! (I'm nitpicking you, billion to mean 1E9 is a US feature, here in Europe we have miljard to mean the same thing, a billion is 1E12 so... this is why you just can't use them across the pond at all) I agree, it is indeed a fantastic number, but you have to compare it with other results. There is comercial tools out there which is only 20-30 dB behind. Actually, the correlation techniques improves the longer you average, so then stability of setup and such becomes the hurdles, without looking I would guess they have put some thought into that. Normal crosscorrelation techniques looks like crude conceptual setups compared to this more elaborate setup. I'm looking forward to read about this. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
