[esa-t474] Typos corrected

[Adolphsen, Chris]

Perhaps, but the other mode produces both a phase and amplitude effect and it is not obvious that this produces a change in the computed position that is linear with the position in the other plane

-----Original Message-----
From: Yury Kolomensky [mailto:YGKolomensky at lbl.gov] 
Sent: Monday, December 03, 2007 1:13 AM
To: Adolphsen, Chris
Cc: Yury Kolomensky; Mark Slater; esa-t474 at hep.ucl.ac.uk
Subject: Re: [esa-t474] Typos corrected

	Hi Chris,

I can understand why a single-frequency fit would be susceptible to the beating between two modes, but why would DDC be ? It is linear by design (we toyed with 2-stage filtering, which would make the algorithm non-linear, but it does not improve resolution much, so this was abandoned). In DDC, the second polarization would show up as a shift in I/Q plane. But that shift would still be proportional to the offset in another direction, which can be taken out by regression (e.g. SVD). This seems to work more reliably than a two-component fit (which was attempted by Mark in NanoBPM analysis, IIRC, w/o much success).

Yury

On Dec 3, 2007, at 1:01 AM, Adolphsen, Chris wrote:

>
> Has anyone compiled a list of the size of the out-of-phase components 
> of the bpm signals - it might explain the 'low signal'
> phenomena that is referred to in the paper (i.e., I believe one is 
> more sensitive to phase errors when the out-of-phase signals 
> dominates).
>
> BTW - Johnny is currently analyzing the bpm 3-5 signals and is seeing 
> that each signal (x and y) contains a mixture of the two polarizations 
> which differ in frequency at the MHz level (although one dominates) - 
> this can cause a pronounced beating effect when the normally dominate 
> mode is small, and will likely worsen the resolution unless the 
> signals are analyzed properly (e.g. doing a two mode fit instead 
> applying the DDC algorithm, which assumes one mode).
>
>
> -----Original Message-----
> From: Mark Slater [mailto:slater at hep.phy.cam.ac.uk]
> Sent: Friday, November 30, 2007 9:49 AM
> To: esa-t474 at hep.ucl.ac.uk
> Subject: [esa-t474] Typos corrected
>
> Dear All,
>
> I have put in all the corrections I recieved except a few:
>
> 1)  I haven't added a measured vs. predicted plot for the resolution
> 2)  I haven't updated the energy vs. residual plot at the end of the 
> paper
> 3)  I still need to try to sort out bibtex for the references
> 4)  I have also yet to get a SLAC pub number or EuroTev number.
>
> I'll get these sorted over the weeked (as much as possible). but I've 
> uploaded everything else and so if I get the all clear on Monday at 
> the phone meeting, I'll submit on Tuesday.
>
> Many Thanks,
>
> Mark
>
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