[esa-t474] more comments, chapter 3

[Bino Maiheu]

Hi Mark,

Here are some more comments and suggestions from me on chapter 3 of the
paper.... Along with some general comments as well that i just put up
for discussion.

I'll send some more comments tonight and tomorrow for the rest of the
chapters.

Cheers,
     bino


Some general comments
---------------------

- General question to the ATF people amongst you guys are there any     
  comments that were sent back to the nanoBPM paper relevant for this 
  paper ?

- Do we want photographs...in the paper ? I personally feel like not. 

- Need to address why RF cavity BPMs are preferable to e.g. strip line
  or buttons or our purposes. I think that just quoting the fact that 
  they can achieve higher resolutions is not enough. In other words, 
  why do RF cavities tend to have a higher resolution ? Is their 
  sensitivity ( V/mm ) typically higher than strip lines or buttons ? 
  Maybe quote some numbers here ??? I don't really have any experience
  in this to be honest.

- Check whether we use the equations in what is coming further. If
  not, don't really seed the need to derive them all. Or alternatively
  we can derive them, but then not just put them in, but we need to
  comment a bit more on what they physically mean !!!

  e.g. :
     - eq 22,23 : comment that these equations effectively indicate
                  that position and tilt can be found by a coordinate
		  system rotation from the IQ plane

- suggest "scaling factor"  -> "calibration scale" ??


Comments to chapter 3
---------------------

 - line 252 : don't like title 
      suggest : "Theory of cavity BPMs"
      or something like that

 - line 254 : "... the dipole fields excited in a cavity..."
      suggest : "... the dipole excitation induced by the beam in the
      cavity..."


 - line 257 : The "(x)", "(\theta)" and "(\alpha)" are in the wrong
              place !
       suggest : "the beam offset $x$ from the [...], the angle
     $\theta$ of the beam trajectory and the rotation $\alpha$ ..."
 
     and don't use brackets around the variables !

 - line 258 : should cite as "[14,15]", not as [14],[15] -> check
              latex manual 

 - line 260 : "($V(t)$)" -> "$V(t)$"

 - line 262 : explicitely mention what you mean with tilt signal,
              refer to $V_theta$ and $V_\alpha$, the word tilt signal
              wasn't mentioned before...

 - line 263 : what do you mean with "single" complex oscillator ?

 - line 266 : "... and $\phi$ is the relative phase."
         suggest : "... and $\phi$ it's relative phase."

 - line 267 -> 272 : need to stress that the second down conversion is
        done in software using a down mixing and filtering algorithm. 

        -> rises important question for the reader... why not mix down
           to base band in hardware ? Need to answer this here !!!!

 - line 273 : you already defined $\omega$ and $\phi$, do they have
              the same meaning here ? 

 - line 277 : Why Gaussian ? ... I know it had to do with the 
              particular phase response of this filter.. need to check
              exactly what the advantages were here .... 


 - line 278 : might want to chose different name for $t_0$, more like
              $t_s$ or $t_{ref}$

 - line 281 : get rid of 2x "in MHz", this is obvious, could quote
              some typical values here, or refer to a later table...

 - line 285 : "power envelope"... hmm, me don't like 

 - line 289 : "depended"  -> "depends" ... this is still the case :)

 - Figure 9. : Get rid of the arrows !!, looks awful ! 
               Rearrange plots, all 3 next to each other
               You didn't mention the "DDC" abbreviation anywhere
               before. Define it in the text before referring to
               figure 9.

 - section 3.2.2 : too much usage of the word "frequency", read very
                   non fluently, suggest to rephrase parts

 - equations 22,23 : I suspect that the tilt signal needs to be 
                     orthogonal to the position signal, so 
		     something like -sin(phi_IQ)*I + cos(phi_IQ)*Q
                     or something like that... need to check on
                     coordinate rotation !!!


 - line 327 : "phase advance" normally used in storage ring lattice
              context, replace by "phase difference"

 - line 331 : "... change in calibration." - > "... change in
              calibration scale."

 - line 323-325 : Maybe mention that the phase dependence is linear
                  having the frequency difference $\omega -
                  \omega_{DDC}$ as slope.... donno ??


 - table 4 : Would not call this precision.
             typo in table as well

             Not sure whether or not this table is useful ? What do we
             want to prove here ? Is it not enough to quote the RMS
             noise of empty pulses ? If you want to check errors
             coming from the DDC algorithm i think we need to do it on 
             simulated waveforms and compare generated amplitudes and
             phases with DDC'ed ones. 

             -> goes for lines 345 -> 352 


 - line 358 : already defined $x$ etc... no need to redefine.

 










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