%Minor Revision - TUFFC-09469-2019
%Transactions on Ultrasonics, Ferroelectrics, and Frequency 
%Control (July 23, 2019 9:29 PM)
%To: arthur.hugeat@femto-st.fr, julien.bernard@femto-st.fr, 
%gwenhael.goavec@femto-st.fr, pyb2@femto-st.fr, pierre-yves.bourgeois@femto-st.fr, 
%jmfriedt@femto-st.fr
%CC: giorgio.santarelli@institutoptique.fr, lewin@ece.drexel.edu
%
%Dear Mr. Arthur HUGEAT
%
%Congratulations! Your manuscript
%
%MANUSCRIPT NO. TUFFC-09469-2019
%MANUSCRIPT TYPE: Papers
%TITLE: Filter optimization for real time digital processing of radiofrequency 
%signals: application to oscillator metrology
%AUTHOR(S): HUGEAT, Arthur; BERNARD, Julien; Goavec-Mérou, Gwenhaël; Bourgeois, 
%Pierre-Yves; Friedt, Jean-Michel
%
%has been reviewed and it has been suggested that it be accepted for publication 
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%Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
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%****************************************************
%REVIEWERS' COMMENTS:

\documentclass[a4paper]{article}
\usepackage{fullpage,graphicx}
\begin{document}
{\bf Reviewer: 1}

%Comments to the Author
%In general, the language/grammar is adequate.

{\bf
On page 2,  "...allowing to save processing resource..." could be improved.

On page 2, "... or thanks at a radiofrequency-grade..." isn't at all clear what 
the author meant.

One page 2, the whole paragraph "The first step of our approach is to model..." 
could be improved.
}

{\bf
I appreciate that the authors attempted and document two optimizations: that 
of maximum rejection ratio at fixed silicon area, as well as minimum silicon 
area for a fixed minimum rejection ratio. For non-experts, it might be very 
useful to compare the results of both optimization paths to the performance and 
resource-utilization of generic low-pass filter gateware offered by device 
manufacturers. I appreciate also that the authors have presented source code 
for examination online.
}

TODO : FIR Compiler et regarder les ressources pour un FIR comparable a ceux monolithiques
fournis dans l'article (memes coefs et meme nombre de coefs)

{\bf
Reviewer: 2
}

%Comments to the Author
%In the Manuscript, the Authors describe an optimization methodology for filter 
%design to be used in phase noise metrology. The methodology is general and can 
%be used for many aspects of the processing chain. In the Manuscript, the Authors 
%focus on filtering and shifting while the other aspects, in particular decimation, 
%will be considered in a future work. The optimization problem is modelled 
%theoretically and then solved by means of a commercial software. The solutions 
%are tested experimentally on the Redpitaya platform with synthetic and real 
%white noises. Two cases are considered as a function of the number of filters: 
%maximum rejection given a fixed amount of resources and minimum resource 
%utilization given a fixed amount of rejection.  
%The Authors find that filtering improves significantly when the number of 
%filters increases. 
%A lot of work has been done in generalizing and automating the procedure so 
%that different approaches can be investigated quickly and efficiently. The 
%results presented in the Manuscript seem to be just a case study based on 
%the particular criterion chosen by the Authors. Different criteria, in 
%general, could lead to different results and it is important to consider 
%carefully the criterion adopted by the Authors, in order to check if it 
%is adequate to compare the performance of filters and if multi-stage 
%filters are really superior than monolithic filters.

{\bf
By observing the results presented in fig. 10-16, it is clear that the 
performances of multi-stage filters are obtained at the expense of their 
selectivity and, in this sense, the filters presented in these figures 
are not equivalent. For example, in Fig. 14, at the limit of the pass band, 
the attenuation is almost 15 dB for n = 5, while it is not noticeable for 
n = 1. 
}

TODO : ajouter les gabarits

Peut etre refaire une serie de simulation dans lesquelles on impose une coupure
non pas entre 40 et 60\% mais entre 50 et 60\% pour demontrer que l'outil s'adapte
au critere qu'on lui impose, et que la coupure moins raide n'est pas intrinseque
a la cascade de filtres.

{\bf
The reason is in the criterion that considers the average attenuation in 
the pass band. This criterion does not take into account the maximum attenuation 
in this region, which is a very important parameter for specifying a filter 
and for evaluating its performance. For example, with this criterion, a 
filter with 0.1 dB of ripple is considered equivalent to a filter with 
10 dB of ripple. This point has a strong impact in the optimization process 
and in the results that are obtained and has to be reconsidered.
}

Je ne pense pas que ca soit le cas : la somme des valeurs absolues des pertes
dans la bande va defavoriser un filtre avec 10 dB de ripples. Il n'a pas compris que
la bandpass s'arrete a 40\% de la bande, donc mettre le gabarit clarifierait ce point je
pense

{\bf
I strongly suggest to re-run the analysis with a criterion that takes also 
into account the maximum allowed attenuation in pass band, for example by 
fixing its value to a typical one, as it has been done for the transition 
bandwidth. 
}

{\bf
In addition, I suggest to address the following points:
- Page 1, line 50: the Authors state that IIR have shorter impulse response 
than FIR. This is not true in general. The sentence should be reconsidered.
}

J'aurais du dire ``lag'' au lieu de ``impulse response'' je pense

{\bf
- Fig. 4: the Author should motivate in the text why it has been chosen 
this transition bandwidth and if it is a typical requirement for phase-noise 
metrology.
- The impact of the coefficient resolution is discussed. What about the 
resolution of the data stream? Is it fixed? If so, which value has been 
used in the analysis? If not, how is it changed with respect to the 
coefficient resolution?
}

Pr\'eciser que le flux de donn\'ees en entr\'ees est de r\'esolution fixe

{\bf
- Page 3, line 47: the initial criterion can be omitted and, consequently, 
Fig. 5 can be removed.
- Page 3, line 55: “maximum rejection” is not compatible with fig. 4. 
It should be “minimum”
- Page e, line 55, second column: “takin”
- Page 3, line 58: “pessimistic” should be replaced with “conservative”
- Page 4, line 17: “meaning” --> “this means”
- Page 4, line 10: how $p$ is chosen? Which is the criterion used to choose 
these particular configurations? Are they chosen automatically?
- Page 4, line 31: how does the delta function transform model from non-linear 
and non-quadratic to a quadratic?
- Captions of figure and tables are too minimal.
- Figures can be grouped: fig. 10-12 can be grouped as three subplots (a, b, c) 
of a single figure. Same for fig. 13-16. 
}

{\bf
- Please increase the number of averages for the spectrum. Currently the noise 
of the curves is about 20 dBpk-pk and it doesn’t allow to appreciate the 
differences among the curves. I suggest to reduce the noise below 1 dBpk-pk.
}

Comment as tu fait tes spectres Arthur ? Si tu as fait une FFT sur e.g. 2048 points
mais que tu as des jeux de donnees de e.g. 10000 points, on peut faire des moyennes
sur les sequences successives. Au pire si pas possible, une moyenne glissante sur
chaque spectre pour affiner les traits ?

%In conclusion, my opinion is that the methodology presented in the Manuscript 
%deserve to be published, provided that the criterion is changed according 
%the indications mentioned above.
\end{document}
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