Position Sensing with a Compact 0.1 THz Amplitude Modulated Source

Round 1

Reviewer 1 Report

No comment.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

This revised paper deals with position measurements based on
THz modulated amplitude source. Although some changes have been introduced, the work still lacks some aspects that I consider important. I mean, in the Introduction the own contribution of the authors does not
emerge clearly. Moreover, the experimental results are still limited, metal plate and metal+styrofoam (which does not have an impact on the measurements) cannot be defined as exhaustive.
I have two suggestions: metal plate+materials with an impact, and substituting the metal plate so as two different dielectrics could be discussed. 

A brieftlist of issues are presented below:

1) p.2 l.56 "Even though the trend in THz radar systems is to develop less expensive and more compact sources, which are still not good enough in some industry applications, due to low power of the source", it seems that something is missing
2) p. 2 l.81, I suggest highlighting your own contribution, this could include the fabrication as well as the method, I think a few sentences could be added. I believe the paper could benefit from these few sentences, otherwise, your own contribution does not again emerge clearly.
3) p.3 l.97 "beam2021" typo?
4) p.3 l.107 "observing object in industry" I suggest "observed object"
5) p.7 l.194, in the previous version it was 53°, why did you change?
6) p.7 l.215 "..Additional measurements were done with .. Styrofoam covering can be seen in the Figure 6..", I suggest moving part of these sentences to the introduction in order to highlight your own contribution
7) fig. 6, since Styrofoam does not have an impact, it could more effective if you could discuss also a material with an impact. Moreover, the paper could benefit from discussing the case of other materials instead of the metal plate.
8) p.8 l.252, I suggest adding more details to this comparison. Did you perform some measurements with commercial devices? if yes please add a discussion.
9) p.8 l.255 "1.875 mm", 1.875 is from your measurements or from literature? if literature please cite the paper, otherwise describe your measurements. Do not be afraid to present your own measurements

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

I've just a small piece of advice, I suggest adding answer n.7 to the paper, just a few sentences would be highly appreciated. After this effort, I believe the paper could be considered for publication.

Author Response

Few sentences were added to the article regarding the answer to n. 7

 

Thank you for the reviews and best regards,

Tadej Krmac

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The work proposed by Krmac et al for publication refers to an object distance measurement with an affordable and compact 0.1 THz amplitude modulated source. Generally, the manuscript can easily be understood, however, the paper could be improved by discussing more details. Therefore, I consider the current paper must be reorganized and there are several remarks needed to be taken into account:

 

1. I suggest the authors that the photos of the instruments should be squeezed and realigned. Maybe one diagram is enough and more scientific design data can be provided in the context. The schematic diagram of the Experimental setup should be drawn.
2. As we know, the penetration of THz wave is attractive and the authors can conduct the experiments with several coverings like polymer, paper and vapour.
3. The language needs to be polished further with proofreading. I suggest the authors delete the sentence of “, designed and fabricated in the Laboratory for Microelectronics (LMFE)” in the abstract.
4. Some works related to THz measurement techniques can be referred to in the introduction. For example

1) Optics and Laser Technology 120 (2019) 105683

2) Infrared Physics & Technology 118 (2021) 103878

3) Photonics 2018, 5(4), 52

5. How long does the actual imaging take for each sample? The author can give an example that contains the hardware time and processing time of the algorithms. What is the spatial resolution of the present system?
6. The authors can give more types of targets with various materials to conduct the experimental verifications, especially, for the natural samples (not only the aluminum plate).

Author Response

Thank you for the review of the article.

Please see the attachment provided with our answers. Everything discussed was added in the revised article.

Best regards,

Tadej Krmac

Author Response File: Author Response.docx

Reviewer 2 Report

The authors presented "Position Sensing with a Compact 0.1 THz Amplitude Modulated Source". Following are my comments;

1. How to maintain sensor position in a stable state?
2. How the impedance matching is achieved after antenna-coupled titanium-based micro-bolometer.
3. No need to include the place of fabrication in the abstract. The abstract should include only finding. 
4. How to maintain the measurement accuracy at THz frequency?
5. Many typos are presented throughout the manuscriptt. 
6. Poor English writting.

Author Response

Thank you for the review of the article

Please see the attachment provided with our answers. Everything discussed was added in the revised article.

Best regards,

Tadej Krmac

Author Response File: Author Response.docx

Reviewer 3 Report

This work is devoted to a novel position measurement system based on THz Amplitude Modulated source.  Although the presented system sounds interesting I've some concerns about the measurements, it could be useful to shorten the state of the art and add more experimental results. Aluminum plate measurements have been described in fig.6 as well as polyethylene plate ones in fig. 7, since this technique is addressed to a specific application (tank liquid level measurements), I suggest adding results of water and/or other liquids. I believe citing in the text that you have obtained results with water without showing them, does not appear convincing for publishing in Applied Sciences.

Here are listed my observations:

Introduction l.32 "Just as there are..", I suggest "just like".

Introduction l.41 "In them, due.." I suggest "these latter".

Introduction l.60 "The trend in THz radar system is to be less.." I suggest "is to develop".

Introduction l.61 and 62, please define the acronyms IWR and AWR.

Introduction l.64 "The weakness of mentioned system", I suggest "the aforementioned system".

Introduction l.69 "additional components and space are", what does it mean? space as encumbrance? please rephrase it.

Introduction l.82 "drawback", why do you only have a drawback in the introduction? What is the advantage of using your system instead of other similar? You have better explain these before presenting the drawbacks, I suggest rephrasing adding a clear explanation of the benefit introduced by your method, as well as shortening the state of the art of THz sources and detectors, there are many review papers devoted to this issue, you can cite them instead of explaining what is already known.

Sec.2 l.90, I suggest adding the schematic diagram (move fig.6) of the entire setup here.

Sec.2 I.93, I suggest adding also the country of your LMFE.

Sec. 2 l.98 "..in more detail later in this section.", I suggest "in next subsections".

sec.2.2 l.139 "..used for focal lenses.." I suggest "the focal lenses where represented by two polyethylene lenses".

Sec. 2.2 l.147-149, please rephrase these three lines, they sound like a repetition.

Sec. 2.2 l.149 "a bolometer", I'm confused, "a" means in general, are you describing your own system? if yes, please change "a" with something that allows the reader to understand that you are describing your own system, otherwise I suggest moving the general features of a bolometer in the introduction.

Sec. 2.2 l.169, It is not clear why did you simulate the water interface (absorbing medium) with a metal plate (reflective medium), please explain it.

Sec.2.2 l.186 "..The idea of the..", I suggest "the working principle".

Sec. 3.1. l.217 why 53°? have you tested other angles? what is the advantage introduced using this particular angle? Please add reasons.

Sec.3.1 l.230, this advantage (low measurement time) should be also introduced in the Introduction section where instead you have presented the drawback of your system.

sec. 3.1 l.234-236, this sentence should be moved to the Conclusion section as future perspective.

sec. 3.1 l.277, how did you manage to avoid air gaps within the aluminum plate and cardboard or polyethylene planes? what thickness has been used? did you perform measurement with the same materials but different thicknesses? these details are important to strengthen your research and should be discussed in the paper.

sec. 3.1 l.285, I guess you made this measurement using a container filled with water. Have you considered the effect of reflection on the container walls? Please add some comments.

sec. 4, l.295 ".. is compared with the FMCW method", I'm confused, where does the reader find this comparison?

sec.3.1 l.289, I suggest adding a graph similar to fig. 7 (aluminum plate) in which you present the results obtained with water. This is crucial since you are addressing this work to this specific application. You could also present aluminum and water in the same graph.

 

 

For these reasons, I believe the current version of this paper is not suitable for publication in Applied Science.

 

 

Round 2

Reviewer 1 Report

According to the  Figure 8. Results of the vertical level measurement of the polyethylene plate,   the proposed method cannot  be a valid  and accurate position sensing  method.  As authors mentioned, multiple reflections inside of the material frustrates the real peaks. It has a serious flaws which should be dealed with.