Photonic Measurement for Doppler Frequency Shift and Angle of Arrival Based on a Dual-Polarization Dual-Drive Mach–Zehnder Modulator

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors:

The authors presented a proposal of photonic-based device for estimation of Doppler-frequency shift and angle-of-arrival of microwave signals simultaneously. Proposed solution needs an external source of optical signal (carrier). There are encountered similar designs made using only microwave components, but sometimes they do not provide sufficient frequency operating bandwidth. Subject investigated by the Authors is very interesting and important, but very complex. Such systems are very much needed for practical civil and special (military) applications.

I. Following are the detail comments:

1. It was impossible to check in detail all the formulas presented in the work in such a short time. Therefore, only their idea was checked, i.e. what elements (parameters) have been taken into account and calculated. The initial basic formulas are correct and the final relations are clear.

2. As I understand correctly, only simulations of the developed system were made, and not measurements on the real measuring stand. OptiSystem is a very advanced, useful tool, but it does not take into account all the real properties of the test bench. The quality of the functioning of the AOA measurement channel will be determined, among others, by properties of the used microwave receiving antennas of the system. I hope that the results of tests of the proposed device carried out in real conditions will be presented by the Authors in the next paper in the near future.

3. A lot of detailed information is provided, but in my opinion it would be worth adding a few generalization in the section 4. Conclusion. For example, it would be important to know about the achievable microwave bandwidth and sensitivity of the device. Moreover, the meaningful would be information whether the presented values of errors of the system is caused by the values of the parameters of the analyzed construction, or they are a property of the developed method of measuring DFS and AOA.

4. I would suggest finding a way to increase the AOA measurement range to 0°±90°. The range of 0°to 90° is insufficient for professional direction finding systems.

8. For common readers, engineers and designers, it would be worth to describe in the introduction of the paper instantaneous frequency measurement (IFM) systems and AOA measurement systems made of microwave components only. Such information can be found under keywords e.g. quadrature microwave frequency discriminators, direction finding using monopulse location system, two-dimensional noise radar demonstrator. Photonic elements can improve the properties of the above-mentioned systems.

 

II. Some minor editing suggestions (in my opinion). It is proposed to review the entire text in terms of, among others:

1. Line 27 – I suppose it should be “radial velocity” and not “radical velocity”.

2. Line 75 – I suppose that according to Fig. 1 it should be (Antenna1 and Antenna2) instead of (Ante1 and Ante2).

3. Line 80 – I suppose that the second phrase “can be” is repeated unintentionally.

4. Fig. 1. – Before PBS, there is the polarization controller PC1 – it seems it should be signed as PC2.

5. Line 154 – There is an abbreviation AoA (angle of arrival) – it is called AOA elsewhere in the text.

 

6. Line 206 – It seems that in the caption for Figure 6 there is no reference to Figure 6(a). 

 

Author Response

Dear Editors and Reviewers:

Thank you very much for your letter and for the reviewer’s comments concerning our manuscript entitled “Photonic Measurement for Doppler-Frequency-Shift and Angle-of-Arrival based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator” (ID: photonics-1848508). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.

We have studied comments carefully and have tried our best to made correction which we hope meet with approval. These changes will not influence the content and framework of the paper. Some grammar and spelling errors had also been corrected. Revised portion are marked in red in the paper. We also responded point by point to the reviewer comments. Please see the attachment.

Hope these will make it more acceptable for publication.

 

Sincerely yours,

Qingqing Meng

Author Response File: Author Response.doc

Reviewer 2 Report

The paper proposed a photonic AOA and DFS measurement system based on a DPol-DDMZM, and simulation results are given to verify the feasibility of the idea. I have the following comments:

1)     Almost the same structure has been published in [R1], so the authors should cite this paper and clearly explain the main difference and improvements compared with [R1].

[R1] Guangyi Li, Difei Shi, Lu Wang, Ming Li, Ninghua Zhu, and Wei Li, "Photonic System for Simultaneous and Unambiguous Measurement of Angle-of-Arrival and Doppler-Frequency-Shift," J. Lightwave Technol. 40, 2321-2328 (2022)

2）Only simulation results are provided in this paper. According to the previous publications from the authors’ group, they have the necessary hardware to carry out an experiment. Therefore, I think it would be better to provide experiment results.

3）Some latest papers should be cited in the manuscript.

Author Response

Dear Editors and Reviewers:

Thank you very much for your letter and for the reviewer’s comments concerning our manuscript entitled “Photonic Measurement for Doppler-Frequency-Shift and Angle-of-Arrival based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator” (ID: photonics-1848508). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.

We have studied comments carefully and have tried our best to made correction which we hope meet with approval. These changes will not influence the content and framework of the paper. Some grammar and spelling errors had also been corrected. Revised portion are marked in red in the paper. We also responded point by point to the reviewer comments . Please see the attachment.

Hope these will make it more acceptable for publication.

 

Sincerely yours,

Qingqing Meng

Author Response File: Author Response.doc

Reviewer 3 Report

This paper proposes a photonics-assisted scheme based on a dual-polarization dual-drive Mach-Zehnder modulator (DPol-DDMZM) for simultaneous measurement of Doppler frequency shift (DFS) and angle of arrival (AOA). The value and direction of DFS can be derived by analyzing the spectra and waveforms of the generated two intermediate frequency (IF) signals, respectively, and the AOA information can be derived by constructing amplitude comparison function. My concerns are as follows: 1. First concern is about the novelty. The proposed system architecture and principle are similar to that reported in “10.1364/AO.422946”. The only difference in this work is absence of optical bandpass filter. 2. I suggest the authors give some references on the application of DFS and AOA measurement in the Introduction and extend to cover more literatures on simultaneous measurement of DFS and AOA. 3. In Abstract, the authors mentioned that the proposed scheme can reduce the AOA measurement error. A more detailed explanation is suggested to be given in the manuscript. 4. How does the proposed scheme solve the synchronization problem? 5. It will be very helpful if the authors can explain in detail how the two echo signals and reference signal are loaded into the RF ports of the DPol-DDMZM in the Principle part. In addition, the composition of the integrated DPol-DDMZM shall also be given. 6. For Fig. 2 and the relevant description in page 4, what is the relation between the power variations and DFS measurement accuracy? For Fig. 5, the units seem to be wrong. 7. Figure 4 demonstrates the spectra of the generated IF signals. However, the spectral resolution looks poor. In this case, how to make the measured DFS error very small? Please give the zoomed in spectra and the global parameter settings. 8. As can be seen from Fig. 7, when AOA is the same but DFS is opposite, the waveforms of the generated two IF signals are identical. How to deduce the direction of DFS? 9. The authors draw conclusion that “effect of the ɑ1, ɑ3 on the ACF curve can be partially offset”. The authors should vouch for the accuracy of the conclusion. As far as I know, the drift of each bias is independent. 10. In page 10, the authors say that “curves rotate at the angles of 36° and 144°”. However, I do not see this trend in Fig. 9.

Author Response

Dear Editors and Reviewers:

Thank you very much for your letter and for the reviewer’s comments concerning our manuscript entitled “Photonic Measurement for Doppler-Frequency-Shift and Angle-of-Arrival based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator” (ID: photonics-1848508). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.

We have studied comments carefully and have tried our best to made correction which we hope meet with approval. These changes will not influence the content and framework of the paper. Some grammar and spelling errors had also been corrected. Revised portion are marked in red in the paper. We also responded point by point to the reviewer comments . Please see the attachment.

Hope these will make it more acceptable for publication.

Sincerely yours,

Qingqing Meng

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

The manuscript is well revised, it can be accepted now.

Author Response

Thank you very much for your comments concerning our manuscript entitled “Photonic Measurement for Doppler-Frequency-Shift and Angle-of-Arrival based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator” (ID: photonics-1848508). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.

Once again, thank you for your valuable comment！

Sincerely yours,

Qingqing Meng

Reviewer 3 Report

In their revised version of the manuscript the authors have  addressed the concerns by myself. The paper is now ready for acception after minor revision.

1.     The last two sentences of the first paragraph in Response 3 was flawed.

2.       After reading Response 3, I understand that the ACF function established in this paper can eliminate the dependence of measurement results on carrier power and modulation indices. However, when the carrier power and modulation indices are known and fixed, the measurement error cannot be reduced.

3.       The correction on Point 10 ‘curves intersect at the angles of 36° and 144°’ has errors. Please check the statements in this paper and Fig. 9 carefully.

Author Response

Dear Reviewer:

Thank you very much for your comments concerning our manuscript entitled “Photonic Measurement for Doppler-Frequency-Shift and Angle-of-Arrival based on a Dual-Polarization Dual-Drive Mach-Zehnder Modulator” (ID: photonics-1848508). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.

We have studied comments carefully and have tried our best to made correction which we hope meet with approval. These changes will not influence the content and framework of the paper. Some grammar and spelling errors had also been corrected. Revised portion are marked in red in the paper. We also responded point by point to the reviewer comments . Please see the attachment.

Once again, thank you for your valuable comment.

Sincerely yours,

Qingqing Meng

Author Response File: Author Response.doc