Differential-Fed Wideband Circularly Polarized SIW Cavity-Backed Slot Antenna Array

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper presents a CP SIW cavity‐backed slot antenna array. There are some issues that need to be resolved before this article can be accepted.

1. The definition of fc1 and fc2 as two resonance points in Fig. 2 is easily misunderstood as two resonance modes, and the reviewer thought that they should be directly defined as the electric field distribution at these two frequencies, and the resonance points are not appropriate. It is obvious that fc1 is contributed by the two resonant modes together, and so is fc2.
2. The electric field distribution in Figure 3 seems to be incorrect, which does not correctly represent the electric field distribution of the four modes. If the resonant modes are orthogonal, the electric field distribution in Fig. 2 should be rotationally symmetric. The authors can analyze the modes using eigenmode or characteristic mode analysis methods.
3. How does the parameter d1 in arc‐shaped microstrips affect performance?
4. Are the data compared in Table 2 measured or simulated? The authors do not appear to have fabricated individual antenna prototypes. Clarification is needed.
5. In Fig. 9, the S-parameter of the feeding network cannot be defined as Sdd11 , the S-parameter of the feeding network should be S11.
6. The error of the measured results is a bit large. The measured AR at 19 GHz is smaller than the simulated results, but the cross-polarization level of its measured radiation pattern is much larger than the simulation.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors This paper presents a novel differential-fed wideband circularly polarized SIW cavity-backed slot antenna array. Here are some points that need to be addressed:

1. The abstract does not mention the specific frequency range over which the proposed antenna array achieves its performance metrics. This is important information for readers to quickly assess the relevance of the paper to their own work.
2. In Figure 3, the current distribution's rainbow bar should be labeled with specific values and units to provide a clear understanding of the current magnitudes.
3. In Figure 7(a) and (b), some curves are overlapping and difficult to distinguish. This issue also exists in Figures 9 and 12, where curve clarity needs improvement to allow for accurate interpretation of the results.
4. Figure 8 lacks axis labels, which are essential for comprehending the depicted configuration and its dimensions.
5. The structural diagrams of the antenna and array in Figures 1 and 8 should include sufficient dimensional information to enable readers to fully understand the design details.
6. Table 2 should specify the operating frequency bands of the compared antennas. Additionally, for a more comprehensive comparison, literature on single-fed antennas that provide both 3-dB Gain BW and Overlaid BW should be selected. Table 3 has similar issues that need to be resolved.
7. The paper should outline the evolution process of the antenna design to provide insights into the design rationale and development.
8. As an antenna array, Table 3 should include the isolation between array elements. Furthermore, Table 2 should incorporate the Peak Gain metric for a more complete performance comparison.

Comments on the Quality of English Language

The English should be improved to more clearly express the research.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents a circularly polarized SIW cavity-backed slot antenna array. While the proposed approach appears promising, several aspects require further clarification and elaboration to strengthen the technical depth of the work. The following comments are provided for the authors’ consideration:

-The SIW cavity serves as a fundamental platform for this design. Although the introduction briefly mentions the advantages of using SIW cavities, the discussion is insufficient. The authors are encouraged to further elaborate on the benefits of SIW cavities in microwave component design, such as DOI: 10.1109/TAP.2022.3232208, 10.1109/TMTT.2024.3486784, among others.

-The operating mechanism underlying the circular polarization of the proposed antenna should be more thoroughly explained to provide clearer physical insight.

-Detailed dimensions of the feeding network should be included to support potential replication and further study.

-The radiation efficiency of the proposed antenna design should be evaluated and discussed.

-Potential application scenarios of the antenna should be outlined to demonstrate its practical relevance and impact.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks to the author's response, most of the questions have been addressed. There is still some confusion about the fifth question. Why did the author compare the port data of the two port1- and port+ with the feeding network added? In practice Sdd11 without feeding network should be compared with Port T1 to make sense.

Author Response

Dear Reviewer,

Thank you for your comment. Please see the attachment for the response of the revision.

Thank you so much for your time.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript has been substantially improved and now meets the standards for acceptance.

Author Response

Dear Reviewer,
Thank you for your positive feedback and for acknowledging the improvements in our manuscript. We appreciate the time and effort you have dedicated to reviewing our work.

Thank you so much.