T-Type Vertical Wall for Decoupling and Pattern Correction of Patch Antenna
and Ahmed A. Kishk 4
Round 1
Reviewer 1 Report
The paper proposes a closely spaced 14 decoupling and pattern correction technique for two patch antennas
with the λ0/20 edge-to-edge distance of the H-plane. Numerical and experimental results are presented, with the two in agreement.
The paper is sufficiently well written, although I suggest an overall minor revision of the text in terms of English.
The numerical results are well presented, showing clearly the effects of the critical parameters variation on coupling strength between the two antennas ports.
The experimental results show good agreement with the numerical ones, but the S-parameter curves differs a little with respect to the numerical ones. Do the authors have an idea of why this happens? Maybe it is due to manufacturing errors, hard to control due to the structure size? Perhaps some clarification about this could be inserted in subsection 3.1.
Author Response
Answer: Thank you for your comments. We know that the measurements agree well with the simulation, and we also find some differences in the S-parameters, patterns etc. In our opinion, this difference is small, and often happens in the antenna design. However, as you mentioned, this difference is caused by the fabrication because we can not realize the antenna as exact as in the simulation, and this is mainly affected by the placement of the vertical wall when it is inserted into the patch substrate. We add this explanation for the realized gain at the end of sub-section 3.2, which is put in the last sentence of the last paragraph. We know that this error will also cause the variation of S-parameters.
Reviewer 2 Report
Although the design of the patch is simple but the technique used to prevent the coupling can be considered as a good contribution. The contents of the paper are well presented, however following changes are recommended.
-Authors proposed the design can be used in the 5G/6G communication, but there is no connection provided between the operating frequency of the design and 5G or 6G.
-A comparison Table should be provided in the end, where the features of the proposed technique/design are compared with the existing and latest techniques from the literature.
-Authors should state how the design complexity issue will be tackled if the proposed design to be used for 5G/6G communication at higher frequencies and shorter wavelengths.
Author Response
Comment 1: -Authors proposed the design can be used in the 5G/6G communication, but there is no connection provided between the operating frequency of the design and 5G or 6G.
Answer 1: We agree with this point; we didn't mention the detailed design for the 5G or 6G. Our work focuses on the miniaturization development trend brought by 5G/6G and develops a new technique to adapt this change for future related applications, while the miniaturization trend for future communication (5G/6G) will be a long way to go. The purpose of our work is to find the common problem in the miniaturization process and try to find a way to solve it, perhaps for the future arrays in many applications. Moreover, we will use it to realize the miniaturization of phased arrays or other arrays. We will also use it to investigate the related 5G/6G techniques in the future.
Comment 2: -A comparison Table should be provided in the end, where the features of the proposed technique/design are compared with the existing and latest techniques from the literature.
Answer 2: We have added the comparison between our work with others in the new additional sub-section 3.3. As the published papers show that the tilt always exists for the close spacing, which is less or more than 0.05 . This tilt will affect the final radiation ability for the broadside direction and the final directional performance of the array. Thus, we list the corresponding tilt angle of the present works except for the cited works [9] and [20] in the introduction. Because the [9] did not show the whole pattern, just the one not deviated, we cannot take the results of [20] as a comparison because the asymmetrical feed causes the tilt in nature.
Comment 3: -Authors should state how the design complexity issue will be tackled if the proposed design to be used for 5G/6G communication at higher frequencies and shorter wavelengths.
Answer 3: Honestly, as we know that the present frequencies of 5G/6G are not too high, which means the patch antenna can work well under this frequency limit, and we can also predict that the proposed decoupling technique can work well in these specific frequencies owing to it is just a resonant structure. That is to say, if we find the corresponding resonant dimension, we can use it to realize the pattern correction at the concerned frequency. However, we mention this meaning in the last sentence of the penultimate paragraph of 'Introduction': "Depending on these steps, we can migrate this technique into the specific frequency of 5G/6G application."
Reviewer 3 Report
This study proposed a closely spaced decoupling and pattern correction technique for the two patch antennas with the λ0/20 edge-to-edge distance of the H-plane. The work is well organized and appropriately carried out. The study lacks a clear comparison between the submitted paper and the more relevant literature contributions, which should highlight the main advantages of the current submission. Thus, recommend providing a summary of relevant literature in a table at the end of Section 1 with a highlight well about the differences in this study. Paper organization at the end of Section1 is missing.
Author Response
Answer: Thank you for this comparison comment. We add this in the new sub-section 3.3 because we think it will be better after the validation of the proposed technique is verified, and then comparing it with present techniques of pattern tilt will be more logical. The detailed explanation is as in the first answer to the second reviewer.
Reviewer 4 Report
This manuscript presents an interesting topic related to space decoupling and pattern correction for designing and optimizing MIMO patch antennas. However, a set of profound improvements must be made to improve the quality and presentation of the manuscript.
- Envelope Correlation Coefficient (ECC), Diversity Gain (DG), and Channel Capacity Loss (CCL) are other important parameters to consider when evaluating the performance of the MIMO antenna. These characteristics of MIMO should be presented in detail in this study.
- How do the authors achieve the optimal dimension of the CPW feeding? Please provide the related theoretical analysis behind this process.
- The T-type Vertical Wall is applied to ensure the isolation between the two rectangular patch antennas. However, it reduces the radiation pattern in terms of the gain, which means degradation of the antenna's performance. Please discuss.
- The realized Gain patterns from the simulation and measurement are different. Please comment.
- It can be seen from the results (Fig. 5) of the measurements obtained that the S21 of the antenna has an optimum value of approximately 5.8 GHz. Please provide the required justification.
- ADS Simulated equivalent circuit can be included.
- Please provide a comparison table to compare the proposed antenna results with recent references in the literature.
- Please provide pieces of information about the simulation software used and the computational method (finite element method (FEM) or moments (MoM)).
- A flowchart must be provided to present the developed antenna's different design stages.
- Please justify the shapes used for the developed MIMO patch antenna, especially the T-shape used for the decoupling element. A detailed explanation is required.
- Please justify the choice of different substrate materials for rectangular patch antennas and T-type Vertical Wall.
- It was not clear how the antenna parameters were optimized. Please provide a detailed explanation of how the parametric analysis is performed. I recommend using a metaheuristic optimizer to improve the antenna design rather than the time-consuming trial and error method.
- The vertical T-shaped element increases the antenna volume, which completely contradicts the principle of miniaturizing the antenna. Also, when integrated into an electronic system, it will require special protection in addition to taking up large system space. Please discuss it in detail and specify the kind of possible applications of it.
- Please provide information on the vector network analyzer used and the anechoic chamber.
- Please improve the abstract by answering the following questions: What problem did you investigate, and why is it important? What techniques did you employ? What were your primary findings? What conclusions can you draw from your findings? Please make your abstract more descriptive and quantitative to reach a wider readership.
- An updated and complete literature review should be conducted to present the state-of-the-art and knowledge gaps of the research with strong relevance to the paper's topic, and the authors must position their work according to the literature review.
- The key elements of innovation need to be highlighted according to the literature review.
- The authors need to re-organize their work as follows: Abstract; Introduction; Related works; Materials and methods; Results and discussions; Conclusion; References.
- The discussion section should be improved with more diagrams and results.
- The quality of some Figures must be enhanced; then, the authors should clearly interpret the results obtained in these figures.
- Proofreading is required to enhance both the language and the presentation of the paper.
Author Response
Comment 1: Envelope Correlation Coefficient (ECC), Diversity Gain (DG), and Channel Capacity Loss (CCL) are other important parameters to consider when evaluating the performance of the MIMO antenna. These characteristics of MIMO should be presented in detail in this study.
Answer: Honestly, we mentioned the MIMO antenna in the beginning. However, our focus is not on this but on the problem brought by the new 5G/6G technology requirement. The miniaturization trend causes the design difficult for the miniaturized antenna system leading to the pattern tilt and reduction of the radiation ability in the broadside direction for the multiple antennas. Thus, we did not discuss the related characteristics of MIMO.
Comment 2: How do the authors achieve the optimal dimension of the CPW feeding? Please provide the related theoretical analysis behind this process.
Answer: Honestly, we do not understand this comment because we did not mention CPW feeding. If you are talking about the feed of the patch antenna, it is the conventional microstrip line. Or we don't know where the other feed exists.
Comment 3: The T-type Vertical Wall is applied to ensure the isolation between the two rectangular patch antennas. However, it reduces the radiation pattern in terms of the gain, which means degradation of the antenna's performance. Please discuss.
Answer: This proposed structure does reduce the realized gain, and we can find similar results in other works. We add this explanation in sub-section 2.2 according to your comment where add the loss tangent analysis of wall substrate to the antenna performance, you can find it in the new 'Figure 4' and the related content. This loss affects not only the S-parameters but also the tilt and the realized gain, which means we can redesign the resonant structure on the wall according to the specific loss if we want a higher realized gain.
Comment 4: The realized Gain patterns from the simulation and measurement are different. Please comment.
Answer: The difference exists between the simulation and the measurement. This is owing to we can't mount the vertical well so exactly as in the simulation. We explain it in the last sentence of the last paragraph of subsection 3.2.
Comment 5: It can be seen from the results (Fig. 5) of the measurements obtained that the S21 of the antenna has an optimum value of approximately 5.8 GHz. Please provide the required justification.
Answer: The optimum value of S21 appears at about 5.8 GHz, which means the best isolation at this frequency. However, for this decoupling technique, the most concerning thing is that we can get good isolation in the concerned frequency band, and if the good isolation is achieved in one frequency, it will be a good thing. And this change can be found by altering the dimension of the T-type metal or the wall substrate losses.
Comment 6: ADS Simulated equivalent circuit can be included.
Answer: The ADS equivalent circuit is gotten and shown in the new section 4 accompanying the mechanism, where this simulation agrees well with those of HFSS.
Comment 7: Please provide a comparison table to compare the proposed antenna results with recent references in the literature.
Answer: We add the comparison in the new sub-section 3.3.
Comment 8: Please provide pieces of information about the simulation software used and the computational method (finite element method (FEM) or moments (MoM)).
Answer: We mention the software HFSS 2019 in the last paragraph of section 2.1, which is based on the FEM.
Comment 9: A flowchart must be provided to present the developed antenna's different design stages.
Answer: Our work is just a simple design process. We did not give the flowchart in the revised manuscript but mention the corresponding design steps in the penultimate paragraph of 'Introduction,' including three steps, 1) conventional patch antenna design, 2) lossy-wall substrate determination, and 3) resonator design on the wall.
Comment 10: Please justify the shapes used for the developed MIMO patch antenna, especially the T-shape used for the decoupling element. A detailed explanation is required.
Answer: We have not used it for the MIMO design. The new requirement causes some unsolved problem faced by the MIMO, so we focus on the close-spacing pattern-corrected decoupling. We will turn our attention to this topic. Thanks.
Comment 11: Please justify the choice of different substrate materials for rectangular patch antennas and T-type Vertical Wall.
Answer: 1) We did not discuss the corresponding influence of different materials for the patch antenna. Because it is just the conventional design, and the material influence has been discussed many times. 2) We add the loss influence of the wall substrate in sub-section 2.2. It affects the S-parameters, the tilt, and the realized gain, and we can get a higher gain if we choose the less lossy material. We did not add the discussion of permittivity because it just affects the corresponding resonant dimension of the resonator of the wall.
Comment 12: It was not clear how the antenna parameters were optimized. Please provide a detailed explanation of how the parametric analysis is performed. I recommend using a metaheuristic optimizer to improve the antenna design rather than the time-consuming trial and error method.
Answer: We used the parametric analysis of HFSS to find the final optimized result, where we adjusted several results for the concerned variable. The detailed optimizer is not employed. Because if we find the related mechanism behind this technique, we need to fix the proper resonant dimension of the concerned frequency, we need not find the optimized values with no fixed reference result. We hope that we understood your meaning correctly.
Comment 13: The vertical T-shaped element increases the antenna volume, which completely contradicts the principle of miniaturizing the antenna. Also, when integrated into an electronic system, it will require special protection in addition to taking up large system space. Please discuss it in detail and specify the kind of possible applications of it.
Answer: This vertical wall does increase the profile of the design. However, we presently want to use it to improve the broadside radiation performance in the future miniaturized array, where the requirement is to bring the present miniaturization trend of 5G/6G. Moreover, we add this application at the end of the 5th paragraph of the 'Introduction.'
Comment 14: Please provide information on the vector network analyzer used and the anechoic chamber.
Answer: We add the analyzer information in the first paragraph of sub-section 3.2, that is, "Agilent N5244A network analyzer, working in 10 MHz~43.5 GHz."
Comment 15: Please improve the abstract by answering the following questions: What problem did you investigate, and why is it important? What techniques did you employ? What were your primary findings? What conclusions can you draw from your findings? Please make your abstract more descriptive and quantitative to reach a wider readership.
Answer: We add the problem for the present close-spacing decoupling techniques in the abstract: ' the present techniques face the common problem that the pattern tilts if the spacing is close.' This will make the work clearer so that we can use the vertical wall to correct the radiation pattern to the broadside direction and improve the gain for the future miniaturized array.
Comment 16: An updated and complete literature review should be conducted to present the state-of-the-art and knowledge gaps of the research with strong relevance to the paper's topic, and the authors must position their work according to the literature review.
Answer: We change the corresponding state in 'Introduction' to highlight the work of close spacing decoupling; like in the new 5th paragraph of 'Introduction,' we mention the common problem faced by the present close-spacing decoupling techniques, that is, the pattern tilt. And compared them in the new sub-section 3.3.
Comment 17: The key elements of innovation need to be highlighted according to the literature review.
Answer: We highlight the novelty in the new 5th and 6th paragraphs in 'Introduction,' they are 'Although excellent isolations have been achieved by taking so many techniques, one common problem exists that the radiation pattern tilt after decoupling…', and 'In this paper, the substrate is replaced by a lower loss tangent material F4BTM440 for the patch antenna to get higher realized gain, and a single substrate vertical wall for simplifying the decoupling structure is used to realize the pattern correction at a single frequency…'
Comment 18: The authors need to re-organize their work as follows: Abstract; Introduction; Related works; Materials and methods; Results and discussions; Conclusion; References.
Answer: We reconsider this comment and find our content covers these aspects, such as we mentioned the 'related works' in the 'Introduction,' the 'materials and methods are included in Section 2, and Sections 3 &4 discuss the 'results and discussions.' On the other hand, we find a similar writing style in the published papers in this journal.
Comment 19: The discussion section should be improved with more diagrams and results.
Answer: In the new content, we add the loss discussion of wall substrate, the equivalent circuit, and the comparisons with other works and different software.
Comment 20: The quality of some Figures must be enhanced; then, the authors should clearly interpret the results obtained in these figures.
Answer: We replace the old figures using high-quality ones and interpret them when the physical mechanism behind them appears.
Comment 21: Proofreading is required to enhance both the language and the presentation of the paper.
Answer: We checked the new manuscript and corrected some errors.
Reviewer 5 Report
The paper may be useful for researchers in the field of antenna design.
1. The statement agree well is too general in the abstract section. Authors need to state extent or the percentage of conformity.
2. Space must be provided between a quantity and a unit. For example- 58GHz should be 58 GHz
3. The abstract section is not well concluded. A statement on application of the developed antenna should be included
4. There are several typo errors which are needed to be corrected
5. Page 6 line 191 should be Figure 7a and not Figure 1a
6. Define all the acronyms
7. Please check the symbol for degree 'o' and not '0'
Author Response
Comment 1: The statement agree well is too general in the abstract section. Authors need to state extent or the percentage of conformity.
Answer: We want to highlight our novelty in facing the pattern tilt problem to focus on the description of the decoupling structure. Besides, this design does not change the conventional characteristics of a patch antenna, which we all know. So we didn't mention the corresponding conformity so extensively. Alternatively, it may lack our discussion focus, in our opinion. However, we can add it in detail if you think it is essential.
Comment 2: Space must be provided between a quantity and a unit. For example- 58GHz should be 58 GHz
Answer: We have corrected all these errors in the new manuscript.
Comment 3: The abstract section is not well concluded. A statement on application of the developed antenna should be included
Answer: We have highlighted our work in the new abstract and shown the common problem in the present close-spacing techniques as 'the present techniques face the common problem that the pattern tilts if the spacing is close. Thus, a pattern-corrected closely-spaced technique is proposed…' in order to emphasize our novelty.
This common problem makes us investigate the high-performance miniaturized array in the future. Thus, we did not mention this application in 'Abstract' but put it in the 5th paragraph of 'Introduction.'
Comment 4: There are several typo errors which are needed to be corrected
Answer: We have corrected them. Thank you.
Comment 5: Page 6 line 191 should be Figure 7a and not Figure 1a
Answer: Yes, it is Figure 1a. We want to say that the excited antenna is the left antenna shown in Figure 1a, and the corresponding patterns are shown in Figure 7a.
Comment 6: Define all the acronyms
Answer: We check all the corresponding results. We added the full name of MIMO at the beginning, and we did not use the new acronyms in the manuscript; the mentioned acronyms, like 'EBG,' were introduced before its use.
Comment 7: Please check the symbol for degree 'o' and not '0'
Answer: We have modified them. Thank you.
Round 2
Reviewer 3 Report
The authors have answered my comments
Author Response
Thanks for your comments.
Reviewer 4 Report
Comments and suggestions were not carefully considered, as the authors did not thoroughly review their initial submission. From my perspective, the manuscript cannot be considered for publication.
Author Response
We strongly recommend to remove this reviewer and let another one review again, the reasons are as follows.
- We replied all of his/her comments, but we guess he/she didn’t see our modification at all. That’s because only him/her among the five reviewers gave us so many comments. Such as, 1) we add the equivalent circuit according to his/her requirement, which is not necessary in the analysis of the antenna performance; honestly, we can find this analysis in few papers, but even no this, we can get the final analysis well; 2) though we didn’t add the flowchart, we use the corresponding words to describe this process; it is very rare to see the flowchart to the antenna design, if we find the corresponding mechanism behind the electromagnetic phenomenon, it will be easy to find the optimum result. We can also find some other problem he/she listed.
Besides the above content, we can judge him/her is not familiar with the antenna design even the electromagnetic theory by the technique detail, we just pick up several from his/her comments as follows.
- The mentioned CPW feeding in his/her second comment, we guess he/she has enough assurance to ensure this question is correct. However, you can find where is it? Why he/she talk about this, or where he/she to find our work is related to this technique?
- He/She wanted us to discuss the ‘different substrate materials for rectangular patch antennas and T-type Vertical Wall’. We all know that we design the antenna according to the concrete specific material and the chosen material is a conventional one. It is not necessary to discuss this choice unless he/she doesn’t focus on the antenna research at all.
- The comment of ‘…S21 of the antenna has an optimum value of approximately 5.8 GHz’. It is kind of weird, why does he/she just focus this point? We can discuss this in the paper sometimes, but it is not an absolute concern in the design for the decoupling. In other words, he/she doesn’t the corresponding decoupling techniques at all.
- Pertaining to the ‘metaheuristic optimizer’, we guess he/she wanted to mention the genetic algorithms, particle swarm algorithm etc. It is very useful involving some electromagnetic problem, like metasurface design. But we needn’t use it in this design, we just need find the resonant theory and structure and use the simple parametric analysis for the specific parameters to get the good result.
We didn’t reply his/her unprofessional comments one by one. In our opinion, that’s enough to replace him by one professional expert who knows the antenna thoroughly.
