Dual Band Electrically Small Complementary Double Negative Structure Loaded Metamaterial Inspired Circular Microstrip Patch Antenna for WLAN Applications
Round 1
Reviewer 1 Report
The paper presented a miniaturized circular patch antenna using double negative metamaterial structured etched on the antenna ground plane. The paper is good in general, more results and explanations are needed.
- Why did the author start with a patch resonates at 6.24 GHz?
- What is the significance of showing the circular patch design procedure and equations since is an obvious and well-known procedure?
- What is the contribution that the authors trying to say by having these steps written in the paper?
- Can the authors explain how the complementary MTM structure miniaturized the antenna structure? And what is the MTM effect mentioned on page 4 of the manuscript?
- Can the authors elaborate more on the main contribution of the paper? The rule of MTM in miniaturization? Effect of the double negative in antenna miniaturization?
- Please add a reference to equations 4-6
- Can the author compare the radiation properties for the circular patch on the conventional and MTM ground plane? For example, gain vs frequency
Author Response
Response to Reviewer 1 Comments
We are grateful for the valuable suggestions and questions listed by you. It enabled us to revisit our paper and modify in accordance with your valuable suggestions.
Point 1: Why did the author start with a patch resonates at 6.24 GHz?
Response 1: We have designed the CDNG structure loaded MTM inspired antenna in order to enable its operation in the most commonly used application bands of 2.4 GHz and 5.2 GHz. In order to achieve this goal we have to start with the initial patch antenna operating frequency of 6.24 GHz. One important characteristic of the proposed antenna is its tunability in S and C bands by a mere alteration of its CDNG- MTM size. Hence in order to achieve the final operating frequencies of 2.4 GHz and 5.2 GHz we had to set the initial patch operating frequency at 6.24 GHz.
As per your suggestion we have incorporated the rationale for choosing the initial resonant frequency of 6.24 GHz in the paper.
Point 2: What is the significance of showing the circular patch design procedure and equations since is an obvious and well-known procedure?
Point 3: What is the contribution that the authors trying to say by having these steps written in the paper?
Response 2 and 3: Our attempt was to present a complete and comprehensive picture of the various procedural steps for evolving our antenna design so that even non- specialist readers and designers can digest and reproduce the proposed antenna.
We are thankful for the reviewer's comment that the basic and obvious procedural steps which are well established and well known in the field may appear non scholarly. Therefore we have eliminated the basic steps from the paper and have retained them as references 27 and 29 in the reference section.
Point 4: Can the authors explain how the complementary MTM structure miniaturized the antenna structure? And what is the MTM effect mentioned on page 4 of the manuscript?
Response 4: In patch antenna miniaturization complementary structures are the most compatible structures that can be loaded on ground planes. We find numerous works with CSRR loading on patch Antennas [22-28]. CDNG structure functions as an additional resonant LC circuit, perturbing the normal resonant effect of patch antenna,thereby reducing its resonant frequency. In addition to this, an extra resonance is produced by the CDNG structure itself. Thus the CDNG structure impacts the antenna design in two ways - both in its own capacity and as an influencer affecting the patch resonance.
Point 5: Can the authors elaborate more on the main contribution of the paper? The rule of MTM in miniaturization? Effect of the double negative in antenna miniaturization?
Response 5: In conventional antennas, miniaturization can be achieved by increasing the substrate permittivity. Without changing the substrate material, effective permittivity can be increased by incorporating an MTM or an MTM effect within the antenna design. This in turn would reduce the size of the antenna. Thus MTMs can function as a material substitute in achieving miniaturization of antennas. In our proposed design also we have utilised the MTM property of increasing the effective permittivity in order to achieve miniaturization.
We are thankful for your suggestion regarding MTM effect in antenna miniaturization. We have incorporated an additional paragraph elaborating upon the effect of MTM on the proposed antenna.
Point 6: Please add a reference to equations 4-6
Response 6: We have added five reference papers as additional references for substantiating the equations for 4-6 (1-3 in revised article)
Point 7: Can the author compare the radiation properties for the circular patch on the conventional and MTM ground plane? For example, gain vs frequency
Response 7: A frequency versus gain graph has been plotted and incorporated into the paper as Figure 8.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Thank you for the opportunity to read your paper! I found your structure and antenna design very interesting. However I have some concerns on how the work is presented. See below for more information:
This is NOT a metamaterial loaded antenna. A metamaterial is a BULK material, that implies multiple unit cells. This is a metamaterial-inspired antenna (https://scholar.google.com/scholar?hl=en&as_sdt=1%2C44&q=metamaterial+inspired+antenna&btnG=). There is a SIGNIFICANT amount of work in this area, and I would need to re-review the work after a good literature review in this area is included.
The title and the article must be re-written. This is in no way a metamaterial and publishing it as such is not correct in anyway.
Because it is a metamaterial-inspired antenna, the S-parameter retrieval that the author uses is VERY incorrect. See Holloway et al "Characterization of a Metafilm/Metasurface" for the difference in characterization between even metasurface and metamaterial characterization. The authors work is just a single element of a complimentary metasurface, thus cannot be characterized in the way presented here.
The author does do a great job of showing a control antenna with a solid groundplane, this should be applauded as many authors fail to include a control.
I have some questions about the response of the patterned ground plane. It seems as though the patch antenna is actually a near-field excitation of the complimentary resonator and there is also significant field interaction with the edges of the ground plane (figure 7). Additionally, the far-field patterns look terrible for any type of directivity. There are no consistent lobes which would make actually using this antenna terrible. Without seeing the fields on the ground plane side of the structure, I am concerned that the antenna is not operating as intended. Instead, the resonance could be due to the interaction between the ring and the edge of the ground plane, i.e. as the ring increases in radius it gets closer to and interacts more with the edge of the ground plane. In my mind, this is confirmed by the lack of directivity in the far-field pattern. Overall, these questions (even if I am incorrect) cause me to thing more work should be done by the authors as an analysis.
Author Response
Response to Reviewer 2 Comments
We are thankful for the valuable suggestions and questions listed by you. It helped us to critically revisit our paper and modify in accordance with your valuable suggestions, where ever possible.
Point 1: This is NOT a metamaterial loaded antenna. A metamaterial is a BULK material, that implies multiple unit cells. This is a metamaterial-inspired antenna (https://scholar.google.com/scholar?hl=en&as_sdt=1%2C44&q=metamaterial+inspired+antenna&btnG=). There is a SIGNIFICANT amount of work in this area, and I would need to re-review the work after a good literature review in this area is included.
Response 1: We have used the term metamaterial loaded in the sense that a metamaterial structure with an additional LC effect has been incorporated on a patch in order to achieve further compactness and increased effective permittivity . The terms SRR loaded and CSRR loaded are already used in literature and SRRs and CSRRs are metamaterial structures. [See Ref.19,23,25,26]. However your valuable suggestion that the term ‘metamaterial loaded’ used here can be misinterpreted as incorporating a bulk material on antenna, needs to be addressed. We therefore agree to your suggestion and has modified the term ‘metamaterial loaded’ as ' CDNG structure loaded metamaterial inspired' in order to clarify any ambiguity regarding the role of MTM loading used in the antenna description.
Point 2: The title and the article must be re-written. This is in no way a metamaterial and publishing it as such is not correct in anyway.
Response 2: As per your valuable suggestion the article title has been changed as “Dual band electrically small complementary double negative structure loaded metamaterial inspired circular microstrip patch antenna for WLAN applications”
Point 3: Because it is a metamaterial-inspired antenna, the S-parameter retrieval that the author uses is VERY incorrect. See Holloway et al "Characterization of a Metafilm/Metasurface" for the difference in characterization between even metasurface and metamaterial characterization. The authors work is just a single element of a complimentary metasurface, thus cannot be characterized in the way presented here.
Response 3: The pioneer in the field of metamaterial characterization is Smith et al. The findings achieved by Smith et al was actually simulated and reproduced using S parameter retrieval method by the authors before applying the same method in the newly designed structure. The parameters retrieved using the S parameter method used here has already been experimentally validated using cavity perturbation method and its findings are published as [35]
In references [26,27]as well as in the reference shown below, published years after Holloway et al paper [2009], single cell metamaterial structures are used and the same parameter retrieval method is employed.
Hence the retrieval methods used in this paper follow the parameter retrieval methods in the papers mentioned above.
Ali T, Khaleeq MM, Pathan S, Biradar RC. A multiband antenna loaded with metamaterial and slots for GPS/WLAN/WiMAX applications. Microw Opt Technol Lett. 2017;60:79–85. https://doi.org/10.1002/mop.30921
Point 4: I have some questions about the response of the patterned ground plane. It seems as though the patch antenna is actually a near-field excitation of the complimentary resonator and there is also significant field interaction with the edges of the ground plane (figure 7). Additionally, the far-field patterns look terrible for any type of directivity. There are no consistent lobes which would make actually using this antenna terrible. Without seeing the fields on the ground plane side of the structure, I am concerned that the antenna is not operating as intended. Instead, the resonance could be due to the interaction between the ring and the edge of the ground plane, i.e. as the ring increases in radius it gets closer to and interacts more with the edge of the ground plane. In my mind, this is confirmed by the lack of directivity in the far-field pattern. Overall, these questions (even if I am incorrect) cause me to thing more work should be done by the authors as an analysis.
Response 4:
The main focus of this paper is to design and develop an electrically small patch antenna which has been successfully accomplished to a certain extend though this work. ESAs generally have some inherent drawbacks such as reduced gain and directivity. Addressing such issues need further investigations and studies in this direction are part of our future project work. Complying with your suggestion for a deeper analysis in the far field a gai vs frequency graph has been plotted and incorporated in this paper.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper titled “Dual band electrically small complementary double negative 2 structure loaded metamaterial inspired circular microstrip patch antenna for WLAN applications” is well written and well structure. The results described are very good and very relevant.
Nevertheless, the description of the prototype designed is very poor. The main advantages of the design and the comparison with another research are missing. The authors should give more detail about the benefits of the antenna prototype described.
Apart from that, there some minor mistakes that it is necessary to modify to improve the quality of this work.
- In the abstract, line 11-13 does not have a sense. What does want to express the authors? Due to in the lines 15-16 the authors indicated that the prototype works at 2.4-5.2GHz instead of 6.2 GHz.
- In line 16-17 the authors described the bandwidth in the upper band, but which is the bandwidth in the lower frequency (2.4GHz)?
- In the introduction, there are a few references. The authors gave a lot of information but the reference are not detailed.
- Moreover, in the introduction is not mentioned the previous work related to the antennas implemented with metamaterial. The authors should include more studies and references about it. Moreover, it is important that they will explain the advantage of the prototype proposed.
- In Section 2, line 80 is mentioned that the initial resonant frequency is 6.2GHz, why? This frequency is the end of the WLAN band. The antennas are designed to the centre frequency of the band. A detail explanation is needed.
- The simulation tool used to design the antenna is indicated in the line 180, but how do the results of the figure 7 and 8 are obtained?
- In the paper the user manual of the software used in the references is not indicated.
- The conclusions are very poor. The prototype is not compared to another kind of the designs. The advantages of the design are not discussed.
Author Response
Response to Reviewer 3 Comments
We are grateful for the valuable suggestions and questions listed by you. It enabled us to revisit our paper and modify in accordance with your valuable suggestions.
Point 1: In the abstract, line 11-13 does not have a sense. What does want to express the authors? Due to in the lines 15-16 the authors indicated that the prototype works at 2.4-5.2GHz instead of 6.2 GHz
Response 1: The primary aim of this work is to reduce the size of a patch antenna using the method of resonant frequency lowering. For that we have to choose one simple patch antenna and then apply metamaterial upon it for obtaining size reduction. That is why we represented the initial resonant frequency of the patch antenna as 6.2 GHz. Our purpose is to demonstrate the extend of size reduction achieved by metamaterial loading. That is why the resonant frequency before metamaterial loading (6.2 GHz) and after the metamaterial loaded prototype is designed (5.2 GHz and 2.4 GHz) are specifically stated in the abstract itself.
As per your suggestion we have incorporated the rationale for choosing the initial resonant frequency of 6.2 GHz in the paper.
“The circular microstrip patch antenna, used for developing the proposed antenna has a resonant frequency of 6.2 GHz with an impedance bandwidth of 3.5% before the metamaterial structure is applied upon it. The loading of the proposed metamaterial structure inspires the antenna to lower its resonant frequecy with enhanced bandwidth and generate one additional resonance. The designed antenna can be tuned throughout the C- band by simply altering the size of metamaterial structure loaded upon it. However, the prototype of the antenna is designed for the most commonly used wireless communication bands at 2.4 GHz and 5.2 GHz”
Point 2: In line 16-17 the authors described the bandwidth in the upper band, but which is the bandwidth in the lower frequency (2.4GHz)?
Response 2: As per your valuable suggestion we have incorporated the bandwidths for both upper and lower frequencies in the abstract itself.
“The 10 dB impedance bandwidth of 1.63% at 2.4 GHz and 13.15% at 5.2 GHz are achieved by this design”
Point 3: In the introduction, there are a few references. The authors gave a lot of information but the reference are not detailed.
Response 3: Your suggestion to give details of the references cited helped us to strengthen the introduction part of our paper. We have attempted a more detailed analysis of the reported works in the field and presented them as two separate paragraphs in the introduction.
Point 4: Moreover, in the introduction is not mentioned the previous work related to the antennas implemented with metamaterial. The authors should include more studies and references about it. Moreover, it is important that they will explain the advantage of the prototype proposed
Response 4: As per your valuable suggestion, works since the pioneer Ziolkowski et.al have been analysed in detail and cited in the introduction of the paper. Moreover, some additional references are added to strengthen the introduction. We have also included a detailed comparative study of the previous works in the field in the conclusion section, inorder to demonstrate the advantages of the proposed work.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The pioneer in the field of metamaterial characterization is Smith et al. The findings achieved by Smith et al was actually simulated and reproduced using S parameter retrieval method by the authors before applying the same method in the newly designed structure.
-Each MM structure is different. Just because you were able to replicate Smith et al, does not imply that all MM structures can be translated in to single elements or retrieved with an S-parameter retrieval. You need to expand the number of unit cells to until the retrieval does not change when you add more unit cells, this will be the bulk response. Some structures behave as a bulk with only 1 unit cell depth and that is OK. It just must be proven. This was a VERY hot point in MM conferences in the late 2000s leading to Holloway's paper.
Not only that, but the retrieval in that case would be for a MS, in this work you show a single metaelement. That in no way can be modeled by S-parameter retrieval as a MS or MM must be arrayed as they operate through mutual coupling.
The main focus of this paper is to design and develop an electrically small patch antenna which has been successfully accomplished to a certain extend though this work.
-Science means explaining how things operate. If you are not able to do that, then the work is not ready to be published.
I am selecting "Reject," because I feel that we may never agree on the above statements and I cannot have a peer review associated with myself that contains these errors. In my opinion, these are extremely serious errors that are made extremely often in literature. As scientists we must attempt to rectify these types of errors whenever possible. I apologize because I did enjoy your article and I look forward to reading more of your work in the future.
Author Response
Thank you for your different perspective on the material characterization methodology. The prototype we developed was validated using cavity perturbation method after the s-parameter retrieval method was used for material characterization. The findings of this validation are published as
Thankachan, S; Paul, B; Pradeep, A; Moolat R. Design and Characterisation of Simple Planar Metamaterial Structure with Double Negative Properties. TENCON 2019 - 2019 IEEE Region 10 Conference (TENCON). 2019,1231-1235.
The fact that the findings of both methodologies are identical prove that s- parameter retrieval method is a scientifically proven method for characterization of single cell MTM structures also.
We are thankful for your valuable time spent on reading our paper and communicating your observations.
Reviewer 3 Report
The authors have done a great work and the paper has been improved. However, it is neccesary to improve the conclusion section it is very poor.
Author Response
Response to Reviewer 3 Comments
We are grateful for the valuable suggestion regarding the conclusion. It enabled us to revisit our paper and strengthen the conclusion in accordance with your valuable suggestion. We thank you for sparing your precious time for reading our paper and proposing suggestions for improving its quality.
Point 1: The authors have done a great work and the paper has been improved. However, it is necessary to improve the conclusion section it is very poor.
Response 1: We have revised the conclusion of our paper as per your suggestion. We have incorporated all the merits of our work and have highlighted the comparative advantages of our proposed antenna in the concluding section of the paper.
Author Response File: Author Response.pdf
