Mutual Coupling Reduction between Finite Spaced Planar Antenna Elements Using Modified Ground Structure

Round 1

Reviewer 1 Report

In this paper, a modified ground structure capable of reducing mutual coupling to provide isolation between adjacent antenna elements is presented. The proposed modified ground structure is a combination of a strategically located ground slot, asymmetric partial ground and a substrate-integrated pin wall.

The novelty of the paper is not clear, I would recommend to clearly highlight the main contribution of the paper.

What is the main challenges of the proposed approach?

 

Author Response

please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents a modified ground structure that is capable to reduce the mutual coupling and hence providing isolation between adjacent patch antenna elements. This is an interesting topic, and it should be of great interest to the readers. However, there are a couple of other issues that have been mentioned in the “comments to the authors” and they need to be addressed by the authors.

• Introduction

1. Line 42, add “full stop” after “system”.
2. Line 45, you need to explain why transceiver antenna (one antenna works as tx and Rx) cannot be used and support your claim with a reference sentences up into multiple sentences.

3. Line 49, You are claiming that the antennas on the plat form are separated from each other to avoid the interference. What about the interference with other electronics on the same platform? This also depending on the radiation pattern of the designed antenna (e.g., Uni-directional, or bi-directional).

• Antenna Design

1. Do not include the figure of proposed antenna with the table of parameters. List the antenna parameters at the end of antenna design geometry section (geometry section) or in a Table.
2. Why the antenna is designed to operate at 4.16 GHz?
3. Labe the patches on Figure 1.
4. Line 91, “bandwidths range from 20MHz to 200MHz” If designs have different operating frequencies, it would be more appropriate to provide relative bandwidth range (%) not absolute impedance bandwidth.
5. The way Figure 2 is presented is confusing. Please label your figure as (a), (b), (c), and (d), then in the caption provide description of what these sub-figures are.
6. Line 103, Which optimization method in HFSS you have used for the optimization. For example, one of the optimization methods in HFSS is Quasi Newton method, In the following paper, the authors used the aforementioned method:

Tubbal, R. Raad amd, KW. Chin, and B. Butters “S-band shorted patch antenna for inter pico satellite communications” 8th International Conference on Telecommunication Systems Services and Applications (TSSA), PP. 1-4, 2014.

7. Figure 3 presents reflection coefficient and not return loss. RL in dB is RL = 10log₁₀(Pi/Pr), where Pi and Pr are the incident and reflected powers, respectively.

S11 in dB is S₁₁ = 20log₁₀ (Er/Ei+ = 10log10 (Pr/Pi), where Er and Ei are the reflected and incident fields, respectively. 

 In general, S11 is a complex quantity and the relationship between RL and S11 is hard to  discern. The relationship between RL and S11 is that RL = -S11. See the following paper,

Bird TS. Definition and misuse of return loss [report of the transactions editor-in-chief]. IEEE Antennas and Propagation Magazine. 2009 Jul 14;51(2):166-7.

8. In figure 4, at what frequency you obtained the Surface current distribution? Is it 4.16 GHz? You need to mention this in your manuscript.

9. Line 136, you mentioned “(patch 1 in Fig. 1)” Label patch 1 and Patch 1 on the figure.

 

• Results

1. Line 152, change “at -10 dB frequency” to “below -10 dB frequency”
2. Line 251’ “170 MHz”, see my comment 4 above, under “Antenna design”
3. Figure 7 (b), why there is discontinued in the measured pattern?
4. Figure 7 (c) is strange, why the gain like a straight line. You presented very small range. You need to show the peak gain in range of 3.6 to 4.8 GHz. You also need to indicate in title of figure 7, at what gain Figure 7 (a) and (b) were obtained. 
5. What is the gain bandwidth of your antenna?
6. What is the efficiency of your proposed antenna? You need to include figure of the efficiency vs frequency.

• Conclusion

10. Line 197, provide relative bandwidth range (%) not absolute impedance bandwidth.

 

 

 

Author Response

please see the attachement

Author Response File: Author Response.pdf

Reviewer 3 Report

Generally well prepared paper. I have few comments:

• Please comment effect of antenna spacing to mutual coupling. It seems that even without the "design steps", the S21 is quite low (say below 20 dB). Line 70 - you state 28 dB, but according to Fig. 3b it is less. It is really required for this sensor to have S21 at levels of -50 dB?
• Did the authors tried to replace shorted pins by just a wall? It might be easier for construction. What is the effect of g_4 parameter to S11/S21?
• Would be interesting to add / comment cross-polarization levels (polarization purity)

Minor issues:

• Line 55 typo
• indexes should be as subscript (epsilon_r, S_11, S_12 etc)

 

Author Response

please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

 Dear Authors, 

Thanks for addressing all comments. 

Regards 

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

In this paper the authors exploit a method for reducing mutual coupling of TX-RX channel of a patch antenna. This method, as well as the reviewer knows, blends different well-known technique for reducing the antennas coupling.

In my opinion the paper, as it is, has to be rejected. Indeed, the paper ‘s contribution is low in terms of novelty, coherence with the contest and scientific soundness. Moreover the presentation is not enough for a scientific paper and presents several weaknesses in Title, Abstract and Introduction. The title suggest that the paper will talk about antennas and altimeters. Instead any measurements or real applications of the antenna proposed have been presented.

The paper needs further correction:

Abstract can be improved, e.g. the acronyms usually are not used in the abstract

Introduction

The first part of introduction is a bit confused and the different paragraphs are not related. From row 40 to row 55 is just a list without any references in the rest of the document.

Row 52, 85db instead 85 dB and it more appropriate mks (30 inches).

The introduction is more appropriate from row 55. EBG was used in row 58 but not declare before.

Antenna design

The English has to be improved because several sentences do not make any sense. The authors do not declare which program was used for simulations. Fig. 4 and Fig. 5 are located before the references in the text. Number in Fig. 7 is wrong, and it is located before references.

References

References 1, 2 and 3?

Reviewer 2 Report

This paper presents a pair of antenna structure having a high isolation characteristic. I have several comments as follows.

1. The antenna spacing in the presented work is very large. If such a large physical spacing is allowed in reality, then why do you need to integrate two antennas together sharing the same ground plane? You can have better isolation and radiation characteristics by having two separate antennas connected to a single T/Rx board.
2. Having a magnetic wall through ground vias and a slot in the ground plane for resonant current path are common techniques to reduce mutual coupling. What is the novelty of your work, especially you have both large spacing and the above-mentioned techinques?
3. The reflection coefficient is very poor and not suitable for implementing the whole application due to impedance loading effect. The reflection coefficient needs to be further improved as well.

Reviewer 3 Report

This paper presents a simple and practical mutual coupling reduction technique using modified ground planes. Paper is well structured with simulated predictions verified by experiments. High gain and low mutual coupling is a plus. Some of my minor comments are shown below:

• Even though the coupling is reduced form -37 dB to -65dB, the antenna gap used in this paper is large, please comment on what is expected this gap is reduced. 
• In section 1, please clearly indicate the difference between defected ground structure and modified ground structure.
• Please proofread for grammatical mistakes and typos