Eight-Element Antenna Array with Improved Radiation Performances for 5G Hand-Portable Devices

Round 1

Reviewer 1 Report

The authors have presented an important and detailed study on a new phase array design for improved communication in 5G network. I have minor recommendations to improve the message conveyed in the article:

1. The acronym MIMO should be defined when first introduced on Page 1, Line 34.

2. The authors report that this novel design of the linear phase array is better than the previously reported designs. The data shown in Section 5 does not seem to clearly support this. It is not clear what negative radiation efficiency means in Figure 14 and why efficiency of 0 dB implies improved performance. The authors should elaborate on how their statement of improved performance is supported by the data shown in this section. How much is the improvement in terms of % loss and total efficiency improvement?

3. How is the efficiency in Figure 15 calculated? Which configuration is better with respect to the efficiency values reported?

4. Line 294 on page 15 states that the effect of user data is not significant but data shows a total loss of 30% and 1.5 dB. The authors should elaborate on why these losses are not significant. 

Author Response

Dear Reviewer

Thank you for your attention. According to your opinion, we have addressed your comments and suggestions in the revised manuscript. We would also like to thank you for your relevant comments. By taking these comments into account, the modifications can be summarized as bellow:

• Improvement of the detailed descriptions of some subsections to give a better understanding.
• We have made a point-to-point response to the comments.

Response to Reviewer’s Comments:

1. Thank you for your suggestion. It is done! multiple-input multiple-output (MIMO)!

2. We appreciate your comment very much. We have modified the text to clarify the description:

“It can be seen that compared with the conventional slot and patch array, the introduced array offers very high efficiency. It should be noted that using x=10log10k, the percentage (linear) value of the antenna efficiency can be converted to dB (logarithmic) [33]. Therefore, as clearly observed, even though the proposed antenna is designed on a lossy substrate (FR4), it offers much higher efficiency (almost 100%) compared to the conventional designs (80-85%). This is mainly due to the employed design technique which eliminates the loss of the substrate material [30].”

We also added a comparison to compare and highlight the novelty and improvement of the proposed design in compared with the previously reported designs.

“Table 2 exhibits a comparative summary of the antenna characteristics for the proposed design with the recently reported smartphone 5G phased arrays available in the literature [37-45]. As depicted in the table, the suggested design can support wide scanning angles with better gain and efficiency characteristics. In addition, different from the reported designs, the gain and efficiency characteristics of the design are almost constant over the main scanning angles (0–60 degrees). In addition, the antenna elements have more than 17 dB isolation. Furthermore, unlike the reported design, the proposed antenna is insensitive to different substrate materials which is a unique function and can be demonstrated in low-cost substrates. Its performance is also almost constant for different ground plane lengths as discussed in Fig. 18.”

Table 2. Comparison between the proposed and the reported mobile handset antennas.

3. Thank you for your attention. We have modified the text to clarify the description:

“The simulations and efficiency/gain calculations for each radiation beam were carried out using computer simulation technology (CST) software. As shown, the efficiency values of the proposed design are better than -0.5 dB (90%), while for the conventional design, the parameter is less than -1 dB (80%).”

4. You are right. The previous description was not giving a clear explanation. Therefore, we modified the text and added specific details about the user effect on the antenna parameters:

“As seen, the total losses of designed array parameters for antenna gain are around 0.5 to 1.5 dB. In addition, in the scanning range of 0° to 50°, the efficiency reduction is less than 0.25 dB (5%). However, as expected, by moving to the higher scanning angles (60°~ 70°), about 15-20% reduction is observed in the antenna efficiency. Therefore, it can be concluded that the effect of the user’s hand is not significant.”

Many thanks for your attention and accuracy about these subjects,

Yours sincerely

Corresponding Author

Author Response File: Author Response.pdf

Reviewer 2 Report

The work presents some interesting numerical results. However, the presentation is poor and the novelty of the scientific contribution is not absolutely clear. Using air slots in antennas is not something new. The authors present little of the relevant literature on the topic. In addition, they treat a 2014 paper as recent (ref. 15). The main problems I see are:

1) It is, eminently, a simulation work with limited experimental results. The measured results are not enough to prove the efficiency of beam steering under large angles.

2) The work presents measurements for a single element and, I suppose (this is not clear in the text), uses array factor to simulate measured results. There are serious problems with this approach, ignoring the coupling effects between elements.

3) The quality of the presentation is not good in the following aspects:

a.) Various errors in writing, typing, and punctuation.

b.) Large figures, with disproportionate font size and some of them not relevant (Ex. Figs. 7, 15, 18).

c.) Graphics with poor editing quality, poorly made and repetitive (i.e. Figs. 10 and 11).

d.) Some unclear passages in the text (i.e. lines 147-149).

Author Response

Dear Reviewer

Thank you for your attention. According to your opinion, we have addressed your comments and suggestions in the revised manuscript. We would also like to thank you for your relevant comments. By taking these comments into account, the modifications can be summarized as bellow:

• Improvement of the detailed descriptions of some subsections to give a better understanding.
• We have made a point-to-point response to the comments.

Response to Reviewer’s Comments:

We appreciate your comments very much. we have addressed your comments and suggestions in the revised version of the manuscript as listed below.

1. We appreciate your comment very much. Unfortunately, due to some restrictions, at the moment, we don’t have enough facilities to provide more experimental results. However, we will consider your valuable comment in our future work which will be in collaboration with other institutes in which we can measure more properties of the future prototypes.

2. Thank you for your attention. We have modified the text to clarify the description:

“The radiation patterns (including E&H planes) of the single-element antenna are also measured. Figure 20 (a) plots the measured 2D polar patterns for the element under experiment. As shown, the single-resonator exhibits quasi omnidirectional radiation shape in E-plane while in H-plane, the radiation’s main direction ended in end-fire mode. Furthermore, in order to study the beam-steering potential of the proposed design with a general perspective, using the measured radiation data of the single antenna, the beam patterns of the introduced array have been synthesized and simulated [36-38]. The calculated results in the scanning range of 0°~70° were illustrated in Fig. 20 (b). As can be observed, a well-defined beam steering function is obtained for the synthesized beams in the range from 0^o to 70°. It is worth mentioning that in the realist approach (where all the elements are measured, mutual couplings and phase shifting are included), the obtained results might be slightly different.”

3.

1. It’s performed! We have checked and corrected the errors. Thank you!

1. Thank you for your attention on this. The requested items have been modified now!

1. We appreciate your comment. We improved the quality of the figures.

1. It’s done. We modified the text to make it clearer.

“As represented, the array offers end-fire radiation mode at the selected scanning angle (0°,15°, 30°,45°, 60°, and 70°) which could provide half-space radiation coverage with point-to-point scanning possibility at a different desired angle [29]. As mentioned earlier, to acquire full radiation coverage, another set of the introduced antenna can be located at the bottom side of the mainboard PCB.”

Many thanks for your attention and accuracy about these subjects,

Yours sincerely

Corresponding Author

Author Response File: Author Response.pdf

Reviewer 3 Report

In this paper Eight-Element Antenna Array with Improved Radiation Performances is proposed. This paper can be considered after major modifications listed as follows:

1-     This paper is not “review” paper and should be considered as “Article” paper.

2-     It is suggested that to change “for Future Smartphones” in the title with “for 5G hand-portable devices” or “for 5G Smartphones”.

3-     The proposed antenna elements are covering the range of 21-23.5 GHz sub-mm-wave, but the  5G standard bands are located at 26 GHz (24.25-27.5) and 28GHz(26.5-29.5), which not matched.

4-     Fig.1 should be modified and demonstrated carefully. There are some mistakes in this figure.

The red and blue boxes are defined but yellow box is not defended in this figure. And also the applications this band (21.2-23.6GHz) should be cited. Why 26GHz band not depicted in this figure?

5-     Line 74, Fig.1 should be changed to Fig.2. (Fig.2 is not cited in the text).

6-     As depicted in fig 2 the antenna arrays are located behind the LCD display of smartphone, which results in undesirable effects on performance of structure kindly add explanations about this issue

7-     As listed in table 1, w3=w4=3.125mm, Which is impractical in fabrication process. Provide minimum step of fabrication process and add relative explanations.

8-     In Lines 97-98, power dividers should be briefly explained, maybe below paper is helpful

“Design of a Patch Power Divider with Simple Structure and Ultra-Broadband Harmonics Suppression. IEEE Access. 2021 Dec 9;9:165734-44.”

9-     In fig 6, which S-parameters for 8 arrays are demonstrated the location of ports should be determined.

10-  Provide specific application of proposed device at 22.5 GHz with citation.

11-  Provide unit of 6.75 in line 177.

12-  Compare results of proposed design which depicted in fig 6 with conventional one depicted in fig 13.

13-  In fig 13 s18 is located above of others curves in both figure (a) and (b) how is it possible? Add sufficient explanations or correct these curves.

14-  In fig 6 simulated s11 for proposed device is about -25dB but in fig 14 this parameter  is about - 30 dB. Correct this mismatches

15-  In fig 14 the measured results is better than simulated rests at 22.5 GHz. Explain this issue and add sufficient explanations corresponding to SMA connectors losses and  simulations and measurement condition

16-   Add compression table and compare the proposed device with some similar new designs

Author Response

Dear Reviewer

Thank you for your attention. According to your opinion, we have addressed your comments and suggestions in the revised manuscript. We would also like to thank you for your relevant comments. By taking these comments into account, the modifications can be summarized as below:

• Improvement of the detailed descriptions of some subsections to give a better understanding.
• We have made a point-to-point response to the comments.

Response to Reviewer’s Comments:

1. Thank you for your attention on this. It is corrected.

2. Thank you for your suggestion. It is done.

3. Apart from the cited frequencies, several bands (beyond 10 GHz) such as 15 GHz and 21 GHz were studied for 5G applications [13-15]. The proposed antenna design is highly flexible, and its operation band can be easily tuned to the desired frequency. By modifying the design parameters of the suggested antenna, the antenna is able to cover various frequencies at higher and lower bands. We have added a new result (Figure 2) to describe this characteristic of the proposed design.

4. We modified the figure as requested.

5. Thank you for your attention on this. It is corrected.

6. The proposed array design is only occupying a small part of the PCB which is L×W_sub. The green colour is showing the space for the LCD display and the full yellow (bottom layer) represents the full ground plane.

7. The fabrication process is described in section 6, as follows:

“During the fabrication process, eight-slot holes with a distance of λ/2 have been made to hold the metal-ring resonators. In the next step, The metal-ring resonators were made separately and then inserted into the slot holes on the PCB.”

8. We modified the text and added new information and the suggested reference.

9. We specified the locations of the antenna ports.

10. Thank you for your suggestion. We have added new references and also some more explanations to cite the application of the proposed design.

11. Thank you for your attention on this. It is performed.

12. It’s done. We modified the text and added new information.

13. Thank you for your attention on this. It is corrected.

14. We appreciate your comment. Figure 6 shows the antenna S-parameters where all elements are excited, and the mutual coupling is involved while in Fig. 14 we have studied the frequency response of a single element (without considering the effect of the adjacent elements). Therefore, a slight difference was discovered.

15. Thank you for your attention on this. It is worth mentioning that due to the flexibility of the employed feeding method and also in order to acquire the best possible measured result and also eliminate the SMA connector/cable losses, the feeding point of the antenna element can be slightly adjusted to obtain a better result. We added new information.

16. Thank you for your suggestion. We added a comparison to compare and highlight the novelty and improvement of the proposed design in compared with the previously reported designs.

“Table 2 exhibits a comparative summary of the antenna characteristics for the proposed design with the recently reported smartphone 5G phased arrays available in the literature [37-45]. As depicted in the table, the suggested design can support wide scanning angles with better gain and efficiency characteristics. In addition, different from the reported designs, the gain and efficiency characteristics of the design are almost constant over the main scanning angles (0–60 degrees). In addition, the antenna elements have more than 17 dB isolation. Furthermore, unlike the reported design, the proposed antenna is insensitive to different substrate materials which is a unique function and can be demonstrated in low-cost substrates. Its performance is also almost constant for different ground plane lengths as discussed in Fig. 18.”

Table 2. Comparison between the proposed and the reported mobile handset antennas.

Many thanks for your attention and accuracy about these subjects,

Yours sincerely

Corresponding Author

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The paper can be accepted in its current form.

Reviewer 3 Report

The authors have been addressed most of my concerns.