Meander Line Super-Wideband Radiator for Fifth-Generation (5G) Vehicles

Round 1

Reviewer 1 Report

1. In Fig. 3(c), when the working frequency is at 5.8 GHz, the gain is very low and its value is not provided as when the working frequency is at 2.4 GHz. Can it meet the gain requirement for vehicle antennas?

2. In Tab. 2, what are the criteria for selecting these antenna designs used for comparison? The antenna in Ref. [44] is an antenna for medical devices, not a vehicle antenna. By the way, the bandwidth ratio of Ref. [44] seems to be miscalculated.

1. Line 159, misspelling of "agreement".

2. Line 95-96, incomplete sentence. Missing "so was" after "and"?

Author Response

Response 1: Thank you for your suggestion. We have included the gain of the reference antenna at 5.8 GHz in Fig. 3c.

The antenna gain at 5.8 GHz exhibits a modest 1.25 dBi, though it's important to note that this design serves as our baseline design and is primarily utilized for validating our mathematical analyses. Our primary focus lies in the creation of an antenna operate for 5G-enabled vehicles functioning within the 28 GHz band. Our efforts in this regard have resulted a good antenna gain surpassing 7 dBi in the 28 GHz band, meeting the essential requirements for 5G vehicular applications.

Comment 2: In Tab. 2, what are the criteria for selecting these antenna designs used for comparison? The antenna in Ref. [44] is an antenna for medical devices, not a vehicle antenna. By the way, the bandwidth ratio of Ref. [44] seems to be miscalculated.

Response 2: The proposed meander line antenna's performance is evaluated by comparing it with several antennas inspired by meander line designs, as detailed in Table 2. The results demonstrate that the proposed antenna exhibits a gain, bandwidth, and compactness on par with those reported in the existing literature. The proposed antenna exhibits a comparable response and suitable for the said application.

The bandwidth ratio of [44] is corrected as 10:1.

Reviewer 2 Report

1. At page 3, why higher dielectric constant substrate can contribute to the higher gain and efficiency?

2. At page 3, the “...... are typically 4.4 and 1.6”, here 1.6 should followed by the unit of mm, and would be 1.6mm as the height.

3. Typos: eq 1 and eq 16 should eq (1) and eq (16), which wouldbe identical with the equations' label.

4. The contents at page 4 are fundamental knowledge which should be shortened and simplified.

5. I do not think Section 2.1 on the antennas with frequencies of 1-8GHz is necessary for this paper.

6. What are the efficiencies of the measured antennas?

No

Author Response

Thank you very much for your constructive comment and recommendation. We have tried our best to address all suggestions in the revised manuscript.

Comment 1: At page 3, why higher dielectric constant substrate can contribute to the higher gain and efficiency?

Response 1: Thank you for your observations. The statement is corrected as:

For higher frequency a low loss higher dielectric constant substrates yields a better radiation performance and bandwidth

Comment 2: At page 3, the “...... are typically 4.4 and 1.6”, here 1.6 should followed by the unit of mm, and would be 1.6mm as the height.

Response 2: The unit is included.

Comment 3: Typos: eq 1 and eq 16 should eq (1) and eq (16), which would be identical with the equations' label.

Response 3: As per your suggestions, we have done the proofreading and tried to eliminate typos.

Comment 4: The contents at page 4 are fundamental knowledge which should be shortened and simplified.

Response 4: Based on the fundamental equations eq. (1) to eq. (13), we have modified the eq. (14) to eq. (16).

Comment 5: I do not think Section 2.1 on the antennas with frequencies of 1-8GHz is necessary for this paper.

Response 5: The proposed antenna is developed using the proposed equations. To validate equations antennas are designed for a lower as well as higher operating bands.

Comment 6: What are the efficiencies of the measured antennas?

Response 6: The radiation efficiency of the antenna is measured at 28 GHz and found 87.9 \%.

Reviewer 3 Report

The authors present an antenna design that is very relevant to the current 5G wireless era. The design approach and ultimate aim of the work are well organized; however, some suggestions and concerns are listed below:

* The first design, Ant 1 is a standard meander line structure whose dimensions look appropriate and results are accurately simulated

* The evolution of subsequent designs: Ant 2 - Ant 4 is confusing; Ant2 and Ant 4 are single line designs with different dimensions, while Ant 3 is an array  design.  Is Ant 4 a hybrid of Ant 2 and Ant 3? Hence, a better explanation is required on how the initial designs lead, at least empirically to the final design

* Figure 6, which summarizes the performance of the final design, shows good gain pattern covering the lower and higher 5G frequencies; however, reflection (S11) pattern may not support that frequency range

* The fabricated version of the final design seems to be rough on the edges (Figure 8); hence, it is very unusual that the simulated and measured reflection patterns (Figure 9a) match almost exactly. Were the imperfections in fabrication also included in HFSS simulation?

While this work is promising in a very applicable area, the authors should clarify the queries and concerns raised above.

Author Response

Thank you very much for your constructive comment and recommendation. We have tried our best to address all suggestions in the revised manuscript.

Comment 1: The first design, Ant 1 is a standard meander line structure whose dimensions look appropriate and whose results are accurately simulated

Response 1: Thank you very much for your encouragement.

Comment 2: The evolution of subsequent designs: Ant 2 - Ant 4 is confusing; Ant2 and Ant 4 are single line designs with different dimensions, while Ant 3 is an array design.  Is Ant 4 a hybrid of Ant 2 and Ant 3? Hence, a better explanation is required on how the initial designs lead, at least empirically to the final design

Response 2: As per your suggestion, we have tried to improve the clarity as follows:

 Antennas Ant2 to Ant4 have been developed based on the key mathematical expressions for 5G FR2, ranging from equation (11) to equation (16). The design process initiates with Ant2 and concludes with Ant4. Figure 5 illustrates the S11 parameter and the design flow gain for Ant2 to Ant4. The 5G FR2 design flow for a super wideband meander line antenna, spanning from 24GHz to 30GHz in terms of s-parameters, is presented in Figure 5(a), with the gain specifically depicted at 28GHz in Figure 5(b). The initial design of Ant2 incorporates a 50 Ω microstrip line feed, measuring 22mm × 12mm× 1.6mm. It primarily focuses on meander width variations with reduced substrate geometry. Ant2 resonates from 26.78GHz to 28.62GHz, exhibiting a -13.25dB reflection coefficient and a peak gain of 7.3dBi, showcasing a single narrowband frequency at the centre frequency of 28GHz. Ant3 extends the structural design of Ant2 by emphasizing meander length and substrate geometry. With dimensions of 34mm × 15mm × 1.6mm, Ant3 introduces a wideband frequency range from 24.47GHz to 30GHz. At 28GHz, it displays a -23.45dB reflection coefficient and a peak gain of 6.10dBi, outperforming Ant2. The meander line configuration of Ant3 involves multiple segments with varying widths and increasing lengths, generating numerous resonances that enhance the antenna’s bandwidth. To broaden the frequency, Ant3 is fed through a quarter-wave transformer (QWT) feed line. Finally, Ant4 is a meander line antenna featuring width and length variations. It is powered by a 50Ω microstrip line feed and constructed on a full ground plane to encompass both the lower and upper bands of the 28GHz range.

Comment 3: Figure 6, which summarizes the performance of the final design, shows good gain pattern covering the lower and higher 5G frequencies; however, reflection (S11) pattern may not support that frequency range

Response 3: Yes, we agree with your comment. However, our VNA is limited to 43.5 GHz so could not perform the measurements for frequency beyond this. We are approaching to different laboratory for the 110 GHz VNA access and will extend frequency band in our future work.

Comment 4: The fabricated version of the final design seems to be rough on the edges (Figure 8); hence, it is very unusual that the simulated and measured reflection patterns (Figure 9a) match almost exactly. Were the imperfections in fabrication also included in HFSS simulation?

Response 4: We have observed a significant variation in simulated and measured results of S11. As a large band is depicted in figure in compact size it is difficult to visualize. However, by magnifying the image, some variations can be observed. Also, as discussed above, our VNA is limited to 43.5 GHz so could not perform the measurements for frequency beyond this. We are approaching to different laboratory for the 110 GHz VNA access and will extend frequency band in our future work.

Round 2

Reviewer 3 Report

The authors are encouraged to complete the work with the help of VNA with enhanced frequency range.