Novel Beam Scan Method of Fabry–Perot Cavity (FPC) Antennas

Round 1

Reviewer 1 Report

Based on the authors' claim, this paper proposes a Fabry-Perot cavity (FPC) antenna for obtaining high gain with reduced Sidelobe Level (SLL) by using a tapered partially reflective surface has been used as  a superstrate. Also, it has been sated that a phase-controllable artificial magnetic conductor (AMC) used to obtain various beam scanning directions.

 The main reviewer concern is about the novelty or contribution of this work since there is no such comparison given in the results section to demonstrate the novelty design in term of gain, bandwidth, antenna size, etc. Additionally, the introduction does not provide enough information and sufficient background about the most recent related works and also the advantage of this work compared to the rivals. To this end, the reviewer believes the paper it is not ready for possible publication with current version. More details are listed below:

1. The list of references in many contexts is long and the papers are lumped into a single citation {[1-6], [7-10] and [11-14]} without a careful review of the exact differences among these alternatives.
2. Regarding Fig. 10, why the Sim__S11 with θ_t = 0^o is much better than the Sim__S11 with θ_t =30^o. It is expected to discuss and explain this difference. The axis label of Fig.12 should be presented in a better way.
3. Although some measured results have been mentioned in Fig. 10 and Fig.12, the measurement protype has not been provided.
4. The proposed antenna should be compared with most recent related works in terms of size, bandwidth, frequency operation, gain, etc.

Author Response

Please see the attached response letter for all details.

Author Response File: Author Response.docx

Reviewer 2 Report

1-The importance of Febry Perot Cavity antennas and their desired features of a simple feed mechanism compared to usually complex feeding in array antennas are masterfully explained in the Introduction. While I give credit to the authors for this aspect, the literature review in terms of PRS (i.e superstructure) is poor and does not review the state-of-the art of FPC antennas. This aspect certainly needs a serious revision. It needs to be explained that superstructure (PRS) can also be made of all-dielectric materials as explained in A methodology to design a low-profile composite-dielectric phase-correcting structure, and also in A high-gain wideband ebg resonator antenna for 60 GHz unlicenced frequency band. The PRS can also be a combination of all-dielectric and all-metal surfaces as explained in  Low-cost nonuniform metallic lattice for rectifying aperture near-field of electromagnetic bandgap resonator antennas. The current explanation in the introduction leaves the impression as if only printed PRS is possible, which is not correct. Plesae consider other types of PRS (i.e all-dielectric and all-dilectric+all-metal) in the introduction

2- argument about improving SLL is not clear. Please explain how the proposed PRS can improve the SLL?

3-What will happen to SLL for different angles when scanning?

4-Different design methodologies in relation to the PRS and AMC design need to be discussed. For example, one approach is using paricle swarm optimization to determin the sizes of the printed patches in AMC as explained in Design of an artificial magnetic conductor surface using an evolutionary algorithm.

A similar approach can be used for PRS design, as explained in Directivity improvement of a Fabry-Perot cavity antenna by enhancing near field characteristic ; However in the PRS design, there are multiple printed surfaces, as opposed to the AMC.

5-Another design approach of PRS is based on low-cost 3D printing technology as explained in Additively manufactured perforated superstrate to improve directive radiation characteristics of electromagnetic source. Another good example is discussed in 3-D-printed phase-rectifying transparent superstrate for the resonant-cavity antenna. These new design approaches, i.e.3D printing and Particle swarm optimization based approaches, also need to be included.

6-Maybe the title could be amended slightly. There are no results (simulated or measured data) about the scanning capability in the paper. I acknowledge that the presented approach can be used for scanning, but it needs additional designs and components

7-In relation to the beam scanning technique, I think the method proposed by the authors is interesting; however, more FPC with bean scanning capabilities should be included in the paper. One of publicised approaches for radiation patterns manipulation is near-field transformation, as explained in All-metal wideband metasurface for near-field transformation of medium-to-high gain electromagnetic sources. Another good example can be found in: Beam-scanning antenna based on near-electric field phase transformation and refraction of electromagnetic wave through dielectric structures. In this approach a superstructure is designed to produce a progressive phase delay achieved by unitcell design.

8-The authors have used a patch antenna as the primary source of the FPC, please mention in the paper that other feeds also can be used as the primary feed, such as slot antennas and add some references in this regard. Here one reference is recommended

• “Single-dielectric Wideband Partially Reflecting Surface with Variable Reflection Components for Realization of a Compact High-gain Resonant Cavity Antenna”, IEEE Transactions On Antennas And Propagation 67 (3), 1916 – 1921.

• “Wideband gain enhancement of slot antenna using superstructure with optimised axial permittivity variation”, Electronics Letters, 2016 - Wiley Online Library

9-Please add 2D radiation patterns at both E and H planes and comment on the results accordingly, Such as beamwidth, SLL etc

Author Response

Please see the attached response letter for all details.

Author Response File: Author Response.docx

Reviewer 3 Report

An interesting work on “Novel Beam Scan Method of Fabry-Perot cavity (FPC) Antennas” has been presented, where a passive PRS is used with active AMC to avoid biasing lines in the FP cavity resonance region. Beam tilt up to 30 deg has been reported. The paper is well presented, however following comments will be useful to further improve it.

• The literature review may be expended by adding more references to provide in-depth background and highlight previous works.
• Add the feed location values for the patch in figure 5.
• Add details on unit cell size, how variation in parameter “a” is linked to the performance of unit cell. Include a graph showing relation between unit cell patch size and performance or response will be good.
• The design details for PRS need to be in details i.e. dimensions diagram may be added.

Author Response

Please see the attached response letter for all details.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The modified version has been significantly improved compared to the previous version by adding the measurement prototype, comparing the proposed design with other related works and presenting the results in a better way.

Although some materials have been added to the introduction section, the reviewer still believes that this section needs further improvements and such a comprehensive literature review of the research problem. 

Author Response

Please see the attached response letter for all details.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper has significantly improved, and most of the concerns are adequately addressed.  There are Just a few minor corrections/additions required.

In response to the authors’ action on comment 1: The authors has removed the ambiguity to some extent. However, there is still no information and references on all-dielectric PRSs. Please also mention in the paper that the PRS can be made of all-dielectric materials as explained in A high-gain wideband EBG resonator antenna for 60 GHz unlicenced frequency band. There are several other examples in the literature such as A methodology to design a low-profile composite-dielectric phase-correcting structure.

In response to the authors action on comment 4. While the PRS has been explained in both design level and literature Artificial Magnetic Conductors (AMCs) plays an important role in this work and needs to be discussed further. Please briefly mention the different design approaches of AMC. One example is Design of an artificial magnetic conductor surface using an evolutionary algorithm.

Author Response

Please see the attached response letter for all details.

Author Response File: Author Response.docx