Z-Transform-Based FDTD Implementations of Biaxial Anisotropy for Radar Target Scattering Problems

Round 1

Reviewer 1 Report

After revision, the manuscript has been much improved. I have one more comment here: Bx^(n+1/2) on the right side of Eq. (16) should be changed to Bx^(n-1/2). Please confirm.

Author Response

Dear Reviewer,

    Thanks a lot for your constructive comment, and please see the attachment. Wish you all the best.

Best regards,
N. Feng

Author Response File: Author Response.doc

Reviewer 2 Report

Now I recommend that this paper will be accepted.

 

Author Response

Dear Reviewer,

    Thanks a lot for your constructive comment, and please see the attachment. Wish you all the best.

Best regards,
N. Feng

Author Response File: Author Response.doc

Reviewer 3 Report

The main contribution of the paper is to apply Z-transform based FDTD for biaxial anisotropy and use CFS-PML for domain truncation. Numerical examples are provided and verified that the formulation is effective. I think that the authors have carefully addressed most of the reviewers’ concerns, the paper has been improved a lot and is acceptable. However, I suggest the authors to check again the following two issues that had been raised by the reviewers.

1. (Concerning the answer to Comment 2 of Reviewer 1). I have read the paper (Ref.[11]). Judging from the formulation (like eq.(1), eq.(14)…, in [11]) and examples in the paper, I almost sure that Ref.[11] has really considered bi-anisotropic materials.
2. (Concerning the answer to Comment3 of Reviewer 2). Although I think it can show the effectiveness by comparing the numerical results with COMSOL simulation results, it is perhaps more convincing to compare the proposed formulation with conventional FDTD algorithm (not FDTD software) on the same or similar grid to show the advantages in efficiency, accuracy, etc, as there exist BA-FDTD for bi-anisotropic materials, and Bi-FDTD for bi-isotropic materials.

Author Response

Dear Reviewer,

    Thanks a lot for your constructive comment, and please see the attachment. Wish you all the best.

Best regards,
N. Feng

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

All my concerns have been addressed by the authors.

Reviewer 3 Report

I think my concerns have been properly addressed.

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

The manuscript presents a Z-transform based FDTD for biaxial anisotropy modeling with CFS-PML. some concerns are shown below.

1. The introduction part needs to be improved to make it more concise. The current way the authors present it is more like a technical report, which shows lots of redundant descriptions.
2. The statement that the Z-transform technique has not been discussed for anisotropic problems is not accurate. e.g., the reference [11] shows Z-transform applied to dispersive bianisotropic media. The main novelty shown in this manuscript seems to be combining CFS-PML with anisotropy for Z-FDTD.
3. I suggest including some discussion in the introduction about the advantage of Z-FDTD over standard FDTD for anisotropy modeling. Because Z-FDTD is originally for dispersion modeling, and anisotropy can be tackled by standard FDTD already without adding too much complexity. 
4. Eqs. (15) and (16) seem to be missing dt on the right-hand side. B^(n+1/2) on the right of Eq. (16) should be changed to B^(n-1/2). Please confirm. 
5. For the CFS-PML formulation part, seems the authors still follow the convolution idea for implementation. Why not use the Z-transform instead?
6. Please change the comma to period for some equations, e.g., Eqs. (23) and (26).
7. For the single brick example, the magnetic conductivity is set to diag(3000, 9000, 1000). Is this some material realistic? Any reference?
8. In the conclusion, " we discuss the relation between the time- or frequency-domain derivative operator and the Z-domain operator,...". I think this is belonging to common knowledge, and it is not appropriate to talk about it in the conclusion.

 

Reviewer 2 Report

The authors developed the novel algorithm of the FDTD method, particularly based on Z-transform. The structure was not bad, but it is difficult to find the originality. Here are some comments on it.

1) Please clarify the new proposal and originality of the article.
1) Comparison with COMSOL was shown. Please also mention what kind of method was used in COMSOL.
2) To clarify the effectiveness of the proposed method, compare it with conventional FDTD software simply. 
3) In Figure 6 and 9, errors were found in the local minima. Please mention it and provide an interpretation.

 

Reviewer 3 Report

This manuscript implemented the Z-transform FDTD along with CFS-PML for simulating the electromagnetic (EM) scattering for a “brick” in biaxial anisotropic media. As a reviewer I have the following comments/suggestions regarding this manuscript.

1. The following questions should be clearly answered or stressed: (1) what is the motivation of this work, or what is the problem the authors tried to solve? (2) what is the typical application scenario of this work? (3) what improvements have been achieved regarding to the Z-transform FDTD and CFS-PML technique?
2. In fact, I think if just implemented the Z-transform FDTD along with CFS-PML boundary condition for simulating the EM scattering by a simple “brick” (I guess it is a metal brick) in biaxial anisotropic media, it is not enough for an article without analyzing what special problems should be treated, what special phenomenon has been observed, and what important conclusions have been made.
3. As for the simulations, the incoming EM waves as well as the coordinates should be depicted in Fig. 4 and Fig.7.
4. Original references for CFS-PML should not be neglected and on the contrary, them must be referenced and cited in both Introduction and in the text where it is implemented.
5. Is the Equation (16) correct? Equations (19), (21) and (24) are questionable.
6. Line 35, “…researchers who put their heart and soul into improving …” is not appropriate for scientific article.
7. The use of “Fully-parametered” is not suggested.