Fast Wide-Band RCS Analysis of the Coated Target Based on PBR Using EFIE-PMCHWT and the Chebyshev Approximation Technique

Round 1

Reviewer 1 Report

The authors proposed a hybrid  EFIE-PMCHWT to calculate the wide-band radar cross section fast and efficiently. The results are interesting; however, the paper lacks a lucid presentation. 

It needs a thorough revision. Grammar is incorrect in many sentences. 

The authors show that the results for the proposed method is better with increasing order. Please expand further on this. In depth analysis on the effect of order on accuracy should be provided.

Fig. 15 shows abrupt jumps in RCS for order 1. Why? 

The proposed method should be compared with other state of the art methods and the comparision table shoudl be presented.

The reasons for choosing the three examples should be provided.

What are the caveats for using this method? Where does the method fail? Please provide couple of sentences. 

 

 

Author Response

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Reviewer 2 Report

In this paper it is tried to propose an effective hybrid method to solve the wide-band EM scattering of the coated target (estimating the RCS) based on the non-cooperative illuminator. It is based on a combination of Chebyshev Approximation Technique (CAT) with the electric-field integral equation (EFIE) and the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT). The comparison of the proposed EFIE-PMCHWT-CAT_L=i and EFIE-PMCHWT in Table 1, shows a good advance in computational cost (CPU run time).

The method is based on analytical approach. The importance of the problem for the researches in this area is moderately high. The structure of the paper and problem is well-defined. The language of the manuscript is fluent. Also, the references are up to date and suitable.

In my point of view, the manuscript can be published in its current version.

Author Response

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Reviewer 3 Report

The authors apply the method of  Chebyshev Approximation Technique  (CAT) and EFIE to arbitrarily shaped 3D-coated targets. Besides, they used the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) method for reducing computational costs. Finally, several numerical results are presented to validate the method and to show the numerical property of the presented method. The manuscript is interesting and the results are novel. However, there are some issues in the paper that should be addressed before publication.

1-The authors hybridized between CAT and EFIE. The hybridization between CAT and EFIE is also put forward in the following paper :

Wang, Xing, Haoxuan Gong, Shuai Zhang, Ying Liu, Ruipeng Yang, and Chunheng Liu. "Efficient RCS computation over a broad frequency band using subdomain MoM and chebyshev approximation technique." IEEE Access 8 (2020): 33522-33531.

What are the differences between this work and the mentioned paper? What are the limitations of the previous work and what are the advantages of this work?

2 -The convergence of the solution is absolutely important to determine the efficiency of the method. In Table 1 for PMCHWT-CAT the authors varied Chebyshev polynomial expansion order  “L” for three different values without any proof. Based on Eqs. (27) the authors should show the convergence of the proposed method by increasing the parameter "L" for the series with a Numerical Error Processing such as Least Square Method (LSM) in a graphical form. The convergence is the possibility of minimization of the error, in some norms. Close inspection shows that, in the publications devoted to numerical methods, it is common to present such plots of error in the logarithmic scale - then the eye is able to see, whether is the convergence present or not. I strongly encourage the authors to carefully read section 3 “Error estimation and validation" and essentially Eq. (45) of the following paper. DOI:”https://doi.org/10.1016/j.enganabound.2020.11.004” and see Fig. 2 of the mentioned paper for using the LSM method to find the proper truncation number “L”.

3- Similar to the previous question, please explain more about how did you find the exact values of N_d and N_c in Eqs (12)-(14)? These numbers are very important for the convergence of Eq. (15).

4. The numerical examples to validate the method are not enough. The authors only compared the results of their method with itself. The results should also be validated by other convinced methods (e.g., FEM, FDTD, MoM). If the authors can plot the results of some other methods, the results should be compared since the ability of the method for solving some problems is the main advantage of the proposed method.

5- There is no need for Figs 8, 12, and 16. Because the data inside them are obvious in Figs 7, 11, and 15.

6-Would you please explain the extraordinary leaps in Fig.15 for L=1?

7-It would be nice if the authors can further compare the numerical property (the accuracy, the memory cost, the CPU time) of other methods (such as FEM, and FDTD) with their method to show the capability of the proposed method.

8-Please note that the sequence of references should be observed. Ref [10] has been called before Ref [9].

9-In line 136 using a cross instead of a star may be better to show the order of the matrix.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors exactly answered all of my questions.