Increasing the Accuracy Characteristics of Focused Electromagnetic Devices for Non-Destructive Testing and Technical Diagnostics by Implementing Sum–Difference Signal Processing

Round 1

Reviewer 1 Report

The results of this manuscript are acceptable. However, the contributions are not obvious. The comparison table with the existing work is suggested to add for showing the novelty.

Author Response

We thank the anonymous Reviewer for the appreciation. To address this remark, illustrative figures have been added (figure 15). The novelty of the proposed work lies in the introduction of additions to the principles of difference-type focused fields formation. In addition, the work proposes the method of sum-difference processing of signals focused in the zone of the near radiated field. We added the following statements to the text (lines 328 – 334) to clarify the novelty: “The usage of the focusing method with the joint use of spatial distributions of the sum and difference types, in comparison with the traditional cases of in-phase and focused aperture, allows to:

- improve the accuracy of determining the spatial position of a small-sized irregularity by reducing the effective size of the focused field area;

- weaken or eliminate the influence of irregularities localized near the region of the focused field.”

Reviewer 2 Report

This manuscript discussed the features of the formation of the sum and difference amplitude distributions and the principles of the sum-difference processing of focused electromagnetic fields. The topic is of interest for this journal; however, it is a simply a case study instead of a technical paper. The novelty and literature work are not discussed in the manuscript. Using focused antennas as sensors is not nothing new, what is the contribution of the proposed work in the field in unclear.

Author Response

We would like to thank the anonymous Reviewer for the comprehensive review of the paper and the valuable remarks. Please, find our replies below.

- This manuscript discussed the features of the formation of the sum and difference amplitude distributions and the principles of the sum-difference processing of focused electromagnetic fields. The topic is of interest for this journal; however, it is a simply a case study instead of a technical paper. The novelty and literature work are not discussed in the manuscript.

The novelty of the proposed work lies in the introduction of additions to the principles of difference-type focused fields formation. The work also proposes the method of sum-difference processing of signals focused in the zone of the near radiated field.

- Using focused antennas as sensors is not nothing new, what is the contribution of the proposed work in the field in unclear.

We added the following statements to the text (lines 322 – 328) to clarify the novelty: “The usage of the focusing method with the joint use of spatial distributions of the sum and difference types, in comparison with the traditional cases of in-phase and focused aperture, allows to:

- improve the accuracy of determining the spatial position of a small-sized irregularity by reducing the effective size of the focused field area;

- weaken or eliminate the influence of irregularities localized near the region of the focused field.”

Figure 15 was also added to illustrate the abovementioned statements. 

Reviewer 3 Report

This submitted manuscript deals with the features of the formation of the sum and difference amplitude distributions and related principles of the sum-difference  processing of focused electromagnetic fields with the  implementation as  technical solutions for non-destructive testing and technical diagnostic tasks. The paper has been structured well. I would ask the authors to include more references to figure out the novelty in the approach stated in the paper. Would you please give more information on the current distributions  for the resulting plots in Figures 3,4 and 5? Would you give more comments on the focusing performance for the resonant and non resonant type current distributions of  the aperture  with the same geometric size?  It is important while the target object to be non-destructively tested is located in the near field, which could deteriorate the input impedance of the detecting radiating system.  

Author Response

We would like to thank the Reviewer for appreciating the paper and the valuable remarks and suggestions.

This submitted manuscript deals with the features of the formation of the sum and difference amplitude distributions and related principles of the sum-difference processing of focused electromagnetic fields with the implementation as technical solutions for non-destructive testing and technical diagnostic tasks. The paper has been structured well. I would ask the authors to include more references to figure out the novelty in the approach stated in the paper.

The authors thank the Reviewer for the remark. The following references have been added to the work:

11. He, X., Geyi, W. and Wang, S. Optimal design of focused arrays for microwave-induced hyperthermia. IET Microw. Antennas Propag., 9. 2015, 1605-1611.
12. Bogosanovic and A. G. Williamson, "Microstrip Antenna Array With a Beam Focused in the Near-Field Zone for Application in Noncontact Microwave Industrial Inspection," in IEEE Transactions on Instrumentation and Measurement, vol. 56, no. 6, pp. 2186-2195, Dec. 2007, doi: 10.1109/TIM.2007.907954.
13. Buffi, Alice, et al. "Near field focused microstrip arrays for gate access control systems." IEEE Antennas and Propagation Society International Symposium. IEEE, 2009
14. Bogosanovich, M., et al. "A comparison of the systems for non-contact and non-destructive natural product inspection." Proc. 5th Int. Conf. ISEMA. 2003
15. He, W. Geyi and S. Wang, "A Hexagonal Focused Array for Microwave Hyperthermia: Optimal Design and Experiment," in IEEE Antennas and Wireless Propagation Letters, vol. 15, pp. 56-59, 2016, doi: 10.1109/LAWP.2015.2429596.
16. Siragusa, P. Lemaitre-Auger and S. Tedjini, "Near field focusing circular microstrip antenna array for RFID applications," 2009 IEEE Antennas and Propagation Society International Symposium, 2009, pp. 1-4, doi: 10.1109/APS.2009.5171607.

The works [11-16] describe the technical applications of focused antenna arrays. For each of them, the use of sum-difference processing of focused fields will improve their technical characteristics.

Would you please give more information on the current distributions for the resulting plots in Figures 3,4 and 5?

During we formation of the focused fields presented in Figures 3, 4 and 5, a uniform distribution of currents in a focused aperture was used. The corresponding comments have been added to the text (lines 105 – 106, 118 – 120).

Would you give more comments on the focusing performance for the resonant and non resonant type current distributions of  the aperture  with the same geometric size?

We added the following statements to the text (lines 322 – 328) to clarify this point: “The usage of the focusing method with the joint use of spatial distributions of the sum and difference types, in comparison with the traditional cases of in-phase and focused aperture, allows to:

- improve the accuracy of determining the spatial position of a small-sized irregularity by reducing the effective size of the focused field area;

- weaken or eliminate the influence of irregularities localized near the region of the focused field.”

We replaced the diagrams in Figure 14 with others for clarification.

The following has also been added to the text (lines 335 – 338): “Thus, the usage of the focused aperture principle with the formation of virtual spatial fields of a difference type makes it possible to perform a more accurate determination of irregularities and to enhance the possibility of their detection and observation in the presence of closely spaced reflecting objects.”

It is important while the target object to be non-destructively tested is located in the near field, which could deteriorate the input impedance of the detecting radiating system.

Thank you for the remark. We are talking about distances to the focusing point of the order of the size of the aperture. The influence of the object location on the input impedance is not observed in this case.

Round 2

Reviewer 2 Report

The topic is of interest for this journal; however, the revised manuscript simply added a few references, and the novelty and literature work were not thoroughly discussed in the manuscript. By evaluating the scientific merit, the proposed method has been well developed in the field. It is the reviewer’s opinion that it is not suitable for publication.

Author Response

First of all, we would like to thank the anonymous Reviewer for the precious comments that allowed us to improve the quality of the paper.

- The topic is of interest for this journal; however, the revised manuscript simply added a few references, and the novelty and literature work were not thoroughly discussed in the manuscript.

Thank you for the concern. The following information has been added to the text (lines 45-61): “A significant number of works [4-9] describe the variants of construction and the technical applications of focused antenna arrays. In the article [4], the authors propose an approach to control the parameters of focused field in problems of microwave hyperthermia. The control is carried out by antenna focused on the area of the fat-mimicking phantom that is subjected to hyperthermia. In papers [5, 6], the results of calculations of the distribution of focused fields are presented. It is shown that the side-lobe level is quite significant, which leads to a deterioration in the resolution of diagnostic industrial complexes. In the articles [7, 8], the authors consider the problems of using focused fields in radio-frequency identification of objects (RFID) and access control. The work [9] considers the hexagonal arrangement of emitters of a focused antenna array used in the problems of tumor hyperthermia.

For most technical applications based on the use of focused antenna arrays, such as those described in [4-9], the using of sum and difference type focused fields can improve their technical characteristics. Therefore, the improvement of methods for the formation of focused electromagnetic fields for their use in non-destructive testing and technical diagnostics tasks is an urgent task. This article focuses on the usage of sum-difference signal processing methods.”

Also, lines 378 – 382: “We are confident that generalization of methods for the formation of difference distributions focused at the near radiated field zone onto flat focused antenna arrays and the usage of sum-difference processing will improve the efficiency of non-destructive testing and medical systems. The produced method is innovative. At the moment, we are making efforts to expand the potential of the application of focused fields.”

Thus, the novelty of the proposed article lies in the fact that the formation of two types of differential focusing at the near radiated field zone (parallel and perpendicular to the linear antenna array) and the use of sum-difference processing of electromagnetic fields focused at the near radiated field zone in the tasks of improving the quality of technical diagnostics was first proposed by us.

For the Reviewer’s convenience, basic information about existing publications and the novelty of the proposed materials in the subject area under consideration is given in the table (see the attached file).

- By evaluating the scientific merit, the proposed method has been well developed in the field.

The early works, which consider the use in radar of antennas with antenna far-field pattern of sum and difference type as well as their construction, are the following:

• Dunn J.H. Precision tracking with monopulse radar ''Electronics'' 1960 vol.33 №17 p.51-57),
• Hannan R.W. I Optimum feed for all three modes of monopulse antenna IEE Trans. 1961, AP-9 p.  444-460.

Eventually, it became classic and was included in the textbooks. Both the formation of sum and difference type in the near radiated field zone, and their usage is not found in the known literature. Therefore, in the current manuscript, this has been proposed for the first time. So, the possibility of improving the efficiency of echolocation sensor systems in the near zone of the emitted field with a difference type of focused fields has not previously been considered by other authors.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

It can be considered for acceptance.