Design of a Wideband Loaded Sleeve Monopole Embedded with Filtering High–Low Impedance Structure

Round 1

Reviewer 1 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

I have no comments.

Author Response

Thank you for your review.

Reviewer 2 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

Thanks for your revision based on my comments. I still have some questions:

1) Authors did not reply to my comments 1 and 2 clearly. No enough comparison plots can be seen in the paper. Please reply them.

2) For comment 5, please provide the curves of the gain variations with different angle changes on the horizontal plane. This should be compared with measurement results.

 

 

Comments on the Quality of English Language

The English quality is better now. However, authors should recheck the parts they added with highlighting. 

Author Response

Comments 1: Authors did not reply to my comments 1 and 2 clearly. No enough comparison plots can be seen in the paper. Please reply them.

Response 1: Thank you for your comment. The comparisons of radiation efficiency among the ordinary monopole, the c ordinary sleeve monopole, and the presented loaded sleeve monopole are provided in Fig. 10. Similarly, Fig. 11 presents a comparison of their VSWR performance. This paper focuses on the development of a compact monopole design that integrates both wideband and filtering functionalities. The design strategy begins with the incorporation of an embedded filtering structure, followed by the addition of loads on the upper radiator to enhance the radiation bandwidth. The resulting wideband and filtering characteristics of the presented monopole superior to the two ordinary monopoles are summarized in Fig. 15.

 

 

 

Comments 2: For comment 5, please provide the curves of the gain variations with different angle changes on the horizontal plane. This should be compared with measurement results.

Response 2: Thank you for your comment. The presented monopole exhibits cylindrical symmetry about the z-axis. Therefore, the radiation and filtering characteristics in the concerned frequency band are consistent at all azimuthal angles on the horizontal plane, as reflected by the gain shown in Fig. 15. The H-plane radiation patterns at representative frequencies within the radiation band are depicted in Fig. 9, illustrating the angular variation of gain across the horizontal plane.

 

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

electronics-3774635, review report

Authors presented a design of a wideband monopole with an integrated low-pass filter. They presented the structure, design, simulation and measurement of the proposed antenna. My comments are as follows.

1. '2.2 Design of filtering structure'

1) Figure 3 shows an equivalent circuit of the designed filter. Please specify the source and load impedances. For the load impedance, it is the monpole's input impedance seen at the top of the sleeve, which should change 200-1500 MHz so a simplifying assumption might have been used.

2) Please explain the underlying physical principles of the inductor and the capacitor need to be clarified. As an analogy, in a microstrip circuit, a thin line and a ground plane form an inductor. For the proposed LC filter structure shown in Figures 2 and 4, please explain the physical principles of the inductor and the capacitor. Does the sleeve (made of metal) work as a ground plane or one of the two electrodes for the inductor and the capacitor. The proposed filter appears to be a type of a coaxial filter similar to the design by D4DBN ('Coaxial Low-Pass Filter for 23 cm'; https://www.g4dbn.uk/?p=517).

3) Please explain how to obtain the physical dimensions from the filter circuit of Figure 3. Are design formulas available?

4) Please explain whether the inductance and capacitance of the structure in Figure 5 remain as a constant value specified in Figure 3 over such a wide frequency ranges as 200-1500 MHz.

2. '2.3 Wide band filtering monopole'

1) The subsection title is likely to mislead readers. Does the loading the monopole with a RLC circuit at three locations do filtering? The word 'filtering' seems unnecessary. Please check.

2) Please add the operating principles of the widebanding of a monopole with RLC circuits.

3) Lines 216-218: ”The positions of the loads and the values of the components in each load 216 are optimized to achieve the desired electrical performance. The optimized parameters of the loads are summarized in Table 1, with the load positions measured from the ground."

I understand that the rigorous design theory is difficult to formulate. Please consider adding the design theory at least in a qualitative way possibly with the design result in Table 1.

3. Figure 11

Please add VSWR of the other two monopoles of Figure 1.

4. Figures 13a, 14, and 15:

It appears that you have used an infinite ground plane judging from the radiation patterns in Figure 8. Figure 13a shows a ground plane whose radius is about two times the monopole height. Please add some comments on the effect of finite ground plane on the surface of the earth in relation to the infinite ground plane model of the simulation regarding measured VSWR (Figure 14) and gain (Figure 15).

5. Figure 15:

The gain pattern of the ordinary monopole and the ordinary sleeve monopole can be omitted since their measured values are not present and they are already given in Figure 7.

6. Table 2:

Antenna size in terms of the wavelength is one of important performance metrics. Place add monopole length normalized by the wavelength at the lowest operating frequency.

Author Response

1. '2.2 Design of filtering structure'

Comments 1: Figure 3 shows an equivalent circuit of the designed filter. Please specify the source and load impedances. For the load impedance, it is the monpole's input impedance seen at the top of the sleeve, which should change 200-1500 MHz so a simplifying assumption might have been used.

Response 1: Thank you for your comment. The source and load impedances are all 50 Ω, as indicated in Figure 3. The inner structure of the sleeve is designed as a 50 Ω transmission line. The replacement of the inner conductor with the presented filtering structure serves solely to introduce a filtering function into the sleeve monopole. The loads at the upper radiator are subsequently optimized to ensure acceptable radiation performance within the desired frequency band.

 

Comments 2: Please explain the underlying physical principles of the inductor and the capacitor need to be clarified. As an analogy, in a microstrip circuit, a thin line and a ground plane form an inductor. For the proposed LC filter structure shown in Figures 2 and 4, please explain the physical principles of the inductor and the capacitor. Does the sleeve (made of metal) work as a ground plane or one of the two electrodes for the inductor and the capacitor. The proposed filter appears to be a type of a coaxial filter similar to the design by D4DBN ('Coaxial Low-Pass Filter for 23 cm'; https://www.g4dbn.uk/?p=517).

Response 2: Thank you for your comment. Additional explanations have been supplemented in the revised paper and are highlighted on lines 120–121 and 122–123 of page 3. The inner side of the sleeve acts as the ground for the filtering structure. The presented filtering structure operates similarly to the device shown in the reference link you provided but is implemented in a sleeve form here to achieve a compact filtering monopole design.

 

Comments 3: Please explain how to obtain the physical dimensions from the filter circuit of Figure 3. Are design formulas available?

Response 3: Thank you for your question. In practical engineering applications, the physical dimensions of this structure can be conveniently determined using commercial microwave circuit design software such as ADS. The underlying theory is based on Richards’s transformation, as mentioned on line 199 of page 6.

 

Comments 4: Please explain whether the inductance and capacitance of the structure in Figure 5 remain as a constant value specified in Figure 3 over such a wide frequency ranges as 200-1500 MHz.

Response 4: Thank you for your question. In the presented design, the lump element is optimized by constant value across this 7.5:1 relative bandwidth. This 7.5:1 relative bandwidth is wide comparing with tens of percent relative bandwidth, but still less than thousands of percent relative bandwidth where frequency-dependent behavior of the components would become more pronounced. In the presented design, constant model for load element is still acceptable.

 

 

 

1. '2.3 Wide band filtering monopole'

Comments 1: The subsection title is likely to mislead readers. Does the loading the monopole with a RLC circuit at three locations do filtering? The word 'filtering' seems unnecessary. Please check.

Response 1: Thank you for your question and advice. We have deleted the word filtering.

 

Comments 2: Please add the operating principles of the widebanding of a monopole with RLC circuits.

Response 2: Thank you for your comment. The RLC circuits create a trap effect, effectively isolating the upper portion of the monopole from the lower portion. This results in a shorter effective electrical length at higher frequencies, allowing the loaded monopole to maintain stable omnidirectional radiation over a wide frequency range. These mechanisms are discussed in detail on lines 135–140 of page 4.

 

Comments 3: Lines 216-218: “The positions of the loads and the values of the components in each load 216 are optimized to achieve the desired electrical performance. The optimized parameters of the loads are summarized in Table 1, with the load positions measured from the ground."

I understand that the rigorous design theory is difficult to formulate. Please consider adding the design theory at least in a qualitative way possibly with the design result in Table 1.

Response 3: Thank you for your comment. Due to the unavoidable mutual coupling between each radiating segment separated by the respective loads, complete isolation between the upper and lower radiators is not achievable. As a result, it is difficult to determine the optimal positions and load values analytically. Therefore, an optimization-based design approach is adopted as a more practical and effective strategy.

 

 

 

1. Figure 11

Comments 1: Please add VSWR of the other two monopoles of Figure 1.

Response 1: Thank you for your comment. The VSWR of the other two monopoles have been provide in figure 11.

 

 

 

1. Figures 13a, 14, and 15:

Comments 1: It appears that you have used an infinite ground plane judging from the radiation patterns in Figure 8. Figure 13a shows a ground plane whose radius is about two times the monopole height. Please add some comments on the effect of finite ground plane on the surface of the earth in relation to the infinite ground plane model of the simulation regarding measured VSWR (Figure 14) and gain (Figure 15).

Response 1: Thank you for your comment. For terrestrial wireless communication, the ground plane is part of radiation system. So, in contrast to free space simulation, an infinite ground is adopted in simulation. To accommodate with simulation, the presented monopole is test in outdoor half plane environment, not anechoic chamber for realize approximate free space environment. In the presented test environment in figure 13, a circle metal plane is place below the fabricated monopole, providing a good connect to ground in near field. The grass plane in the test environment is flat between transmitting and receiving antennas, providing acceptable half plane for experiment. These discussions have been added in the revised paper and is highlighted on lines 251 to 256 of page 9.

 

 

 

1. Figure 15:

Comments 1: The gain pattern of the ordinary monopole and the ordinary sleeve monopole can be omitted since their measured values are not present and they are already given in Figure 7.

Response 1: Thank you for your comment. Figure 15 confirms that the proposed monopole exhibits the desired radiation characteristics. To further demonstrate the filtering performance, we think that comparing the gain patterns of the ordinary monopole and the ordinary sleeve monopole provides a clearer illustration of the achieved filtering functionality.

 

 

 

1. Table 2:

Comments 1: Antenna size in terms of the wavelength is one of important performance metrics. Place add monopole length normalized by the wavelength at the lowest operating frequency.

Response 1: Thank you for your comment. The electrical length of each monopole has been added in table 2.

 

Round 2

Reviewer 2 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

Thanks for your revision.

I know that it is not easy to do pattern measurements on fields. Have you checked the radiations at some angles? As I mentioned, it is important to show the gain variations along angles.

 

Author Response

Comments 1: I know that it is not easy to do pattern measurements on fields. Have you checked the radiations at some angles? As I mentioned, it is important to show the gain variations along angles.

Response 1: Thank you for your comment. The structure of the presented monopole is cylindrical symmetry about the z-axis. And in the test, transmitting antenna and the presented monopole are place on flat plane. For terrestrial wireless omnidirectional communication, the test gain in figure 15 typically represents gain of monopole in azimuthal plane.

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

Comments and Suggestions for Authors

The paper is poorly prepared.

Firstly, the writing must be significantly improved. Many grammar mistakes exist in the paper:

1. line 8 page 1, a capital A is used after the comma.
2. line 8 page 1, "applying in" should be deleted.
3. line 22 page1, the authors states "the development of demand ... puts forward...".  How could the demand be developed? 
4. line 42 page 1, what does "it is eager to resolve" mean? 
5. line 49 page 2, what is an "appendix radiation structure"? Can the author check the meaning of appendix with a dictionary?
6. line 51 to 52, the subject of the sentence is "numbers", which lead to a strange sentence "numbers play a role" if other unimportant parts are omitted. What does that mean?
7. The authors use too many "the" in their writing. For example, in line 60, 61, and 63, what are "the filter", "the antenna", " the transmission line"?  
8. The above issues are only a small portion of the problem. Please use a language polishing service to improve the quality.

There are many other similar grammar related issues. They make reading the paper a painful job. 

 Secondly, the authors claim the antenna has a bandwidth ranging from 200 MHz to 1500 MHz with its VSWR smaller than 2.5. However, the curves shown in Fig. 15 suggest that the VSWR is larger than 2.5 in several portions of the frequency band. 

Thirdly, the paper presents the results of the antenna but does not explain the mechanism of the parallel circuit loadings, the high-low impedance transmission line section, and the sleeve. It is better to let the readers know what their functions are, how they work, etc. 

Reviewer 2 Report

Comments and Suggestions for Authors

The is paper present a wideband and filtering monopole is presented for applying in 8 remote terrestrial omnidirectional communication systems, there are some questions should be clarified.

1. In the abstract part, “A wideband ---”, the “A” should be a lowercase “a”.
2. In Section 2.3, how the loading sleeve antenna can broaden the bandwidth is not introduced in detail, please supplement some related principles and design process.
3. In Section 4, the comparative analysis is not enough, and there are few comparative articles in recent years, please supplement the discussion of comparative analysis and highlight the advantages of the proposed design.
4. In the caption of the Figures, some words should be in lowercase. Please check the whole text. Such as Figure 5 “(b) High-low”.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors present a monopole antenna with a modified structure. The loaded filtering structure can be used to get a good stop band at a high-frequency range. 

Some issues must be addressed before acceptance.

1) the proposed structure should be compared with the classical monopole and the monopole with sleeve regarding (1) impedance bandwidth, (2) radiation pattern with two cuts (E-plane and H-plane) (0-360deg. cuts, not half sphere cuts); (3) radiation efficiency; (4)  gain changes with frequencies. 

2) the evolution process of the antenna needs to be shown clearly. in every step, the comparison plots for (1) - (4) metrics in the first concern should be shown. 

3) experiment setups should be shown clearly with antenna connections to test devices.

4) How do you ensure the simulation results are so close to the measurement results? In the measurement setup, you placed the antenna on the grass yard. In simulation, how do you set the simultion enviroment?

5) gain variation along the horizontal plane should be shown clearly. 

6) How do you design the loads and the stepped lines? Please be clear.

 

 

 

Comments on the Quality of English Language

Some terms are not correct to use. Please carefully check the terminology based on some good  references.