Postwall-Slotline Stepped Impedance Resonator and Its Application to Bandpass Filter with Improved Upper Stopband

Round 1

Reviewer 1 Report

This paper proposes a novel postwall-slotline stepped impedance resonators (PWS-SIR). The proposed resonator is applied to a bandpass filter (BPF) to achieve a wide stopband. The manuscript can be accepted with minor revision. The reviewer feels that the authors should provide the following mandatory revisions.

• The introduction section is short and it needs to be revised with adequate study of related works.
• The authors are requested to provide a frequency response simulation of the proposed U-shaped PWS resonator, and show the position of the first spurious resonance frequency of the PWS-SIR.
• The equation (4) seems to be incorrect, and it is equal to 4.71.
• The table of comparison need to be improve. It will be good to compare the proposed filter with newer reported woks.

Author Response

Thanks very much for taking your precious time to review this manuscript. Figures could not be uploaded in this textbox, the complete response is provided as an attached file.

This paper proposes a novel postwall-slotline stepped impedance resonators (PWS-SIR). The proposed resonator is applied to a bandpass filter (BPF) to achieve a wide stopband. The manuscript can be accepted with minor revision. The reviewer feels that the authors should provide the following mandatory revisions.

Thanks very much for taking your precious time to review this manuscript. We really appreciate all of the comments, suggestions and encouragements, which enable us to improve our work significantly.

 

The introduction section is short and it needs to be revised with adequate study of related works.

Thank you for the kindly reminder and constructive suggestion. The introduction has been totally revised, and key information has been added into the revised manuscript, and all the revisions have been highlighted with red color.

 

The authors are requested to provide a frequency response simulation of the proposed U-shaped PWS resonator, and show the position of the first spurious resonance frequency of the PWS-SIR.

Thank you for the kindly reminder and constructive suggestion. We have simulated a frequency response of a filter with the proposed U-shaped PWS resonator, as shown in Fig. R1. The simulation shows that the position of the first spurious resonance frequency is at 2f₀, and it is the same as what the theory predicts. The Fig. 5 in the manuscript shows that the position of the first spurious resonance frequency of the filter with PWS-SIRs is at 4.7f₀. Therefore, PWS-SIR could expand the upper stopband of a PBF.

We also simulated the resonant frequencies of a U-shaped PWS resonator and a PWS-SIR, and the results are shown in the Table R1. It shows that the resonant frequency of the first high-order mode in a PWS-SIR is much higher than a U-shaped PWS resonator, even the resonant frequencies of their fundamental modes are almost the same.

 

 

 

Fig. R1 Simulated frequency response of U-shaped PWS BPF

 

Table R1

	Fundamental mode resonate frequency/GHz	First high-order mode resonance frequency/GHz
U-shaped PWS resonator	4.89	10.12
PWS-SIR	5.10	20.63

 

 

 

The equation (4) seems to be incorrect, and it is equal to 4.71.

Thank you for the kindly reminder and constructive suggestion. We have made certain mistakes which lead to some confusions. In fact, the equation (4) is equal to 3.66 rather than 4.71. For a better matching, the sizes of the first PWS-SIR in the proposed filter have been changed from their original sizes. Therefore, the resonant characteristics of the first PWS-SIR and the coupling coefficient between it and its neighboring PWS-SIR have also change. According, the propose PWS-SIR filter has the first upper stopband at 4.71f₀ rather than 3.66f₀

 

The table of comparison need to be improve. It will be good to compare the proposed filter with newer reported woks.

Thank you for the kindly reminder and constructive suggestion. Some new reported works have been added the table. For a clear comparison, the structure features of the filters have also added in the table, and some microstrip based filters have been replaced with conventional slotline SIR filters. In addition, the explanation to the table has been also revised.

Author Response File: Author Response.docx

Reviewer 2 Report

The present paper proposes postwall-slotline stepped impedance resonators. The work is very interesting but it requires improvements before publication. First the introduction is very short. At least, the scientific problem should be clearly stated and more relevant literature should be added to explain the problem. What kind of research questions you tried to investigate in this work? The scope of this work is not available in the introduction and conclusion.  Further, some symbols introduced in the manuscript are not clear and even some are not explained. Also, your conclusion is very short. It is not telling that how will your work could make the scientific and industrial society better. Readers may find hard time to study your work. Therefor, I will strongly recommend you to improve the manuscripts according to the comments provided in the attached .pdf.

 

Comments for author File: Comments.pdf

Author Response

Thanks very much for taking your precious time to review this manuscript. The complete response is provided as an attached file.

The present paper proposes postwall-slotline stepped impedance resonators. The work is very interesting but it requires improvements before publication. First the introduction is very short. At least, the scientific problem should be clearly stated and more relevant literature should be added to explain the problem. What kind of research questions you tried to investigate in this work? The scope of this work is not available in the introduction and conclusion.  Further, some symbols introduced in the manuscript are not clear and even some are not explained. Also, your conclusion is very short. It is not telling that how will your work could make the scientific and industrial society better. Readers may find hard time to study your work. Therefore, I will strongly recommend you to improve the manuscripts according to the comments provided in the attached .pdf.

Thanks very much for taking your precious time to review this manuscript. We really appreciate all of the comments, suggestions and encouragements, which enable us to improve our work significantly.

The problem addressed in the manuscript is to develop a slotline SIR with a low impedance ratio to achieve a slot-line filter with a wide upper stopband. Accordingly, the introduction and the conclusion have been fully revised. More features of the proposed filter have been included in the conclusion in the revised manuscript. In addition, the Table 2 has been revised, and some new reported works have been added the Table 2. For a clear comparison, the structure features of the filters have also added in the Table 2, and the explanation to the Table 2 has been also revised. 

The manuscript has been revised based on the pdf provided by you.

Key information has been added into the revised manuscript, and all the revisions have been highlighted with red color.

Reviewer 3 Report

In this letter, a postwall-slotline stepped impedance resonators (PWS-SIR) is proposed and applied to a bandpass filter (BPF) with a wide stopband. However, I have some problems, as following:

1. The title is “..Bandpass Filter with Improved Upper Stopband”. However, some filters have wider stopband. The author should give some explain on the table.
2.  How to control the TZ.

Author Response

Thanks very much for taking your precious time to review this manuscript. The complete response is provided as an attached file.

In this letter, a postwall-slotline stepped impedance resonators (PWS-SIR) is proposed and applied to a bandpass filter (BPF) with a wide stopband. However, I have some problems, as following:

Thanks very much for taking your precious time to review this manuscript. We really appreciate all of the comments, suggestions and encouragements, which enable us to improve our work significantly.

 

The title is “..Bandpass Filter with Improved Upper Stopband”. However, some filters have wider stopband. The author should give some explain on the table.

Thank you for the kindly reminder and constructive suggestion. Due to different structure features, an SIR based on microstrip lines could achieve much lower impedance ratio than an SIR based on slotlines. Therefore, as Reviewer said, the stopband performance of a slotline SIR filter is usually worse than that a microstrip SIR filter. Filters have diverse types of structures, and each type of filter has certain application scenarios. It is better to compare performances among the filters with the same or the similar structures. Therefore, according to Reviewer’s suggestion, the Table 2 has been revised, and some new reported works have been added the Table 2. For a clear comparison, the structure features of the filters have also added in the Table 2, and some microstrip based filters have been replaced with conventional slotline SIR filters. In addition, the explanation to the Table 2 has been also revised.

 

How to control the TZ.

Thank you for the kindly reminder and constructive suggestion. The proposed filter is a direct coupling BPF without cross couplings and transmission zero points. Therefore, the TZ cannot be controlled.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

This version of manuscript looks better in quality. I do not have further any concern on this version of manuscript.