Miniaturized Microstrip Dual-Channel Diplexer Based on Modified Meander Line Resonators for Wireless and Computer Communication Technologies

Round 1

Reviewer 1 Report

The paper uses two meandered line resonator to miniaturize the diplexer. However, the design method is not clearly described. Meanwhile, the performances of the diplexer are not good.

 1.     The simulated and measured return losses of the dual-channel in Figure 12 related to S11 did not reach 31.6/29.2 dB as shown in Table 3. Please check the results.

2.     In Part 3 Line 192, the characteristic impedance Z0 should in the same format as that in equation (1). The variables in Figure 2 and Figure 3 should keep as the same format as those in the text.

3.     The format should be checked, such as Line 253 and Line 254, the format of the equations. Two equations are labeled as (4).

4.     In Table 1, the frequency response has been described to choose Chebyshev prototype. However, the parameters of the resonator related to the values of the Chebyshev prototype are not shown in the paper.

5.     From the structure of the diplexer, it uses two meandered stepped impedance resonators, which do not have stubs at the middle part. What is the purpose of introducing the resonator in Figure 4 and the related equations?

6.     How to determine the parameters of the meandered resonators?

7.     What is the reason for producing negative group delay? The measured group delay should be shown.

Author Response

Response to Reviewers

Reviewer 1

The paper uses two meandered line resonator to miniaturize the diplexer. However, the design method is not clearly described. Meanwhile, the performances of the diplexer are not good.

1. The simulated and measured return losses of the dual-channel in Figure 12 related to S11 did not reach 31.6/29.2 dB as shown in Table 3. Please check the results.

@@@Author Reply: Thanks for your precious comments and notices .Corrected

2. In Part 3 Line 192, the characteristic impedance Z0 should in the same format as that in equation (1). The variables in Figure 2 and Figure 3 should keep as the same format as those in the text.

@@@Author Reply: Corrected

3. The format should be checked, such as Line 253 and Line 254, the format of the equations. Two equations are labeled as (4).

@@@Author Reply: Done

4. In Table 1, the frequency response has been described to choose Chebyshev prototype. However, the parameters of the resonator related to the values of the Chebyshev prototype are not shown in the paper.

@@@Author Reply:

Thanks for your precious comments. While we did not explicitly provide the specific parameters of the resonators related to the values of the Chebyshev prototype in Table 1, the design process involved determining the resonator dimensions based on the desired Chebyshev response. These parameters include the resonator lengths, widths, and step changes in impedance to achieve the required frequency response characteristics.  Chebyshev prototype parameters are planned in another paper to be submitted in future with extended parametric studies.

5. From the structure of the diplexer, it uses two meandered stepped impedance resonators, which do not have stubs at the middle part. What is the purpose of introducing the resonator in Figure 4 and the related equations?

@@@Author Reply:

In the microstrip diplexer design presented in our paper, the meandered stepped impedance resonators play a crucial role in achieving the desired performance characteristics. These resonators are introduced to provide the necessary isolation between the two output ports of the diplexer.The purpose of incorporating meandered stepped impedance resonators is to create a compact and efficient filtering structure that can separate the desired frequency bands for transmission and reception. By carefully designing the geometries and dimensions of these resonators, we can tailor their impedance characteristics to match the requirements of the diplexer circuit.The meandering of the resonators helps to increase their effective electrical length, allowing for better impedance matching and improved filtering performance. The stepped impedance profile helps in achieving a smooth transition between different impedance levels, which is essential for minimizing signal reflections and losses in the circuit.Overall, the meandered stepped impedance resonators in our microstrip diplexer design serve as key components that enable the diplexer to effectively separate and route signals at different frequencies while maintaining high isolation between the output ports. Their design and implementation are critical for realizing the desired performance goals of the diplexer, such as high return loss, high isolation, and narrow bands.

6. How to determine the parameters of the meandered resonators?

@@@Author Reply: By trial and error, we conducted iterative optimization by comparing simulation results with design specifications. Fine-tune the parameters such as length, width, spacing, and number of turns in the meandered resonators to achieve optimal performance in terms of isolation  bandwidth, insertion loss, and return loss.

7. What is the reason for producing negative group delay? The measured group delay should be shown.

@@@Author Reply:

Producing negative group delay in a microstrip diplexer involves manipulating the phase response of components like meandered line resonators to achieve a desired phase shift. This can synchronize signals, enhance signal processing, filtering, and equalization, and improve performance in advanced communication systems by reducing latency and improving data transmission rates. Careful design and optimization are key to achieving negative group delay for specific application requirements.

Reviewer 2 Report

The authors propose a microstrip duplexer that uses meander lines, uniform and stepped impedance resonators. They report a good isolation of 31 dB between two frequency channels.

The manuscript requires careful corrections for a better presentation. A native English speaker would be a good idea to finally check the text.

References [23] and [24] are identical. Please correct.

Several English mistakes should be corrected such as

·         At line 37, instead “effectual signal management”, should be “effective signal management”.

·         At line 47 –in the sentence “An increase in the number of study articles that have been written about the concept by a number of researchers from different countries [8].” Please delete “that”

·         At line 53 – instead “each of these components perform” please write “each of these components performs”

·         At line 57 - instead “a marching circuit” please “write a matching circuit”

·         Ay line 69 please correct the text: “The usage of each of these filters in conjunction with each other. As different instance, the utilization of two band-stop filters, each of which possesses a center frequency that is distinct from that of the other, is required.”

·         At line 197, instead “But UIR topologies don't depend on anything other than line length to produce resonance.” Should be “But UIR topologies don't depend on anything else than line length to produce resonance.”

Much more corrections have to be performed in the text.

At line 281 the authors write that “As shown in Figure 2, the BPF can be constructed by utilizing a series connection between the C and L terminals.” – However, Fig. 2 does not show anything of that

In Table 3  the return loss is reported 29-32 dB but in Fig. 12 |S11| is less than 20 dB. In addition the insertion loss should be reduced.

A native English speaker would be a good idea to finally check the text.

Several English mistakes should be corrected such as

·         At line 37, instead “effectual signal management”, should be “effective signal management”.

·         At line 47 –in the sentence “An increase in the number of study articles that have been written about the concept by a number of researchers from different countries [8].” Please delete “that”

·         At line 53 – instead “each of these components perform” please write “each of these components performs”

·         At line 57 - instead “a marching circuit” please “write a matching circuit”

·         Ay line 69 please correct the text: “The usage of each of these filters in conjunction with each other. As different instance, the utilization of two band-stop filters, each of which possesses a center frequency that is distinct from that of the other, is required.”

·         At line 197, instead “But UIR topologies don't depend on anything other than line length to produce resonance.” Should be “But UIR topologies don't depend on anything else than line length to produce resonance.”

Much more corrections have to be performed in the text.

Author Response

The authors propose a microstrip duplexer that uses meander lines, uniform and stepped impedance resonators. They report a good isolation of 31 dB between two frequency channels.

The manuscript requires careful corrections for a better presentation. A native English speaker would be a good idea to finally check the text.

1.References [23] and [24] are identical. Please correct.

@@@Author Reply: Thanks for your notice. Corrected.

2. Several English mistakes should be corrected such as

• At line 37, instead “effectual signal management”, should be “effective signal management”.
• At line 47 –in the sentence “An increase in the number of study articles that have been written about the concept by a number of researchers from different countries [8].” Please delete “that”
• At line 53 – instead “each of these components perform” please write “each of these components performs”
• At line 57 - instead “a marching circuit” please “write a matching circuit”
• Ay line 69 please correct the text: “The usage of each of these filters in conjunction with each other. As different instance, the utilization of two band-stop filters, each of which possesses a center frequency that is distinct from that of the other, is required.”
• At line 197, instead “But UIR topologies don't depend on anything other than line length to produce resonance.” Should be “But UIR topologies don't depend on anything else than line length to produce resonance.”

Much more corrections have to be performed in the text.

@@@Author Reply: Thanks for your notice. Corrected.

At line 281 the authors write that “As shown in Figure 2, the BPF can be constructed by utilizing a series connection between the C and L terminals.” – However, Fig. 2 does not show anything of that

In Table 3  the return loss is reported 29-32 dB but in Fig. 12 |S11| is less than 20 dB. In addition the insertion loss should be reduced.

@@@Author Reply: Thanks for your notice. Corrected.

Reviewer 3 Report

1. The comments to the authors are:
2. 1- The literature review needs to encompass a broader range of research. you can consider incorporating the following papers in line 50:

• "Fractal quasi-self-complimentary miniaturized UWB antenna"
• "Performance improvement of substrate integrated cavity-fed dipole array antenna using ENZ metamaterial for 5G applications"
• "
• Additionally, you can refer to the following research in line 53:
• "Dual-band broadside-coupled-based BPF with improved performance"
• 2- It is necessary to revise the equation numbering. After the revision, please ensure that the text referring to these equations is corrected accordingly.

2. 3- Kindly verify the figure number mentioned in line 281.

3. 4- In Figure 7, ensure that all dimensions are included. Please review and incorporate all necessary dimensions.

4. 5- The selectivity of the diplexer appears to be poor. Please justify this observation.

5. 6- Incorporate the measured phase results to compare with the simulated ones in Figure 10.

6. 7- Include a photograph of the measurement setup with the VNA, depicting the sample under test connected to the VNA.

7. 8- What are the factors contributing to the high insertion loss?

8. 9- In the comparison table, it is essential to provide the size relative to the guided wavelength for a fair comparison.

9. 10- The English language throughout the manuscript requires revision for clarity and coherence. Please review and edit as necessary.

10. 11- Please, consider incorporating colored geometries throughout the manuscript instead of black and white. This change will enhance the attractiveness of the manuscript to the readers.

The English language throughout the manuscript requires revision for clarity and coherence. Please review and edit as necessary.

Author Response

Reviewer 3

The comments to the authors are:

1- The literature review needs to encompass a broader range of research. You can consider incorporating the following papers in line 50:

"Fractal quasi-self-complimentary miniaturized UWB antenna"

"Performance improvement of substrate integrated cavity-fed dipole array antenna using ENZ metamaterial for 5G applications"

Additionally, you can refer to the following research in line 53:

"Dual-band broadside-coupled-based BPF with improved performance"

@@@Author Reply : Thanks for your precious comments .These papers have been added in the literature review

2- It is necessary to revise the equation numbering. After the revision, please ensure that the text referring to these equations is corrected accordingly.

@@@Author Reply: Thanks for your precious comments. Corrected

3- Kindly verify the figure number mentioned in line 281.

@@@Author Reply: Corrected

4- In Figure 7, ensure that all dimensions are included. Please review and incorporate all necessary dimensions.

@@@Author Reply: All dimensions are included and incorporated all necessary dimensions.

5- The selectivity of the diplexer appears to be poor. Please justify this observation.

@@@Author Reply : In the case of the diplexer in question, the rejection band levels of around 30 dB may indeed indicate a relatively lower selectivity compared to ideal filter performance, but it is acceptable based on reported papers [15, 16, 24, 29] . While the rejection band levels are an important factor in determining selectivity, it is also essential to consider the bandwidth of the passbands. Narrower bandwidths generally result in better performance by reducing[ the overlap between adjacent frequency bands and minimizing potential interference. Also, we gained very good compactness and band isolation.

The selectivity can be optimized by optimization techniques or using software defined diplexer, WE         INDICATED THAT IN FUTURE TREND SECTION.

6- Incorporate the measured phase results to compare with the simulated ones in Figure 10.

@@@Author Reply: Done.

7- Include a photograph of the measurement setup with the VNA, depicting the sample under test connected to the VNA.

@@@Author Reply : Done.Please kindly be informed that our Arnist VNA shows one S parameter in single display. However, we have shown the measurement setup with the VNA, depicting the sample under test connected to the VNA in Figure 12.

8- What are the factors contributing to the high insertion loss?

@@@Author Reply:

High insertion loss in a system can be influenced by factors such as the high loss tangent of FR4 material, dielectric losses, conductor losses, impedance mismatch, connector and junction losses, and environmental factors. Dielectric losses result from energy dissipation within the dielectric material, while conductor losses stem from resistance in the conductive material. In fabrication, Impedance mismatch can lead to reflections and increased insertion loss, and poor-quality connectors and junctions can contribute to loss. Environmental conditions like temperature and electromagnetic interference also play a role. By optimizing material properties, design considerations, and environmental factors, it is possible to minimize insertion loss and enhance system performance.

9- In the comparison table, it is essential to provide the size relative to the guided wavelength for a fair comparison.

@@@Author Reply: I agree with your comment. However, the required inputs for calculating guided wavelength are still tricky from [33-43] that may lead to non-accurate values. Based on our opinion, most diplexer designs are based on FR4 like ours. Also, the fundamental frequency (1.66 GHz) in our design diplexer is mostly smaller than others that gives initial impression it requires higher surface area. However , the more compactness (packaging)of our projected diplexer has gained by modified meandering  and SIR techniques as compared with [33-43].

10- The English language throughout the manuscript requires revision for clarity and coherence. Please review and edit as necessary.

@@@Author Reply: English language has been improved.

11- Please, consider incorporating colored geometries throughout the manuscript instead of black and white. This change will enhance the attractiveness of the manuscript to the readers

@@@Author Reply: Done..

Round 2

Reviewer 1 Report

1. What is the order of the utilized Chebyshev lowpass prototype? The number of resonator is one in the filter. The resonator is a meander line. What is the relationship of the meander line resonator with the stepped impedance resonator described in the paper? The stub in the SIR is not used in the meander line resonator.

2. The measurement of the diplexer in Figure 12 is wrong. It is a three-port component. The third port is not open when working. The setup of the measurement is not in agreement with the simulation and utilization.

Author Response

Response to Reviewers

Reviewer 1

1. What is the order of the utilized Chebyshev lowpass prototype? The number of resonator is one in the filter. The resonator is a meander line. What is the relationship of the meander line resonator with the stepped impedance resonator described in the paper? The stub in the SIR is not used in the meander line resonator.

@@@Author Reply: . The microstrip diplexer has Chebychev response based on frequency responses gotten by the AWR simulator. Each filter for the projected microstrip diplexer has only one resonator and can be considered as first order filter. Meander line resonators, patches, SIR, and UIR components are utilized in the construction of the suggested diplexer, which is illustrated in Figure 7. Intended to improve band isolation and achieve satisfactory frequency responses, the diplexer was projected to operate under frequency channels of 1.66 and 2.52 GHz. The meander line resonator and SIR are two common types of resonators used in microwave and RF filter designs. The meander line stands for serpentine shaped topology which can create resonance through induction and capacitance without the use of other stubs, perfect for impedance matching. Such arrangement gains compactness and it is very easy to be integrated to stripline or microstrip circuits. On the opposite, SIR which consists of a branched line sections taking different characteristic impedances connected in series, aims to use resistance mismatch at junctions to achieve the impedance. SIR, on the other hand, is known to enable the achievement of narrow bands or harmonics blocking or sharp transitions between passbands and stopbands, which can also include stubs or tuning elements to be able to adjust a certain band. In the present study, design nullification of stubs in the meander line, as opposed to SIR suggests structural deviation in addition to varying operational principles. This also implies that the frequency responses demanded and suitability of the SIR and the meander line are structured in qualitatively different ways, for a wide range of microwave and RF applications.

2. The measurement of the diplexer in Figure 12 is wrong. It is a three-port component. The third port is not open when working. The setup of the measurement is not in agreement with the simulation and utilization

@@@Author Reply: Thanks for your precious comments and notices .I added 50 ohm terminal in third port and I got somewhat similar measurements. I updated them in the manuscript. Following the completion of the measurements, comparisons are made between the results obtained from the experiment and those obtained from the simulation, as depicted in Figure 13-15 in terms of S parameters, phase and group delay. All measurement are in acceptable agreements with the simulations.

Here are a few reasons why adding the termination might not have significantly impacted the results:

1. Good Isolation: The diplexer already has good isolation between its ports, which prevents significant signal leakage or interference even without the termination.

2. Matched Impedances: The diplexer's internal design and matching networks may already ensure proper impedance matching, reducing the impact of the termination on the overall performance.

3. Measurement Accuracy: The measurement equipment and calibration may be accurate enough to provide reliable results even without the termination load.

Reviewer 2 Report

The authors performed the corrections required by the reviewer. Moreover, they added significant data, discussion, setup configuration, etc.  

The authors added the measurement setup in Fig. 12. They can measure S11, S33, S31 and S13. However, for correct measurements of the above parameters, please connect to port 2 a 50 Ohms load.

Author Response

Thanks for your precious comments and notices .I added 50 ohm terminal in third port and I got somewhat similar measurements. I updated them in the manuscript. Following the completion of the measurements, comparisons are made between the results obtained from the experiment and those obtained from the simulation, as depicted in Figure 13-15 in terms of S parameters, phase and group delay. All measurement are in acceptable agreements with the simulations.

Here are a few reasons why adding the termination might not have significantly impacted the results:

1. Good Isolation: The diplexer already has good isolation between its ports, which prevents significant signal leakage or interference even without the termination.

2. Matched Impedances: The diplexer's internal design and matching networks may already ensure proper impedance matching, reducing the impact of the termination on the overall performance.

3. Measurement Accuracy: The measurement equipment and calibration may be accurate enough to provide reliable results even without the termination load.

Reviewer 3 Report

The  quality of the article has been improved, I have no further comments. However, I have only one minor comment:

-In Figure 12, In the measurement setup, a 50 Ohm termination should be attached to the third port during measuring the S-Parameters of the other ports.

 Minor editing of English language required

Author Response

The  quality of the article has been improved, I have no further comments. However, I have only one minor comment:

-In Figure 12, In the measurement setup, a 50 Ohm termination should be attached to the third port during measuring the S-Parameters of the other ports.

Reviewer 3

@@@Author Reply: Thanks for your precious comments and notices .I added 50 ohm termination in third port and I got somewhat similar measurements. I updated them in the manuscript.

Here are a few reasons why adding the termination might not have significantly impacted the results:

1. Good Isolation: The diplexer already has good isolation between its ports, which prevents significant signal leakage or interference even without the termination.

2. Matched Impedances: The diplexer's internal design and matching networks may already ensure proper impedance matching, reducing the impact of the termination on the overall performance.

3. Measurement Accuracy: The measurement equipment and calibration may be accurate enough to provide reliable results even without the termination load.

Round 3

Reviewer 1 Report

The authors have replied my comments.

Author Response

Thank You for your useful review comments.