Wearable Displacement Sensor Using Inductive Coupling of Printed RFID Tag with Metallic Strip

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Title: Wearable Displacement Sensor using Inductive Coupling of Printed RFID Tag with Metallic Strip

 

 

Dear authors,

 

In the next paragraphs my comments and suggestions:

 

Point 1: The use of radiation diagrams would be useful to visually characterize the antenna's behaviour in terms of directivity and efficiency, especially for applications such as respiratory monitoring in real environments. Adding these diagrams could strengthen the presentation of the antenna's performance data.

 

Point 2: Although the manuscript mentions the use of CST Studio Suite 2024, additional details on the specific configurations used in the simulations could increase the reproducibility of the study.

Experimental Equipment: The description of the experimental setup could be enhanced with detailed specifications of the equipment used, such as the RFID reader model and characteristics of the reader antenna. This information is essential to validate the results and facilitate replication by other researchers.

 

 

 

Point 3: The manuscript presents several relevant parameters, including impedance, reflection coefficient and transmission coefficient, which are fundamental. However, it is recommended to include:

-Total Efficiency: Include calculations or measurements of the antenna's total efficiency.

-Gain Diagram: A radiation diagram to highlight the gain in different directions could complement the analysis.

-Operating Bandwidth: Ensure that the analysis covers the full operating bandwidth and any deviations caused by proximity to the human body.

 

Point 4: The experimental results section could be better organized, clearly highlighting innovative contributions such as the relationships between displacement, RSSI and reading range.

 

Point 5: Expand the discussion on possible implementations of the chip-free sensors and conductive fabrics mentioned in the conclusion, including potential technical challenges. It is recommended that the authors consider the possibility of transforming the sensor described in the manuscript into an RFID tag, thus broadening its application potential in commercial and industrial environments. This approach has clear advantages, such as reduced large-scale production costs and the possibility of integration into existing systems. Adaptation would require optimizing the geometry of the antenna, ensuring that it fits the typical compact format of RFID tags, without compromising coupling performance and sensitivity. It would also be relevant to explore the impact of different environments on the tag's functionality, as well as ensuring that the proposed design maintains sufficient durability and flexibility for applications such as logistics, environmental monitoring or wearable devices. In addition, the technical feasibility stands out, considering the use of flexible substrates, such as Kapton, and manufacturing techniques already mentioned, such as direct printing by DIW. Finally, the authors could expand the discussion of future applications, highlighting the potential use in sectors such as health, fashion, logistics and IoT, reinforcing the relevance and innovation of the work presented.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper introduces a passive displacement sensor that capitalizes on the inductive coupling between a printed UHF RFID tag and a metallic strip, exhibiting sensitivity to displacement through fluctuations in RSSI and read range, with potential applications in wearable technology for respiratory monitoring. The study presents a cost-effective and battery-free solution for remote monitoring capabilities in wearable applications. The aesthetics of the paper are commendable, and it is well-organized, which could be published if the following suggestions are adequately addressed:

1. After Equation (6), the word "where" should not be indented at the beginning of a new line. Please correct similar issues throughout the text.

2. How is the operating frequency determined in this work?

3. Figure 2 provides numerous dimensional marks. However, the authors do not explain the optimization process and methods for these parameters but instead directly present their values.

4. In practical applications, is the acquisition of displacement essentially based on impedance lookup tables? This would require prior acquisition of impedance spectra. Is there a more general method available?

5. Besides copper, what other materials could the metal strip be made of? The interaction effects between different metals and RFID tags vary, and the authors should refer to and cite the following article titled A comprehensive investigation of thermal risks in wireless EV chargers considering spatial misalignment from a dynamic perspective.

6. Please standardize the reference formatting. For example, should only the first letter of the first word in article titles be capitalized, or should all words be capitalized?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have no more comments.