Review Reports

Round 1

Reviewer 1 Report

The paper would be very interesting for readers with some major improvements: 

1) the reference papers are cited from [3] jumped to [40] in the text. Please fix it. 

2) could the author use a table instead of listed paraments in figure 2? 

3) sections 2-5 are design fabrication, and methods mixed with some results. Could the authors reorganize and consider moving some results in section 6?

4) Tt would be better to make results and discussions into one section

Author Response

Authors thank the reviewer for the valuable comments and advices. A thorough proof-reading has been performed.

1) the reference papers are cited from [3] jumped to [40] in the text. Please fix it. 

Reviewer is correct. Most of the references appear in Figure 1 and were not repeated in the text. The text is modified to attract the reader‘s attention on the references in Figure 1. Here are some of the modifications (indicated in red in the revised manuscript)

• “Figure 1 pictures a landscape of representative results of rectenna from literature, where the maximum efficiency is mentioned along with the related input RF power level [5 ]-[39 ].”
• “…Colors and symbols identify the various results in Figure 1.”
• “… one-diode topology (symbols ⊕ and ⊗ in Figure 1)..”

2) could the author use a table instead of listed paraments in figure 2? 

A table was introduced with the geometrical parameter values.

3) sections 2-5 are design fabrication, and methods mixed with some results. Could the authors reorganize and consider moving some results in section 6?

Reviewer’s advice is highly pertinent. The paper discusses gradually the main aspects of a rectenna, given a material and a manufacturing process that are not supposed to be suitable for RF applications. The sections cover the aspects sequentially with results for partial conclusion. Aspects are organized so that the outcome of one result is presented first when it is necessary to investigate another aspect. In that perspective it is not straightforward to imagine an organization of the paper that would separate statements from results.

The introduction is modified so as to explain more specifically the paper organization.

“The paper discusses gradually the main aspects of a rectenna (antenna, rectifier, voltage conversion), given a material and a manufacturing process that are not supposed to be suitable for RF applications. The sections cover the aspects sequentially with results for partial conclusion. The paper content is organized as follows. Section II details the two-transmission-line method introduced to evaluate the electromagnetic properties of the printed substrate. A simple patch antenna supports a comparison between Rogers substrate and the printed one to confirm the applicability to RF applications. Section III details a modified patch antenna and the array of four-antenna. Section IV covers the series, one diode rectifier. Particularly the internal impedance of the rectifier is a major parameter for the power management unit. Section V summarizes the design of the power management circuit deduced from literature. Section VI details important system-level measurements and comparison to the state-of-art. The principal knowledge deduced from the case study is discussed prior to the conclusion.”

Section III title is also modified as “3. Modified patch antenna and Array of four antennas”.

Section VI title is modified as “6. System-level measurements and discussion”

4) Tt would be better to make results and discussions into one section

Well received. Section VI has been modified to reflect “6. System-level measurements and discussion”.

Sub-sections have been introduced to help clarify the paper content. Modifications appear in red in the revised manuscript.

Reviewer 2 Report

In this manuscript, the author investigated a far-field RF energy-harvesting platform by using printed microstrip patch antenna. The method is interesting, and the results are comprehensively demonstrated, from both theoretical and experimental points of view. Therefore, I only have several minor comments for the manuscript. 

1) The author designed circular patch with resonance at 2.45 GHz. Perhaps reflection coefficient could be added for better explanations.

2) Typically for the circular polarization antenna, we show the radiation pattern as RHCP gain and LHCP gain as co-and cross- polarization. But here, the author reported vertical and horizontal, so if no specific reason for this, I do recommend to change to RHCP gain, since only vertical and horizontal miss the phase information.

3) For Figure 8(b), the author mentioned "two rectifier inputs are supplied with -10 dBm". That means each one is fed with -10 dBm or a power divider is utilized? It is better to clarify further. 

4) Since it is circular polarization, in Table 3, unit dBic would be better.

5) In Figure 4(b), parts of the labels are blocked. 

6) In Table 3, there is a typo. It should be "curved patch". 

Author Response

Reviewer #2

Authors thank the reviewer for the valuable comments and advices. A thorough proof-reading has been performed.

1) The author designed circular patch with resonance at 2.45 GHz. Perhaps reflection coefficient could be added for better explanations.

The measurement of the reflection parameter has been added.

2) Typically for the circular polarization antenna, we show the radiation pattern as RHCP gain and LHCP gain as co-and cross- polarization. But here, the author reported vertical and horizontal, so if no specific reason for this, I do recommend to change to RHCP gain, since only vertical and horizontal miss the phase information.

Reviewer is correct when speaking in a generic manner of a circular polarization antenna. Indeed, the targeted application is related to the field amplitude (energy) without too much interest in the spread of phase. Hence it was decided to focus on the radiation pattern in reception mode with respect to polarization orientation (V or H) only. RHCP and LHCP gain measurements require both antennas. If the fabricated antenna is considered the RHCP, an LHCP version should be redesigned and fabricated. This is not complicated but authors have not thought about it and there is not enough time to do it in the allotted revision time. So far, the phase information is missing and accounting for in the system global performances. Review is correct when pointing this little weakness in measurement.

3) For Figure 8(b), the author mentioned "two rectifier inputs are supplied with -10 dBm". That means each one is fed with -10 dBm or a power divider is utilized? It is better to clarify further. 

Reviewer is correct and a clarification has been introduced in the text.

“In the case where two rectifier inputs are supplied simultaneously with -10 dBm and the other ports short-circuited on 50 Ω (Figure 9), the conversion efficiency is over 10% at an optimal load of 1.2 kΩ.”

4) Since it is circular polarization, in Table 3, unit dBic would be better.

The modification has been introduced in the text.

5) In Figure 4(b), parts of the labels are blocked. 

The figure has been improved to eliminate the issue.

6) In Table 3, there is a typo. It should be "curved patch". 

The typo has been corrected

Round 2

Reviewer 1 Report

Accepted authors revision.