Use Ultra-Wideband Discone Rectenna for Broadband RF Energy Harvesting Applications†
, Demosthenes Vouyioukas 1, Dimitrios Stratakis 2 and Traianos Yioultsis 3Round 1
Reviewer 1 Report
In this paper, the authors presents a a broadband RF energy harvester implementation. The system uses a broadband discone antenna, but the matching is not very well. The S11 level is very high (near -10 dB).
Moreover, there are not new in the manuscript to improve the state of the art. I recognized an incremental contribution but in my opinion don't improve the state of the art. All the concepts used are well known. The antenna design is conventional, the information of figure 2 is repeated. The information with the S11 level and the SWR is the same in practical terms. The dickson typology is not new, the Rectifier Circuit Design is not presented, but there are not new. The measured values are the expected.
In conclusion, what is the contribution of this manuscript?
Author Response
Comment #
In this paper, the authors presents a a broadband RF energy harvester implementation. The system uses a broadband discone antenna, but the matching is not very well. The S11 level is very high (near -10 dB). Moreover, there are not new in the manuscript to improve the state of the art. I recognized an incremental contribution but in my opinion don't improve the state of the art. All the concepts used are well known. The antenna design is conventional, the information of figure 2 is repeated. The information with the S11 level and the SWR is the same in practical terms. The Dickson typology is not new, the Rectifier Circuit Design is not presented, but there are not new. The measured values are the expected. In conclusion, what is the contribution of this manuscript?
Answer:
In this work, is presented an approach for the total efficiency estimation of the RF harvesting system, taking into consideration that the average power of a harvester’s storage capacitor is a function of charging, as enhancing the work in MOCAST 2019 Conference paper. A broadband RF energy harvester was fabricated and the prototype was tested on the laboratory and also in urban environment.
The main contributions of this study are:
- The design and fabrication of a broadband discone antenna, with efficiently operation in a wide frequency spectrum to acquire ambient RF energy from many electromagnetic field sources, with excellent broadband characteristics
- The introduction of the energy harvester’s total efficiency maximization, at the transient state, as proved from laboratory measurements. The total efficiency (α) of the proposed harvester system is maximized at the beginning of the storage capacitor’s charge. Thus, a future aspect can be a construction of a pulse harvester system by switching of storage elements to utilize the efficiency maximization at the transient state.
Reviewer 2 Report
Very well written paper, describing a very interesting application and well-presented theoretical analysis and experimental results. Although the performance of previous similar works in the literature are mentioned in the introduction, I would suggest to include those figures in a table as “comparative results” between the proposed solution and those from the literature, to make the comparison more straight forward. Also, some more details for the simulation work of the antenna, like the tool used, possible issues, simulation time, could be given.
Author Response
REFEREE 2
Comments and Suggestions for Authors:
Comment #1
Very well written paper, describing a very interesting application and well-presented theoretical analysis and experimental results. Although the performance of previous similar works in the literature are mentioned in the introduction, I would suggest to include those figures in a table as “comparative results” between the proposed solution and those from the literature, to make the comparison more straight forward.
- Answer:
Thank you very much for your comments. The proposed table could be as the following one (attached).
Unfortunately, due to lack of space in the paper, I could not include the table with comparative results in the paper. I will ask the editor if I can add it as an appendix section. In addition, a paragraph which compare the proposed solution with the literature have been added in Section 1.
To the best of the authors’ knowledge the innovation of our approach summarized in:
(a) The presentation of a capacitor-based energy harvester’s total efficiency maximization, at the transient state, as proved from laboratory measurements. The total efficiency (α) of the proposed harvester system is maximized at the beginning of the storage capacitor’s charge (transient state), taking into consideration that the capacitor's average power, is a function of charging.
(b) Thus, a future aspect can be a construction of a pulse harvester system by switching of storage elements to utilize the efficiency maximization at the transient state, taking full advantage of inactive charging time.
To be noticed that these innovation points are presented in Sections 1 & 9.
Changes in Document (Section 1):
“… Although the above systems can effectively operate in several microwave frequency bands (1 to 6 GHz), none of them is a capacitor-based RF harvester. To the best of the authors’ knowledge, the only proposed capacitor-based RF harvester is the work in [24], which can efficiently operate in the medium wave frequency band (531-1.611 KHz) using a tunable loop antenna. The system was able to harvest enough energy to charge a super capacitor to 2.8V, and sustain the voltage while no load connected to the circuit. This charge is sufficient to power a 1kΩ load for approximately 1 hour. However, in the latest system the efficiency estimation as a function of time not mentioned. ..”
---------------------------------------------------------------------------------------------------------------------------
Comment #2
Also, some more details for the simulation work of the antenna, like the tool used, possible issues, simulation time, could be given.
- Answer:
The simulation results of the antenna were carried out with Antenna Magus software, in cooperation with CST Microwave Studio Suite. The behavior of this antenna as a function of frequency, is like a high-pass filter as shown clearly in Figure 2b. Simulation results fully confirmed the theoretical lower cut-off frequency of the proposed prototype antenna (corresponds on Fcut:750 MHz) as given by equation (1). Radiation patterns simulations were done at minimum (Fmin: 0.75GHz), center (Fcent: 1.5GHz) and maximum (Fmax: 3GHz) operation frequencies respectively (Figures 3 a,b,c).
Also:
- The rectifier's specific design was studied and simulated on Agilent ADS software. For the simulation of HMSM-2862 Schottky diode, were used the corresponded models and for the passive components general purpose models of ADS library were used respectively.
Changes in Document (Section 2.4):
“..Simulation results fully confirmed the theoretical lower cut-off frequency of the proposed prototype antenna as given by equation (1). The 3D radiation charts were carried out in cooperation with CST Microwave Studio Suite software, as shown in Figure 3. Radiation patterns simulations were done at minimum (Fmin: 0.75GHz), center (Fcent: 1.5GHz) and maximum (Fmax: 3GHz) operation frequencies respectively…”
---------------------------------------------------------------------------------------------------------------------------
We would like to thank you very much for all your comments, resulting in a significant contribution to the improvement of the article
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The submitted paper presents the design of Broadband RF Energy Harvesting Using a UWB Discone Rectenna. The discone antenna construction, the rectifier circuit design and an analytical formulation for the efficiency estimation are discussed in the paper.
In my opinion the following points must be clarified in the paper:
- What is the applicability of the proposed system? Who benefits from the proposed system? Which electronic devices can be powered with the proposed system?
- In the literature, some works presents the design and construction of energy harvesting system. What is the innovation of the proposed work with respect to the others presented in the literature?
- The system was tested in the laboratory with an incident wave of 3 V/m. Note that, this field can be obtained only nearby a base station. What is the system performance in the situation in which the field intensity is on the order of mV/m or smaller (a condition far from base station)?
- Why the authors did not perform the experiment in urban environment?
Author Response
REFEREE 3
Comments and Suggestions for Authors:
The submitted paper presents the design of Broadband RF Energy Harvesting Using a UWB Discone Rectenna. The discone antenna construction, the rectifier circuit design and an analytical formulation for the efficiency estimation are discussed in the paper.
In my opinion the following points must be clarified in the paper:
Comment #1
What is the applicability of the proposed system?
- Answer:
The applicability of the proposed improved version of storage-based RF energy harvesting system could be the power supply of a WSN's node for Internet of Things (IoT) applications. A WSN' node can be self-powered from ambient RF energy by the harvester when the "wake-up" mode is active (e.g. wireless data transmission). On the contrary, at "sleep" mode of WSN's node, the harvester's storage capacitor will be charge from the beginning etc.
To be noticed that a new Section (6) has been added for this description.
Changes in Document (Section 6 - New):
“…In general, small electronic devices with minimum power consumption requirements (e.g WSN's node), can be powered from ambient RF Energy. The applicability of the proposed improved version of storage-based RF energy harvesting system could be the power supply of a WSN's node for Internet of Things (IoT) applications [28]. A WSN' node can be self-powered from ambient RF energy by the storage-based harvester when the "wake-up" mode is active (e.g. for wireless data transmission). On the contrary, at "sleep" mode of WSN's node, the harvester's storage capacitor will be charge from the beginning etc [28]. …”
-----------------------------------------------------------------------------------------
Comment #2
Who benefits from the proposed system?
- Answer:
The main focus in this work is an approach for the total efficiency estimation of a storage capacitor-based RF harvesting system, as enhancing the work in MOCAST 2019 Conference paper.
-Summarizing, the main contributions of this study are:
- The design and fabrication of a broadband discone antenna, with efficiently operation in a wide frequency spectrum to acquire ambient RF energy from many electromagnetic field sources, with excellent broadband characteristics. Thus, this type of antenna can be ideal for RF energy harvesting applications, beside of large size and its 3D geometry.
- The presentation of a capacitor-based energy harvester’s total efficiency maximization, at the transient state, as proved from laboratory measurements. The total efficiency (α) of the proposed harvester system is maximized at the beginning of the storage capacitor’s charging (transient state), taking into consideration that the average power of the element is a function of charging time.
Changes in Document (Section 1):
“..In our work, we introduce an approach of a capacitor-based energy harvester’s total efficiency estimation, and its maximization at the transient state, as proved from laboratory measurements. ..”
Changes in Document (Section 9):
“ The total efficiency a of the proposed harvester system is maximized at the beginning of the storage capacitor’s charge, as proved from measurements. Thus, a future aspect can be a construction of a pulse harvester system by switching of storage elements to utilize the efficiency maximization at the transient state, taking full advantage of inactive charging time. ..”
-----------------------------------------------------------------------------------------
Comment #3
Which electronic devices can be powered with the proposed system?
- Answer:
In general, small electronic devices with minimum power consumption requirements (e.g WSN's node), can be powered from ambient RF Energy. From the obtained measurements, the storage capacitor's (330 uF) maximum voltage value (Vmax) is about 1 Volts. Thus, the stored energy can be calculated according to equation (10), corresponds about 165uJ. The storage element could have higher value, for higher energy storage in contrast to slower charging time. For a 10 KΩ terminal load and the harvester's storage capacitor (330uF) the constant time is τ=3.3sec. With these component's setup, knowing that a capacitor is completely discharged at a time of 5τ, it can be assumed that for 15 sec the capacitor's voltage will exponentially reduce to zero (eq. 7). Thus, is sufficient to power a load of 10kΩ for 15 sec.
To be noticed that a new Section (6) has been added for this description.
Changes in Document (Section 6 - New):
“…From the obtained measurements, the storage capacitor's (330 uF) maximum voltage value (Vmax) is about 1 Volts. Thus, the stored energy can be calculated according to equation (10), and corresponds about to 165uJ. The storage element could have higher value, for higher energy storage in contrast to slower charging time. …”
“…In general, small electronic devices with minimum power consumption requirements (e.g WSN's node), can be powered from ambient RF Energy. The applicability of the proposed improved version of storage-based RF energy harvesting system could be the power supply of a WSN's node for Internet of Things (IoT) applications [28]. A WSN' node can be self-powered from ambient RF energy by the storage-based harvester when the "wake-up" mode is active (e.g. for wireless data transmission). On the contrary, at "sleep" mode of WSN's node, the harvester's storage capacitor will be charge from the beginning etc [28]. …”
Comment #4
In the literature, some works presents the design and construction of energy harvesting system. What is the innovation of the proposed work with respect to the others presented in the literature?
- Answer:
A paragraph which compare the proposed solution with the literature have been added in Section 1.
Changes in Document (Section 1):
“… Although the above systems can effectively operate in several microwave frequency bands (1 to 6 GHz), none of them is a capacitor-based RF harvester. To the best of the authors’ knowledge, the only proposed capacitor-based RF harvester is the work in [24], which can efficiently operate in the medium wave frequency band (531-1.611 KHz) using a tunable loop antenna. The system was able to harvest enough energy to charge a super capacitor to 2.8V, and sustain the voltage while no load connected to the circuit. This charge is sufficient to power a 1kΩ load for approximately 1 hour. However, in the latest system the efficiency estimation as a function of time not mentioned. ..”
To the best of the authors’ knowledge the innovation of our approach summarized in:
(a) The presentation of a capacitor-based energy harvester’s total efficiency maximization, at the transient state, as proved from laboratory measurements. The total efficiency (α) of the proposed harvester system is maximized at the beginning of the storage capacitor’s charge (transient state), taking into consideration that the capacitor's average power, is a function of charging.
(b) Thus, a future aspect can be a construction of a pulse harvester system by switching of storage elements to utilize the efficiency maximization at the transient state and taking advantage of inactive charging time.
To be noticed that these innovation points are presented in Sections 1 & 9
-----------------------------------------------------------------------------------------
Comment #5
The system was tested in the laboratory with an incident wave of 3 V/m. Note that, this field can be obtained only nearby a base station. What is the system performance in the situation in which the field intensity is on the order of mV/m or smaller (a condition far from base station)?
- Answer:
The harvester of this experiment has not a high sensitivity rectifier. The electric field threshold value for harvesting activation, is about 2.5V/m. In future work, a prototype rectifier with higher harvesting sensitivity will be a new challenge.
Changes in Document (Section 8):
“…A prototype rectifier implementation with higher harvesting sensitivity characteristics, will be a new challenge as another future aspect. …”
-----------------------------------------------------------------------------------------
Comment #6
Why the authors did not perform the experiment in urban environment?
- Answer:
The harvester was placed for testing in urban environment in the town of Heraklion, Crete, Greece, as shown at Figure 6a. The place of this experiment setup, was nearby DCS, UMTS, LTE base stations (about 200m distance). The broadband electric field average value (about 3V/m) and the equivalent power density average value (about 0,023 W/m2) measured from a Narda AMS-8061/G frequency selective EMF area monitor. At laboratory, we tried to create the same conditions about the electric field average value for the harvester's performance evaluation in several frequencies.
Changes in Document (Section):
“…The proposed RF harvester was placed for testing at the laboratory and nearby a base station in urban environment, with transmissions from wireless communications systems, such as DCS-1800, LTE, UMTS in the town of Heraklion, Crete, Greece. At the place of harvester installation, the broadband electric field average value (about 3 V/m) and the equivalent power density average value (about 0,023 W/m2) measured from a Narda AMS-8061/G frequency selective EMF area monitor of the EMF project [21]. The storage capacitor’s voltage at a given time t, was measured with an Axiomet AX-176 True RMS Multimeter / Datalogger. At the laboratory, harvester was irradiated from a 3115 ETS LINDGREN Horn antenna driven by Agilent E4438C generator, for the performance evaluation of the system in several frequencies. The electric field value E and the equivalent power density average value S, were measured from a Rohde & Schwarz - FSH8 Spectrum Analyzer (Figure 9a), at the place of harvester installation. …”
-----------------------------------------------------------------------------------------
We would like to thank you very much for all your comments, resulting in a significant contribution to the improvement of the article.
Author Response File: Author Response.pdf
Reviewer 4 Report
The authors designed and fabricated an ultra-wideband antenna to harvest the radio frequency energy, characterized the antenna using simulations and measurements. The layout is clear and the content is easy to understand, the research is interesting.
Major comments:
1, In section 7.2, the authors present the theoretical formula to calculate the total efficiency for the broadband RF system, however, the results calculated shown in figure 8 is for narrowband. Since the focus of the manuscript is for broadband system, reader expect the total efficiency for the broadband system. So, I feel an important result is missing.
Minor comments:
1, line 1, title. How about change to title to: Use ultra-wideband dicone rectenna for broadband RF energy harvesting applications.
2, line 6, a comma is missing: …Systems Engineering,
3, line 18. This sentence is confusing, one suggestion: The system is able to harvest energy from various electromagnetic field sources, thus has the potential to charge a storage energy element efficiently in a short time.
4, line 73-76, this sentence is too long and confusion, please rewrite.
5, line 82, this is the first time to introduce SWR, provide the full name and explain it.
6, line 60, rf should be capitalized to make it consistence across the whole manuscript.
7, line 93, the beginning of the paragraph, how about change it like this: The dicone antenna is a version of biconical antenna, in which one of the two cones have been replaced by a disc.
8, line 97-100, the logic is unclear, please rewrite.
9, line 163. What kind of software did you use to perform the simulation, please add in this section.
10, line 165-167. Since you mentioned the figure 3 first, better to move figure 3 before figure 2, so figure numbers are in sequence.
11, line 179, the subtitle. How about change it to: Basic Theory of the Dickson N-state Rectifier
12, line 180, change 2 to two.
13, line 201. You can change the title of the figure: Basic topology of the …
14, line 211, For the circuit design, it is better to create a figure and place it to figure 4(B).
15, line 218. There is a space between the value and the unit, such as 0.58 ns, 1700 MHz, please also take care of all the other expressions shown in the manuscript.
16, line 223, HSMS-2862.
17, line 263. Label the two figures with (a) and (b) respectively.
18, line 276, Label the two figures with (a) and (b), for the fight figure, increase the range to 1 V like the left one, place the legend on top or close to the lines, and move the Time (Min.) bellow like the left figure.
19, line 282 and line 288, remove the dot between R and C in equation (6) or add a dot in (7), basically, keep consistent.
20, line 290, at time t=0, there are commas before and after, please use period where it is necessary, otherwise, it confuse this sentence.
21, line 300, how about change the subtitle to: Total Efficiency of Narrow Band RF Energy harvesting systems. Similarly, title 7.2.
22, line 301, line 316, etc. make sure you use a or alpha to represent the efficiency.
23, line 319, how about change this sentence to: it is worth mention that, all quantities in the above equations are measurable, and important to determine the efficiency of the harvesting systems.
24, line 323, in the equation 15, delete the third part. It is obvious that if t is a constant, then equation 16 can be obtained.
25, line 366, exponentially reduce to Vmax, isn’t it zero instead?
26, line 436, should be only one comma before 2017.
Author Response
Major comments:
Comment #1
1, In section 7.2, the authors present the theoretical formula to calculate the total efficiency for the broadband RF system, however, the results calculated shown in figure 8 is for narrowband. Since the focus of the manuscript is for broadband system, reader expect the total efficiency for the broadband system. So, I feel an important result is missing.
Answer: The proposed change has been added.
Changes in Document: The total efficiency for the broadband system has been added at Figure 9b
Minor comments:
Comment #1
line 1, title. How about change to title to: Use ultra-wideband dicone rectenna for broadband RF energy harvesting applications.
Answer: The title has been changed.
Changes in Document: “Use ultra-wideband dicone rectenna for broadband RF energy harvesting applications.“
Comment #2
a comma is missing: …Systems Engineering,
Answer: A comma has been added.
Changes in Document: “Department of Information and Communication Systems Engineering,”
Comment #3
line 18. This sentence is confusing, one suggestion: The system is able to harvest energy from various electromagnetic field sources, thus has the potential to charge a storage energy element efficiently in a short time.
Answer: The proposed suggestion has been added.
Changes in Document: “The system is able to harvest energy from various electromagnetic field sources, thus has the potential to charge a storage energy element efficiently in a short time.”
Comment #4
line 73-76, this sentence is too long and confusion, please rewrite.
Answer: The sentence has been changed.
Changes in Document: “For the total efficiency estimation of the harvesting system was followed a methodology, as enhancing the work in [25]. In our approach has been taken into consideration the average power of a capacitor which is a function of charging time and corresponds to the variation rate of its energy”
Comment #5
line 82, this is the first time to introduce SWR, provide the full name and explain it.
Answer: The full name of Standing wave ration has been included in the manuscript.
Changes in Document: “with excellent broadband characteristics (1.5:1 or less standing wave ratio (SWR) at a frequency range up to 10:1).”
Comment #6
line 60, rf should be capitalized to make it consistence across the whole manuscript.
Answer: The proposed change has been added.
Changes in Document: “whole the manuscript”
Comment #7
line 93, the beginning of the paragraph, how about change it like this: The dicone antenna is a version of biconical antenna, in which one of the two cones have been replaced by a disc.
Answer: The proposed suggestion has been added.
Changes in Document: “The discone antenna is a version of biconical antenna, in which one of the two cones have been replaced by a disc.”
Comment #8
line 97-100, the logic is unclear, please rewrite.
Answer: The proposed change has been added.
Changes in Document: “The sensitivity of this antenna is highest in the direction of the horizon because of the narrow radiation pattern in the vertical plane.”
Comment #9
line 163. What kind of software did you use to perform the simulation, please add in this section.
Answer: The simulation results were carried out with ADS software, CST software and Antenna Magus Software (student version).
Changes in Document: “The simulation of this antenna type was carried out with Antenna Magus software, to extract the electrical characteristics and the radiation patterns in polar and cartesian form. The SWR is about 1.5:1, and the reflection coefficient (S11) ranges from -10 dB to -20 dB in a wide band of frequencies, as shown in Figure 2. The 3D radiation charts were carried out in cooperation with CST Microwave Studio Suite software, as shown in Figure 3.”
Comment #10
line 165-167. Since you mentioned the figure 3 first, better to move figure 3 before figure 2, so figure numbers are in sequence.
Answer: The sentences of the paragraph have been moved for sequence of the figures
Changes in Document: “The simulation of this antenna type was carried out with Antenna Magus software, to extract the electrical characteristics and the radiation patterns in polar and cartesian form. The SWR is about 1.5:1, and the reflection coefficient (S11) ranges from -10 dB to -20 dB in a wide band of frequencies, as shown in Figure 2. The 3D radiation charts were carried out in cooperation with CST Microwave Studio Suite software, as shown in Figure 3.”
Comment #11
line 179, the subtitle. How about change it to: Basic Theory of the Dickson N-state Rectifier
Answer: The subtitle has been changed
Changes in Document: “3. Basic Theory of the Dickson N-stage Rectifier”
Comment #12
line 180, change 2 to two.
Answer: The suggestion has been added
Changes in Document: “A famous RF signal rectifier topology is the Dickson rectifier with two or N-stages,….”
Comment #13
line 201. You can change the title of the figure: Basic topology of the …
Answer: The title has been added
Changes in Document: “Figure 4. (a) Basic topology of the Dickson N-Stage Rectifier,”
Comment #14
line 211, For the circuit design, it is better to create a figure and place it to figure 4(B).
Answer: The figure 4b, has been added
Changes in Document: “Figure 4. (a) Basic topology of the Dickson N-Stage Rectifier, (b) The proposed rectifier circuit implementation from FR4 PCB board with dielectric constant εr = 4.35.”
Comment #15
line 218. There is a space between the value and the unit, such as 0.58 ns, 1700 MHz, please also take care of all the other expressions shown in the manuscript.
Answer: The proposed change has been added.
Changes in Document: “whole the manuscript”
Comment #16
line 223, HSMS-2862.
Answer: The proposed change has been added.
Changes in Document: “HSMS-2862.”
Comment #17
1line 263. Label the two figures with (a) and (b) respectively.
Answer: The proposed change has been added.
Changes in Document: “Figure 6. (a) The broadband Discone rectenna experiment setup nearby a base station in urban environment, at Heraklion, Crete, Greece and (b) testing at N.I.R.L laboratory of the Hellenic Mediterranean University (HMU).”
Comment #18
line 276, Label the two figures with (a) and (b), for the fight figure, increase the range to 1 V
like the left one, place the legend on top or close to the lines, and move the Time (Min.) bellow like the left figure.
Answer: The proposed change has been added.
Changes in Document: Figures have been labeled with (a) and (b) and the Time (Min.) has been moved bellow.
Comment #19
line 282 and line 288, remove the dot between R and C in equation (6) or add a dot in (7), basically, keep consistent.
Answer: The proposed change has been added.
Changes in Document: The dot between R and C in equation (6) has been removed
Comment #20
line 290, at time t=0, there are commas before and after, please use period where it is necessary, otherwise, it confuse this sentence.
Answer: The proposed change has been added.
Changes in Document: “charging at time t=0,….”
Comment #21
line 300, how about change the subtitle to: Total Efficiency of Narrow Band RF Energy harvesting systems. Similarly, title 7.2.
Answer: The suggestion has been added
Changes in Document: “7.1 Total Efficiency of Narrow Band RF Energy harvesting systems.” and “7.2. Total Efficiency of Broadband RF Energy Harvesting Systems” respectively
Comment #22
line 301, line 316, etc. make sure you use a or alpha to represent the efficiency.
Answer: The proposed change has been added. For the efficiency presentation “alpha” has been used.
Changes in Document: ““whole the manuscript””
Comment #23
23, line 319, how about change this sentence to: it is worth mention that, all quantities in the above equations are measurable, and important to determine the efficiency of the harvesting systems.
Answer: The proposed suggestion has been added.
Changes in Document: “It is worth mention that, all quantities in the above equations are measurable, and important to determine the efficiency of the harvesting systems.”
Comment #24
24, line 323, in the equation 15, delete the third part. It is obvious that if t is a constant, then equation 16 can be obtained.
Answer: The proposed change has been added
Changes in Document: The third part in equation 16 has been deleted.
Comment #25
25, line 366, exponentially reduce to Vmax, isn’t it zero instead?
Answer: The proposed change has been added
Comment #26
26, line 436, should be only one comma before 2017.
Answer: The proposed change has been added
Changes in Document: One comma has been deleted at the reference
Reviewer 5 Report
Please add recent publication as below;
RF energy harvesting systems: An overview and design issues, International Journal of RF and Microwave Computer-Aided Engineering · Jan 2019
Author Response
REFEREE 5
Comments and Suggestions for Authors
Comment #1
Please add recent publication as below;
Divakaran SK,Krishna DD, Nasimuddin. RF energy harvesting systems: An overview and design issues. Int J RF Microw Comput Aided Eng. https://doi.org/10.1002/mmce.21633
- Answer: Thank you very much for your comments. It is added.
Changes in Document (Section 1):
“…A rectenna is a rectifying antenna, a special type of receiving antenna that is used for converting electromagnetic energy into direct current (DC), and usually found in the bibliography to describe both the antenna and the rectifier sections of a harvesting system [27]. …”
(Section References):
- Divakaran, S.K.; Krishna, D.D.; Nasimuddin. RF energy harvesting systems: An overview and design issues. Int. J. RF Microw. Comput. Aided Eng., 2019, 29, 1-15. [CrossRef]
-----------------------------------------------------------------------------------------
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
My opinion about the paper is the same.
There are no modifications.
The authors only change some sentences.
I recommend the rejection of the paper.
Author Response
REFEREE 1
Comments and Suggestions for Authors
My opinion about the paper is the same. There are no modifications. The authors only change some sentences. I recommend the rejection of the paper.
- Answer:
Thank you very much for your comments. To the best of the authors’ knowledge the innovation of our approach summarized in:
To the best of the authors’ knowledge the innovation of our approach summarized in:
(a) The presentation of a capacitor-based energy harvester’s total efficiency maximization, at the transient state, as proved from laboratory measurements. The total efficiency (α) of the proposed harvester system is maximized at the beginning of the storage capacitor’s charge (transient state), taking into consideration that the capacitor's average power, is a function of charging.
(b) Thus, a future aspect can be a construction of a pulse harvester system by switching of storage elements to utilize the efficiency maximization at the transient state and taking advantage of inactive charging time.
Changes in Document (Section 1):
“… Although the above systems can effectively operate in several microwave frequency bands (1 to 6 GHz), none of them is a capacitor-based RF harvester. To the best of the authors’ knowledge, the only proposed capacitor-based RF harvester is the work in [24], which can efficiently operate in the medium wave frequency band (531-1.611 KHz) using a tunable loop antenna. The system was able to harvest enough energy to charge a super capacitor to 2.8V, and sustain the voltage while no load connected to the circuit. This charge is sufficient to power a 1kΩ load for approximately 1 hour. However, in the latest system the efficiency estimation as a function of time not mentioned. ..”
To be noticed that a new Section (6) has been also added for the applicability description of the proposed system.
Changes in Document (Section 6 - New):
“…In general, small electronic devices with minimum power consumption requirements (e.g WSN's node), can be powered from ambient RF Energy. The applicability of the proposed improved version of storage-based RF energy harvesting system could be the power supply of a WSN's node for Internet of Things (IoT) applications [ ]. A WSN' node can be self-powered from ambient RF energy by the storage-based harvester when the "wake-up" mode is active (e.g. for wireless data transmission). On the contrary, at "sleep" mode of WSN's node, the harvester's storage capacitor will be charge from the beginning etc [ ]. …”
Author Response File: Author Response.pdf
Reviewer 3 Report
After the modifications performed by the authors, I consider the paper suitable for publication.
