Preliminary report for Final Year Project

Development of a broadbandwireless energy harvesting system

Author name Ruimin Zhao

Author ID 201139030

Project Supervisor Yi Huang

Project Assessor Miguel Lopez-Benitez

October 14, 2016

Abstract

This project aims to develop a broadband wireless energy harvesting system pri-marily by designing, simulating and manufacturing an antenna with specializedbandwidth and optimized performance. Since the core part of this project is aboutthe antenna design, the initial stage of the project would be literature review whichmainly include two pieces of paper whose topics are about antenna design devel-opment for wireless energy harvesting, and several course slides of antenna modulein university. More papers are read for better overview of this project as well.

The conducting methodology of this project would be mainly about utilizingsoftware named Advance Design System (ADS) to design and simulate the recti-fying antenna, deciding the overall circuit configuration of the system, conductingnecessary mathematical derivation and calculation, physically assembling the de-signed antenna, and testing the actual performance of the prototype using themeasurement tools available in school lab.

This particular preliminary report will mainly focus on the literature reviewprogress, some self-study summary of the related basic knowledge such as antenna,some comprehension about carefully read pieces of paper, and future plan aboutthis one-year project with the aid of a Gantt chart.

Declaration

I confirm that I have read and understood the Universitys Academic In-tegrity Policy. I confirm that I have acted honestly, ethically and profes-sionally in conduct leading to assessment for the programme of study. Iconfirm that I have not copied material from another source nor commit-ted plagiarism nor fabricated, falsified or embellished data when completingthe attached piece of work. I confirm that I have not copied material fromanother source, nor colluded with any other student in the preparation andproduction of this work.

Figure 1: Signature

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Contents

1 Introduction 3

2 Project Description 4

3 Methodology 53.1 Apparatus perspective . . . . . . . . . . . . . . . . . . . . . . . . . 53.2 Procedure perspective . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Project Plan 74.1 Overall plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74.2 Detailed Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.2.1 Tasks Description . . . . . . . . . . . . . . . . . . . . . . . . 84.2.2 Milestone Description . . . . . . . . . . . . . . . . . . . . . . 8

5 Project Rationale and Industrial Relevance 95.1 Significance of this project . . . . . . . . . . . . . . . . . . . . . . . 95.2 Industrial application and potential . . . . . . . . . . . . . . . . . . 10

6 Literature Review 116.1 History and challenges . . . . . . . . . . . . . . . . . . . . . . . . . 116.2 Latest results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7 Results 13

8 Conclusion 14

References 15

9 Appendix 169.1 A Gantt chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169.2 Three forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

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Chapter 1

Introduction

Battery-free world is likely to be achieved by the development of wireless energy

harvesting system witch convert ambient radio frequency (RF) power into usable

DC power, a conceptual structure can be seen in Figure 1.1.

RF is everywhere, and this electromagnetic (EM) signal can be transmitted to

space and received from space using Antenna [1]. The most important function of

antenna, the core component to achieve a wireless energy harvesting system is to

radiate the energy in the desired direction.

This piece of writing is a preliminary report for the project of “Development of

a broadband wireless energy harvesting system” which primarily covers the project

description, plan, method, rationale consideration, literature review, and results

so far. An overall understanding about this project is to be presented clearly.

Figure 1.1: Wireless energy harvesting system

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Chapter 2

Project Description

Overall, this project is aimed at developing a broadband energy harvesting system

(e.g. from such as 700 to 3700 MHz) to cover some popular wireless bands.

The specific objectives are to design and conduct a broadband and multi-band

wireless energy harvesting system with reasonably high RF-to-DC conversion ef-

ficiency, compact size, and stable performance under various conditions. Besides

these concrete experimental results expectation, if time and resources are adequate,

it is also expected to be adjusted to specific bandwidths or specific practical con-

dition to be utilized in the Internet of Things domain if possible.

The wireless energy harvesting system design primarily include the design of

four sections which are a rectifying circuit design, an antenna, an impedance

matching, and some harmonic-rejected filters. The general design direction would

be: To achieve multiband and broadband energy harvesting simultaneously, an

advanced impedance matching circuit should be designed.

To improve the RF-to-DC conversion efficiency, the high order harmonics gen-

erated due to the linearity characteristics of rectifier should be rejected by adding

filters, such as slot filter or flower-shaped filter, to the circuit. To achieve com-

pact size of the harvesting system, the added filters should be embedded onto the

antenna, that is to say, structures such as antenna-filter structure or annular ring

structure should be considered.

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Chapter 3

Methodology

3.1 Apparatus perspective

The design will be completed primarily with the aid of a simulation software named

Advance Design System (ADS) owned by a technical company name Agilent. This

software is selected primarily because it is particularly powerful in terms of model

development and simulation of RF wave related devices and systems, and quite

widely used in wireless energy harvesting domain.

After the completion of the design and simulation of the system, the prototype

product would be composed of basic electronic components for building rectifying

antenna system including iron ring, antenna, wire, diode, breadboard and so on.

Specific commercial components would also be included with the practical issues

taken into account. They may include some type of diode with high efficiency of

rectifying function, and substrate materials with reasonable price and so on.

Besides, related tutorial resources about how to use the design software should

be found mainly from on-line website such as YouTube. Basic knowledge about

covered technical subjects such as antenna should be obtained with the aid of

related slides and weekly tutorial section delivered by the supervisor.

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3.2 Procedure perspective

The most crucial stage would be the design stage. For the design process, different

already available structures provided by former papers can be used together to

achieve an initial system design made up of a combination of multiple advantages

as the starting point. After the combining those selected structures together to

form the initial system, the innovative design on some particular component will

be conducted to improve the initial design to make this project distinguish from

previous ones.

Concretely, the initial step would be to analyse the rectifier characteristics, es-

pecially its non-linearity characteristics, which is the core reason why an impedance

matching system is needed in the whole system to connect the antenna and the

rectifier.

After comprehensive quantified analysis of the rectifying circuit features, the

idea that the impedance matching circuit should solve the various impedance of

the rectifier due to its non-linearity feature should be understood more clearly

and corresponding actual advanced impedance matching circuit can be design, for

example by modifying a broadband dual linear polarization cross dipole into a

frequency-independent dual circular polarization cross dipole[2]. One point worth

especially noticing is that to achieve the multiband energy harvesting, this match-

ing part is the crucial part. For the concrete bandwidth, it can be decided based

on the areas such as city region and countryside region [3].

Then, the antenna can be designed based on the known parameters such as the

bandwidth expected to be covered. Besides, some filters structure can be designed

embedded onto the antenna board to [4]. Also, to limit the size of the antenna

is also am important consideration for improving the performance efficiency, and

some strategies used can be to have a annular ring-shape structure can be applied

here [2].

Finally, when combining all the designed sections together to form the whole

circuit for the system, the actual performance would be compared for different

choice of the structures of individual section, and after careful consideration of

trade-off among all the performance elements, a relatively best combination would

be decided after thorough simulation process and comparison.

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Chapter 4

Project Plan

4.1 Overall plan

Generally, the plan is to first see what other people did, then to make your ideas,

then to simulate the design, then to optimise the design, and finally to compare it

to other design (detailed process plan shown in Appendix).

However, for the concrete choice of all the available structures such as various

types of antenna, it requires future work in the following months to actually com-

pare each of structures individually for each different individual purposes such as

reducing the antenna size, and also use simulation software to test different com-

bination of these structures to examine the trade-off and decide a finalized version

of the whole design of the system using optimized structures for each of these four

main sections.

It worth particularly noticing that there are some basic knowledge should be

comprehensively studied at the beginning stage of this project before actually mov-

ing on the concrete design, simulation and conduction stages. The core knowledge

bound to be learnt first includes the Antenna theory which provides the basis un-

derstanding of wireless energy radiation and output, various antenna types which

suit different application purposes, some typical antenna design samples, rectifying

circuit basics such as diode properties, filter design basics and so on. Self-study

using online resources and weekly tutorial sections provided by supervisor should

be the main method for this crucial stage.

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4.2 Detailed Tasks

4.2.1 Tasks Description

• Learn necessary basic knowledge such as typical antenna design process and

rectifying system working principle before the start of design

• Literature review for obtaining some ideas about what kinds of structures

to apply on each of the four core design sections of the system (milestone

one)

• Design of the antenna, the rectifying circuit, the impedance matching circuit

and some additional components such as filters as different design packages

• Combine the individual packages together and adjust some of them if neces-

sary to complete an initial version of the system design (milestone two)

• Simulate the system under some specific multiband conditions such as WLAN

bandwidth

• Further improve the overall design by making some innovative improvement

which has not been done before in similar projects (milestone three)

• Finalise the design on simulation software

• Construct the prototype of this system (milestone four)

• Test the performance of the prototype and compare it with the simulation

and as well as the calculated purely theoretical results (milestone five)

• Compare the performance with that of other previous similar projects and

conclude some insights and reflections on this project outcome and finish the

thesis report

4.2.2 Milestone Description

1. Completion of the preparation work including learning necessary related en-

gineering knowledge and literature review before the actual design

2. Completion of an initial design which should be a normally working system

but not necessarily with completely innovative individual structures

3. Completion of the design of the system in software level

4. Completion of the design in hardware level

5. Completion of the test of the product

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Chapter 5

Project Rationale and Industrial

Relevance

5.1 Significance of this project

The topic of this project is fairly significant for many reasons which include its

essential role for electronic students and its particular potential for future devel-

opment of energy use. The core component of this wireless harvesting energy

harvesting system is antenna design.

Antenna is an essential object in the study of telecommunication domain, which

is also one of the most focused topics of the research done by my supervisor’s team.

As a result, it is expected that during the process of completing this project, both

the fundamental knowledge about antenna and some advanced research skills can

be obtained by I myself working hard on doing self-study about all these related

subjects and also with the help of the supervisor.

Moreover, this subject itself is currently a fairly hot topic with the increasing

demand for alternative multiple methods of charging without the constrain of

physical medium connection to a battery. The basic knowledge behind this wireless

energy harvesting system idea is a quite classic topic in telecommunication study,

which is the use of radio wave energy [2]. Therefore, it is expected to have progress

not so slow since its basic knowledge has already been researched and discussed

comprehensively and there are a variety of papers to review as a valid start point

of project focused on such topic.

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5.2 Industrial application and potential

This project is definitely related to potential industrial values. Generally, Wireless

energy harvesting system can be utilized upon various small-scale and low-power

devices since briefly saying, the primary feature of this technology is to achieve

“battery-free” electronic products.

One typical application using the expected outcome of this project would be

medical-used low-power devices which are supposed to stay within human bodies

for a long time without being taken out to be charged.

Moreover, for large scale of use when this technology become mature enough,

the idea of “smart home” might be achieved which requires lots of wireless charged

low-power sensors, and an conceptual graph of this smart home can be seen in

Figure 5.1.

For even more imaginary perspective, the achievement of the innovative idea

Internet of Things might speed up if this wireless energy harvesting system tech-

nology is developed to a certain advanced stage.

Figure 5.1: Smart home [5]

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Chapter 6

Literature Review

6.1 History and challenges

Actually, since the electricity occurred, the idea of wireless energy transfer had

started to appear, which is the very beginning of today’s wireless energy harvesting

system concept [6]. The core idea of this wireless energy harvesting concept is the

RF energy harvesting, which has more than 50 years’ history in research [3], and

the concrete core component in such system is antenna, which has experienced

an even longer history of research. Antenna has long been a fairly hot subject in

wireless engineering and has developed various types with different features, one

example of which can be logarithmically periodic antenna which has particularly

stable impedance characteristic regardless of the change of frequency [7]. Also for

the rectifying circuit, stable performance rectifier which can maintain high RF-

to-DC conversion efficiency with a quite wide range of load resistance has been

developed [8].

However, challenges have been laid on this way such as the unstable perfor-

mance of the rectifying circuit with various load resistance and input RF power [8],

the difficulty of effectively harvesting the ambient RF power which is very weak

signal therefore the bandwidth decided to be covered into the transmission has long

been tricky [9], poor sensitivity of wireless sensor power extracting caused by the

limited harvesting of RF [10], and the need of advanced impedance matching cir-

cuit between antenna and rectifying circuit due to the non-linearity characteristic

of rectifier [4].

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6.2 Latest results

The recent results in terms of wireless energy harvesting system lay in multiple

aspects from bandwidth coverage to efficiency increase.

A typical one is to achieve system that can cover multiband, and apparently as

a result to be able to cover broadband, RF power. For example, wireless RF energy

harvesting system than specially designed to cover four most common RF band-

widths in London has been developed [3] and even six-band system was developed

recently[2]. This broadband and multiband coverage is an important improvement

which widens the practical potential of the wireless energy harvesting system.

To more concrete perspective regarding the individual sections of the system,

there are so many innovative improvements achieving higher efficiency for wireless

energy harvesting system. For example for the converter between rectifying circuit

and output, resistance compression network structure was recently designed and

improved to enhance the DC-to-DC conversion by adding a buck-boost converter

thus contributing to the improvement of efficiency for the whole system [11].

More improvements are still expected especially in terms of further increasing

the conversion efficiency, broadening the bandwidth, increasing the output DC

power, and minimizing the antenna size.

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Chapter 7

Results

Till this stage and the main results gained till this stage is some inspirations in

terms of design process organization from previous works.

From the paper of increasing system efficiency mainly by optimizing the rectifier

[4], it is learnt that during the concrete design, it can necessary to compare the

performances of different types of antenna comprehensively to make the best choice

and also provided convincing reasoning process of proving why use certain antenna

structure.

From the paper of achieving multiband system using improved impedance

matching technique[2], it is learnt that to improve the rectifier performance in

various conditions, the impedance matching structures can be designed to both

ensure the rectifier efficiency and the multiband coverage target. A clever individ-

ual design can achieve many advantages and usually started by reviewing many

conventional basic alternatives first to prepare well for improved design.

Also, from this paper, it is learnt that to start the main design by first illustrat-

ing the characteristics of related basic components characteristics can be a good

way to decide the design conduction process. For example, the non-linearity fea-

ture of rectifier was first comprehensively analyzed using mathematical equations,

then the correspondingly designed advanced impedance matching system was de-

signed based on these functioning features. This structure design taught me that,

for the project conduction, the most innovative design should come from thorough

and in-depth understanding of related basic knowledge and only in this way the

innovative design can come up more naturally in the design stage.

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Chapter 8

Conclusion

The preparation word so far has been covering primarily the literature review, the

basic knowledge self-study, and project plan in the form of Gannt chart.

More in-depth literature review is going to be done, and weekly tutorial for

learning basic knowledge about related electronic component such as antenna will

be attended. Self study on the usage of ADS will be conducted before the actual

design and simulation.

Overall, this project is about a quite hot topic in telecommunication domain.

Though with multiple incredible development these decades, there is still a long

way to go for further development so that this broadband wireless energy harvest-

ing technology can actually benefit our daily life.

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References

[1] Y. Huang, “Antennas,” Department of Electrical Engineering ElectronicsThe University of Liverpool Liverpool L69 3GJ.

[2] P. C. C. Song, Y. Huang, “A novel six-band dual cp rectenna using improvedimpedance matching technique for ambient rf energy harvesting,” Departmentof Electrical Engineering Electronics The University of Liverpool LiverpoolL69 3GJ, 2016.

[3] S. L. M. Piuela, P. Mitcheson, “Ambient rf energy harvesting in urbanand semi-urban environments,” http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6519964, 2013.

[4] P. C. C. Song, Y. Huang, “A high-efficiency broadband rectenna for ambientwireless energy harvesting,” Department of Electrical Engineering ElectronicsThe University of Liverpool Liverpool L69 3GJ, 2015.

[5] J. Enocean, “Energy harvesting wireless solutions: Building management andbeyond,” http://rtcmagazine.com/articles/view/103744, 2014.

[6] G. D. D. C. R. Valenta, “High efficiency resonant dc/dc converter utilizinga resistance compression network,” https://www.mtt.org/sites/default/files/content/AWARDS media/Microwave Magazine Best Papers/2015.pdf, 2014.

[7] F. R. O. R. H. DuHamel, “Logarithmically periodic antenna designs,” http://157.92.49.120/materias/6654/download/01150707.pdf, 1957.

[8] T. M. Y. Huang, N. Shinohara, “A constant efficiency of rectifying circuit inan extremely wide load range,” http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6656026, 2014.

[9] W. Brown, “The history of power transmission by radio waves,” http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=1132833, 1984.

[10] H. H. Z. Safarian, “Wirelessly powered passive systems with dynamic energystorage mechanism,” http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6742626, 2014.

[11] D. J. P. W. Inam, K. K. Afridi, “High efficiency resonant dc/dc converterutilizing a resistance compression network,” http://www.rle.mit.edu/per/wp-content/uploads/2014/05/Inam-High-Efficiency-TPELS.pdf, 2014.

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Chapter 9

Appendix

9.1 A Gantt chart

Figure 9.1: Gantt Chart

9.2 Three forms

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