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Wirelessly Powered Communications: From Signal Optimization to Antenna Design
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Information Science and Engineering.ORCID iD: 0000-0002-4362-9795
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Future internet-of-things (IoT) and beyond 5G communication systems are envisioned to offer large-scale wireless connectivity where the different components of life, society and industry are connected in a smart yet sustainable way. The need for continuous battery charging and/or replacement is a bottleneck for sustainability in these systems. As the number of battery-powered wireless devices grows, it is associated with an increase in both the maintenance costs and the impact on the environment. Wireless power transfer (WPT) is a promising solution to enable self-sustainable operation and limit battery usage in the enormous amount of devices that the future wireless systems will bring.

WPT co-exists by nature with other well-established communication systems. However, WPT signals are usually transmitted at a higher power level than information signals to overcome propagation losses and provide sufficient power to the receiver. Therefore, when designing a WPT system, it is essential to consider and minimize its impact on the co-existing and co-located communication systems. Moreover, in order to enable wirelessly powered communication (WPC) nodes, efficient WPT is not enough on its own but it is also important to minimize the power consumption of the node and optimize its energy usage. This thesis investigates the above described issues from both a theoretical and an implementation perspectives. It is divided into two parts; the first part focuses on signals and system level optimization with the goal of achieving wirelessly powered sensing nodes, the second part concerns enabling simultaneous wireless information and power transfer (SWIPT) by exploring novel designs of antennas and microwave components.

In the first part of the thesis, we first study the optimization of multi-tone signals to maximize the efficiency of WPT. We discuss and consider different practical non-linear energy harvester models in the problem formulation. Taking into account the in-band co-existing communication links, we provide the optimal weights for the multi-tone signals that maximizes the efficiency of WPT while minimizing the interference. The performance gains obtained using our optimization methods are highlighted through comparisons with other solutions existing in the literature. Furthermore, we present a low-complexity algorithm for designing the multi-tone signal in order to enable practical implementation. Secondly, we study the use of analog joint source-channel coding (AJSCC) in low-power sensing schemes. We propose a novel low-complexity dimension reduction mapping that is used to compress multiple sensor readings into one signal, and thus, limits the power consumption at the sensing node. We provide a comprehensive analysis of the distortion performance of our proposed mapping. We also show that energy scheduling can be utilized to improve the distortion performance of the compression mapping. Moreover, we discuss the practical circuit implementation of our proposed mapping and explain that it provides a very good distortion performance compared to the other AJSCC benchmarks despite having a much lower complexity circuit implementation. The findings of the first part of the thesis are valuable within the context of efficient and practical usage of WPT to energize a low-power IoT sensing node.

Motivated by the need for high isolation between co-located SWIPT antennas, the second part of the thesis first presents a SWIPT antenna design utilizing differential feeding in addition to an electromagnetic bandgap (EBG) structure to minimize mutual coupling between the antennas dedicated for power transmission and information exchange. Second, it investigates exploiting glide symmetry in designing EBG structures and microwave filters. We demonstrate that glide symmetry can increase the operational bandwidth of mushroom-type EBG structures without any additional manufacturing costs. A detailed equivalent circuit model is derived in order to explain this bandwidth increment. Full-wave simulations as well as experimental results are presented to verify the benefits of the glide-symmetric versions compared to the conventional structures without glide symmetry. As an alternative to the use of mushroom-type EBGs, a detailed study on the application of glide symmetry to defected ground structures (DGSs) is also conducted. We show that glide-symmetric DGSs can provide a higher rejection level as well as a higher rejection bandwidth compared to their conventional versions without symmetry. The improvement in the rejection level and bandwidth of both mushroom-type EBGs and DGSs is also explained to be useful in common-mode rejection filters. Finally, we show that fully planar EBG structures can utilize glide symmetry for size reduction and providing an increased level of isolation between microstrip patch antennas. The results of the second part of the thesis enable a new class of hardware designs that are useful for the practical realization of SWIPT systems.

Abstract [sv]

Framtida sakernas internet, internet-of-things (IoT), och kommunikationssystembortom 5G är tänkta att erbjuda storskalig trådlös uppkoppling där olika komponenter av livet, samhället och industrin är sammankopplade på ett smart men ändå hållbart sätt. Behovet av kontinuerlig laddning och/eller utbyte av batterier är en flaskhals för hållbarheten i dessa system. I takt med att antalet batteridrivna trådlösa enheter växer är det förknippat med en ökning av både underhållskostnader och miljöpåverkan. Trådlös effekttöverföring är en lovande lösning för att möjliggöra självförsörjande drift och begränsa batterianvändningen i den enorma mängd enheter som framtidens trådlösa system kommer att ge upphov till.

Trådlös effekttöverföring samexisterar till sin natur med andra väletablerade kommunikationssystem. Vanligtvis sänds emellertid trådlösa effekttöverföringssignaler med en högre effektnivå än kommunikationssignaler för att övervinna utbredningsförlusterna och ge tillräcklig effekt till mottagaren. När man utformar ett trådlöst effektöverföringssystem är det därför viktigt att överväga och minimera dess inverkan på de samexisterande och samlokaliserade kommunikationssystemen. Dessutom, för att möjliggöra trådlöst drivna kommunikationsnoder, är det inte tillräckligt med effektiv trådlös effektöverföring, utan det är också viktigt att minimera nodens strömförbrukning och optimera dess energianvändning. Denna doktorsavhandling undersöker de ovan beskrivna frågeställningarnaur både teoretiska och implementeringsaspekter. Den är uppdelad i två delar; den första delen fokuserar på signal- och systemnivåoptimering med målet att uppnå trådlöst drivna sensornoder. Den andra delen handlar om att möjliggörasimultan trådlös kommunikation- och effektöverföring (SWIPT-simultaneous wirelessinformation and power transfer), genom att utforska nya konstruktioner avantenner och mikrovågskomponenter.

I den första delen av avhandlingen studerar vi först optimering av flertonssignaler för att maximera effektiviteten hos den trådlösa effektöverföringen. Vi diskuterar och överväger olika praktiska icke-linjära energiskördarmodeller i problemformuleringen. Med hänsyn till de samexisterande kommunikationslänkarna tillhandahåller vi de optimala vikterna för flertonssignalerna som maximerar effektiviteten hos den trådlösa effektöverföringen samtidigt som störningarna minimeras. De prestandavinster som erhålls med våra optimeringsmetoder framhävs genom jämförelser med andra lösningar i litteraturen. Dessutom presenterar vi en lågkomplexitetsalgoritm för att designa flertonssignalen som möjliggör en praktisk implementering. För det andra studerar vi användningen av analog gemensam källa-kanal-kodning (AJSCC-analog joint source-channel coding), i avkänningsscheman med låg effekt. Vi föreslår en ny dimensionsreducerande avbildning med låg komplexitet som kan användas för att komprimera ihop flera sensoravläsningar till en signal och därmed begränsa strömförbrukningen vid avkänningsnoden. Vi tillhandahåller en omfattande analys av distorsionsprestandan för vår föreslagna avbildning. Vi visar också att energischemaläggning kan användas för att förbättra distorsionsprestandan för kompressionen. Dessutom diskuterar vi den praktiska kretsimplementeringen av vår föreslagna avbildning och visar att den ger en mycket bra distorsionsprestanda jämfört med andra AJSCC-metoder trots att den har en mycket lägre kretsimplementeringskomplexitet. Resultaten av den första delen av avhandlingen är betydelsefulla inom ramen för effektiv och praktisk användning av trådlös effektöverföring för att aktivera en IoT-avkänningsnod med låg effekt.

Den andra delen av avhandlingen, motiverat av behovet av hög isolering mellan samlokaliserade SWIPT-antenner, presenterar först en design av SWIPT-antenner som använder differentiell överföring utöver en struktur för elektromagnetiskt bandgap (EBG) för att minimera ömsesidig koppling mellan antennerna avsedda för kraftöverföring och informationsutbyte. Sedan undersöks utnyttjandet av glidsymmetri vid design av EBG-strukturer och mikrovågsfilter. Vi visar att glidsymmetri kan öka den operativa bandbredden för svampformade EBG-strukturer utan några ytterligare tillverkningskostnader. En detaljerad ekvivalent kretsmodell härleds för att förklara denna bandbreddsökning. Helvågssimuleringar såväl som experimentella resultat presenteras för att verifiera fördelarna med de glidsymmetriska versionerna jämfört med konventionella strukturer utan glidsymmetri. Som ett alternativ till användningen av svampformad EBG genomförs också en detaljerad studie om tillämpningen av glidsymmetri på defekta markstrukturer (DMS). Vi visar att glidsymmetriska DMS:er kan ge en högre förkastningsnivå såväl som en högre förkastningsbandbredd jämfört med konventionella versioner utan symmetri. Förbättringen av förkastningsnivån och bandbredden för både DMS:er och svampformade EBG:er förklaras också vara användbar i förkastningsfilter baserade på gemensamma typvärden. Slutligen visar vi att helt plana EBG-strukturer kan använda glidsymmetri för storleksminskning och ge en ökad nivå av isolering mellan mikrostrippatchantenner. Resultaten i den andra delen av avhandlingen möjliggör en ny klass av hårdvarudesigner som är användbara för praktisk realisering av SWIPT-system.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2022. , p. xiv, 211
Series
TRITA-EECS-AVL ; 2022:36
Keywords [en]
Wireless power transfer, multi-tone signals, non-linear energy harvester, wirelessly powered sensors, joint source-channel coding, analog mappings, energy scheduling, mutual coupling reduction, electromagnetic bandgap, glide symmetry.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-312464ISBN: 978-91-8040-237-8 (print)OAI: oai:DiVA.org:kth-312464DiVA, id: diva2:1659495
Public defence
2022-06-15, Kollegiesalen, Brinellvägen 6, plan 4, KTH Campus, Stockholm, 13:30 (English)
Opponent
Supervisors
Note

QC 20220520

Available from: 2022-05-20 Created: 2022-05-19 Last updated: 2022-06-29Bibliographically approved
List of papers
1. Multi-tone Signal Optimization for Wireless Power Transfer in the Presence of Wireless Communication Links
Open this publication in new window or tab >>Multi-tone Signal Optimization for Wireless Power Transfer in the Presence of Wireless Communication Links
2020 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 19, no 5, p. 3575-3590Article in journal (Refereed) Published
Abstract [en]

In this paper, we study optimization of multi-tone signals for wireless power transfer (WPT) systems. We investigate different non-linear energy harvesting models. Two of them are adopted to optimize the multi-tone signal according to the channel state information available at the transmitter. We show that a second-order polynomial curve-fitting model can be utilized to optimize the multi-tone signal for any RF energy harvester design. We consider both single-antenna and multi-antenna WPT systems. In-band co-existing communication links are also considered in this work by imposing a constraint on the received power at the nearby information receiver to prevent its RF front end from saturation. We emphasize the importance of imposing such constraint by explaining how inter-modulation products, due to saturation, can cause high interference at the information receiver in the case of multi-tone signals. The multi-tone optimization problem is formulated as a non-convex linearly constrained quadratic program. Two globally optimal solution approaches using mixed-integer linear programming and finite branch-and-bound techniques are proposed to solve the problem. The achieved improvement resulting from applying both solution methods to the multi-tone optimization problem is highlighted through simulations and comparisons with other solutions existing in the literature.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-269164 (URN)10.1109/TWC.2020.2974950 (DOI)000536297700048 ()2-s2.0-85084924633 (Scopus ID)
Note

QC 20200623

Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2022-06-26Bibliographically approved
2. A Novel Low-Complexity Power-Allocation Algorithm for Multi-Tone Signals for Wireless Power Transfer
Open this publication in new window or tab >>A Novel Low-Complexity Power-Allocation Algorithm for Multi-Tone Signals for Wireless Power Transfer
2020 (English)In: IEEE Conference on Wireless Communications and Networking, Institute of Electrical and Electronics Engineers (IEEE) , 2020, p. -6Conference paper, Published paper (Refereed)
Abstract [en]

Recent studies proved that optimized multi-tone signals can significantly enhance the performance of wireless power transfer (WPT) systems. However, optimizing the power allocation for multi-tone signals in order to maximize the efficiency of WPT is a computationally complex task. In this paper, a novel low-complexity algorithm, the truncated maximum-ratio transmission (TMRT) algorithm, for allocating power to multitone signals for WPT is proposed. The algorithm exploits the fact that optimal algorithms tend to allocate power to tones having the strongest channels and no power to weaker channels, and therefore, performs maximum ratio transmission power allocation on the subset of the m strongest channels. In this way, the power allocation problem is reduced to finding the optimal m that maximizes the efficiency. Simulation results confirm that the proposed TMRT algorithm achieves a performance very close to the optimal power allocation, despite its very low complexity, and significantly outperforms other low-complexity solutions.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2020
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-280453 (URN)10.1109/WCNC45663.2020.9120666 (DOI)000569342900211 ()2-s2.0-85087274238 (Scopus ID)
Conference
2020 IEEE Wireless Communications and Networking Conference (WCNC), Seoul, South Korea, 25-28 May 2020
Note

QC 20200923

Available from: 2020-09-08 Created: 2020-09-08 Last updated: 2023-03-30Bibliographically approved
3. Optimizing Low-Complexity Analog Mappings for Low-Power Sensors with Energy Scheduling Capabilities
Open this publication in new window or tab >>Optimizing Low-Complexity Analog Mappings for Low-Power Sensors with Energy Scheduling Capabilities
2022 (English)In: IEEE Internet of Things Journal, ISSN 2327-4662, p. 1-1Article in journal (Refereed) Published
Abstract [en]

Power consumption is a major challenge for massive deployment of wireless sensors in internet of things (IoT) networks. This paper studies the use of analog joint source-channel (AJSCC) mappings in low-power sensing schemes. In particular, we propose a novel triangular mapping geometry as a low-complexity dimension reduction mapping. The proposed triangular mapping is employed for analog compression of multiple sensor readings into one signal, and thus, limits the need for power-hungry analog-to-digital conversion and processing at the sensing nodes. A comprehensive performance analysis of the proposed triangular mapping in terms of the mean squared error (MSE) performance is provided analytically and verified numerically. The problem of mapping adaptation to different source distributions is also studied. Moreover, the proposed triangular mapping is adopted in an energy scheduling problem in which the sensing nodes schedule their use of the received powers at different time instants and adjust the mapping parameters accordingly with the goal of minimizing the sum distortion at the receiver. We present a fast low-complexity algorithm for optimal energy scheduling and verify its performance in comparison with commercial convex optimization solvers. It is shown that the proposed mapping provides a very good MSE performance compared to the AJSCC benchmarks despite having a much lower complexity circuit implementation.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-312458 (URN)10.1109/jiot.2022.3156865 (DOI)000884575200053 ()2-s2.0-85125694763 (Scopus ID)
Note

QC 20220530

Available from: 2022-05-18 Created: 2022-05-18 Last updated: 2023-09-21Bibliographically approved
4. A Dual-Polarized Multi-Antenna Structure for Simultaneous Transmission of Wireless Information and Power
Open this publication in new window or tab >>A Dual-Polarized Multi-Antenna Structure for Simultaneous Transmission of Wireless Information and Power
2019 (English)In: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings, IEEE, 2019, p. 1805-1806, article id 8889079Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a dual-polarized multi-antenna structure is designed at 2.45 GHz with the goal of allowing simultaneous transmission of wireless information and power. Differential feeding was used to minimize the mutual coupling due to radiation leakage in addition to a mushroom-type EBG structure for suppressing the surface waves. Simulation results for the proposed structure show a mutual coupling level lower than -40 dB between the information transmitting antenna and the power transmitting antennas for both polarizations. The isolation level between the antennas is improved by at least 22 dB and 14 dB for the E-plane and H-plane coupling, respectively.

Place, publisher, year, edition, pages
IEEE, 2019
Series
IEEE Antennas and Propagation Society International Symposium, ISSN 1522-3965
National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-269165 (URN)10.1109/APUSNCURSINRSM.2019.8889079 (DOI)000657207106005 ()2-s2.0-85075233043 (Scopus ID)
Conference
2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, Atlanta, 7 July 2019, through 12 July 2019
Note

QC 20220928

Part of proceedings: ISBN 978-1-7281-0692-2

Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2022-09-28Bibliographically approved
5. On the Increment of the Bandwidth of Mushroom-Type EBG Structures With Glide Symmetry
Open this publication in new window or tab >>On the Increment of the Bandwidth of Mushroom-Type EBG Structures With Glide Symmetry
Show others...
2020 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670Article in journal (Refereed) Published
Abstract [en]

Mushroom-type electromagnetic bandgap (EBG) structures are known to operate as high-impedance surfaces at low-frequency bands. They are broadly used in the microwave regime. However, one of the main drawbacks of mushroom-type EBG structures is their narrow bandwidth. In this article, we propose a mushroom-type EBG structure with glide-symmetric edge vias to increase the operational bandwidth. This bandwidth increment is explained by the physical insight provided by an equivalent circuit model of the structure as well as the description of the field behavior. Simulation and measurement results show an improvement of approximately 67% over the case without glide symmetry in the structure. We conclude that applying glide symmetry to the mushroom-type EBG structures can improve their bandwidth without adding additional manufacturing costs.

National Category
Telecommunications
Identifiers
urn:nbn:se:kth:diva-269163 (URN)10.1109/TMTT.2020.2966700 (DOI)000525333900015 ()2-s2.0-85083036719 (Scopus ID)
Note

QC 20200428

Available from: 2020-03-04 Created: 2020-03-04 Last updated: 2022-06-26Bibliographically approved
6. Glide Symmetry Applied to Printed Common-Mode Rejection Filters
Open this publication in new window or tab >>Glide Symmetry Applied to Printed Common-Mode Rejection Filters
Show others...
2022 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 70, no 2, p. 1198-1210Article in journal (Refereed) Published
Abstract [en]

In this article, we present a novel application of glide symmetry to differential lines with common-mode (CM) rejection filter properties. Two different topologies are investigated. First, glide symmetry is applied to a pair of differential lines where ground-connected mushrooms are employed as a CM rejection structure. The same idea is also used in a pair of differential lines where defective ground structures are introduced to stop the CM propagation. It is demonstrated that the CM rejection bandwidth is drastically increased when glide symmetry is exploited in both topologies when compared with their corresponding structures without glide symmetry. Furthermore, we show that the differential-mode propagation is hardly affected by the use of glide symmetry, ensuring the good integrity of the transmitted information. Experimental demonstration for both mushroom and defected ground structure is provided. Good agreement between simulations and measurements results is observed.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2022
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-312463 (URN)10.1109/tmtt.2021.3127933 (DOI)000728185500001 ()2-s2.0-85120581898 (Scopus ID)
Note

QC 20220530

Available from: 2022-05-18 Created: 2022-05-18 Last updated: 2022-06-25Bibliographically approved
7. Glide-Symmetric Planar EBG Structure for Mutual Coupling Reduction Between Microstrip Patch Antennas
Open this publication in new window or tab >>Glide-Symmetric Planar EBG Structure for Mutual Coupling Reduction Between Microstrip Patch Antennas
2021 (English)In: 2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI), Institute of Electrical and Electronics Engineers (IEEE) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

In this paper, a fully planar electromagnetic bandgap (EBG) structure exploiting glide symmetry is proposed for mutual coupling reduction between microstrip patch antennas. The proposed structure is studied in terms of dispersion diagrams and full-wave simulations showing a size reduction as well as an increased level of isolation when compared to its corresponding conventional structure without glide symmetry.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2021
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-312459 (URN)10.1109/APS/URSI47566.2021.9703889 (DOI)2-s2.0-85126844405 (Scopus ID)
Conference
2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (APS/URSI)
Note

Part of proceedings: ISBN 978-1-7281-4670-6

QC 20220530

Available from: 2022-05-18 Created: 2022-05-18 Last updated: 2023-01-17Bibliographically approved

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