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@ -143,7 +143,7 @@
isbn = {978-1-4503-4139-4} isbn = {978-1-4503-4139-4}
} }
@inproceedings{arpPrivacyThreatsUltrasonic2017a, @inproceedings{arpPrivacyThreatsUltrasonic2017,
title = {Privacy {{Threats}} through {{Ultrasonic Side Channels}} on {{Mobile Devices}}}, title = {Privacy {{Threats}} through {{Ultrasonic Side Channels}} on {{Mobile Devices}}},
booktitle = {2017 {{IEEE European Symposium}} on {{Security}} and {{Privacy}} ({{EuroS}}\&{{P}})}, booktitle = {2017 {{IEEE European Symposium}} on {{Security}} and {{Privacy}} ({{EuroS}}\&{{P}})},
author = {Arp, Daniel and Quiring, Erwin and Wressnegger, Christian and Rieck, Konrad}, author = {Arp, Daniel and Quiring, Erwin and Wressnegger, Christian and Rieck, Konrad},
@ -1033,7 +1033,7 @@
file = {/home/jaseg/Sync/Research/Zotero/Couteau et al_2021_Silver.pdf} file = {/home/jaseg/Sync/Research/Zotero/Couteau et al_2021_Silver.pdf}
} }
@article{cuellarStaticFatigueLifetime1987, @article{cuellarStaticFatigueLifetime1987a,
title = {Static Fatigue Lifetime of Optical Fibers in Bending}, title = {Static Fatigue Lifetime of Optical Fibers in Bending},
author = {Cuellar, E. and Roberts, D. and Middleman, L.}, author = {Cuellar, E. and Roberts, D. and Middleman, L.},
date = {1987-01-01}, date = {1987-01-01},
@ -2013,16 +2013,16 @@
@online{IEEEXploreFullTexta, @online{IEEEXploreFullTexta,
title = {{{IEEE Xplore Full-Text PDF}}:}, title = {{{IEEE Xplore Full-Text PDF}}:},
url = {https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6520632}, url = {https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8558378},
urldate = {2024-09-10}, urldate = {2024-09-10},
file = {/home/jaseg/Zotero/storage/PQYCW7K7/stamp.html} file = {/home/jaseg/Zotero/storage/HJJK32NF/stamp.html}
} }
@online{IEEEXploreFullTextb, @online{IEEEXploreFullTextb,
title = {{{IEEE Xplore Full-Text PDF}}:}, title = {{{IEEE Xplore Full-Text PDF}}:},
url = {https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=8558378}, url = {https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6520632},
urldate = {2024-09-10}, urldate = {2024-09-10},
file = {/home/jaseg/Zotero/storage/HJJK32NF/stamp.html} file = {/home/jaseg/Zotero/storage/PQYCW7K7/stamp.html}
} }
@online{ImpactPolarizationMode, @online{ImpactPolarizationMode,
@ -2516,11 +2516,11 @@
issn = {2511-9044, 2511-9044}, issn = {2511-9044, 2511-9044},
doi = {10.1002/qute.201800011}, doi = {10.1002/qute.201800011},
url = {http://arxiv.org/abs/1703.09278}, url = {http://arxiv.org/abs/1703.09278},
urldate = {2024-05-27}, urldate = {2024-05-02},
abstract = {Quantum key distribution using weak coherent states and homodyne detection is a promising candidate for practical quantum-cryptographic implementations due to its compatibility with existing telecom equipment and high detection efficiencies. However, despite the actual simplicity of the protocol, the security analysis of this method is rather involved compared to discrete-variable QKD. In this article we review the theoretical foundations of continuous-variable quantum key distribution (CV-QKD) with Gaussian modulation and rederive the essential relations from scratch in a pedagogical way. The aim of this paper is to be as comprehensive and self-contained as possible in order to be well intelligible even for readers with little pre-knowledge on the subject. Although the present article is a theoretical discussion of CV-QKD, its focus lies on practical implementations, taking into account various kinds of hardware imperfections and suggesting practical methods to perform the security analysis subsequent to the key exchange. Apart from a review of well known results, this manuscript presents a set of new original noise models which are helpful to get an estimate of how well a given set of hardware will perform in practice.}, abstract = {Quantum key distribution using weak coherent states and homodyne detection is a promising candidate for practical quantum-cryptographic implementations due to its compatibility with existing telecom equipment and high detection efficiencies. However, despite the actual simplicity of the protocol, the security analysis of this method is rather involved compared to discrete-variable QKD. In this article we review the theoretical foundations of continuous-variable quantum key distribution (CV-QKD) with Gaussian modulation and rederive the essential relations from scratch in a pedagogical way. The aim of this paper is to be as comprehensive and self-contained as possible in order to be well intelligible even for readers with little pre-knowledge on the subject. Although the present article is a theoretical discussion of CV-QKD, its focus lies on practical implementations, taking into account various kinds of hardware imperfections and suggesting practical methods to perform the security analysis subsequent to the key exchange. Apart from a review of well known results, this manuscript presents a set of new original noise models which are helpful to get an estimate of how well a given set of hardware will perform in practice.},
langid = {english}, langid = {english},
keywords = {Quantum Physics}, keywords = {Quantum Physics},
file = {/home/jaseg/Zotero/storage/I7UL2SKX/Laudenbach et al. - 2018 - Continuous-Variable Quantum Key Distribution with .pdf} file = {/home/jaseg/Zotero/storage/A2BQHUUW/Laudenbach et al. - 2018 - Continuous-Variable Quantum Key Distribution with .pdf}
} }
@article{laudenbachContinuousVariableQuantumKey2018a, @article{laudenbachContinuousVariableQuantumKey2018a,
@ -2538,11 +2538,11 @@
issn = {2511-9044, 2511-9044}, issn = {2511-9044, 2511-9044},
doi = {10.1002/qute.201800011}, doi = {10.1002/qute.201800011},
url = {http://arxiv.org/abs/1703.09278}, url = {http://arxiv.org/abs/1703.09278},
urldate = {2024-05-02}, urldate = {2024-05-27},
abstract = {Quantum key distribution using weak coherent states and homodyne detection is a promising candidate for practical quantum-cryptographic implementations due to its compatibility with existing telecom equipment and high detection efficiencies. However, despite the actual simplicity of the protocol, the security analysis of this method is rather involved compared to discrete-variable QKD. In this article we review the theoretical foundations of continuous-variable quantum key distribution (CV-QKD) with Gaussian modulation and rederive the essential relations from scratch in a pedagogical way. The aim of this paper is to be as comprehensive and self-contained as possible in order to be well intelligible even for readers with little pre-knowledge on the subject. Although the present article is a theoretical discussion of CV-QKD, its focus lies on practical implementations, taking into account various kinds of hardware imperfections and suggesting practical methods to perform the security analysis subsequent to the key exchange. Apart from a review of well known results, this manuscript presents a set of new original noise models which are helpful to get an estimate of how well a given set of hardware will perform in practice.}, abstract = {Quantum key distribution using weak coherent states and homodyne detection is a promising candidate for practical quantum-cryptographic implementations due to its compatibility with existing telecom equipment and high detection efficiencies. However, despite the actual simplicity of the protocol, the security analysis of this method is rather involved compared to discrete-variable QKD. In this article we review the theoretical foundations of continuous-variable quantum key distribution (CV-QKD) with Gaussian modulation and rederive the essential relations from scratch in a pedagogical way. The aim of this paper is to be as comprehensive and self-contained as possible in order to be well intelligible even for readers with little pre-knowledge on the subject. Although the present article is a theoretical discussion of CV-QKD, its focus lies on practical implementations, taking into account various kinds of hardware imperfections and suggesting practical methods to perform the security analysis subsequent to the key exchange. Apart from a review of well known results, this manuscript presents a set of new original noise models which are helpful to get an estimate of how well a given set of hardware will perform in practice.},
langid = {english}, langid = {english},
keywords = {Quantum Physics}, keywords = {Quantum Physics},
file = {/home/jaseg/Zotero/storage/A2BQHUUW/Laudenbach et al. - 2018 - Continuous-Variable Quantum Key Distribution with .pdf} file = {/home/jaseg/Zotero/storage/I7UL2SKX/Laudenbach et al. - 2018 - Continuous-Variable Quantum Key Distribution with .pdf}
} }
@article{laudenbachContinuousVariableQuantumKey2018b, @article{laudenbachContinuousVariableQuantumKey2018b,
@ -2588,7 +2588,7 @@
file = {/home/jaseg/Zotero/storage/SPNJ8KBL/Launchbury et al. - 2014 - Application-Scale Secure Multiparty Computation.pdf} file = {/home/jaseg/Zotero/storage/SPNJ8KBL/Launchbury et al. - 2014 - Application-Scale Secure Multiparty Computation.pdf}
} }
@article{leePrintedSpiralWinding2011a, @article{leePrintedSpiralWinding2011,
title = {Printed {{Spiral Winding Inductor With Wide Frequency Bandwidth}}}, title = {Printed {{Spiral Winding Inductor With Wide Frequency Bandwidth}}},
author = {Lee, Chi Kwan and Su, Y. P. and Ron Hui, S. Y.}, author = {Lee, Chi Kwan and Su, Y. P. and Ron Hui, S. Y.},
date = {2011-10}, date = {2011-10},
@ -2740,6 +2740,21 @@
file = {/home/jaseg/Sync/Research/Zotero/2015_Li_Mi_Wireless Power Transfer for Electric Vehicle Applications.pdf;/home/jaseg/Zotero/storage/QYEZNYUG/6804648.html} file = {/home/jaseg/Sync/Research/Zotero/2015_Li_Mi_Wireless Power Transfer for Electric Vehicle Applications.pdf;/home/jaseg/Zotero/storage/QYEZNYUG/6804648.html}
} }
@inproceedings{liWirelessPowerTransfer2021,
title = {Wireless {{Power Transfer System}} for {{Long-term Sensor}} on {{Rotating Plane}}},
booktitle = {2021 {{IEEE Industrial Electronics}} and {{Applications Conference}} ({{IEACon}})},
author = {Li, Tao and Chen, Xiyou and Lang, Zhengying and Jin, Xin and Qi, Chen and Wang, Yijie},
date = {2021-11},
pages = {136--140},
doi = {10.1109/IEACon51066.2021.9654747},
url = {https://ieeexplore.ieee.org/document/9654747/?arnumber=9654747},
urldate = {2024-12-10},
abstract = {This paper presents a wireless power transfer system (WPT) for long-term sensor rotating around an axis on a plane. The system is suitable for powering long-term sensor and does not need to replace the battery periodically. By designing a new type of magnetic coupler, the coupling coefficient between the receiving coil and the transmitting coil can be maintained in a certain range. On the transmitting side, six planar spiral coils are evenly distributed in a circular array, so that the magnetic field on the path of the sensor is always strong. On the receiving side, two planar spiral coils are partially overlapped. The magnetic field generated by the magnetic coupler is analyzed theoretically and simulated by finite element method. The experimental results verify that the WPT system can continuously supply power for 5W load during rotation.},
eventtitle = {2021 {{IEEE Industrial Electronics}} and {{Applications Conference}} ({{IEACon}})},
keywords = {Couplers,Finite element analysis,long-term sensor,magnetic coupler,Maintenance engineering,Power supplies,Rectifiers,rotation,Spirals,Wireless power transfer,wireless power transfer (WPT)},
file = {/home/jaseg/Sync/Research/Zotero/Li et al_2021_Wireless Power Transfer System for Long-term Sensor on Rotating Plane.pdf;/home/jaseg/Zotero/storage/DQ9TIGTB/9654747.html}
}
@article{loMeasurementDeviceIndependentQuantumKey2012, @article{loMeasurementDeviceIndependentQuantumKey2012,
title = {Measurement-{{Device-Independent Quantum Key Distribution}}}, title = {Measurement-{{Device-Independent Quantum Key Distribution}}},
author = {Lo, Hoi-Kwong and Curty, Marcos and Qi, Bing}, author = {Lo, Hoi-Kwong and Curty, Marcos and Qi, Bing},
@ -2775,7 +2790,7 @@
file = {/home/jaseg/Zotero/storage/WBSKAYAN/Long et al. - 2024 - EM Eye Characterizing Electromagnetic Side-channe.pdf} file = {/home/jaseg/Zotero/storage/WBSKAYAN/Long et al. - 2024 - EM Eye Characterizing Electromagnetic Side-channe.pdf}
} }
@article{lopeFirstSelfResonant2021, @article{lopeFirstSelfresonantFrequency2021,
title = {First Self‐resonant Frequency of Power Inductors Based on Approximated Corrected Stray Capacitances}, title = {First Self‐resonant Frequency of Power Inductors Based on Approximated Corrected Stray Capacitances},
author = {Lope, Ignacio and Carretero, Claudio and Acero, Jesus}, author = {Lope, Ignacio and Carretero, Claudio and Acero, Jesus},
date = {2021-02}, date = {2021-02},
@ -3149,7 +3164,7 @@
file = {/home/jaseg/Zotero/storage/EBAXQHG5/Mosavirik et al. - 2022 - ImpedanceVerif On-Chip Impedance Sensing for Syst.pdf} file = {/home/jaseg/Zotero/storage/EBAXQHG5/Mosavirik et al. - 2022 - ImpedanceVerif On-Chip Impedance Sensing for Syst.pdf}
} }
@article{mosavirikSiliconEchoesNonInvasive2023a, @article{mosavirikSiliconEchoesNonInvasive2023,
title = {Silicon {{Echoes}}: {{Non-Invasive Trojan}} and {{Tamper Detection}} Using {{Frequency-Selective Impedance Analysis}}}, title = {Silicon {{Echoes}}: {{Non-Invasive Trojan}} and {{Tamper Detection}} Using {{Frequency-Selective Impedance Analysis}}},
shorttitle = {Silicon {{Echoes}}}, shorttitle = {Silicon {{Echoes}}},
author = {Mosavirik, Tahoura and Monfared, Saleh Khalaj and Safa, Maryam Saadat and Tajik, Shahin}, author = {Mosavirik, Tahoura and Monfared, Saleh Khalaj and Safa, Maryam Saadat and Tajik, Shahin},
@ -4261,6 +4276,24 @@
file = {/home/jaseg/Zotero/storage/DVUMANPK/Song and Mittal - 2017 - POSTER Inaudible Voice Commands.pdf} file = {/home/jaseg/Zotero/storage/DVUMANPK/Song and Mittal - 2017 - POSTER Inaudible Voice Commands.pdf}
} }
@article{songRotationLightweightWirelessPower2019,
title = {A {{Rotation-Lightweight Wireless Power Transfer System}} for {{Solar Wing Driving}}},
author = {Song, Kai and Ma, Bingqing and Yang, Guang and Jiang, Jinhai and Wei, Ruizhi and Zhang, Hang and Zhu, Chunbo},
date = {2019-09},
journaltitle = {IEEE Transactions on Power Electronics},
volume = {34},
number = {9},
pages = {8816--8830},
issn = {1941-0107},
doi = {10.1109/TPEL.2018.2886910},
url = {https://ieeexplore.ieee.org/document/8576647/?arnumber=8576647},
urldate = {2024-12-10},
abstract = {In this paper, a novel magnetic coupler of wireless power transfer system for the solar wing driving of the spacecraft is designed. Compared with the traditional slip-ring power supply, the proposed magnetic coupler is characterized by non-contact, high efficiency, wear free, safety, and reliability. Particularly, it can be applied to the rotating condition. To realize light weight and small volume of the receiver, the magnetic coupler has been optimized from both compensation topology and coil configuration. First, a series-none topology is employed to eliminate the bulky secondary-side compensation capacitor. Second, a new nested solenoid coil with strip core is proposed to ensure miniaturization, stable power transfer, and high efficiency. Finally, the experimental setup is built to verify the performance of the designed magnetic coupler. Experimental results are well matched to simulations, demonstrating that the weight of the prototype is 1.3 kg and the transfer power is 3 kW at an ac-dc efficiency of 92.7\%.},
eventtitle = {{{IEEE Transactions}} on {{Power Electronics}}},
keywords = {Couplers,Couplings,Magnetic cores,Magnetic flux,Power generation,Resistance,Rotary magnetic coupler,series-none (S-0) topology,solar wing driving,solenoid coil,strip core,Topology,wireless power transfer (WPT)},
file = {/home/jaseg/Sync/Research/Zotero/Song et al_2019_A Rotation-Lightweight Wireless Power Transfer System for Solar Wing Driving.pdf;/home/jaseg/Zotero/storage/7DHIZ9WS/8576647.html}
}
@inproceedings{sozioPatchableHardwareSecurity2021, @inproceedings{sozioPatchableHardwareSecurity2021,
title = {Patchable {{Hardware Security Module}} ({{PHaSM}}) for {{Extending FPGA Root-of-Trust Capabilities}}}, title = {Patchable {{Hardware Security Module}} ({{PHaSM}}) for {{Extending FPGA Root-of-Trust Capabilities}}},
booktitle = {2021 {{IEEE Physical Assurance}} and {{Inspection}} of {{Electronics}} ({{PAINE}})}, booktitle = {2021 {{IEEE Physical Assurance}} and {{Inspection}} of {{Electronics}} ({{PAINE}})},
@ -4387,7 +4420,7 @@
isbn = {978-1-119-64468-2}, isbn = {978-1-119-64468-2},
langid = {english}, langid = {english},
keywords = {banking community,FPGAs,hardware security modules,security engineer,smartcards,tamper resistance}, keywords = {banking community,FPGAs,hardware security modules,security engineer,smartcards,tamper resistance},
file = {/home/jaseg/Zotero/storage/DSFCQBZB/9781119644682.html} file = {/home/jaseg/Sync/Research/Zotero/2020_Tamper Resistance.pdf;/home/jaseg/Zotero/storage/EMWJABZF/9781119644682.html}
} }
@incollection{TamperResistance2020a, @incollection{TamperResistance2020a,
@ -4403,7 +4436,7 @@
isbn = {978-1-119-64468-2}, isbn = {978-1-119-64468-2},
langid = {english}, langid = {english},
keywords = {banking community,FPGAs,hardware security modules,security engineer,smartcards,tamper resistance}, keywords = {banking community,FPGAs,hardware security modules,security engineer,smartcards,tamper resistance},
file = {/home/jaseg/Sync/Research/Zotero/2020_Tamper Resistance.pdf;/home/jaseg/Zotero/storage/EMWJABZF/9781119644682.html} file = {/home/jaseg/Zotero/storage/DSFCQBZB/9781119644682.html}
} }
@article{tangMeasurementDeviceIndependentQuantumKey2016, @article{tangMeasurementDeviceIndependentQuantumKey2016,
@ -4623,6 +4656,23 @@
file = {/home/jaseg/Zotero/storage/KBKFVCHU/Wang and Liu - 2021 - Cascading attack on trusted-relay quantum key dist.pdf} file = {/home/jaseg/Zotero/storage/KBKFVCHU/Wang and Liu - 2021 - Cascading attack on trusted-relay quantum key dist.pdf}
} }
@article{wangCoaxialNestedCouplersBased2020,
title = {Coaxial {{Nested Couplers-Based Offset-Tolerance Rotary Wireless Power Transfer Systems}} for {{Electric Excitation Motors}}},
author = {Wang, Longyang and Li, Jiangui and Nie, Hui and Liu, Jincheng and Ke, Shaoxing},
date = {2020},
journaltitle = {IEEE Access},
volume = {8},
pages = {44913--44923},
issn = {2169-3536},
doi = {10.1109/ACCESS.2020.2978130},
url = {https://ieeexplore.ieee.org/document/9022913/?arnumber=9022913},
urldate = {2024-12-10},
abstract = {In order to improve poor anti-offset capability of rotary transformer in electric excitation motor, a coaxial nested rotary wireless power transfer (CNR-WPT) system has been proposed in this paper. Firstly, considering the spatial geometric relationship of the coils and the power transmission efficiency of the CNR-WPT, the preliminary coil structure has been proposed. Secondly, through theoretical derivation, the specific relationship between the mutual inductance of the coils and the offset have been studied to verify the feasibility of the preliminary design. Thirdly, aiming at the problem that the CNR-WPT is susceptible to steel interference, the magnetic field has been optimized by adding ferrite and introducing a protective casing in this paper. Finally, an experimental platform for CNR-WPT system has been built. The experimental results verify that the power transmission efficiency of the CNR-WPT system can reach 90\% when the radial offset and axial offset are below 5 mm, and the angular offset is below 5°. The energy losses can be reduced by adding ferrite and protecting the casing. The CNR-WPT system thereof can also be applied to other rotary power transmission occasions.},
eventtitle = {{{IEEE Access}}},
keywords = {anti-offset capability,Brushless motors,coaxial nested rotary wireless power transfer system,Coils,Electric excitation motor,Induction motors,power transmission efficiency,Reluctance motors,Shafts,Wireless power transfer},
file = {/home/jaseg/Sync/Research/Zotero/Wang et al_2020_Coaxial Nested Couplers-Based Offset-Tolerance Rotary Wireless Power Transfer.pdf;/home/jaseg/Zotero/storage/XK24S953/9022913.html}
}
@inproceedings{wangGhostTalkInteractiveAttack2022, @inproceedings{wangGhostTalkInteractiveAttack2022,
title = {{{GhostTalk}}: {{Interactive Attack}} on {{Smartphone Voice System Through Power Line}}}, title = {{{GhostTalk}}: {{Interactive Attack}} on {{Smartphone Voice System Through Power Line}}},
shorttitle = {{{GhostTalk}}}, shorttitle = {{{GhostTalk}}},
@ -4683,6 +4733,26 @@
file = {/home/jaseg/Zotero/storage/CMWK7SHH/Wang et al. - 2017 - Long-distance copropagation of quantum key distrib.pdf} file = {/home/jaseg/Zotero/storage/CMWK7SHH/Wang et al. - 2017 - Long-distance copropagation of quantum key distrib.pdf}
} }
@article{wangNovelRotatingWireless2024,
title = {A {{Novel Rotating Wireless Power Transfer System}} for {{Slipring}} with {{Redundancy Enhancement Characteristics}}},
author = {Wang, Qiyue and Wang, De’an and Zhang, Jiantao},
date = {2024-01},
journaltitle = {Sustainability},
volume = {16},
number = {13},
pages = {5628},
publisher = {Multidisciplinary Digital Publishing Institute},
issn = {2071-1050},
doi = {10.3390/su16135628},
url = {https://www.mdpi.com/2071-1050/16/13/5628},
urldate = {2024-12-10},
abstract = {This study investigates the dynamics of wireless power supply technology under rotation and its system redundancy, aiming to design a redundant, rotating wireless power supply system. In order to satisfy specifications of redundancy and fault tolerance, the circuit design of the wireless power transmission system was developed, and a planar three-sector coil coupling mechanism was designed; finally, the stability and power output characteristics of the system were assessed under static and dynamic working conditions, and the results show that the maximum output power of the system can reach 3 kW and the efficiency is more than 91\% under both static and dynamic working conditions. The study improved the rotating wireless charging system’s efficiency, which improves the energy utilization efficiency.},
issue = {13},
langid = {english},
keywords = {multi-coil coupling mechanism,rotating equipment,wireless power supply},
file = {/home/jaseg/Sync/Research/Zotero/Wang et al_2024_A Novel Rotating Wireless Power Transfer System for Slipring with Redundancy.pdf}
}
@article{wangTopologicalOptimizationHybrid2020, @article{wangTopologicalOptimizationHybrid2020,
title = {Topological Optimization of Hybrid Quantum Key Distribution Networks}, title = {Topological Optimization of Hybrid Quantum Key Distribution Networks},
author = {Wang, Yaxing and Li, Qiong and Mao, Haokun and Han, Qi and Huang, Furong and Xu, Hongwei}, author = {Wang, Yaxing and Li, Qiong and Mao, Haokun and Han, Qi and Huang, Furong and Xu, Hongwei},
@ -4799,6 +4869,23 @@
file = {/home/jaseg/Zotero/storage/DNUS4DNE/Xiao et al. - 2024 - From Hardware Fingerprint to Access Token Enhanci.pdf} file = {/home/jaseg/Zotero/storage/DNUS4DNE/Xiao et al. - 2024 - From Hardware Fingerprint to Access Token Enhanci.pdf}
} }
@article{xiaRotaryWirelessPower2024,
title = {A {{Rotary Wireless Power Transfer System With Rail-Type Coupling Structure}}},
author = {Xia, Kun and Zhu, Benjing and Lou, Yang and Huang, Daming},
date = {2024},
journaltitle = {IEEE Access},
volume = {12},
pages = {63967--63975},
issn = {2169-3536},
doi = {10.1109/ACCESS.2024.3393943},
url = {https://ieeexplore.ieee.org/document/10508729/?arnumber=10508729&tag=1},
urldate = {2024-12-10},
abstract = {Traditional power supply methods for rotating mechanisms are found to face problems, including complex structures, limited functionality, and potential safety hazards. To address these problems, a rotary wireless power transfer system with new rail-type coupling structure (RTR-WPT) is proposed in this paper. This system, characterized by safety, reliability, and flexible installation, is designed to provide power to devices mounted on rotating shafts. Firstly, the topological structure of the RTR-WPT system is introduced, and the corresponding circuit model is established. Secondly, MAXWELL is utilized for finite element analysis to design and optimize the rail-type rotary coupler. Finally, an experimental platform for the RTR-WPT system is built and tested. From the experimental results, it is validated that the new rail-type coupler and the design methodology are feasible, and the system can achieve a power transmission of 10.33W with an overall efficiency of 72.1\% under rotating conditions.},
eventtitle = {{{IEEE Access}}},
keywords = {Coils,Couplers,Couplings,finite element analysis,Finite element analysis,Power supplies,rail-type coupling structure,Reliability,Rotating mechanism,Topology,wireless power transfer,Wireless power transfer},
file = {/home/jaseg/Sync/Research/Zotero/Xia et al_2024_A Rotary Wireless Power Transfer System With Rail-Type Coupling Structure.pdf;/home/jaseg/Zotero/storage/SVKEQEZL/10508729.html}
}
@article{xuMeasurementdeviceindependentQuantumCryptography2015, @article{xuMeasurementdeviceindependentQuantumCryptography2015,
title = {Measurement-Device-Independent Quantum Cryptography}, title = {Measurement-Device-Independent Quantum Cryptography},
author = {Xu, Feihu and Curty, Marcos and Qi, Bing and Lo, Hoi-Kwong}, author = {Xu, Feihu and Curty, Marcos and Qi, Bing and Lo, Hoi-Kwong},
@ -4868,6 +4955,24 @@
urldate = {2024-07-25} urldate = {2024-07-25}
} }
@article{yanFreeRotationWirelessPower2023,
title = {Free-{{Rotation Wireless Power Transfer System Based}} on {{Composite Anti-Misalignment Method}} for {{AUVs}}},
author = {Yan, Zhengchao and Wu, Min and Zhao, Chenxu and Hu, Qianyu and Zhu, Lei and Qiao, Lin and Wang, Laili},
date = {2023-04},
journaltitle = {IEEE Transactions on Power Electronics},
volume = {38},
number = {4},
pages = {4262--4266},
issn = {1941-0107},
doi = {10.1109/TPEL.2023.3238066},
url = {https://ieeexplore.ieee.org/document/10021879/?arnumber=10021879},
urldate = {2024-12-10},
abstract = {In the underwater environment, the ocean current will have a great influence on the anti-misalignment performance of the wireless power transfer (WPT) system for the autonomous underwater vehicles (AUVs). In this letter, a free-rotation WPT system with a new magnetic coupler for AUVs is proposed to improve the rotational and axial misalignment tolerance. The magnetic coupler has two decoupled transmitters and one segmented arc solenoid receiver with reversely wound adjacent receiver coils. The mutual inductances between the receiver and the two transmitters can compensate each other. Moreover, cooperated with the phase control between the two transmitters, the system can achieve more stable output power under the rotational and axial misalignment. A free-rotation WPT prototype was set up and the experimental results showed that the output power can reach 700 W and the output power fluctuation is below 5\% based on the proposed anti-misalignment method.},
eventtitle = {{{IEEE Transactions}} on {{Power Electronics}}},
keywords = {Anti-misalignment,autonomous underwater vehicle (AUV),Couplers,Ferrites,Fluctuations,free-rotation,Magnetic resonance,Power generation,Receivers,Transmitters,wireless power transfer (WPT)},
file = {/home/jaseg/Sync/Research/Zotero/Yan et al_2023_Free-Rotation Wireless Power Transfer System Based on Composite.pdf;/home/jaseg/Zotero/storage/KL3X7E4B/10021879.html}
}
@article{yangFPGABasedLDPCDecoder2021, @article{yangFPGABasedLDPCDecoder2021,
title = {An {{FPGA-Based LDPC Decoder With Ultra-Long Codes}} for {{Continuous-Variable Quantum Key Distribution}}}, title = {An {{FPGA-Based LDPC Decoder With Ultra-Long Codes}} for {{Continuous-Variable Quantum Key Distribution}}},
author = {Yang, Shen-Shen and Liu, Jian-Qiang and Lu, Zhen-Guo and Bai, Zeng-Liang and Wang, Xu-Yang and Li, Yong-Min}, author = {Yang, Shen-Shen and Liu, Jian-Qiang and Lu, Zhen-Guo and Bai, Zeng-Liang and Wang, Xu-Yang and Li, Yong-Min},
@ -4953,6 +5058,24 @@
file = {/home/jaseg/Sync/Research/Zotero/2018_Zeppelzauer et al_SoniControl - A Mobile Ultrasonic Firewall.pdf} file = {/home/jaseg/Sync/Research/Zotero/2018_Zeppelzauer et al_SoniControl - A Mobile Ultrasonic Firewall.pdf}
} }
@article{zhangBallJointWirelessPower2018,
title = {Ball-{{Joint Wireless Power Transfer Systems}}},
author = {Zhang, Cheng and Lin, Deyan and Hui, S. Y. Ron},
date = {2018-01},
journaltitle = {IEEE Transactions on Power Electronics},
volume = {33},
number = {1},
pages = {65--72},
issn = {1941-0107},
doi = {10.1109/TPEL.2017.2700898},
url = {https://ieeexplore.ieee.org/document/7918527/?arnumber=7918527},
urldate = {2024-12-10},
abstract = {A new wireless power transfer (WPT) system based on ball-joint structure is presented in this paper. A ball-joint WPT system consists of a ball structure with a mechanical rod attached to the ball and a ball socket that accommodates the ball structure. This ball-joint structure comprises at least one winding in the ball structure and at least one winding in the ball socket structure. The ball structure can be flexibly rotated over a wide range of angle inside the ball socket, while wireless power can still be transferred from the transmitter winding to the receiver winding through magnetic resonance. The magnetic coupling coefficient between the transmitter and receiver coil over a wide rotating angular range has been analyzed and experimentally checked. Experimental results confirm that an energy efficiency of up to 81\% can be achieved.},
eventtitle = {{{IEEE Transactions}} on {{Power Electronics}}},
keywords = {Ball-joint structure,Inductance,magnetic resonance,Magnetic resonance,Receivers,Sockets,Transmitters,Windings,Wireless power transfer,wireless power transfer (WPT)},
file = {/home/jaseg/Sync/Research/Zotero/Zhang et al_2018_Ball-Joint Wireless Power Transfer Systems.pdf;/home/jaseg/Zotero/storage/C376LBE8/7918527.html}
}
@inproceedings{zhangDolphinAttackInaudibleVoice2017, @inproceedings{zhangDolphinAttackInaudibleVoice2017,
title = {{{DolphinAttack}}: {{Inaudible Voice Commands}}}, title = {{{DolphinAttack}}: {{Inaudible Voice Commands}}},
shorttitle = {{{DolphinAttack}}}, shorttitle = {{{DolphinAttack}}},

331
paper/paper.tex
View file

@ -43,8 +43,6 @@
% Put explanation of WPT to front of related work % Put explanation of WPT to front of related work
% One plot instead of big table % One plot instead of big table
% Move measeurements column to the left? % Move measeurements column to the left?
% In experiment schematic / setup schema: what is moving, what is stationary?
% Tone down mentioning of inspiration
% Go into way more detail on use case % Go into way more detail on use case
\date{November 14 2024} \date{November 14 2024}
@ -126,14 +124,21 @@ capacitor on the secondary side if the application can accomodate such component
While there exist a corpus of prior work focusing on efficient power transfer between two coils whose position relative While there exist a corpus of prior work focusing on efficient power transfer between two coils whose position relative
to one another cannot be precisely controlled as is the case in wireless phone charging systems as well as in proposed to one another cannot be precisely controlled as is the case in wireless phone charging systems as well as in proposed
WPT electric vehicle chargers, WPT electric vehicle chargers\cite{liWirelessPowerTransfer2015,mouEnergyEfficientAdaptiveDesign2017},
% TODO cite
it is generally assumed that the two coils remain quasi-stationary with respect to one another. it is generally assumed that the two coils remain quasi-stationary with respect to one another.
There exists a small body of work on inductive power transfer through rotating There exists a small body of work on inductive power transfer through rotating
joints\cite{fanSimultaneousWirelessPower2024}, but here the focus lies on higher power budgets than our application joints\cite{
requires, which in practice requires more space and a ferrite or laminated iron core. Therefore, this paper bridges the fanSimultaneousWirelessPower2024,
gap between existing literature on low-power planar WPT inductor design and high-power WPT through rotating joints. xiaRotaryWirelessPower2024,
songRotationLightweightWirelessPower2019,
wangNovelRotatingWireless2024,
yanFreeRotationWirelessPower2023,
wangCoaxialNestedCouplersBased2020},
but here the focus usually lies on higher power budgets than our application requires, which in practice requires more
space and a ferrite or laminated iron core. Therefore, this paper bridges the gap between existing literature on
low-power planar WPT inductor design and high-power WPT through rotating joints.
% FIXME refer to wangNovelRotatingWireless2024,yanFreeRotationWirelessPower2023,liWirelessPowerTransfer2021 as segmented approaches. our system performs better
\subsection{Twisted inductors} \subsection{Twisted inductors}
@ -153,20 +158,121 @@ parasitic capacitance of the inductor and increases its Self-Resonant Frequency
operating frequency and improving its efficiency at lower operating frequencies. operating frequency and improving its efficiency at lower operating frequencies.
\subsection{Contributions} \subsection{Contributions}
% TODO itemize this. Our contributions in this paper include:
In this paper, we introduce twisted inductors, a planar inductor layout that both improves rotational symmetry in \begin{itemize}
rotating wireless power transfer interface as well as quality factor in other applications. We provide detailed layout \item We introduce twisted inductors, a planar inductor layout that both improves rotational symmetry in rotating
instructions, including a mathematical analysis of the available parameter space and an analytical model of both wireless power transfer interface as well as quality factor in other applications.
inductance and DC equivalent series resistance of our scheme. Validating our scheme, we provide laboratory measurements \item We provide detailed instructions for the construction of such layouts, including a mathematical analysis of
of the basic parameters of 39 test specimens comparing our scheme to conventional layouts. We further present the the available parameter space.
results of Finite Element Method (FEM) simulations to validate our inductance and ESR approximations. Finally, to \item We provide an analytical model of inductance and DC equivalent series resistance of our scheme.
analyze the degree of rotational symmetry in our proposed scheme, we provide the results of a large number of automated \item Validating our scheme, we provide laboratory measurements of the basic parameters of 39 test specimens
measurements of coupling between pairs of inductors under various rotations, offsets, distances and load conditions. comparing our scheme to conventional layouts.
\item We further present the results of Finite Element Method (FEM) simulations to validate our inductance and ESR
approximations.
\item Finally, to analyze the degree of rotational symmetry in our proposed scheme, we provide the results of a
large number of automated measurements of coupling between pairs of inductors under various rotations, offsets,
distances and load conditions.
\end{itemize}
\section{Related Work} \section{Related Work}
% TODO cite \cite{mullenEffectMisalignmentInductive} below (misaligned coils) % TODO cite \cite{mullenEffectMisalignmentInductive} below (misaligned coils)
\subsection{Inductive WPT in Practice}
Inductive WPT has been proposed in a large number of
scenarios\cite{zhangWirelessPowerTransfer2019,mouWirelessPowerTransfer2015}, each of which comes with a set of unique
constraints. When WPT is used to charge an electric toothbrush, the implementation cost of the system is critical, while
efficiency and total power output are of little concern. Mechanically, in an electric toothbrush's charging system, the
position and spacing of the transmitter and receiver coils can easily be controlled down to millimeter precision.
In contrast to this, wireless smartphone charging is a much more demanding application. Here, the total cost of the
system is only secondary, but the receiver's form factor is critical, and total power output as well as efficiency
become major objectives. At the same time, in wireless smartphone charging, position tolerances are very coarse, and the
two coils in the charging base and in the phone may be positioned more than a centimeter off-axis, with a gap of several
millimeters and potentially not even in parallel planes.
Power transfer across large distances is even more of a concern in implantable medical
devices\cite{mooreApplicationsWirelessPower2019}. Where a wireless phone charger must be able to bridge distances of a
few millimeters, an implantable medical device might be situated underneath several centimeter of tissue and bones. At
the same time, cost is of (almost) no concern in this medical application, which enables the use of complex
manufacturing techniques, customized electronic components and exotic materials.
While all of the aforementioned applications transfer somewhere between a few hundred milliwatts and several watts of
power, at the other end of the spectrum there is a large body of research suggesting the use of inductive wireless power
transfer for the charging of electric vehicles
(EVs)\cite{liWirelessPowerTransfer2015,mouEnergyEfficientAdaptiveDesign2017}. In this application, the wireless power
transfer system usually replaces the conventional wired charging connector, which improves the systems' user experience
given the strong force required to seat or unseat these rather large connectors, as well as the heft of the required
water-cooled cables. In this application, size is of (almost) no concern, but at charging rates up to tens of kilowatt,
efficiency becomes critical. When charging an EV at a rate of \qty{10}{\kilo\watt}, an efficiency improvement of just
$0.1\%$ corresponds to a reduction in power dissipation of \qty{10}{\watt}. Besides the monetary cost of the power lost
this way, each small improvement enables a reduction in size of heat sinks and other cooling components, which directly
translates to a decrease in cost.
\subsection{Air-Core Inductors in WPT}
Across application areas, air-core inductors are often used for WPT since in most applications, an air gap of several
millimeters or more is expected, and adding a ferrite core would not change the system's performance by much in these
circumstances. A common way to use ferrites in WPT applications is by magnetically shielding the inductor's back side
with a ferrite plate such that the field does not extend beyond the coil's back side, thereby increasing the intended
mutual inductance while simultaneously reducing eddy current losses when the WPT coils are placed near metal
objects\cite{batraEffectFerriteAddition2015,leeSimpleWirelessPower2017,muehlmannMutualCouplingModeling2012}.
\subsection{PCB inductor design for wireless power transfer}
Today, air-core inductors are the standard solution in inductive WPT links. Since in most WPT applications an air gap of
several millimeters between the sending and receiving assemblies is expected, adding a ferrite core does not result in a
large improvement in coupling. Instead, the impact of this misalignment is reduced by maximizing the area of the
air-core inductors used.
WPT inductors tend to be mostly planar coils with only a few layers, so implementing them in a PCB process seems
natural. Using a PCB for the inductor has the potential to reduce implementation cost since PCBs are cheap, and they can
also serve as structural support.
Implementing inductors in PCBs has several disadvantages. First, due to the limited layer count of common PCB
processes and due to structure size limitations, the number of windings that can be fit into a given volume is much
lower than in wire-wound inductors. Second, due to a PCB's copper layers being thin compared to its dielectric
substrate\footnote{common values are \qtyrange{15}{30}{\micro\meter} copper thickness and
\qtyrange{600}{1600}{\micro\meter} substrate thickness} PCB inductors tend to have poor DC resistance, albeit the thin
copper layer decreases skin effect losses compared to a solid, round conductors of the same cross-sectional area.
However, PCBs can still not approach the performance of litz wire used in high-frequency WPT coils, which commonly use
wire diameters in the range of tens of micrometer\cite{zhaoDesignOptimizationLitzWire2023}.
\textcite{lopeFrequencyDependentResistancePlanar2014} and \textcite{nomotoSplittingConductorsCoils2024} propose a
mitigation that aims to emulate a litz wire's structure in large, high-current PCB inductors, but their mitigation is
heavily limited by the structure size achievable in common PCB manufacturing
processes\cite{nguyenReviewComparisonSolid2020}.
A further factor that limits the high-frequency performance of PCB inductors is distributed capacitance. Not only does a
large air coil exhibit more parasitic capacitance than an equivalent, smaller ferrite-core inductor simply due to its
size, when implemented in a PCB process a large fraction of the electrical fields responsible for this capacitance pass
through the PCB's substrate, not air. The relative permittivity $\epsilon_r$ of common PCB substrates typically lies in
the range of $4$ to $5$ \cite{mumbyDielectricPropertiesFR41989}, which increases the distributed capacitance compared to
a pure air-core inductor by approximately that same factor.
\subsection{Twisted Inductors in RFIC Design}
Beyond WPT, planar inductors are commonly used in radio frequency integrated circuits (RFICs). In RFIC design, the major
challenges are area optimization and precisely predicting the inductor's characteristics during the design phase. Common
optimizations include applying a variable trace pitch to reduce distributed
capacitance\cite{lopez-villegasImprovementQualityFactor2000}, and applying variable trace width to decrease equivalent
series resistance while preserving total inductance and quality factor\cite{hsuAnalyticalDesignAlgorithm2008}.
In RFICs, inductors are commonly designed as \emph{balanced} inductors with a grounded central node. Such designs
interleave two counter-wound planar spiral inductors on the same layer with the help of some jumper connections on a
second layer\cite{daneshDifferentiallyDrivenSymmetric2002,martinMultiturnTwistedInductor2016}. The use of such designs
in RFIC design is mainly focused on their electrical symmetry, so that the two input ports can be fed with a fully
differential signal, with the inductor loading both driver outputs equally across the inductor's frequency range.
Setting the inversion count to $k=1$ in our proposed scheme as shown below yields the counterwound scheme that is
commonly used for two-layer planar
inductors\cite{lopeFirstSelfresonantFrequency2021,sproHighVoltageInsulationDesign2021,leePrintedSpiralWinding2011}, and
which has been used to stack planar coils for more than a century\cite{flemingPrinciplesElectricWave1910}.
% Note: They note that the main point behind the design is electrical symmetry of the two ports to make driving the
% thing differentially cleaner. We should adopt this observation for our inductors, which likewise are electrically
% symmetric when compared to a single-layer spiral inductor.
\subsection{A Brief Historical Diversion on Basket-Woven Air Coils} \subsection{A Brief Historical Diversion on Basket-Woven Air Coils}
Since the early days of radio engineering, the parasitic capacitance of inductors has been a point of Since the early days of radio engineering, the parasitic capacitance of inductors has been a point of
@ -233,102 +339,6 @@ inversions within each turn that we describe for our twisted inductors below, al
historic literature where this condition was explicitly stated \cite{eppenAnforderungenEinzelteileRundfunkempfanger1927, historic literature where this condition was explicitly stated \cite{eppenAnforderungenEinzelteileRundfunkempfanger1927,
kleinSpulenUndSchwingungskreise1941, wiggeRundfunktechnischesHandbuch1930, querfurthCoilWindingDescription1954}.} kleinSpulenUndSchwingungskreise1941, wiggeRundfunktechnischesHandbuch1930, querfurthCoilWindingDescription1954}.}
\subsection{PCB inductor design for wireless power transfer}
Today, air-core inductors are the standard solution in inductive WPT links. Since in most WPT applications an air gap of
several millimeters between the sending and receiving assemblies is expected, adding a ferrite core does not result in a
large improvement in coupling. Instead, the impact of this misalignment is reduced by maximizing the area of the
air-core inductors used.
WPT inductors tend to be mostly planar coils with only a few layers, so implementing them in a PCB process seems
natural. Using a PCB for the inductor has the potential to reduce implementation cost since PCBs are cheap, and they can
also serve as structural support.
Implementing inductors in PCBs has several disadvantages. First, due to the limited layer count of common PCB
processes and due to structure size limitations, the number of windings that can be fit into a given volume is much
lower than in wire-wound inductors. Second, due to a PCB's copper layers being thin compared to its dielectric
substrate\footnote{common values are \qtyrange{15}{30}{\micro\meter} copper thickness and
\qtyrange{600}{1600}{\micro\meter} substrate thickness} PCB inductors tend to have poor DC resistance, albeit the thin
copper layer decreases skin effect losses compared to a solid, round conductors of the same cross-sectional area.
However, PCBs can still not approach the performance of litz wire used in high-frequency WPT coils, which commonly use
wire diameters in the range of tens of micrometer\cite{zhaoDesignOptimizationLitzWire2023}.
\textcite{lopeFrequencyDependentResistancePlanar2014} and \textcite{nomotoSplittingConductorsCoils2024} propose a
mitigation that aims to emulate a litz wire's structure in large, high-current PCB inductors, but their mitigation is
heavily limited by the structure size achievable in common PCB manufacturing
processes\cite{nguyenReviewComparisonSolid2020}.
A further factor that limits the high-frequency performance of PCB inductors is distributed capacitance. Not only does a
large air coil exhibit more parasitic capacitance than an equivalent, smaller ferrite-core inductor simply due to its
size, when implemented in a PCB process a large fraction of the electrical fields responsible for this capacitance pass
through the PCB's substrate, not air. The relative permittivity $\epsilon_r$ of common PCB substrates typically lies in
the range of $4$ to $5$ \cite{mumbyDielectricPropertiesFR41989}, which increases the distributed capacitance compared to
a pure air-core inductor by approximately that same factor.
\subsection{Twisted Inductors in RFIC Design}
Beyond WPT, planar inductors are commonly used in radio frequency integrated circuits (RFICs). In RFIC design, the major
challenges are area optimization and precisely predicting the inductor's characteristics during the design phase. Common
optimizations include applying a variable trace pitch to reduce distributed
capacitance\cite{lopez-villegasImprovementQualityFactor2000}, and applying variable trace width to decrease equivalent
series resistance while preserving total inductance and quality factor\cite{hsuAnalyticalDesignAlgorithm2008}.
In RFICs, inductors are commonly designed as \emph{balanced} inductors with a grounded central node. Such designs
interleave two counter-wound planar spiral inductors on the same layer with the help of some jumper connections on a
second layer\cite{daneshDifferentiallyDrivenSymmetric2002,martinMultiturnTwistedInductor2016}. The use of such designs
in RFIC design is mainly focused on their electrical symmetry, so that the two input ports can be fed with a fully
differential signal, with the inductor loading both driver outputs equally across the inductor's frequency range.
Setting the inversion count to $k=1$ in our proposed scheme as shown below yields the counterwound scheme that is
commonly used for two-layer planar
inductors\cite{lopeFirstSelfresonantFrequency2021,sproHighVoltageInsulationDesign2021,leePrintedSpiralWinding2011}, and
which has been used to stack planar coils for more than a century\cite{flemingPrinciplesElectricWave1910}.
% They note that the main point behind the design is electrical symmetry of the two ports to make driving the thing
% differentially cleaner. We should adopt this observation for our inductors, which likewise are electrically symmetric
% when compared to a single-layer spiral inductor.
% TODO abbrev WPT, move earlier
\subsection{Inductive Wireless Power Transfer in Practice}
Inductive WPT has been proposed in a large number of
scenarios\cite{zhangWirelessPowerTransfer2019,mouWirelessPowerTransfer2015}, each of which comes with a set of unique
constraints. When WPT is used to charge an electric toothbrush, the implementation cost of the system is critical, while
efficiency and total power output are of little concern. Mechanically, in an electric toothbrush's charging system, the
position and spacing of the transmitter and receiver coils can easily be controlled down to millimeter precision.
In contrast to this, wireless smartphone charging is a much more demanding application. Here, the total cost of the
system is only secondary, but the receiver's form factor is critical, and total power output as well as efficiency
become major objectives. At the same time, in wireless smartphone charging, position tolerances are very coarse, and the
two coils in the charging base and in the phone may be positioned more than a centimeter off-axis, with a gap of several
millimeters and potentially not even in parallel planes.
Power transfer across large distances is even more of a concern in implantable medical
devices\cite{mooreApplicationsWirelessPower2019}. Where a wireless phone charger must be able to bridge distances of a
few millimeters, an implantable medical device might be situated underneath several centimeter of tissue and bones. At
the same time, cost is of (almost) no concern in this medical application, which enables the use of complex
manufacturing techniques, customized electronic components and exotic materials.
While all of the aforementioned applications transfer somewhere between a few hundred milliwatts and several watts of
power, at the other end of the spectrum there is a large body of research suggesting the use of inductive wireless power
transfer for the charging of electric vehicles
(EVs)\cite{liWirelessPowerTransfer2015,mouEnergyEfficientAdaptiveDesign2017}. In this application, the wireless power
transfer system usually replaces the conventional wired charging connector, which improves the systems' user experience
given the strong force required to seat or unseat these rather large connectors, as well as the heft of the required
water-cooled cables. In this application, size is of (almost) no concern, but at charging rates up to tens of kilowatt,
efficiency becomes critical. When charging an EV at a rate of \qty{10}{\kilo\watt}, an efficiency improvement of just
$0.1\%$ corresponds to a reduction in power dissipation of \qty{10}{\watt}. Besides the monetary cost of the power lost
this way, each small improvement enables a reduction in size of heat sinks and other cooling components, which directly
translates to a decrease in cost.
\subsection{Air-Core Inductors in WPT}
Across application areas, air-core inductors are often used for WPT since in most applications, an air gap of several
millimeters or more is expected, and adding a ferrite core would not change the system's performance by much in these
circumstances. A common way to use ferrites in WPT applications is by magnetically shielding the inductor's back side
with a ferrite plate such that the field does not extend beyond the coil's back side, thereby increasing the intended
mutual inductance while simultaneously reducing eddy current losses when the WPT coils are placed near metal
objects\cite{batraEffectFerriteAddition2015,leeSimpleWirelessPower2017,muehlmannMutualCouplingModeling2012}.
\section{Twisted Inductor Design} \section{Twisted Inductor Design}
In this section, we present a detailed derivation of the layout of twisted inductors. We approach this layout In this section, we present a detailed derivation of the layout of twisted inductors. We approach this layout
@ -339,7 +349,7 @@ connections, inductors are usually designed with both ports close to one another
aligns with the $x$-Axis. aligns with the $x$-Axis.
The trace trajectory of a standard planar spiral inductor can be parameterized in polar coordinates $r, \varphi$ based The trace trajectory of a standard planar spiral inductor can be parameterized in polar coordinates $r, \varphi$ based
on an Archimedean spiral: \todo{For the lulz, cite Archimedes here} on an Archimedean spiral:
\begin{equation} \begin{equation}
r = a\cdot\varphi r = a\cdot\varphi
@ -349,19 +359,7 @@ on an Archimedean spiral: \todo{For the lulz, cite Archimedes here}
An Archimedean spiral defined this way always starts at the origin, and it continues to infinity. Let us re-parameterize An Archimedean spiral defined this way always starts at the origin, and it continues to infinity. Let us re-parameterize
this spiral to a curve parameter $t$ with range $\left[0,1\right]$, such that $t=0$ corresponds to the start of the this spiral to a curve parameter $t$ with range $\left[0,1\right]$, such that $t=0$ corresponds to the start of the
inductor and $t=1$ corresponds to its end. As is customary in PCB inductors, we place the inductor's start on its outer inductor and $t=1$ corresponds to its end. As is customary in PCB inductors, we place the inductor's start on its outer
circumference. To make handling of this easier, we introduce a variable $r' \in \left[0,1\right]$ representing the circumference.
radius normalized to the spiral's width. Let $n$ be the turn count of our inductor. The resulting parametrization is:
\begin{align}
\varphi &= 2\pi n t\\
r' &= 1 - t \\
r &= r_1 + r' \left(r_2 - r_1\right)
\label{eqn_simple_spiral_ind}
\end{align}
The resulting spiral trace starts at radius $r_2$ on the positive $x$ axis, and spirals inward until it meets $r_1$. In
its PCB realization, at $r_1$, a via would be placed to connect the end of the spiral trace to a jumper trace on another
layer of the PCB leading back to the start.
To improve layer utilization, a common technique in PCB inductor design is to use both layers of the PCB for the To improve layer utilization, a common technique in PCB inductor design is to use both layers of the PCB for the
inductor's spiral trace, instead of only using the bottom layer for a straight jumper trace. Using both layers this way inductor's spiral trace, instead of only using the bottom layer for a straight jumper trace. Using both layers this way
@ -370,23 +368,30 @@ re-defining our normalized radius to allow both positive and negative values, de
traces on the PCB's bottom layer as follows. Figure\ \ref{fig_nk_combined} shows both a simple and a two-layer traces on the PCB's bottom layer as follows. Figure\ \ref{fig_nk_combined} shows both a simple and a two-layer
spiral inductor in the first two columns. spiral inductor in the first two columns.
Let $n$ be the turn count of our inductor. The resulting parametrization is:
\begin{align} \begin{align}
\varphi &= 2\pi n t\\ \varphi &= 2\pi n t\\\nonumber
r' &= 1 - 2 t \\ r &= r_1 + \left|1 - 2 t\right| \left(r_2 - r_1\right)
r &= r_1 + \left|r'\right| \left(r_2 - r_1\right)
\label{eqn_twolayer_spiral} \label{eqn_twolayer_spiral}
\end{align} \end{align}
The resulting spiral trace starts at radius $r_2$ on the positive $x$ axis, and spirals inward until it meets $r_1$,
where the sign indicates a layer change, and the trace reverses to continue back to $r_2$ on another layer. In its PCB
realization, at $r_1$, a via would be placed to connect the end of the spiral trace to a jumper trace on the other layer
of the PCB leading back to the start.
\subsection{From Spiral to Twisted Inductor} \subsection{From Spiral to Twisted Inductor}
Extending the above parametrization of a spiral inductor's layout, we propose planar \emph{twisted inductors} based on Extending the above parametrization of a spiral inductor's layout, we propose planar \emph{twisted inductors} based on
two core observations: two core observations:
\begin{description} \begin{description}[\IEEEsetlabelwidth{foo}]
\item[Observation 1.] When using an archimedean spiral, multiple such spirals using the same pitch can be \item[Observation 1.]\hfill\\When using an archimedean spiral, multiple such spirals using the same pitch can be
interleaved by spreading out their start and end points at regular angular intervals. interleaved by spreading out their start and end points at regular angular intervals.
\item[Observation 2.] In a two-layer spiral inductor (Figure\ \ref{fig_nk_combined}), we can adjust the turn count \item[Observation 2.]\hfill\\In a two-layer spiral inductor (Figure\ \ref{fig_nk_combined}), we can adjust the turn
of the pair of traces to move the end point of the bottom layer trace anywhere on the inductor's outer radius. count of the pair of traces to move the end point of the bottom layer trace anywhere on the inductor's outer
radius.
\end{description} \end{description}
Combining these two observations, we find that by choosing a number $k$ of inversions, i.e. layer jumps, that is coprime Combining these two observations, we find that by choosing a number $k$ of inversions, i.e. layer jumps, that is coprime
@ -395,9 +400,16 @@ naturally connect in series, with the resulting spirals on the top and bottom la
\ref{fig_nk_combined} shows a layout with $n=3$ turns with both a single inversion ($k=1$) as in a conventional \ref{fig_nk_combined} shows a layout with $n=3$ turns with both a single inversion ($k=1$) as in a conventional
two-layer inductor, and with $k=2$ inversions, creating two interleaved spirals on both the top and the bottom layer of two-layer inductor, and with $k=2$ inversions, creating two interleaved spirals on both the top and the bottom layer of
the PCB. Figure\ \ref{fig_nk_complex_illust} in Appendix\ \ref{sec_appendix_layout_examples} shows additional layout the PCB. Figure\ \ref{fig_nk_complex_illust} in Appendix\ \ref{sec_appendix_layout_examples} shows additional layout
examples for other values of $n$ and $k$. For $k=0$, we get a standard single-layer planar spiral inductor for any turn examples for other values of $n$ and $k$. For $k=\frac{1}{2}$, we get a standard single-layer planar spiral inductor for
count $n$, and for $k=1$ we get a standard two-layer planar spiral inductor for any turn count $n$. In this paper, we any turn count $n$, and for $k=1$ we get a standard two-layer planar spiral inductor for any turn count $n$. In this
will call all layouts with $k\ge 2$ \emph{Twisted Inductors}. paper, we will call all layouts with $k\ge 2$ \emph{Twisted Inductors}. The coordinate description of Equation\
\ref{eqn_twolayer_spiral} thus becomes:
\begin{align}
\varphi &= 2\pi n t\\\nonumber
r &= r_1 + \left|1 - \left( 2 k t \mod 2 \right) \right| \left(r_2 - r_1\right)
\label{eqn_twisted_spiral}
\end{align}
%\begin{figure} %\begin{figure}
% \begin{center} % \begin{center}
@ -423,14 +435,13 @@ will call all layouts with $k\ge 2$ \emph{Twisted Inductors}.
Topologically, the shape of our inductors can be described as a $(k, n)$-torus knot. From knot theory, we know that such Topologically, the shape of our inductors can be described as a $(k, n)$-torus knot. From knot theory, we know that such
a torus knot exists if and only if both $n$ and $k$ are co-prime. Figure\ \ref{fig_nk_combined} illustrates a derivation a torus knot exists if and only if both $n$ and $k$ are co-prime. Figure\ \ref{fig_nk_combined} illustrates a derivation
of the coprimality requirement. \todo{Cleanly handle $k=0$ case.} If we plot the spiral in polar coordinates on a of the coprimality requirement. If we plot the spiral in polar coordinates on a cartesian plot we observe that for a
cartesian plot we observe that for a $n$-turn coil with $k$ inversions, the trace crosses the $\varphi$ axis once for $n$-turn coil with $k$ inversions, the trace crosses the $\varphi$ axis once for each inversion, wrapping around $r$.
each inversion, wrapping around $r$. Likewise, it crosses the $r$ axis once for each turn of the inductor, wrapping Likewise, it crosses the $r$ axis once for each turn of the inductor, wrapping around $\varphi$. Based on this, we can
around $\varphi$. Based on this, we can re-label the angular axis in steps from $0$ to $k$, and re-label the radial axis re-label the angular axis in steps from $0$ to $k$, and re-label the radial axis in steps from $0$ to $n$. Labelling the
in steps from $0$ to $n$. Labelling the new angular axis $i$ and the new radial axis $j$, in the resulting integer new angular axis $i$ and the new radial axis $j$, in the resulting integer lattice, the trace has slope $1$. We can
lattice, the trace has slope $1$. We can state the trace's trajectory as a function of a curve parameter $t \in [0, nk]$ state the trace's trajectory as a function of a curve parameter $t \in [0, nk]$ as $f(t) = (i, j) = (t \mod n, t \mod
as $f(t) = (i, j) = (t \mod n, t \mod k)$. To produce a valid inductor, the trace must not intersect anywhere. Thus, the k)$. To produce a valid inductor, the trace must not intersect anywhere. Thus, the system of congruences
system of congruences
\begin{align} \begin{align}
t &\equiv i \mod n\\ t &\equiv i \mod n\\
@ -462,7 +473,7 @@ inductor does not change its turn count or dimensions, the combined arc length o
does not change. Twisted inductors require two additional vias per inversion, which will increase DC resistance does not change. Twisted inductors require two additional vias per inversion, which will increase DC resistance
slightly, but the contribution of these vias will remain small in practical applications since the overall number of slightly, but the contribution of these vias will remain small in practical applications since the overall number of
vias is still no more than a couple per turn, and since each via only bridges the short distance between the inductor's vias is still no more than a couple per turn, and since each via only bridges the short distance between the inductor's
layers.\todo{Does the skin effect affect the influence of vias?} layers.
As a general expression, for a standard or twisted inductor with turn count $n$ and twist count~$k$, given via As a general expression, for a standard or twisted inductor with turn count $n$ and twist count~$k$, given via
resistance $R_\text{via}$ we derive a first order approximation of the inductor's DC resistance as follows. resistance $R_\text{via}$ we derive a first order approximation of the inductor's DC resistance as follows.
@ -539,7 +550,6 @@ Our inductor design tool is available in this paper's supplementary material as
the end of this paper. the end of this paper.
\section{FEM Simulation} \section{FEM Simulation}
% TODO figure out where to abbreviate FEM, spell out once, compare with other TPEL papers.
To validate our analytical approximations, we performed a series of FEM simulations in Elmer FEM. For a number of To validate our analytical approximations, we performed a series of FEM simulations in Elmer FEM. For a number of
inductor layouts, we performed simulations to determine ohmic resistance and inductance. Due to limitations in our inductor layouts, we performed simulations to determine ohmic resistance and inductance. Due to limitations in our
@ -562,7 +572,7 @@ We let Elmer determine inductance by first using its coil solver to determine th
given a test current, then applying its magnetodynamics solver to solve the electromagnetic field. Elmer provides given a test current, then applying its magnetodynamics solver to solve the electromagnetic field. Elmer provides
routines to derive the total magnetic field energy $U_\text{mag}$ from an EM field solution. Since we have only our routines to derive the total magnetic field energy $U_\text{mag}$ from an EM field solution. Since we have only our
inductor under test inside the simulation volume, with test current $I_\text{test}$, we can then derive the inductor's inductor under test inside the simulation volume, with test current $I_\text{test}$, we can then derive the inductor's
inductance according to the well-known relation\todo{Find decent source}: inductance according to the well-known relation\cite{meeekerFiniteElementMethod2015}:
\begin{equation} \begin{equation}
L = \frac{2\cdot U_\text{mag}}{I_\text{test}^2} L = \frac{2\cdot U_\text{mag}}{I_\text{test}^2}
@ -572,9 +582,9 @@ inductance according to the well-known relation\todo{Find decent source}:
\label{sec_experiments} \label{sec_experiments}
To experimentally validate our design with real-world inductors, we produced test coupons with a number of variations of To experimentally validate our design with real-world inductors, we produced test coupons with a number of variations of
twisted inductors with winding count $n$ between $1$ and $25$, and twist count ranging from $k=0$ (simple single-sided twisted inductors with winding count $n$ between $1$ and $25$, and twist count ranging from $k=\frac{1}{2}$ (simple
spiral inductor) to $k=37$. All test inductors had an inner diameter of \qty{15}{\milli\meter} and an outer diameter of single-sided spiral inductor) to $k=37$. All test inductors had an inner diameter of \qty{15}{\milli\meter} and an outer
\qty{35}{\milli\meter} corresponding to the space available in our IHSM implementation. diameter of \qty{35}{\milli\meter} corresponding to the space available in our IHSM implementation.
\subsection{Inductance and DC resistance} \subsection{Inductance and DC resistance}
@ -683,7 +693,7 @@ additional cost and without compromising other performance parameters.
\caption{Inductor sample design parameters and measured characteristics. All inductors have outer diameter \caption{Inductor sample design parameters and measured characteristics. All inductors have outer diameter
\qty{35}{\milli\meter} and inner diameter \qty{15}{\milli\meter}. The missing values in the simulation results \qty{35}{\milli\meter} and inner diameter \qty{15}{\milli\meter}. The missing values in the simulation results
columns result from the solver failing to converge. Bolded values highlight the best performing two-layer coil columns result from the solver failing to converge. Bolded values highlight the best performing two-layer coil
of each turn count. Shaded rows indicate conventional single-layer ($k=0$) or two-layer ($k=1$) planar of each turn count. Shaded rows indicate conventional single-layer ($k=\frac{1}{2}$) or two-layer ($k=1$) planar
inductors.} inductors.}
\label{tab_coupons} \label{tab_coupons}
\end{table*} \end{table*}
@ -784,8 +794,8 @@ using Keysight 34465A multimeters in AC Root Mean Square (RMS) mode.
\includegraphics[width=\figurescale]{figures/symmetry_3turn_n_twist.pdf} \includegraphics[width=\figurescale]{figures/symmetry_3turn_n_twist.pdf}
\end{center} \end{center}
\caption{RMS output voltage of the test circuit from Figure\ \ref{fig_test_schematic} for three pairs of matching \caption{RMS output voltage of the test circuit from Figure\ \ref{fig_test_schematic} for three pairs of matching
inductors with one inductor rotating w.r.t.\ the other. The inductors have $n=3$ turns each and $k=0$, $k=1$, and inductors with one inductor rotating w.r.t.\ the other. The inductors have $n=3$ turns each and $k=\frac{1}{2}$,
$k=3$, respectively. For each $k$, voltage curves are plotted for a number of different radial offsets $k=1$, and $k=3$, respectively. For each $k$, voltage curves are plotted for a number of different radial offsets
between the two inductor's centers.} between the two inductor's centers.}
\label{fig_symmetry_3turn_n_twist} \label{fig_symmetry_3turn_n_twist}
\end{figure} \end{figure}
@ -831,7 +841,8 @@ pitch, as their turns deviate the furthest from a set of ideal, concentric circl
% \begin{center} % \begin{center}
% \includegraphics[width=.6\figurescale]{figures/field_plot_3d_n5_k0.pdf} % \includegraphics[width=.6\figurescale]{figures/field_plot_3d_n5_k0.pdf}
% \end{center} % \end{center}
% \caption{The coupling between a pair of identical coils (here two simple spiral inductors with $n=5$ and $k=0$) % \caption{The coupling between a pair of identical coils (here two simple spiral inductors with $n=5$ and
% $k=\frac{1}{2}$)
% visualized in three dimensions. The $x$ and $y$ axis show in-plane displacement, and the $z$ axis shows output % visualized in three dimensions. The $x$ and $y$ axis show in-plane displacement, and the $z$ axis shows output
% amplitude in arbitrary units. Height and rotation are fixed to \qty{1}{\milli\meter} and \qty{0}{\degree}, % amplitude in arbitrary units. Height and rotation are fixed to \qty{1}{\milli\meter} and \qty{0}{\degree},
% respectively. The most prominent aspects of this plot are that coupling falls off steeply with distance, and that % respectively. The most prominent aspects of this plot are that coupling falls off steeply with distance, and that
@ -872,7 +883,10 @@ native file format, as well as the Gerber file format supported by the majority
On the theoretical side, the fact that our twisted inductor model generalizes both one- or two-layer planar spiral On the theoretical side, the fact that our twisted inductor model generalizes both one- or two-layer planar spiral
inductors as well as planar toroidal inductors would make the deduction of key parameters such as inductance and inductors as well as planar toroidal inductors would make the deduction of key parameters such as inductance and
distributed capacitance by mathematical analysis or by finite element methods interesting. distributed capacitance by mathematical analysis or by finite element methods interesting. Furthermore, the precise
contribution of vias to the twisted inductor's parasitics is interesting, especially for layouts with large values of
inversion count $k$. We suspect that via influence will be frequency dependant as vias and traces have distinct DC
resistances, and skin effect will affect both to a differring extent.
\section{Conclusion} \section{Conclusion}
@ -898,8 +912,7 @@ This is version \texttt{\input{version.tex}\unskip} of this paper, generated on
The git repository with the LaTeX source for this paper, the data analysis code underlying our measurements as well the The git repository with the LaTeX source for this paper, the data analysis code underlying our measurements as well the
set of tools for the generation of twisted inductor layouts that we wrote can be found at: set of tools for the generation of twisted inductor layouts that we wrote can be found at:
\todo{link here} \center{\url{https://git.jaseg.de/nice-coils.git}}
% \center{\url{https://git.jaseg.de/nice-coils.git}}
\printbibliography[heading=bibintoc] \printbibliography[heading=bibintoc]
@ -911,8 +924,8 @@ set of tools for the generation of twisted inductor layouts that we wrote can be
% \begin{center} % \begin{center}
% \includegraphics[width=\figurescale]{figures/symmetry_10turn_n_twist.pdf} % \includegraphics[width=\figurescale]{figures/symmetry_10turn_n_twist.pdf}
% \end{center} % \end{center}
% \caption{Coupled RMS output voltage of three pairs of matching inductors with $n=10$ turns each and $k=0$, $k=1$, % \caption{Coupled RMS output voltage of three pairs of matching inductors with $n=10$ turns each and
% and $k=3$, respectively, shown as in Figure\ \ref{fig_symmetry_3turn_n_twist}} % $k=\frac{1}{2}$, $k=1$, and $k=3$, respectively, shown as in Figure\ \ref{fig_symmetry_3turn_n_twist}}
% \label{fig_symmetry_10turn_n_twist} % \label{fig_symmetry_10turn_n_twist}
%\end{figure} %\end{figure}