From 51abb45ce23444f87a6f09c2b3c24313a84f484a Mon Sep 17 00:00:00 2001 From: jaseg Date: Tue, 3 Dec 2024 12:57:02 +0100 Subject: [PATCH] Incorporate first batch of Leo's comments --- paper/paper.bib | 157 ++++++++++++++++++++++++++++++++---- paper/paper.tex | 206 +++++++++++++++++++++++++----------------------- 2 files changed, 250 insertions(+), 113 deletions(-) diff --git a/paper/paper.bib b/paper/paper.bib index d51965c..db6d1a7 100644 --- a/paper/paper.bib +++ b/paper/paper.bib @@ -106,6 +106,20 @@ file = {/home/jaseg/Sync/Research/Zotero/2020_Amitonova et al_Quantum key establishment via a multimode fiber.pdf} } +@book{andersonSecurityEngineeringGuide2020, + title = {Security {{Engineering}}: {{A Guide}} to {{Building Dependable Distributed Systems}}}, + shorttitle = {Security {{Engineering}}}, + author = {Anderson, Ross}, + date = {2020-12-22}, + edition = {1}, + publisher = {Wiley}, + doi = {10.1002/9781119644682}, + url = {https://onlinelibrary.wiley.com/doi/book/10.1002/9781119644682}, + urldate = {2024-12-03}, + isbn = {978-1-119-64278-7 978-1-119-64468-2}, + langid = {english} +} + @online{AntimatterAlgorithmThat, title = {Antimatter: An Algorithm That Prunes {{CRDT}}/{{OT}} History}, url = {https://braid.org/antimatter}, @@ -129,7 +143,7 @@ isbn = {978-1-4503-4139-4} } -@inproceedings{arpPrivacyThreatsUltrasonic2017, +@inproceedings{arpPrivacyThreatsUltrasonic2017a, title = {Privacy {{Threats}} through {{Ultrasonic Side Channels}} on {{Mobile Devices}}}, booktitle = {2017 {{IEEE European Symposium}} on {{Security}} and {{Privacy}} ({{EuroS}}\&{{P}})}, author = {Arp, Daniel and Quiring, Erwin and Wressnegger, Christian and Rieck, Konrad}, @@ -402,7 +416,7 @@ @article{bennettGeneralizedPrivacyAmplification1995, title = {Generalized Privacy Amplification}, author = {Bennett, C.H. and Brassard, G. and Crepeau, C. and Maurer, U.M.}, - year = {Nov./1995}, + date = {1995-11}, journaltitle = {IEEE Transactions on Information Theory}, shortjournal = {IEEE Trans. Inform. Theory}, volume = {41}, @@ -784,6 +798,24 @@ file = {/home/jaseg/Zotero/storage/LZU2NVHW/Castryck and Decru - 2023 - An Efficient Key Recovery Attack on SIDH.pdf} } +@article{chafiDesignMethodPCB2021, + title = {Design {{Method}} of {{PCB Inductors}} for {{High-Frequency GaN Converters}}}, + author = {Chafi, Ammar and Idir, Nadir and Videt, Arnaud and Maher, Hassan}, + date = {2021-01}, + journaltitle = {IEEE Transactions on Power Electronics}, + volume = {36}, + number = {1}, + pages = {805--814}, + issn = {1941-0107}, + doi = {10.1109/TPEL.2020.3000438}, + url = {https://ieeexplore.ieee.org/document/9110799/?arnumber=9110799&tag=1}, + urldate = {2024-11-14}, + abstract = {The new power Gallium Nitride transistors allow to increase the operating frequency of converters to megahertz range, thanks to their low switching time that is of a few nanoseconds or less. This permits to reduce the values and the volume of the passive components, and enhance the power density of power converters. However, inductors needed for energy storage still take a large volume in converters compared with the others components, because of their weak energy density. Furthermore, high-frequency operation require low-losses magnetic materials. In this article, a design method of PCB inductors is proposed. A flexible ferrite sheet is used to enhance the inductance value and ease the realization of custom-shape devices. The design method of the inductor is based on the optimization of the inductor volume taking into account thermal issues of the magnetic sheets. Also a simulation method is proposed to calculate the equivalent stray capacitance of the inductors. The proposed method provides a losses volume tradeoff that helps designers to optimize the inductor for their application.}, + eventtitle = {{{IEEE Transactions}} on {{Power Electronics}}}, + keywords = {Copper,Flexible magnetic sheets,Gallium nitride,GaN converters,Inductance,Inductors,Magnetic resonance imaging,optimization of volume,PCB inductor,Saturation magnetization,thermal issues,Toroidal magnetic fields}, + file = {/home/jaseg/Sync/Research/Zotero/Chafi et al_2021_Design Method of PCB Inductors for High-Frequency GaN Converters.pdf;/home/jaseg/Zotero/storage/WNNSSCEQ/9110799.html} +} + @incollection{chanCommittingAuthenticatedEncryption2022, title = {On {{Committing Authenticated-Encryption}}}, booktitle = {Computer {{Security}} – {{ESORICS}} 2022}, @@ -1001,7 +1033,7 @@ file = {/home/jaseg/Sync/Research/Zotero/Couteau et al_2021_Silver.pdf} } -@article{cuellarStaticFatigueLifetime1987a, +@article{cuellarStaticFatigueLifetime1987, title = {Static Fatigue Lifetime of Optical Fibers in Bending}, author = {Cuellar, E. and Roberts, D. and Middleman, L.}, date = {1987-01-01}, @@ -1424,6 +1456,35 @@ file = {/home/jaseg/Zotero/storage/68BWJ8CR/Garb et al. - 2022 - The Wiretap Channel for Capacitive PUF-Based Secur.pdf} } +@software{GerbonaraToolsHandle, + title = {Gerbonara: {{Tools}} to Handle {{Gerber}} and {{Excellon}} Files in {{Python}}}, + shorttitle = {Gerbonara}, + url = {https://gitlab.com/gerbolyze/gerbonara}, + urldate = {2024-12-03}, + version = {1.4.0}, + keywords = {Artistic Software,excellon,gerber,Multimedia - Graphics,pcb,Printing,Scientific/Engineering,Scientific/Engineering - Electronic Design Automation (EDA),Scientific/Engineering - Image Processing,Utilities}, + file = {/home/jaseg/Zotero/storage/9XQ63WGV/gerbonara.html} +} + +@article{geuzaineGmsh3DFinite2009, + title = {Gmsh: {{A}} 3‐{{D}} Finite Element Mesh Generator with Built‐in Pre‐ and Post‐processing Facilities}, + shorttitle = {Gmsh}, + author = {Geuzaine, Christophe and Remacle, Jean‐François}, + date = {2009-09-10}, + journaltitle = {International Journal for Numerical Methods in Engineering}, + shortjournal = {Numerical Meth Engineering}, + volume = {79}, + number = {11}, + pages = {1309--1331}, + issn = {0029-5981, 1097-0207}, + doi = {10.1002/nme.2579}, + url = {https://onlinelibrary.wiley.com/doi/10.1002/nme.2579}, + urldate = {2024-12-03}, + abstract = {Abstract Gmsh is an open‐source 3‐D finite element grid generator with a build‐in CAD engine and post‐processor. Its design goal is to provide a fast, light and user‐friendly meshing tool with parametric input and advanced visualization capabilities. This paper presents the overall philosophy, the main design choices and some of the original algorithms implemented in Gmsh. Copyright © 2009 John Wiley \& Sons, Ltd.}, + langid = {english}, + file = {/home/jaseg/Sync/Research/Zotero/2009_Geuzaine_Remacle_Gmsh.pdf} +} + @inproceedings{gevorgianLineCapacitanceImpedance2001, title = {Line {{Capacitance}} and {{Impedance}} of {{Coplanar-Strip Waveguides}} on {{Substrates}} with {{Multiple Dielectric Layers}}}, booktitle = {31st {{European Microwave Conference}}, 2001}, @@ -1952,16 +2013,16 @@ @online{IEEEXploreFullTexta, 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}, - file = {/home/jaseg/Zotero/storage/HJJK32NF/stamp.html} + file = {/home/jaseg/Zotero/storage/PQYCW7K7/stamp.html} } @online{IEEEXploreFullTextb, 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}, - file = {/home/jaseg/Zotero/storage/PQYCW7K7/stamp.html} + file = {/home/jaseg/Zotero/storage/HJJK32NF/stamp.html} } @online{ImpactPolarizationMode, @@ -2132,6 +2193,15 @@ file = {/home/jaseg/Zotero/storage/M6LSM6ML/Keller et al. - 2017 - Faster Secure Multi-party Computation of AES and D.pdf} } +@online{KiCadEDA, + title = {{{KiCad EDA}}}, + url = {https://www.kicad.org/}, + urldate = {2024-12-03}, + abstract = {A Cross Platform and Open Source Electronics Design Automation Suite}, + langid = {american}, + file = {/home/jaseg/Zotero/storage/IYJUIHPL/www.kicad.org.html} +} + @article{kimAdvancementFlexibleRobot2022, title = {Advancement of {{Flexible Robot Technologies}} for {{Endoluminal Surgeries}}}, author = {Kim, Joonhwan and family=Mathelin, given=Michel, prefix=de, useprefix=true and Ikuta, Koji and Kwon, Dong-Soo}, @@ -2170,6 +2240,18 @@ file = {/home/jaseg/Sync/Research/Zotero/Kiselev et al_2020_Analysis of the chromatic dispersion effect on the subcarrier wave QKD system.pdf} } +@online{kissaneDarkForest2024, + title = {Against the Dark Forest}, + author = {Kissane, Erin}, + date = {2024-11-22T15:26:10}, + url = {https://www.wrecka.ge/against-the-dark-forest/}, + urldate = {2024-11-23}, + abstract = {The complex of ideas I’m going to call the Dark Internet Forest emerges from mostly insidery tech thinking, but from multiple directions.}, + langid = {english}, + organization = {wreckage/salvage}, + file = {/home/jaseg/Zotero/storage/HCXPR3XB/against-the-dark-forest.html} +} + @book{kleinSpulenUndSchwingungskreise1941, title = {Spulen Und {{Schwingungskreise}}}, author = {Klein, Paul-Eduard}, @@ -2434,11 +2516,11 @@ issn = {2511-9044, 2511-9044}, doi = {10.1002/qute.201800011}, 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.}, langid = {english}, 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{laudenbachContinuousVariableQuantumKey2018a, @@ -2456,11 +2538,11 @@ issn = {2511-9044, 2511-9044}, doi = {10.1002/qute.201800011}, 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.}, langid = {english}, 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{laudenbachContinuousVariableQuantumKey2018b, @@ -2506,7 +2588,7 @@ file = {/home/jaseg/Zotero/storage/SPNJ8KBL/Launchbury et al. - 2014 - Application-Scale Secure Multiparty Computation.pdf} } -@article{leePrintedSpiralWinding2011, +@article{leePrintedSpiralWinding2011a, title = {Printed {{Spiral Winding Inductor With Wide Frequency Bandwidth}}}, author = {Lee, Chi Kwan and Su, Y. P. and Ron Hui, S. Y.}, date = {2011-10}, @@ -2693,7 +2775,7 @@ file = {/home/jaseg/Zotero/storage/WBSKAYAN/Long et al. - 2024 - EM Eye Characterizing Electromagnetic Side-channe.pdf} } -@article{lopeFirstSelfresonantFrequency2021, +@article{lopeFirstSelfResonant2021, title = {First Self‐resonant Frequency of Power Inductors Based on Approximated Corrected Stray Capacitances}, author = {Lope, Ignacio and Carretero, Claudio and Acero, Jesus}, date = {2021-02}, @@ -2983,7 +3065,7 @@ @article{mohanSimpleAccurateExpressions1999, title = {Simple Accurate Expressions for Planar Spiral Inductances}, author = {Mohan, S.S. and Del Mar Hershenson, M. and Boyd, S.P. and Lee, T.H.}, - year = {Oct./1999}, + date = {1999-10}, journaltitle = {IEEE Journal of Solid-State Circuits}, shortjournal = {IEEE J. Solid-State Circuits}, volume = {34}, @@ -3067,7 +3149,7 @@ file = {/home/jaseg/Zotero/storage/EBAXQHG5/Mosavirik et al. - 2022 - ImpedanceVerif On-Chip Impedance Sensing for Syst.pdf} } -@article{mosavirikSiliconEchoesNonInvasive2023, +@article{mosavirikSiliconEchoesNonInvasive2023a, title = {Silicon {{Echoes}}: {{Non-Invasive Trojan}} and {{Tamper Detection}} Using {{Frequency-Selective Impedance Analysis}}}, shorttitle = {Silicon {{Echoes}}}, author = {Mosavirik, Tahoura and Monfared, Saleh Khalaj and Safa, Maryam Saadat and Tajik, Shahin}, @@ -3841,6 +3923,19 @@ file = {/home/jaseg/Zotero/storage/9EWXN9MY/Ruhrmair et al. - 2015 - Virtual Proofs of Reality and their Physical Imple.pdf} } +@software{ruokolainenElmerCSCElmerfemElmer2023, + title = {{{ElmerCSC}}/Elmerfem: {{Elmer}} 9.0}, + shorttitle = {{{ElmerCSC}}/Elmerfem}, + author = {Ruokolainen, Juha and Malinen, Mika and Råback, Peter and Zwinger, Thomas and Takala, Eelis and Kataja, Juhani and Gillet-Chaulet, Fabien and Ilvonen, Sami and Gladstone, Rupert and Byckling, Mikko and {Mondher Chekki} and Gong, Cheng and Ponomarev, Pavel and Van Dongen, Eef and Robertsen, Fredrik and Wheel, Iain and Cook, Samuel and {T7saeki} and {Luzpaz} and {Rich\_B}}, + date = {2023-05-03}, + doi = {10.5281/ZENODO.7892181}, + url = {https://zenodo.org/record/7892181}, + urldate = {2024-12-03}, + abstract = {Elmer Release Notes for version 9.0 Previous release: {$<$}strong{$>$}8.4{$<$}/strong{$><$}br{$>$} Period covered: {$<$}strong{$>$}Dec 18 2018 - Nov 10 2020{$<$}/strong{$><$}br{$>$} Number of commits: {$<$}strong{$>$}\textasciitilde 1340{$<$}/strong{$>$} (excluding merges) These release notes provide information on the most essential changes. You can get a complete listing of commit messages, for example, with:{$<$}br{$>$} git log --since="2018-12-18" \> log.txt Apart from the core Elmer team at CSC (Juhani K., Mika M., Juha R., Peter R., Thomas Z.) git log shows contributions from Daniel B., Denis C., Eef v. D., Eelis T., Fabien G-C, Foad S. F., Fredrik R., Olivier G., Joe T., Luz P., Mondher C., Rupert G., Sami I., Sami R., Samuel C., and Saeki T. to this release. Additionally there are many ongoing developments in several branches that have not been merged to this release and are not therefore covered here. Also sometimes the code has been passed on by the original author by other means than the git, and in such cases the names may have been accidentally omitted. The contributions of all developers are gratefully acknowledged! New Solver Modules IncompressibleNSVec Incompressible Navier-Stokes solver utilizing vectorized and threaded assembly Includes built-in support for block preconditioning (Schur complement approximation included) Includes non-Newtonian material laws Intended for Elmer/Ice community but also other may find it useful. BeamSolver3D Solver for the Timoshenko equations of elastic beams embedded in 3-D space (see Elmer Models Manual for documentation) GmshReader Reads the mesh and results from simple Gmsh file format (that can be written by ElmerSolver as well) Solver includes interpolation of the fields to the current mesh May be used for hierarchical simulations where results are inherited from previous simulations ModelMixedPoisson A general-purpose mixed FEM solver for the Poisson equation (see Elmer Models Manual for documentation) Employs a div-conforming (face) finite element approximation SpringAssembly A generic utility to add node-wise springs and masses to structural models (see Elmer Models Manual for documentation) MarchingODESolver A solver that can compute ordinary differential equations on a moving mesh. It is assumed that the mesh is structured and there is a known draw speed. This makes it possible to relate timestep and mesh parameter directly with each other. Enhanced Solver Modules ElasticSolve Adding a new UMAT material model is simplified: compilation with an elmerf90 command is sufficient The state variables of UMAT material model can be written to a result file and visualized UMAT implementation updated to support axial symmetry EMWaveSolver The solver updated to support the basis functions of second order and simulation in 2D The solver is now documented in Elmer Models Manual MagnetoDynamics Fixes and generalization to the source projection (the determination of Jfix). A surface impedance condition for the time-harmonic AV model Thin region formulation for 1D wires in transient analysis Magnetic anisotropy (a complex-valued reluctivity tensor) enabled for the time-harmonic AV model MagnetoDynamics2D A velocity field can be given to add a Lorentz term to the equations Coreloss a posteriori formulas (Bertotti + extended Bertotti) MagnetoDynamicsCalcFields Enabled postprocessing in the case of a complex-valued reluctivity tensor Enabled the computation of magnetic co-energy ResultOutputSolver Vtu format: Enable saving of pieces, i.e. bodies and boundaries Improved saving of elemental, DG and IP fields Gmsh format: Improved use of masking features in output ShellSolver Eigenanalysis with the shell solver enabled Spring, resultant force and couple BCs added Combined analysis of 2-D shells and 1-D beams enabled Fully coupled analysis of 2-D shells and 3-D solids enabled (still subject to some geometric constraints on the mesh) Partial support for using an alternate formulation with drilling degrees of freedom StructuredMeshMapper Enable arbitrary number of layers, before limited to three. HeatSolver A new tentative vectorized version: HeatSolverVec Enable symmetric 3D cases for view factor computation to obtain significant timesavings Make Gebhart factors linear system symmetric, if possible "ViewFactor Symmetry" StressSolver Added a Maxwell visco-elastic model to linear elasticity solver Possible also to be run as incompressible (introducing pressure variable) Optional pre-stress advection term for layered Earth-deformation model WaveSolver The solver can be used to model harmonic and eigenmode cases as well. ParticleAdvector Allow particles to be sent from Gaussian integration points as well. This is beneficial for robustness since they are not located at surface. Local integration time based on local Courant number. ElmerSolver library functionality Treatment of block systems The block matrix approach for solving complicated problems has been enhanced. Currently the block approach can be used in several ways during some stage of the solution. Split up monolithic equations into subproblems that are easier to solve (e.g. IncompressibleNS) Combine linear multiphysical (coupled) problems into a block matrix (e.g. FSI problems) For problems belonging to class 1) we may perform recreation of a monolithic matrix. This will allow better use of standard linear algebra to utilize direct solvers, or change the system to be harmonic or eigenvalue problem. For the documentation of utilizing block-matrix construct in connection with the fully coupled simulation of multiphysical problems see the new chapter "Block-matrix construct to build tightly coupled solvers" in ElmerSolver Manual. More economical integration rules A collection of economical Gauss quadrature rules for prismatic elements are introduced to replace tensor product rules for quadrilateral p-elements when 1 \< p \<= 8. The tensor product rule with n = (p+1)**2 points is now replaced by more economical ones. Dirichlet BCs for div-conforming vector finite elements (face elements) A sif command of the form Q \{f\} j = Real ... can be used to specify vector-valued data whose normal component is then used to integrate the values of DOFs for vector-valued interpolation of the data. Here Q is an Elmer variable which is approximated with face finite elements. Conforming BCs by elimination System can identify conforming boundaries such that dofs related to nodes or edges on opposing sides may be assembled into one degree of freedom. This decreases the size of the linear system and is numerically favourable. Antiperiodicity may be included. For vector-valued problems all components must be treated alike. Conforming BCs for edge dofs may consider the direction of edge. See test cases with "Apply Conforming BCs" and "Conforming BC" defined. Improved internal partitioning with Zoltan Enable internal partitioning with Zoltan to honor connected boundaries. Enable primary solver to call other solvers For documentation see the section "Solver execution by a master solver" in ElmerSolver Manual. Enables calling before and after solving the primary problem. Also possible to call before and after each nonlinear iteration. Anderson Acceleration for nonlinear systems Implemented a version of Anderson Acceleration where previous solutions and residuals are used to accelerate the nonlinear convergence. May increase nonlinear convergence to quadratic, quadratic convergence (Newton's method) is not improved. Swapping meshes on-the-fly Implemented library functionality to swap meshes during the simulation. Currently no history data is interpolated. ListGetElemental routines More flexible routines for obtaining material parameters for the Gaussian integration points. Detects automatically what kind of fields the dependency depends on (nodal, DG, elemental, IP points) Vectorized versions to be used with vectorized finite element assembly View factors Allow computation of view factors in 3D cases with symmetry. Speed-up computation for cases where emissivity not equal to one. Enable view factors to be used in conjunction with DG (in HeatSolveVec) Run Control Enable external loop control over the simulation. May be used in optimization and parametric scanning etc. Applicable also to transient systems as the variable "time" is not used for the control level. Inline parameters Enable inline keywords -rpar and -ipar They are followed by the number of argument + values of the arguments. Generic source control We may tune a r.h.s. load vector such that the solution (or reaction force) at given node is the desired one. Mimics the old Smart Control operation of HeatSolve but on a library level. ElmerGrid Fixes for UNV, mptxt and Gmsh file format import. Tentative reader for FVCOM format Add possibility to define seed for Metis partitioning (-metisseed). Maintain entity names in extrusion ElmerGrid and its plugin under ElmerGUI were harmonized such that they use the same codebase. ElmerGUI Huge number of improvements by Saeki! Highlights include: Object browser to view the case at a glance and to easily access the most windows. Removed sif auto-generation functionality to avoid unintended overwriting of sif file. "Generate, save and run" button to quickly run the case modifed via GUI. "Save and run" button on sif window to quickly run the case modifed via sif window. Postprocessor button selectable from ElmerVTK, ElmerPost or ParaView. "New project..." menu as an alternative way to start a new project. Seperated "Save project as..." menu from "Save project" menu to save the project in a different directory. Improved and more robust project loading "Preference" menu on sif window and on solver log window for syntax highlighting and font selection. "Recent projects" in File menu for quick loading of recently used projects. Improved ElmerVTK postprocessor (reading simple .vtu file, bottom toolbar including time-step control and displace button, etc) Configuration \& Compilation New Windows installer utilizing msys2 either with or without ElmerGUI + with or without MPI installers Elmer/Ice New features in Elmer/Ice are documented in elmerfem/elmerice/ReleaseNotes/release\_elmerice\_9.0.md Other FreeCADBatchFEMTools improvements and added tests New Contributors @frroberts made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/176 @mmcker made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/118 @Foadsf made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/207 @dremerb made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/210 @Kezii made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/234 @kinnala made their first contribution in https://github.com/ElmerCSC/elmerfem/pull/243 {$<$}strong{$>$}Full Changelog{$<$}/strong{$>$}: https://github.com/ElmerCSC/elmerfem/compare/release-8.4...release-9.0}, + organization = {Zenodo}, + version = {release-9.0} +} + @book{saackeRadiotechnikIIIEmpfanger1926, title = {Radiotechnik {{III}}: {{Die Empfänger}}}, author = {Saacke, Hermann}, @@ -4279,6 +4374,38 @@ file = {/home/jaseg/Zotero/storage/XURXLX9C/Takeoka et al. - 2014 - Fundamental rate-loss tradeoff for optical quantum.pdf} } +@incollection{TamperResistance2020, + title = {Tamper {{Resistance}}}, + booktitle = {Security {{Engineering}}}, + date = {2020}, + pages = {599--637}, + publisher = {John Wiley \& Sons, Ltd}, + doi = {10.1002/9781119644682.ch18}, + url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119644682.ch18}, + urldate = {2024-12-03}, + abstract = {The security engineer needs to understand what tamper resistance is, and what it can and can't do. In this chapter, the author takes the reader through the past thirty years of evolution of attack and defence. The banking community realised that commercial operating systems were likely to remain insufficient to protect PINs, particularly from bank insiders, and decided to use separate hardware to manage them. This led to the development of standalone cryptographic modules or hardware security modules (HSMs). The chapter provides a few comments about the evaluation of HSMs. Each of the product categories discussed in this chapter, from HSMs down through FPGAs to smartcards, has a wide range of offerings with wide variability in the quality of protection. The security engineer will therefore have to pay attention to the many failure modes of systems involving tamper-resistant processors that are more or less independent of the price or technical tamper-resistance of the device.}, + isbn = {978-1-119-64468-2}, + langid = {english}, + keywords = {banking community,FPGAs,hardware security modules,security engineer,smartcards,tamper resistance}, + file = {/home/jaseg/Zotero/storage/DSFCQBZB/9781119644682.html} +} + +@incollection{TamperResistance2020a, + title = {Tamper {{Resistance}}}, + booktitle = {Security {{Engineering}}}, + date = {2020}, + pages = {599--637}, + publisher = {John Wiley \& Sons, Ltd}, + doi = {10.1002/9781119644682.ch18}, + url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119644682.ch18}, + urldate = {2024-12-03}, + abstract = {The security engineer needs to understand what tamper resistance is, and what it can and can't do. In this chapter, the author takes the reader through the past thirty years of evolution of attack and defence. The banking community realised that commercial operating systems were likely to remain insufficient to protect PINs, particularly from bank insiders, and decided to use separate hardware to manage them. This led to the development of standalone cryptographic modules or hardware security modules (HSMs). The chapter provides a few comments about the evaluation of HSMs. Each of the product categories discussed in this chapter, from HSMs down through FPGAs to smartcards, has a wide range of offerings with wide variability in the quality of protection. The security engineer will therefore have to pay attention to the many failure modes of systems involving tamper-resistant processors that are more or less independent of the price or technical tamper-resistance of the device.}, + isbn = {978-1-119-64468-2}, + langid = {english}, + 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} +} + @article{tangMeasurementDeviceIndependentQuantumKey2016, title = {Measurement-{{Device-Independent Quantum Key Distribution}} over {{Untrustful Metropolitan Network}}}, author = {Tang, Yan-Lin and Yin, Hua-Lei and Zhao, Qi and Liu, Hui and Sun, Xiang-Xiang and Huang, Ming-Qi and Zhang, Wei-Jun and Chen, Si-Jing and Zhang, Lu and You, Li-Xing and Wang, Zhen and Liu, Yang and Lu, Chao-Yang and Jiang, Xiao and Ma, Xiongfeng and Zhang, Qiang and Chen, Teng-Yun and Pan, Jian-Wei}, diff --git a/paper/paper.tex b/paper/paper.tex index 9abc676..7ba235f 100644 --- a/paper/paper.tex +++ b/paper/paper.tex @@ -59,13 +59,13 @@ Achieving Rotation-Invariant Coupling using Twisted Multi-Layer PCB Inductors} \maketitle \begin{abstract} - We present \emph{twisted inductors}, a generalization of planar single- or two-layer spiral inductors as well as + We present \emph{twisted inductors}, a generalization of planar single- and two-layer spiral inductors as well as planar toroidal inductors. Compared to conventional planar spiral inductors, twisted inductors generate a magnetic - field with better rotational symmetry, resulting in decreased output ripple in Wireless Power Transfer applications - with an axially rotating receiver. Additionally, we found that twisted inductors can simultaneously yield a - significantly improved self-resonant frequency and a higher inductance in the same area as a conventional planar - spiral inductor, up to \qty{50}{\percent} improved SRF and \qty{6.5}{\percent} increased inductance among our test - samples. We base our conclusions on several simulations and an extensive set of practical measurements. + field with better rotational symmetry, resulting in decreased output ripple in Wireless Power Transfer (WPT) + applications with an axially rotating receiver. Additionally, we found that twisted inductors can simultaneously + yield a significantly improved self-resonant frequency and a higher inductance in the same area as a conventional + planar spiral inductor, up to \qty{50}{\percent} improved SRF and \qty{6.5}{\percent} increased inductance among our + test samples. We base our conclusions on several simulations and an extensive set of practical measurements. \end{abstract} \section{Introduction} @@ -76,31 +76,38 @@ fanSimultaneousWirelessPower2024, leeSimpleWirelessPower2017, liWirelessPowerTra maierContributionSystemDesign2019, mooreApplicationsWirelessPower2019, mouEnergyEfficientAdaptiveDesign2017, mouWirelessPowerTransfer2015, mullenEffectMisalignmentInductive, rezmeritaSelfMutualInductance2017, zhangWirelessPowerTransfer2019}. -While working on a novel application of Inductive WPT in a Inertial Hardware Security Module (IHSM) as previously -published in\textcite{gotteCantTouchThis2022}, we found ourselves presented with an unusual set of constraints -attempting WPT through a rotating joint using a PCB inductor---a set of constraints that does not yet seem to be -addressed adequately in the existing literature on inductive WPT. +While working on an application of Inductive WPT in a Inertial Hardware Security Module (IHSM) as previously +published by \textcite{gotteCantTouchThis2022}, we found ourselves presented with an unusual set of constraints +attempting WPT through a rotating joint using a planar inductor implemented in a Printed Circuit Board (PCB)---a set of +constraints that does not seem to be addressed adequately in the existing literature on inductive WPT yet. -Our application poses the challenge of transferring power between a stationary part of an -IHSM\cite{gotteCantTouchThis2022} and part that rotates at high speed (\qtyrange{1000}{3000}{\rpm}) through a pair of -WPT inductors located on the IHSM's axis of rotation. The large centrifugal acceleration prohibits the use of liquid -electrolyte capacitors on the rotating part, and makes heavy components such as large MLCCs challenging to balance. To -reduce manufacturing cost of both parts, and to reduce weight and thereby inertia as well as susceptibility to vibration -in the rotating part, we decided to use inductors that are directly patterned onto the IHSM's printed circuit boards. -The primary constraint that results from this choice is that the PCB manufacturing processes' pattern resolution results -in a strict upper limit to the turn count that can be achieved in an inductor with a given area. +Inertial Hardware Security Modules are a hardware security primitive that discourages tampering with a payload (e.g.\ a +single-board computer) by rotating a tamper-sensing enclosure around the payload. The tamper-sensing enclosure +continuously monitors itself for tampering using sensors such as tamper-sensing meshes\cite{TamperResistance2020a} and +accelerometers. When the tamper-sensing enclosure signals a tamper alarm to the payload, the payload immediately +destroys all sensitive data to prevent the attacker from gaining access to it. In principle, an IHSM is similar to an +ATM that responds to attempts at opening its vault by dispensing dye over the bank notes within, rendering them unusable. -While planar inductors are usually considered approximately axisymmetric, we found that at the small turn counts in our -application, the asymmetry in a planar spiral inductors's field is large enough that the resulting oscillation of the -coupling coefficient of two such inductors with the inductor's revolution leads to voltage ripple on the secondary side, -an issue which is exacerbated by radial misalignment of the coils. +In our IHSM implementation, the tamper-sensing enclosure rotates at \qtyrange{1000}{3000}{\rpm}. The rotating enclosure +is powered through a pair of WPT inductors located on the IHSM's axis of rotation. The large centrifugal acceleration +prohibits the use of batteries or liquid electrolyte capacitors on the rotating part, and makes heavy components such as +large Multilayer Ceramic Capacitors (MLCCs) challenging to balance. To reduce manufacturing cost of both parts, and to +reduce weight and thereby inertia as well as susceptibility to vibration in the rotating part, we decided to use +inductors that are directly patterned onto the IHSM's printed circuit boards. The primary constraint that results from +this choice is that the PCB manufacturing processes' pattern resolution results in a strict upper limit to the turn +count that can be achieved in an inductor with a given area. -In other inductive wireless power transfer systems, this issue is mitigated by one of several factors: First, for this -effect to matter in the first place, the two coils have to be rotating with respect to one another. In ferrite core -inductors, the core is the major factor shaping the magnetic field and evens out the small effect of winding asymmetry. -In wire-wound inductors, the often higher turn count and the tightly packed, circular wires reduce this effect to almost -nothing. Finally, the output ripple caused by this oscillation can be filtered through a voltage regulator or by using a -large decoupling capacitor on the secondary side if the application can accomodate such components on the rotating part. +Planar inductors are usually considered approximately axisymmetric. In our application, we found that at small turn +counts, the asymmetry in a planar spiral inductors's field is large enough that the resulting oscillation of the +coupling coefficient of two such inductors with the inductor's revolution leads to voltage ripple on the secondary side. +Radial misalignment of the coils further exacerbates this issue. + +In other inductive WPT systems, this issue is mitigated by one of several factors: First, for this effect to matter in +the first place, the two coils have to be rotating with respect to one another. In ferrite core inductors, the core is +the major factor shaping the magnetic field and evens out the small effect of winding asymmetry. In wire-wound +inductors, the often higher turn count and the tightly packed, circular wires renders this effect negligible. Finally, +the output ripple caused by this oscillation can be filtered through a voltage regulator or by using a large decoupling +capacitor on the secondary side if the application can accomodate such components on the rotating part. 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 @@ -110,18 +117,18 @@ it is generally assumed that the two coils remain quasi-stationary with respect 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 -requires, which in practice requires more space and a ferrite or laminated iron core. +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. \subsection{Twisted inductors} In this paper, we propose a novel way of laying out circular PCB inductors that twists the inductor's windings around one another using a ring of vias each on the inside and outside of the inductor's windings. To fit our unique use case, we applied a principle which the polygonal basket-woven air coils used in early radio sets are based on to an approach -inspired by contemporary planar inductor layouts. Applying some math, we show that we can layout a twisted inductor for -any number of twists that is co-prime to the inductor's turn count, and that in fact, our approach opens up a large -design space for inductor layouts that interpolate between planar spiral inductors on one end, and planar toroidal -inductors on the other end. Our approach thus generalizes a number of previous approaches to the design of planar -inductors. +inspired by contemporary planar inductor layouts. We show that we can layout a twisted inductor for any number of twists +that is co-prime to the inductor's turn count, and that in fact, our approach opens up a large design space for inductor +layouts that interpolate between planar spiral inductors on one end, and planar toroidal inductors on the other end. Our +approach thus generalizes a number of previous approaches to the design of planar inductors. We observe that in high-frequency applications, a moderate number of twists increases the spacing between the beginning and end of the inductor's conductor, where the majority of the inductor's AC current flows. This decreases the parasitic @@ -136,9 +143,9 @@ rotational symmetry in rotating wireless power transfer interface as well as qua provide detailed layout instructions, including a mathematical analysis of the available parameter space and an analytical model of both inductance and DC equivalent series resistance of our scheme. Validating our scheme, we provide laboratory measurements of the basic parameters of a number of test specimens comparing our scheme to conventional -techniques. We furhter performed a number of FEM simulations to validate our inductance and ESL approximations. 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 +techniques. We furhter present the results of FEM simulations to validate our inductance and ESL approximations. +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. \section{Related Work} @@ -161,20 +168,21 @@ inductor with many turns on multiple layers, which improves compactness and leak rise to increased distributed capacitance as now turns with a large voltage differential are layered right on top of each other. -Back then, a number of ways were devised to decrease distributed capacitance in multilayer inductors. These methods can -be divided into two general categories: Optimizing the connecting order of turns to minimize the voltage differential -between adjacent turns---a technique that is still used to this day\cite{lopeFirstSelfresonantFrequency2021}, and -optimizing the winding schema to increase the separation between turns. The main technique in the first category -concerns winding the turns of a cylindrical multilayer inductor not layer by layer, but instead layering them -diagonally, effectively connecting adjacent turns in a diagonal zigzag pattern. Then as now, wound inductors applying -this technique were not feasible to manufacture reliably by machine, but the technique can be closely replicated in PCB -inductors as shown in \textcite{leePrintedSpiralWinding2011}. The main limiting factors in a PCB implementation are the -requirement for a large number of vias inside the inductor's turns limiting the achievable turn count\footnote{In PCBs, -as opposed to ICs, vias limit the achievable turn count when they need to be placed in-line inside the turns as opposed -to on the inside or outside because a PCB's minimum trace/space widths are usually much smaller than the smallest -feasible via, consisting of a minimum-size drill surrounded by a minimum-size annular ring.} and increasing ESR through -the thin trace sections that are necessary to accomodate the via structure, as well as the layer pairing limitations -when blind vias are used in multilayer PCBs. +Before the invention of ferrites, a number of ways were devised to decrease distributed capacitance in multilayer +inductors. These methods can be divided into two general categories: Optimizing the connecting order of turns to +minimize the voltage differential between adjacent turns---a technique that is still used to this +day\cite{lopeFirstSelfresonantFrequency2021}, and optimizing the winding schema to increase the separation between +turns. The main technique in the first category concerns winding the turns of a cylindrical multilayer inductor not +layer by layer, but instead layering them diagonally, effectively connecting adjacent turns in a diagonal zigzag +pattern. Then as now, wound inductors applying this technique were not feasible to manufacture reliably by machine, but +the technique can be closely replicated in PCB inductors as shown in \textcite{leePrintedSpiralWinding2011}. The main +limiting factors in a PCB implementation are the requirement for a large number of vias inside the inductor's turns +limiting the achievable turn count\footnote{In PCBs, as opposed to integrated circuits (ICs), vias limit the achievable +turn count when they need to be placed in-line inside the turns as opposed to on the inside or outside because a PCB's +minimum trace/space widths are usually much smaller than the smallest feasible via, consisting of a minimum-size drill +surrounded by a minimum-size annular ring.} and increasing equivalent series resistance (ESR) through the thin trace +sections that are necessary to accomodate the via structure, as well as the layer pairing limitations when blind vias +are used in multilayer PCBs. \begin{figure} \begin{center} @@ -225,12 +233,12 @@ kleinSpulenUndSchwingungskreise1941, wiggeRundfunktechnischesHandbuch1930, querf \subsection{PCB inductor design for wireless power transfer} -For wireless power transfer, air-core inductors with or without ferrite magnetic shielding are the standard solution. -Since in most 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. Meanwhile, in many WPT applications, -especially for charging portable devices or medical implants, some misalignment between the sending and receiving coils -is expected. Using the available space with an air-core inductor that has a large cross-sectional area reduces the -impact of this misalignment. +Air-core inductors with or without ferrite magnetic shielding are the standard solution in inductive WPT links. Since in +most 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. Meanwhile, in many WPT applications, especially for +charging portable devices or medical implants, some misalignment between the sending and receiving coils is expected. +Using the available space with an air-core inductor that has a large cross-sectional area reduces the impact of this +misalignment. Looking at such WPT inductors, they 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 @@ -239,28 +247,30 @@ 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, PCB inductors tend to have poor DC resistance. A PCBs' thin but wide trace cross-section helps with -skin effect compared to a solid conductor. However, PCBs can still not approach the performance of litz wire used in -high-frequency WPT coils, which commonly use wire diameters in the tens of micrometer -range\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}. +substrate---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 provides some +advantage over a solid, round conductors of the same cross-sectional area at higher frequencies due to skin effect. +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 do large air coils exhibit more parasitic capacitance than much smaller ferrite-core inductors simply due to their 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 +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} -Planar inductors are commonly used in RF ICs. 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}. +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 @@ -304,24 +314,23 @@ transfer for the charging of electric vehicles 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 10 kW, an efficiency improvement of just $0.1\%$ -corresponds to a reduction in power dissipation of 10 W. 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. +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 for Inductive Power Transfer} +\subsection{Air-Core Inductors in WPT} -Across application areas, air-core inductors are often used for wireless power transfer 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 +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} -In this section, we will provide a detailed derivation of the layout of twisted inductors. We can approach this layout +In this section, we present a detailed derivation of the layout of twisted inductors. We approach this layout by construction. Let us first consider a simple, planar, circular spiral coil with a fixed pitch. We will ignore trace width for now, and consider the trace a thin wire. We will assume the inductor's ports are both located on the positive $x$-Axis. We can rotate it so its first port aligns with the $x$-Axis. To minimize the loop area of the inductor's @@ -372,12 +381,12 @@ spiral inductor in the first two columns. Extending the above parametrization of a spiral inductor's layout, we propose planar \emph{twisted inductors} based on two core observations: -\begin{itemize} - \item 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. - \item In a two-layer spiral inductor (Figure\ \ref{fig_nk_combined}), we can adjust the turn count of the - pair of traces to move the end point of the bottom layer trace anywhere on the inductor's outer radius. -\end{itemize} +\begin{description} + \item[Observation 1.] 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. + \item[Observation 2.] In a two-layer spiral inductor (Figure\ \ref{fig_nk_combined}), we can adjust the turn 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} Combining these two observations, we find that by choosing a number $k$ of inversions, i.e. layer jumps, that is coprime to the number of total turns of the inductor $n$, we achieve a layout where all $k$ pairs of top and bottom-layer traces @@ -452,7 +461,7 @@ slightly, but the contribution of these vias will remain small in practical appl 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?} -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. \begin{equation} @@ -512,15 +521,16 @@ case. To allow for easy design with twisted inductors and to speed up the laboratory prototyping we performed for this paper, we created a tool that generates arbitrary twisted inductor layouts, and that is able to output these layouts as PCB -footprint files for the open source KiCad EDA CAD tool. We integrated the ESR and ESL approximations as derived above -with our tool, so that it provides immediate design feedback when generating inductors. In order to minimize ESR and -maximize PCB area utilization, we made the tool automatically calculate the largest possible trace width when given a -minimum clearance specification. +footprint files for the open source KiCad EDA CAD tool\cite{KiCadEDA}. We integrated the ESR and inductance +approximations as derived above with our tool, so that it provides immediate design feedback when generating inductors. +In order to minimize ESR and maximize PCB area utilization, we made the tool automatically calculate the largest +possible trace width when given a minimum clearance specification. To handle outputting PCB geometry in a format that can be read from KiCad, we utilized the open source EDA file format -library \emph{gerbonara}\todo{Cite gerbonara}. To support the FEM simulations that are described in the next section -below, our tool contains functionality to map gerbonara's geometry representation into that of gmsh\todo{Cite gmsh}, the -FEM mesher that we chose to interface with Elmer FEM\todo{Cite Elmer}. +library \emph{gerbonara}\cite{GerbonaraToolsHandle}. To support the FEM simulations that are described in the next +section below, our tool contains functionality to map gerbonara's geometry representation into that of +gmsh\cite{geuzaineGmsh3DFinite2009}, the FEM mesher that we chose to interface with Elmer +FEM\cite{ruokolainenElmerCSCElmerfemElmer2023}. Our inductor design tool is available in this paper's supplementary material as well as at the git repository linked at the end of this paper. @@ -881,8 +891,8 @@ basket-wound inductors used in the early days of radio. Our \emph{twisted} induc conventional planar inductors including conventional single- or two-layer planar spiral inductors as well as planar toroidal inductors. For inversion count parameter $k\ge 2$, twisted inductors produce magnetic field distributions that have better rotational symmetry along the inductor's main axis compared to either single- or two-layer planar spiral -inductors, which yields lower output ripple in Wireless Power Transfer through rotating joints and enables the use of -smaller and lighter secondary-side circuitry, improving efficiency. +inductors, which yields lower output ripple in WPT through rotating joints and enables the use of smaller and lighter +secondary-side circuitry, improving efficiency. Furthermore, besides the advantages twisted inductors show in our particular application, we found that our sample twisted inductors have up to \qty{50}{\percent} improved self-resonant frequency as well as up to \qty{6.5}{\percent}