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  • 1.
    Alex-Amor, Antonio
    et al.
    Univ Malaga, Dept Lenguajes & Ciencias Computac, Malaga 29071, Spain.;Univ Politecn Madrid, Informat Proc & Telecommun Ctr, Madrid 28040, Spain..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, Lab Genie Elect & Elect Paris, CNRS, F-75252 Paris, France.;Univ Paris Saclay, Cent Supelec, CNRS, Lab Genie Elect & Elect Paris, F-91192 Gif Sur Yvette, France..
    Ebrahimpouri, Mahsa
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, Granada 18071, Spain..
    Fernandez Gonzalez, Jose Manuel
    Univ Politecn Madrid, Informat Proc & Telecommun Ctr, Madrid 28040, Spain..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Glide-Symmetric Metallic Structures With Elliptical Holes for Lens Compression2020Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 68, nr 10, s. 4236-4248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, we study the wave propagation in a metallic parallel-plate structure with glide-symmetric elliptical holes. To perform this study, we derived a mode-matching technique based on the generalized Floquet theorem for glide-symmetric structures. This mode-matching technique benefits from a lower computational cost since it takes advantage of the glide symmetry in the structure. It also provides physical insight into the specific properties of Floquet modes propagating in these specific structures. With our analysis, we demonstrate that glide-symmetric structures with periodic elliptical holes exhibit an anisotropic refractive index over a wide range of frequencies. The equivalent refractive index can be controlled by tuning the dimensions of the holes. Finally, by combining the anisotropy related to the elliptical holes and transformation optics, a Maxwell fish-eye (MFL) lens with a 33.33% size compression is designed. This lens operates in a wideband frequency range from 2.5 to 10 GHz.

  • 2.
    Alex-Amor, Antonio
    et al.
    Tech Univ Madrid, Informat Proc & Telecommun Ctr, Madrid 28040, Spain..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, UR2, Lab Elect & Electromagnetisme, F-75005 Paris, France..
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, Granada 18071, Spain..
    Fernandez-Gonzalez, Jose M.
    Tech Univ Madrid, Informat Proc & Telecommun Ctr, Madrid 28040, Spain..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Elliptical Glide-Symmetric Holey Metasurfaces for Wideband Anisotropy2020Ingår i: 2020 14th European Conference on Antennas and Propagation (EUCAP 2020), Institute of Electrical and Electronics Engineers (IEEE) , 2020Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a mode-matching technique to study the dispersive features of periodic structures composed of glide-symmetric elliptical holes. As a difference from purely numerical methods, our formulation provides physical insight on the Floquet harmonics. At the same time, the computational cost is reduced compared to general purpose commercial software. The fields inside the holes are described by means of Mathieu functions and subsequently used to compute the full 2-D dispersion diagrams. With the presented analysis, we demonstrate that glide-symmetric periodic structures with elliptical holes offer anisotropic refractive indexes over a wide range of frequencies.

  • 3.
    Alex-Amor, Antonio
    et al.
    Univ Politecn Madrid, Informat Proc & Telecommun Ctr, E-28040 Madrid, Spain.;Univ Granada, Dept Teoria Senal Telemat & Comunicac, E-18071 Granada, Spain..
    Valerio, Guido
    Sorbonne Univ, CNRS, Lab Genie Elect & Elect Paris, F-75252 Paris, France.;Univ Paris Saclay, Cent Supelec, CNRS, Lab Genie Elect & Elect Paris, F-91192 Gif Sur Yvette, France..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Mesa, Francisco
    Univ Seville, Microwaves Grp, Dept Appl Phys 1, Escuela Tecn Super Ingn Informat, E-41012 Seville, Spain..
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, E-18071 Granada, Spain..
    Fernandez-Gonzalez, Jose M.
    Univ Politecn Madrid, Informat Proc & Telecommun Ctr, E-28040 Madrid, Spain..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Wave Propagation in Periodic Metallic Structures with Equilateral Triangular Holes2020Ingår i: Applied Sciences, E-ISSN 2076-3417, Vol. 10, nr 5, artikel-id 1600Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper studies wave propagation in a periodic parallel-plate waveguide with equilateral triangular holes. A mode-matching method is implemented to analyze the dispersion diagram of the structure possessing glide and mirror symmetries. Both structures present an unexpected high degree of isotropy, despite the triangle not being symmetric with respect to rotations of 90 degrees. We give some physical insight on the matter by carrying out a modal decomposition of the total field on the hole and identifying the most significant modes. Additionally, we demonstrate that the electrical size of the triangular hole plays a fundamental role in the physical mechanism that causes that isotropic behavior. Finally, we characterize the influence of the different geometrical parameters that conform the unit cell (period, triangle size, hole depth, separation between metallic plates). The glide-symmetric configuration offers higher equivalent refractive indexes and widens the stopband compared to the mirror-symmetric configuration. We show that the stopband is wider as the triangle size is bigger, unlike holey structures composed of circular and elliptical holes where an optimal hole size exists.

  • 4.
    Arnberg, Philip
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Petersson, Oscar Barreira
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Dahlberg, Oskar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    High Refractive Index Electromagnetic Devices in Printed Technology Based on Glide-Symmetric Periodic Structures2020Ingår i: Applied Sciences, E-ISSN 2076-3417, Vol. 10, nr 9, artikel-id 3216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate the beneficial effects of introducing glide symmetry in a two-dimensional periodic structure. Specifically, we investigate dielectric parallel plate waveguides periodically loaded with Jerusalem cross slots in three configurations: conventional, mirror- and glide-symmetric. Out of these three configurations, it is demonstrated that the glide-symmetric structure is the least dispersive and has the most isotropic response. Furthermore, the glide-symmetric structure provides the highest effective refractive index, which enables the realization of a broader range of electromagnetic devices. To illustrate the potential of this glide-symmetric unit cell, a Maxwell fish-eye lens is designed to operate at 5 GHz. The lens is manufactured in printed circuit board technology. Simulations and measurements are in good agreement and a measured peak transmission coefficient of -0.5 dB is achieved.

  • 5.
    Chen, Qiao
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion. Southeast Univ, State Key Lab Millimeter Wave, Nanjing 210096, Jiangsu, Peoples R China..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Dispersion Analysis of Coaxial Line Loaded with Twist-Symmetric Half-Rings2018Ingår i: 2018 IEEE International Workshop on Antenna Technology, iWAT2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    A coaxial line with half-rings connected to its external conductor is proposed in this paper, to investigate the dispersion properties of a twist-symmetric electromagnetic configuration. We demonstrate that the propagating modes in a twist-symmetric structure are more linear than a conventional structure. Additionally, the bandgap at the Brillouin zone boundaries can be manipulated by tuning the relative angular orientation or translation of the rings. This tuning is equivalent to changing the order of the twist symmetry from 4- to 2-fold. Our proposed geometry finds potential application in fully-metallic reconfigurable filters and phase shifters.

  • 6.
    Chen, Qiao
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion. Southeast Univ, State Key Lab Millimeter Waves, Nanjing 210096, Jiangsu, Peoples R China.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, Lab Elect & Electromagnetisme, F-75005 Paris, France..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Modeling and Dispersion Analysis of Coaxial Lines With Higher Symmetries2018Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 66, nr 10, s. 4338-4345Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, 1-D periodic structures possessing higher symmetries are proposed and investigated in terms of their dispersion properties. The proposed structures are coaxial lines with coaxial rings periodically loaded on their inner or outer conductors. The higher symmetries, namely, glide and twist symmetries, are obtained by performing an additional geometrical operation within the unit cell of the periodic structure. We demonstrate that the propagating modes exhibit a lower frequency dispersion in higher symmetric coaxial lines. Moreover, the conventional stopbands of periodic structures at their Brillouin zone boundaries can be controlled by breaking the higher symmetry or changing the order of the twist symmetry. A circuit-based analytical method is proposed to calculate the dispersion diagram of the glide-symmetric coaxial lines. The results are validated with a full-wave simulation. Moreover, several prototypes of the twist-symmetric coaxial lines are manufactured and measured. A remarkable agreement is achieved between the measurements and simulations, validating the theoretical results. The proposed structures find potential applications in leaky-wave antennas and fully metallic reconfigurable filters and phase shifters.

  • 7.
    Dahlberg, Oskar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, Lab Electron & Electromagnetisme, F-75005 Paris, France..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Propagation characteristics of periodic structures possessing twist and polar glide symmetries2019Ingår i: EPJ Applied Metamaterials, ISSN 2272-2394, Vol. 6, artikel-id 14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, we provide an overview of the current state of the research in the area of twist symmetry. This symmetry is obtained by introducing multiple periods into the unit cell of a periodic structure through a rotation of consecutive periodic deformations around a symmetry axis. Attractive properties such as significantly reduced frequency dispersion and increased optical density, compared to purely periodic structures, are observed. The direct link between the symmetry order and these properties is illustrated through numerical simulations. Moreover, polar glide symmetry is introduced, and is shown to provide even further control of the dispersion properties of periodic structures, especially when combined with twist symmetry. Twist symmetries can, with benefit, be employed in the development of devices for future communication networks and space applications, where fully metallic structures with accurate control of the dispersion properties are desired.

  • 8.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Analyzing Glide-Symmetric Holey Metasurfaces Using a Generalized Floquet Theorem2018Ingår i: IEEE Access, E-ISSN 2169-3536Artikel i tidskrift (Refereegranskat)
  • 9.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Periodic Structures with Higher Symmetries: Analysis and Applications2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna avhandling behandlar periodiska strukturer med högre symmetrier. Deras vågutbredningsegenskaper undersöks och deras potentiella tillämpningar diskuteras.

    Periodiska strukturer med högre symmetrier beskrivs med ytterligare en geometrisk operator, utöver den translationsoperator. Två specialfall av högre symmetrier är glid- och vridsymmetrier. Glidsymmetriska periodiska strukturer är invarianta under en translation (glidning) på en halvperiod följt av en reflektion med avseende på ett glidplan. Vridsymmetriska periodiska strukturer är invarianta under en translation längs med följt av en rotation kring en vridningsaxel.

    I en högsymmetrisk periodisk struktur, innehrillande flera högre ordningens moder, fås en dramatisk minskning av frekvensdispersionen för den första moden, varigenom den bandbreddsbegränsning som finns i konventionella periodiska strukturer kan övervinnas. Därigenom kan högsymmetriska strukturer användas vid utformandet av bredbandiga antenner baserade på metaytor. Till exempel kan urkärnade glidsymmetriska metallstrukturer användas för att utforma bredbandiga Luneburg-linser med låga förluster, vilka för millimetervågor har tillämpningar inom femte generationens kommunikationssystem (5G). Dessutom kan dessa strukturer utnyttjas som kostnadseffektiva elektromagnetiska bandgap (EBG)-strukturer för millimetervågor.

    På grund av förekomsten av högre ordningens moder kan emellertid inte högsymmetriska periodiska strukturer med starkt kopplade skikt analyseras med användning av den konventionella transversella resonansmetoden. Därför används i denna avhandling en modanpassningsmetod, vars formulering bygger på den generaliserade versionen av Floquets teorem, för att analysera glidsymmetriska urkärnade periodiska strukturer där hålen har godtyckligt tvärsnitt. Användingen av Floquets generaliserade teorem halverar storleken på beräkningsdomänen och metoden är både snabbare och effektivare än kommersiella programvaror som CST Microwave Studio. Dessutom bidrar den föreslagna metoden till fysikalisk förståelse genom symmetriegenskaperna hos de Floquet-moder som utbreder sig i de högsymmetriska strukturerna.

    Vidare definieras polär glidssymmetri, som motsvarar glidsymmetri i ett cylindriskt koordinatsystem, och en förklaring ges hur den tillsammans med vridsymmetri kan tillämpas på koaxiella strukturer. Det visas att vrid- och polärglidssymmetrier ger ytterligare en frihetsgrad vid utformandet av dispersionsegenskaperna hos periodiska strukturer. Dessutom demonstreras att kombinationen av dessa två symmetrier ger möjligheten att designa omkonfigurerbara filter. Slutligen visas att dispersionsegenskaperna associerade med vridsymmetri kan efterliknas i plana strukturer.

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  • 10.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH.
    Remote contact-free reconstruction of currents in two-dimensional parallel conductors2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis, the theory of the remote contact-free reconstruction of currents in two-dimensional parallel conductors is investigated. The motivation of this study is finding a complement technique to measurement transformers which are the well-established devices to measure currents in power transmission lines. This technique would provide the possibility of measuring currents at different locations of a power system, as well as, at different frequencies.

     

    Remote contact-free determination of currents is an electromagnetic inverse source problem in which the currents are reconstructed from the magnetic field data collected by a set of sensors located in the vicinity of the conductors. Since the sensors are not too close to the conductors, the main challenge is the effect of the disturbance fields produced by the external sources in the measurement.

     

    In the case that the external sources produce three-dimensional disturbance fields, the magnetic field due to the external sources is expressed as a truncated expansion of the spherical harmonics and both the currents in the conductors and the expansion coefficients are determined by applying the least square method. To overcome the ill-posedness of the problem, the functional to be minimized is augmented by a Tikhonov regularization term that penalizes unphysical solutions introduced by the expansion coefficients.

     

    Finally, the problem of selecting a limited number of optimal sensor positions among a set of predetermined sensor positions is considered. Using the relaxation method, this optimization problem is changed to a convex optimization problem which can be readily solved using the CVX package.

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  • 11.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Alex-Amor, Antonio
    Valerio, Guido
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Analysis and Applications of Glide-Symmetric Holey Metasurfaces2019Konferensbidrag (Refereegranskat)
  • 12.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ebrahimpouri, Mahsa
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Mode matching analysis of two dimensional glide-symmetric corrugated metasurfaces2017Ingår i: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 749-751, artikel-id 7928533Konferensbidrag (Refereegranskat)
    Abstract [en]

    The mode matching method for analysing two dimensional doubled corrugated metasurfaces, including glide-symmetric corrugated metasurfaces, embedded in a thin parallel plate waveguide is presented. This method is accurate, fast, and without any limitations on the parameters.

  • 13.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Johansson, M.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Current reconstruction from magnetic field using spherical harmonic expansion to reduce impact of disturbance fields2016Ingår i: Inverse Problems in Science and Engineering, ISSN 1741-5977, E-ISSN 1741-5985, s. 1-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A current reconstruction method, for determining currents in a set of parallel infinitely long conductors located above the ground from measured magnetic field, is developed. The method is designed to work even if three-dimensional external disturbance fields from external sources are present. The external field is written as an expansion in spherical harmonics. Therefore, the field in the different measurement points is regarded as a linear combination of the expansion coefficients and the currents to be determined. A linear equation system is formed with the currents and the expansion coefficients as the unknowns. The currents are reconstructed by solving the equation system using least squares method and Tikhonov regularization. If the characteristics of the ground below the conductors are known with sufficient precision, the ground effect can also be included into the model. Results of various simulations show that the method works well and noise in the measured magnetic field can be handled.

  • 14.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Mesa, Francisco
    Univ Seville, Dept Appl Phys 1, Seville, Spain..
    Valerio, Guido
    Sorbonne Univ, Lab Elect & Electromagnetisme, Paris, France..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Propagation Characteristics in Substrate Integrated Holey Metasurfaces2020Ingår i: Proceedings 14th European Conference on Antennas and Propagation (EuCAP), Institute of Electrical and Electronics Engineers (IEEE) , 2020Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we discuss the dispersion properties of a particular type of holey metasurfaces, named here "substrate integrated holey" (SIH) metasurface. SIH is a metallic holey structure manufactured in printed circuit board (PCB) technology by using densely metallized posts. We demonstrate that, differently to the case of holes fully covered with metal, in SIH, the height of the holes has a significant effect on the dispersion properties. In addition, in SIH metasurfaces, apart from the conventional stopband caused by its periodicity, there are stopbands due to the resonance modes trapped in the hole due to the posts. These stopbands are narrow and have a high rejection.

  • 15.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Contact-free Measurement of Currents inTwo-dimensional Parallel Conductors Using the Green Identity Approach2016Ingår i: 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016, IEEE, 2016, s. 338-340, artikel-id 7571391Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Green identity approach is used to reconstructcurrents in very long parallel conductors above the groundfrom magnetic field data measured at some points under theconductors. By assuming that the conductor positions are known,this method can be used for contact-free measurement of currentsin transmission lines in power system. This method gives thepossibility of measuring high-frequency currents which cannotbe measured with current transformers.

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  • 16.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Handling the ill-posedness of current retrieval in power lines from magnetic field data using Tikhonov regularization method2015Ingår i: 2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC-URSI 2015 - Proceedings, 978-147997817-5: IEEE , 2015, s. 56-56Konferensbidrag (Refereegranskat)
    Abstract [en]

    An inverse source problem of reconstructing the currents in parallel conductor structures from magnetic field data is considered. In this kind of inverse source problems which arise in contact-free measurements of currents in bus bars, power lines, and cables, the magnetic field data collected by a set of sensors in the vicinity of the conductors is used to determine the currents in conductors. The method is based on inversion of the direct map from the currents to the magnetic field data using a proper model of the problem.

  • 17.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Sensor Selection via Convex Optimization in Remote Contact-free Measurement of Currents2017Ingår i: 2017 International Applied Computational Electromagnetics Society Symposium - Italy, ACES 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 7916351Konferensbidrag (Refereegranskat)
    Abstract [en]

    The sensor positions have substantial effect on the accuracy of remote contact-free reconstruction of currents in power transmission lines from magnetic field data, measured by a set of sensors located under the conductors. By maximizing a performance metric, based on the Fisher information matrix, Nopt sensors are selected from N candidate sensors. The main optimization problem is changed to a convex optimization problem using a relaxation of the integer constraints. The result for optimized sensor positions for a remote current reconstruction in power transmission lines using a planar sensor array is demonstrated.

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  • 18.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Dispersion Analysis of 2-D Glide-Symmetric Corrugated Metasurfaces Using Mode-Matching Technique2018Ingår i: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 28, nr 1, s. 1-3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this letter, wave propagation in 2-D doubled corrugated metasurfaces, including glide-symmetric corrugated metasurfaces, embedded in a thin parallel plate waveguide have been analyzed using the mode matching method. The general dispersion equation for propagation at different directions is derived and dispersion surfaces have been obtained for three different cases. The results are in good agreement with reference results obtained using CST Microwave Studio. Moreover, the method is accurate and computationally much faster than CST Microwave Studio and similar commercial software.

  • 19.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Twist and Polar Glide Symmetries: an Additional Degree of Freedom to Control the Propagation Characteristics of Periodic Structures2018Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    New high-frequency 5G and satellite communication systems require fully-metallic antennas and electromagnetic components. These components can be implemented with truncated versions of periodic structures. In order to achieve the desired performance of these future devices, it is of crucial importance to have a precise control of the propagation properties, i.e. the frequency dispersion behavior and stop-bands. Here, we demonstrate the potential use of higher symmetries to diminish the frequency dispersion of periodic structures and control the width of stop-bands with a new type of fully-metallic transmission line, which is loaded with holes on a twist-symmetric configuration. Simulated and experimental results confirm the intrinsic link between the propagation characteristics and the symmetries of a periodic structure. Additionally, we provide a definitive explanation of the recently discovered polar glide symmetry and its potential combination with twist symmetries to produce low-dispersive materials and reconfigurable stop-bands. The promising properties of these structures are demonstrated with a fully-metallic reconfigurable filter, which could be used for future high-frequency 5G and satellite communication systems.

  • 20.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Salcedo, Andreu
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Mimicking Twist Symmetry Properties in Flat Structures2019Ingår i: 13th European Conference on Antennas andPropagation (EUCAP), Institute of Electrical and Electronics Engineers (IEEE), 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Twist symmetry provides an additional degree of freedom to control the wave propagation in periodic structures. However, real twist-symmetric structures are cylindrical structures that have a high cost of manufacturing. In addition, they are not compatible with the available, low-cost and flat technologies, such as microstrip technology. Here, we investigate the possibility of mimicking the dispersion properties of twist symmetry in flat structures.

  • 21.
    Ghasemifard, Fatemeh
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, G.
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Analysis of wave propagation in plasmonic holey metasurfaces with cylindrical holes2018Ingår i: IET Conference Publications, Institution of Engineering and Technology , 2018, nr CP741Konferensbidrag (Refereegranskat)
    Abstract [en]

    The wave propagation along a plasmonic holey metasurface when a metallic plate is located in its proximity has been analyzed using a mode matching technique. With this analysis, we demonstrate that decreasing the distance between the metallic plate and the holey surface excites nonresonant higher order modes in the structure. Therefore, considering only the dominant mode inside the holes, as the previous simpler models assumed, is not sufficient to analyze this type of metasurfaces.

  • 22.
    Liu, Kexin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Broadband metasurface Luneburg lens antenna based on glide-symmetric bed of nails2017Ingår i: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 358-360, artikel-id 7928545Konferensbidrag (Refereegranskat)
    Abstract [en]

    A broadband metasurface Luneburg lens based on glide-symmetric bed of nails is designed. First, the Luneburg lens was re-shaped using quasi-conformal transformation optics. With this technique, the original circular focal curve of the lens is changed to a straight line. Afterwards, the refractive index distribution of the optically transformed lens is realized by changing the height of the pins in a bed of nails configuration. The complete Luneburg lens is simulated in CST Microwave Studio and the results demonstrate that the lens has 8-16 GHz bandwidth.

  • 23.
    Norgren, Martin
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Dalarsson, Mariana
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Scattering of lower order modes in a parallel plate waveguide loaded with a slightly deformed layer of conducting strips2016Ingår i: 2016 URSI INTERNATIONAL SYMPOSIUM ON ELECTROMAGNETIC THEORY (EMTS), IEEE, 2016, s. 349-352Konferensbidrag (Refereegranskat)
    Abstract [en]

    The lower order modes are derived for a parallel plate waveguide loaded with a sheet of parallel conducting strips. Using a first order perturbation method, we derive the scattering parameters due to a small deformation of the sheet. Results for scattering within and between the novel slow mode and the ubiquitous TEM-mode are presented. With increasing angle between the strips and the direction of propagation, the interaction between the slow mode and the deformation shifts downwards in frequency, due to the reduced phase velocity.

  • 24.
    Quevedo-Teruel, Oscar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Ebrahimpouri, Mahsa
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Lens Antennas for 5G Communications Systems2018Ingår i: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 56, nr 7, s. 36-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Here, we explain the principles of operating lens antennas, and discuss their potential application for future 5G communications systems. We discuss the connection between the nomenclature employed in the optics and microwave communities, such as the direct relationship between aberrations and directivity and side lobe levels. Furthermore, we explain the potential of two innovative techniques: transformation optics and metasurfaces. Transformation optics, and specifically the concept of bespoke lenses, can be employed to make lenses ad hoc for specific feedings. Metasurfaces can be employed to produce two-dimensional low-cost lenses that can be fully metallic, which is an advantage in terms of losses. Finally, we introduce the concept of higher symmetries that can be used to increase the bandwidth of operation of these metasurfaces lenses.

  • 25.
    Quevedo-Teruel, Oscar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, G.
    Sipus, Z.
    Implications of Higher Symmetries in Periodic Structures2018Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018, Institute of Electrical and Electronics Engineers Inc. , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we explain the concept of higher symmetries, their implications and possible applications-within electromagnetic technology.

  • 26. Selva, Kruphalan Tamil
    et al.
    Forsberg, Olof A.
    KTH.
    Merkoulova, Daniel
    KTH.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Taylor, Nathaniel
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Non-contact Current Measurement in Power Transmission Lines2015Ingår i: SMART GRID TECHNOLOGIES (ICSGT- 2015), Elsevier, 2015, s. 498-506Konferensbidrag (Refereegranskat)
    Abstract [en]

    This project deals with the technique of measurement of current in power transmission lines without the need for actual contact with the wires. Magnetic fields emitted by the wires are sensed using hall-effect based magnetic field sensors. Signals from these sensors are utilized for computing or 'reconstructing' the currents. Algorithms are developed in Matlab to facilitate the computation process. The algorithm also considers the challenge of interference due to Earth's magnetic field and stray magnetic fields. The study is performed on a scaled down model of a three phase three wire power transmission line configuration. This technology is aimed at improving the flexibility and portability of present day current measurement technology related to power transmission lines. They can be used as a secondary or temporary measurement system to complement measurements from the current transformers (CT) or be installed in places where CTs are absent. As the measurement system will be completely isolated from the power lines, they possess numerous advantages.

  • 27.
    Shanei, Mohammad Mahdi
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion. Tarbiat Modares Univ, Dept Mat Engn, Nanomat Grp, POB 14115-143, Tehran, Iran..
    Fathi, Davood
    Tarbiat Modares Univ, Dept Mat Engn, Nanomat Grp, POB 14115-143, Tehran, Iran.;Tarbiat Modares Univ, Dept Elect & Comp Engn, POB 14115-194, Tehran, Iran..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    All-silicon reconfigurable metasurfaces for multifunction and tunable performance at optical frequencies based on glide symmetry2019Ingår i: Scientific Reports, E-ISSN 2045-2322, Vol. 9, artikel-id 13641Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dielectric metasurfaces have opened promising possibilities to enable a versatile platform in the miniaturization of optical elements at visible and infrared frequencies. Due to high efficiency and compatibility with CMOS fabrication technology, silicon-based metasurfaces have a remarkable potential for a wide variety of optical devices. Adding tunability mechanisms to metasurfaces could be beneficial for their application in areas such as communications, imaging and sensing. In this paper, we propose an all-silicon reconfigurable metasurface based on the concept of glide symmetry. The reconfigurability is achieved by a phase modulation of the transmitted wave activated by a lateral displacement of the layers. The misalignment between the layers creates a new inner periodicity which leads to the formation of a metamolecule with a new sort of near-field interaction. The proposed approach is highly versatile for developing multifunctional and tunable metadevices at optical frequencies. As a proof of concept, in this paper, we design a bifunctional metadevice, as well as a tunable lens and a controllable beam deflector operating at 1.55 mu m.

  • 28. Valerio, G.
    et al.
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    A generalized mode-matching method for glide-symmetric structures2019Ingår i: 2019 URSI International Symposium on Electromagnetic Theory, EMTS 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, artikel-id 8931540Konferensbidrag (Refereegranskat)
    Abstract [en]

    The new discovery of the extraordinary properties of meta-surfaces possessing higher symmetries is encouraging new studies to better understand the fundamental role of the symmetry, as well as to produce efficient numerical methods for enabling a fast optimization. Here, we propose a mode matching technique to explain the operation of glide-symmetric fully-metallic surface made of holes of arbitrary shape. The mode-matching is formulated to take into account the glide symmetry of the unit cell and isolate its impact. This formulation leads to a reduction of the computational domain to a half cell, and to derive the symmetry properties of the modal fields propagating in the metasurface. Numerical results from commercial software are employed to validate our method.

  • 29.
    Valerio, Guido
    et al.
    Sorbonne Univ, Lab Elect & Electromagnetisme, UR2, F-75005 Paris, France..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Sipus, Zvonimir
    Univ Zagreb, Fac Elect Engn & Comp, HR-10000 Zagreb, Croatia..
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Glide-Symmetric All-Metal Holey Metasurfaces for Low-Dispersive Artificial Materials: Modeling and Properties2018Ingår i: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 66, nr 7, s. 3210-3223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the wave propagation between two glide-symmetric metallic plates drilled with periodic rectangular holes. A mode-matching method is proposed in order to derive efficiently the dispersive properties of these periodic structures. The method takes advantage of the higher symmetry of the structure reducing the computational cost by enforcing boundary conditions on the field on only one of the two surfaces. Physical insight on specific symmetry properties of Floquet harmonics in glide-symmetric structures is also gained. The code is validated with commercial software assessing its accuracy when varying the most influential/critical parameters. We confirm the potential of glide-symmetric structures to tune the effective refractive index. Specifically, we demonstrate that glide-symmetric structures with rectangular shapes can be employed to synthesize anisotropic refractive indexes with a large band of operation, which makes such metasurface structures applicable for the realization of ultrawideband planar lenses.

  • 30.
    Zetterström, Oskar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, Lab Genie Elect & Elect Paris, CNRS, F-75252 Paris, France..
    Mesa, Francisco
    Univ Seville, Dept Fis Aplicada 1, ETS Ingn Informat, Seville 41004, Spain..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Dispersion Analysis of Periodically Loaded Transmission Lines with Twist Symmetry Using the Mode-Matching Technique2020Ingår i: Applied Sciences, E-ISSN 2076-3417, Vol. 10, nr 17, artikel-id 5990Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mode-matching formulation is presented and used to analyze the dispersion properties of twist-symmetric transmission lines. The structures are coaxial lines periodically loaded with infinitely thin screens, which are rotated with respect to each other to possess twist symmetry. The results obtained using the proposed formulation are in good agreement with those of commercial simulators. Furthermore, using the presented mode-matching formulation, it is demonstrated that the propagation characteristics in the twist-symmetric structures are linked to the scattering and coupling of the higher order modes. The physical insight offered by this analysis is valuable for the design of various electromagnetic devices, such as filters, antennas, and phase-shifters.

  • 31.
    Zetterström, Oskar
    et al.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Valerio, Guido
    Sorbonne Univ, Lab Elect & Electromagnetisme, Paris, France..
    Mesa, Francisco
    Univ Seville, ETS Ingn Informat, Dept Fis Aplicada 1, Seville, Spain..
    Ghasemifard, Fatemeh
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Quevedo-Teruel, Oscar
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektroteknik, Elektroteknisk teori och konstruktion.
    Mode-matching Analysis of Loaded Transmission Lines with Twist Symmetries2020Ingår i: Proceedings 14th European Conference on Antennas and Propagation (EuCAP), Institute of Electrical and Electronics Engineers (IEEE) , 2020Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies the propagation characteristics in twist-symmetric structures by means of a mode-matching approach. The studied structures are coaxial transmission lines periodically loaded with 1- and 3-fold twist-symmetric infinitely thin sectorial sheets. The mode-matching formulation is validated with the commercial software CST Microwave Studio. In addition, the impact of adding twist symmetry to a coaxial line on the coupling of the higher order TM modes is discussed.

1 - 31 av 31
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