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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Broadband Linear Polarization Conversion Metasurface Based on Grounded Vias
摘要： An anisotropic high-impedance surfaces is applied to achieve perfect polarization rotation. Three multiple resonances are generated by electric and magnetic resonances which contributed to bandwidth expansion of the proposed polarization converter. The simulation results showed that maximum conversion ef?ciency is nearly 100% at mentioned three resonance frequencies. Here, 107 % bandwidth with polarization conversion ratio of above 90% is achieved. The proposed polarization conversion unit-cell is examined for oblique incidence, as well. It is observed that the bandwidth of the proposed unit-cell is not sensitive to the non-orthogonal incidence angles up to 40?. This observation veri?es applicability of proposed polarization rotator unit-cell.
关键词： polarization conversion,metasurface,high impedance surface
更新于2025-09-23 15:23:52
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Application of metasurfaces in the design of performance-enhanced low-profile antennas
摘要： This paper presents a review of metasurface-based antennas conducted at the Microwave Communication Laboratory (MCL) of Ajou University in the Republic of Korea. In this paper, pro?le miniaturization, bandwidth enhancement, multiband operation, and radiation pattern control of metasurface-based antennas are considered. The paper ?rst presents metasurface-based antennas implemented by placing various radiators on top of the metasurface. It then presents antennas implemented by placing the radiators below the metasurface with and without the ground plane. Metasurface-based antennas are not only able to achieve high ef?ciency with a low pro?le but they are also able to generate extra resonances from the metasurface structures, which signi?cantly enhances the overall performance of the antennas. These additional resonances were utilized in multiband and/or wideband operations. In addition, the design of a planar compact wide-gain-bandwidth metasurface-based antenna and its radiation characteristics are presented at a terahertz (THz) frequency range. The THz antennas were designed with metasurfaces and a planar leaky-wave feeding structure. Finally, the outlook on future research at the MCL for antenna-related work and their applications using metasurfaces is provided.
关键词： surface wave resonance,sequential rotation,crossed dipole,arti?cial magnetic conductor,metamaterial,wideband,circular polarization,leaky-wave,Antenna,array,metasurface
更新于2025-09-23 15:23:52
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Modified dielectric and ferroelectric properties in the composite of ferrimagnetic Co1.75Fe1.25O4 ferrite and ferroelectric BaTiO3 perovskite in comparison to Co1.75Fe1.25O4 ferrite
摘要： The ferrimagnetic Co1.75Fe1.25O4 ferrite with cubic spinel structure (space group Fd3m) was made into composite by mixing with ferroelectric BaTiO3 perovskite with tetragonal structure (space group P4mm) at the mass ratio 50:50. Disc shaped composite powder was finally heated at 1000 °C to study the structure, dielectric and ferroelectric properties. The electrical conductivity, dielectric response and ferroelectric properties of the composite samples are remarkably modified in comparison to their ferrite counterparts before making the composite. The composite system has shown improvement of dielectric constant with reduced dielectric loss factor and electrical conductivity in comparison to the ferrite samples. The mechanism of modified dielectric properties was understood by analyzing ac conductivity data using Jonscher's power law, complex impedance spectra in Cole-Cole plots using equivalent circuit model, and complex electrical modulus spectra using Kohlrausch, Williams and Watts (KWW) proposed model. Electrical conductivity in the composite material was determined by small polaron hoping (SPH) up to measurement temperature 400 K (close to ferroelectric transition of BaTiO3) and overlapping large polaron hopping conductivity at higher temperatures. In contrast, SPH dominates throughout the measurement temperature range for ferrite samples. The space charge polarization, which was largely effective at low frequencies and high measurement temperatures, is significantly reduced in composite samples. High capacitive response in composite samples and its extension up to high measurement temperature is confirmed from the temperature dependence of phase shift and well defined ferroelectric polarization loop and associated electrical parameters.
关键词： Composite dielectric,Polaron hopping,Ferroelectric polarization,Co rich spinel oxide
更新于2025-09-23 15:23:52
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Characterization of beam splitters in the calibration of a six-channel Stokes polarimeter
摘要： Polarization distortion in a beam splitter is a phenomenon where the polarization state of output light deviates from the theoretical expectation, which is inevitable and will result in significant errors in the optical systems. A theoretical analysis method based on Mueller matrix ellipsometry is proposed for characterizing the beam splitters and the application in the calibration of a six-channel Stokes polarimeter (SP) is shown. In this study, polarization distortions in the beam splitters including depolarization, linear birefringence, circular birefringence, linear dichroism, and circular dichroism have been considered. With the proposed method, the beam splitters are characterized by the polarization distortions and the effective optical parameters extracted. In our experiment, the Mueller matrices of two different commonly used beam splitters measured by a commercial Mueller matrix ellipsometer (MME) are consistently fitted by the proposed method and the residual errors have shown improvement compared to the conventional methods. A practical application of the proposed method is exhibited by calibrating a SP system containing two non-polarization beam splitters and three polarization beam splitters. With the proposed method introduced, the general error of the measured Stokes vector can be reduced from 3% to 1%, and the errors of the thickness measurement of standard SiO2 thin film samples are within 1 nm compared with the results reported by a commercial MME.
关键词： beam splitter,characterization,calibration,Stokes polarimeter,polarization distortion
更新于2025-09-23 15:23:52
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by isovalent doping at the fluorite sublattice
摘要： Bismuth titanate, Bi4Ti3O12 (BiT), is a complex layered ferroelectric material that is composed of three perovskite-like units and one fluorite-like unit stacked alternatively along the transverse direction. The ground-state crystal structure is monoclinic with the spontaneous polarization (～50 μC/cm2) along the plane. BiT typically grows along the c direction in thin-film form, and having the polarization vector aligned with the growth orientation can be beneficial for several potential device applications. It is well known that judicious doping of ferroelectrics is an effective method in adjusting the magnitude and the orientation of the spontaneous polarization. Here, we show using first-principles density-functional theory and a detailed phonon analysis that Bi atoms in the fluorite-like layers have significantly more impact on the magnitude and orientation of the spontaneous polarization vector as compared to the perovskite-like layer. The low-energy hard-phonon modes are characterized by fluorite-like layers experiencing transverse displacements and large changes in Born effective charges on Bi atoms. Thus, the breaking of symmetry caused by doping of Bi sites within the fluorite-like layer leads to the formation of uncancelled permanent dipole moments along the transverse direction. This provides an opportunity for doping the Bi site in the fluorite-like layer. Isovalent dopants P, As, and Sb were studied. P is found to be most effective in the reorientation of the spontaneous polarization. It leads to a threefold enhancement of the out-of-plane component of polarization and to a commensurate rotation of the spontaneous polarization vector by 36.2° towards the transverse direction.
关键词： phonon analysis,doping,ferroelectric,Bi4Ti3O12,first-principles,polarization
更新于2025-09-23 15:23:52
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Supersymmetric Polarization Anomaly in Photonic Discrete-Time Quantum Walks
摘要： Quantum anomalies lead to finite expectation values that defy the apparent symmetries of a system. These anomalies are at the heart of topological effects in electronic, photonic, and atomic systems, where they result in a unique response to external fields but generally escape a more direct observation. Here, we implement an optical-network realization of a discrete-time quantum walk, where such an anomaly can be observed directly in the unique circular polarization of a topological midgap state. We base the system on a single-step protocol overcoming the experimental infeasibility of earlier multistep protocols. The evolution combines a chiral symmetry with a previously unexplored unitary version of supersymmetry. Having experimental access to the position and the coin state of the walker, we perform a full polarization tomography and provide evidence for the predicted anomaly of the midgap states. This approach opens the prospect to dynamically distill topological states for quantum information applications.
关键词： quantum anomalies,supersymmetry,polarization,discrete-time quantum walks,topological states
更新于2025-09-23 15:23:52
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[IEEE 2018 International Flexible Electronics Technology Conference (IFETC) - Ottawa, ON, Canada (2018.8.7-2018.8.9)] 2018 International Flexible Electronics Technology Conference (IFETC) - Circularly Polarized Microstrip Antenna on Ultrathin PET Substrate for UHF RFID Applications
摘要： Design of a circularly polarized microstrip patch antenna on an ultrathin PET substrate of 125 μm thickness is proposed for RFID applications. Screen-printed silver coating of 25 μm thickness serves as the antenna metallization. Improved feed-design and systematic optimization of the antenna overcomes the intrinsic constrains of designing microstrip antennas on extremely thin substrate. Optimally designed feed excites a nearly square patch antenna with truncated corners to achieve good impedance and radiation characteristics. The proposed antenna exhibiting 48 MHz impedance bandwidth (896 MHz to 944 MHz) and a 16 MHz AR bandwidth (907-923 MHz), can serve as a potential candidate as a low cost UHF reader antenna for RFID applications.
关键词： Microstrip Antenna,radio-frequency identification (RFID),Circular Polarization (CP),Quarter Wave Transformer,Axial Ratio (AR)
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Oil Slick Detection in the Offshore Domain: Evaluation of Polarization-Dependent Sar Parameters
摘要： Remote sensing technology is an essential link in the global monitoring of the ocean surface and radars are efficient sensors for detecting marine pollution. When used operationally, a tradeoff must usually be made between the covered area and the quantity of information collected by the radar. To identify the most appropriate imaging mode, a methodology based on Receiver Operating Characteristic (ROC) curve analysis has been applied to an original dataset collected by an airborne system, SETHI, characterized by a very low instrument noise floor. The dataset was acquired during an oil spill clean-up exercise carried out in 2015 in the North Sea. Various polarization-dependent quantities are investigated and a relative ordering of the main polarimetric parameters is reported. VV offers the best tradeoff between the benefit of detection performance and the instrument and data requirements. When the sensor has a sufficiently low noise floor, HV is also recommended because it provides strong slick-sea contrast. Among all the investigated quad-polarimetric settings, no significant added value compared to single-polarized data was found.
关键词： NESZ,noise floor,sea,spill,detection,SAR,noise,slick,radar,marine pollution,probability of detection,oil,ROC curves,probability of false alarm,ocean,polarization
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Design of the Complete Polarization Converter Using Dielectric Periodic Structures
摘要： Polarization converter is used in the applications of the polar SAR observations. There exists coupling between TE and TM modes when plane wave is oblique incident on the surface of dielectric periodic structure, the single TE or TM polarized wave incident will cause TE and TM mixed transmission wave. In some proper incident conditions, complete polarization conversion can be realized between TE and TM mode. In this work, a design of complete polarization converter by using dielectric periodic structure is designed and it is carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. We revealed TE/TM complete polarization conversion characteristics of dielectric periodic structure, and also analyzed the effects of structure parameters. These investigations provide important guideline for accurate designing new millimeter wave polarization converters.
关键词： dielectric periodic structure,TE/TM converters.,complete polarization convertor
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Characterization of Multilayered Ceramic Capacitors via Piezoelectric Force Microscopy
摘要： The coupling between an electrical and mechanical response in a material is a fundamental property that provides functionality to a variety of applications ranging from sensors and actuators to energy harvesting and biology. Most materials exhibit electromechanical coupling in nanometer-sized domains. Therefore, to understand the relationship between structure and function of these materials, characterization on the nanoscale is required. This property can be directly measured in a non-destructive manner using piezoelectric force microscopy (PFM), a mode that comes standard in all atomic force microscopes (AFMs) from Park Systems. Additionally, PFM can be used as a spectroscopic tool to evaluate switching of piezoelectric domains. Here we demonstrate the utility of PFM for failure analysis of a multilayered ceramic capacitor. Correlative imaging of topography and electrical signals revealed discontinuous structures in the device that likely had a direct effect on device performance. Spectroscopy was also performed at a specific piezoelectric region to measure domain properties, such as the electric field required to flip the polarization direction (coercive voltage).
关键词： topography,atomic force microscopy,multilayered ceramic capacitor,electromechanics,piezoelectric microscopy,polarization,failure analysis
更新于2025-09-23 15:23:52