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Now showing items 1 - 16 of 34

  • Guest Editorial: Special Cluster on Antennas for Wireless Body Area Networks

    Skrivervik, Anja K.   Marrocco, Gaetano  

    The papers in this special section highlight current and emerging research in antennas for WBAN, as well as applications of this technology. This ssection brings together the latest work in antennas for in-, on-, and off-body communication, the WBAN channels, the measurement of wearable and implantable antennas, and also considers the important aspect of specific absorption rate (SAR) estimation and measurement.
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  • Fundamental Limits for Implanted Antennas: Maximum Power Density Reaching Free Space

    Skrivervik, Anja K.   Bosiljevac, Marko   Sipus, Zvonimir  

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    Koohestani, Mohsen   Pires, Nuno   Skrivervik, Anja K.   Moreira, Antonio A.  

    A dielectric sandwich loading technique is proposed to enhance impedance matching bandwidth of an antenna when it is placed close to the human body. This technique mitigates the body influence by confining the reactive fields in the dielectric loads. This has no side effects on the antenna performance. Unloaded and loaded prototypes of a recently developed UWB antenna have been measured both in free space and near a human arm. Free space results confirm that loading the antenna neither detune |S-11| nor decrease efficiency. It was found that in a body proximity scenario, loading the antenna increases the impedance matching by 22% with respect to the unloaded antenna. These results show the suitability of this technique to design antennas for WBAN applications. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2965-2967, 2013
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  • PDMS, A Robust Casing for Flexible W-BAN Antennas

    Trajkovikj, Jovanche   Zuercher, Jean-Francois   Skrivervik, Anja K.  

    This paper describes a new technology for the realization of soft, flexible, and robust antennas intended to operate in a harsh environment. One of the main characteristics of the proposed technology is the ease of fabricating antennas in a simple lab environment. The method is based on the use of a silicon-based elastomer, polydimethylsiloxane (PDMS), for the substrate material, and copper meshes or any kind of perforated metal plates as flexible conductive materials. The initial liquid state of the PDMS allows a lot of freedom in the fabrication process, both from the electrical and mechanical points of view. The electrical and mechanical properties of the substrate can be adjusted by loading the PDMS with inclusions having low or high permittivity and/or density, thus controlling the permittivity and the rigidity. Another good characteristic of the initial low viscosity of PDMS is the possibility of shaping the antennas and substrates in in-house fabricated moulds. Copper meshes or perforated metal structures enable good adhesion between the substrate and conductor, and improve the overall flexibility. Measured results showed good repeatability of the substrate samples, both with or without inclusions. To demonstrate the versatility of the proposed technique, several antenna prototypes were built and characterized. All the antennas were flexible and showed good radiation characteristics. The antennas were exposed to tests such as washing and bending, in order to assess their robustness to environmental changes.
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  • Single-Layer Quad-Band Printed Reflectarray Antenna with Dual Linear Polarization

    Hasani, Hamed   Peixeiro, Custodio   Skrivervik, Anja K.   Perruisseau-Carrier, Julien  

    A novel single layer, dual linear polarized unit cell is introduced for a quad-band reflectarray antenna in the Ku-band centered around 12, 13, 14, and 15.5 GHz. The unit-cell design is such that the resultant reflectarray antenna can be considered as four different reflectarray antennas, each with a specific beam shape, sharing one aperture. As proof-of-concept, two quad-band reflectarray antenna prototypes having a plate size of 20 x 20 cm(2) have been designed and fabricated each with a certain beam direction versus frequency. Measurement and simulation results show satisfactory performance of both reflectarray antennas at each frequency.
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  • System Fidelity Factor: A New Method for Comparing UWB Antennas

    Quintero, Gabriela   Zuercher, J. -F.   Skrivervik, Anja K.  

    The main purpose of the System Fidelity Factor (SFF) is to incorporate frequency and time domain characteristics of an antenna system into a comparison method for ultrawideband (UWB) antennas. The SFF is an interesting tool because both simulations and measurements can be done in a simple and straight-forward manner. Simulations of a single antenna are combined into a two-antennas system analysis by means of a simple post-processing, where the transfer function of the transmitting and receiving antennas are calculated. Measurements of the SFF are done using a two port Vector Network Analyzer (VNA). The polar representation of the SFF allows an equitable comparison between antennas. The procedure to derive the SFF is described in detail in the paper. Two examples are given where the UWB performance of three antenna systems are compared. In the first example antenna systems of two identical monopoles are studied. In the second example the transmitting antenna is a Vivaldi and the receiving antenna a monopole.
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  • The Effect of Insulating Layers on the Performance of Implanted Antennas

    Merli, Francesco   Fuchs, Benjamin   Mosig, Juan R.   Skrivervik, Anja K.  

    This work presents the analysis of the influence of insulation on implanted antennas for biotelemetry applications in the Medical Device Radiocommunications Service band. Our goal is finding the insulation properties that facilitate power transmission, thus enhancing the communication between the implanted antenna and an external receiver. For this purpose, it has been found that a simplified model of human tissues based on spherical geometries excited by ideal sources (electric dipole, magnetic dipole and Huygens source) provides reasonable accuracy while remaining very tractable due to its analytical formulation. Our results show that a proper choice of the biocompatible internal insulation material can improve the radiation efficiency of the implanted antenna (up to six times for the investigated cases). External insulation facilitates the electromagnetic transition from the biological tissue to the outer free space, reducing the power absorbed by the human body. Summarizing, this work gives insights on the enhancement of power transmission, obtained with the use of both internal, biocompatible and external, flexible insulations. Therefore, it provides useful information for the design of implanted antennas.
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    Fuchs, Benjamin   Golubovic, Ruzica   Skrivervik, Anja K.   Mosig, Juan R.  

    A design procedure for spherical lens antennas is described. A particle swarm optimization (PSO) algorithm is coupled to a mode matching technique based on spherical wave expansion to analyze the lens antennas. The proposed methodology is applied to three optimization problems using real-number and binary PSO. First, the maximization of the directivity of Luneburg lens antennas is addressed. Then, amplitude shaped radiation patterns are synthesized by optimizing, both amplitude and position of each element of an array that illuminates a lens. Finally, a dual-beam reconfigurable lens antenna is optimized. By only switching properly the elements of an array, the lens antenna radiates either a directive or a sectoral beam. Numerical comparisons with a full wave commercial software successfully validate the proposed design procedure. (C) 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1655-1659, 2010; Published online in Wiley InterScience ( DOI 10.1002/mop.25278
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  • Analysis, Design and Realization of a Novel Directive Ultrawideband Antenna

    Merli, Francesco   Zuercher, Jean-F.   Freni, Angelo   Skrivervik, Anja K.  

    In this paper, we present a simple log-periodic-dipolearray (LPDA) solution that allows us to achieve good ultrawideband (UWB) performances. The antenna has been manufactured and the measurements agree well with the theoretical predictions. The antenna presents an average gain of 8 dB and a return loss better than -10 dB over the band from 4.2 to 10.6 GHz. Both the measured antenna transfer function and the computed effect on pulse transmission show good performances in comparison with already known UWB antennas.
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  • Design and Measurement of a Differential Printed Antenna for a Wireless Sensor Network Node

    Pires, Nuno   Parra, Tiago   Skrivervik, Anja K.   Moreira, Antonio A.  

    This letter presents the design and measurement of an antenna integrated into an agricultural sensor network node operating on the 2.4-GHz ISM band using the ZigBee protocol stack. The novel structure, coined bowtie-shaped folded dipole (BSFD), has a differential 100-Omega input impedance matching a particular controller widely used in wireless sensor network (WSN) applications. This letter also presents a survey of existing WSN antennas to which the proposed design compares favorably. The challenges of testing a differential antenna using conventional single-ended equipment are addressed regarding antenna impedance and radiation pattern measurements. The differential antenna input impedance was confirmed with four different test setups using a conventional vector network analyzer. The radiation pattern of the proposed antenna was measured in-prototype resorting to a spectrum analyzer. The measured patterns show that the proposed antenna has a maximum received power over 4 dB compared to two early versions of the WSN node that used commercial off-the-shelf antenna solutions. The performance was also confirmed in a field test where a BSFD-equipped prototype achieved close to a 300-m range, tripling that typical for ZigBee applications.
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  • Design of atomic clock cavity based on a loop-gap geometry and modified boundary conditions

    Ivanov, Anton E.   Affolderbach, Christoph   Mileti, Gaetano   Skrivervik, Anja K.  

    In this study, we investigate a concept that can be used to improve the magnetic field homogeneity in a microwave cavity applied in a novel, high-performance atomic frequency standard. We show that by modifying the boundary conditions in the case of a loop-gap geometry, a good improvement of the field homogeneity can be obtained. Such a design demonstrates high potential to improve the frequency stability; it is compact and hence suitable for a future generation of compact, high-precision frequency standards based on vapor cells and a pulsed optical pumping (POP) regime (POP atomic clocks).
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  • Circuit model and design of silicon-integrated CRLH-TLS analogically controlled by MEMS

    Perruisseau-Carrier, Julien   Lisec, Thomas   Skrivervik, Anja K.  

    We present an integrated composite right/left handed transmission line (CRLH-TL) phase shifter analogically controlled by means of a MEMS series capacitor. The device is based on coplanar waveguide (CPW) technology and operates at a central frequency of 18 GHz. An accurate and physical circuit model including parasitics inherent to this MEMS realization is presented. We describe the method used to design the presented structure, which consists in a mixed approach using the developed circuit model and full-wave simulations. The MEMS-controlled CRLH-TL has been fabricated and characterized, showing good agreement with predicted performances. (c) 2006 Wiley Periodicals, Inc.
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  • Tri-Band,Polarization-Independent Reflectarray at Terahertz Frequencies:Design,Fabrication,and Measurement

    Hasani, Hamed   Tamagnone, Michele   Capdevila, Santiago   Moldovan, Clara F.   Maoddi, Pietro   Ionescu, Adrian M.   Peixeiro, Custodio   Mosig, Juan R.   Skrivervik, Anja K.   Perruisseau-Carrier, Julien  

    In this paper, two THz reflectarray surfaces have been designed and fabricated in order to deflect a plane wave with any polarization and with a specific incident angle to three different specific directions each at distinct three frequencies of 0.7, 1.0 and 1.5 THz. The surface is composed of an array of 100 100 cells, each comprised of gold crosses and parasitic dipoles printed on thin grounded high resistivity silicon. Finite-element method (FEM) simulations are in line with the measurement results obtained using THz time-domain spectroscopy (THz TDS) showing the intended deflections for the two fabricated samples each with an arbitrary frequency-vs-deflection angle relationship. In addition, the use of silicon as the substrate paves the way for the integration of reconfigurable technologies which enhances the reflectarray versatility.
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  • Anja K?nig

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  • ANJA OSTROWITZKI: Die Ausbreitung der Zisterzienserinnen im Erzbistum K?ln

    Rehm   Gerhard  

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  • Varia Issue || Sonja O. k?vi t??ll?by Anja Kauranen

    Review by: Philip Binham  

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