Experimental investigation of the effects of polarization on the measured radiation efficiency of a dielectric resonator antenna

©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.The radiation efficiencies of two rectangular dielectric resonant antennas (DRAs) were investigated using the directivity/ gain (D/G) method and the Wheeler cap method. Both antennas are linearly polarized but have different linear polarization purities. Through comparison of their radiation efficiencies, itpsilas shown that the polarization purity strongly affects the D/G measurement of the DRAspsila radiation efficiency.Qinghua Lai, Georgios Almpanis, Christophe Fumeaux, Hansruedi Benedickter, and Rüdiger Vahldiec

An Investigation of the Accuracy of Finite-Volume Radial Domain Truncation Technique

© Copyright 2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.The accuracy and performance of the radial domain truncation technique is presented in the framework of finite-volume time-domain method. In the present approach all the electromagnetic field quantities are co-located in both space and time and the performance is evaluated using unstructured grid. The influence of the radius of curvature of the absorber is investigated using a waveguide and a horn-antenna as practical examples. Numerical reflection errors are computed using a reference solutions and the convergence of the results is studied for increasing radius of curvature of the absorber. Low-level effects on the antenna radiation patterns further illustrates the convergence of the technique.Krishnaswamy Sankaran, Christophe Fumeaux and Rudiger Vahldiec

A novel wave-separation scheme for the extraction of S-parameters in non-TEM waveguides for the FVTD method

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.This paper proposes an extended scheme for the extraction of scattering parameters for the Finite-Volume Time-Domain (FVTD) method. The flux-splitting algorithm that is inherent to the FVTD method is exploited to compute the incident and reflected fields in a port. A novel correction scheme for the magnetic field is applied that yields accurate results of the scattering parameters in non-TEM structures by performing an artificial flux separation. Multimode S-parameters of a waveguide discontinuity, that are determined using the proposed approach, are successfully validated with a Mode-Matching analysis. © 2005 IEEE.Dirk Baumann, Christophe Fumeaux, and Rüdiger Vahldiec

FVTD simulations of Archimedean spiral Antennas on thin substrates in planar and conformal configurations

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.This paper demonstrates the applicability of the finite-volume time-domain (FVTD) method to the simulation of two-arm substrate-supported Archimedean spiral antennas. The FVTD method uses an unstructured tetrahedral mesh to model precisely the fine spiral structures and the thin underlying substrate. Time-domain simulation results are presented to demonstrate the substrate influence on the current distribution on the metallic spiral arms. Application of the FVTD method to conformal spiral geometries is suggested in two further examples.Christophe Fumeaux, Dirk Baumann, Rüdiger Vahldiec

Wearable Quarter-Wave Folded Microstrip Antenna for Passive UHF RFID Applications

A wearable low-profile inset-fed quarter-wave folded microstrip patch antenna for noninvasive activity monitoring of elderly is presented. The proposed antenna is embedded with a sensor-enabled passive radio-frequency identification (RFID) tag operating in the ultra-high frequency (UHF) industrial-scientific-medical (ISM) band around 900 MHz. The device exhibits a low and narrow profile based on a planar folded quarter-wave length patch structure and is integrated on a flexible substrate to maximise comfort to the wearer. An extended ground plane made from silver fabric successfully minimises the impact of the human body on the antenna performance. Measurements on a prototype demonstrate a reflection coefficient (S₁₁) of −30 dB at resonance and a −10 dB bandwidth from 920 MHz to 926 MHz. Simulation results predict a maximum gain of 2.8 dBi. This is confirmed by tag measurements where a 4-meter read range is achieved using a transmit power of 30 dBm, for the case where the passive wearable tag antenna is mounted on a body in a practical setting. This represents an almost 40% increase in read range over an existing dipole antenna placed over a 10 mm isolator layer on a human subject.Thomas Kaufmann, Damith C. Ranasinghe, Ming Zhou, and Christophe Fumeau

Finite-volume time-domain (FVTD) method and its application to the analysis of hemispherical dielectric-resonator antennas

©2003 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.In this paper, the finite-volume time-domain (FVTD) method is refined and applied to analyze a probe-fed hemispherical dielectric resonator antenna (DRA). To improve the applicability of the FVTD method to microwave problems, a new scheme is introduced taking advantage of the method's inherent flux separation into incoming and outgoing waves. A 3D simulation is performed using an unstructured tetrahedral mesh permitting precise modeling of curved surfaces and fine structures. The obtained results are compared to those from other methods.Dirk Baumann, Christophe Fumeaux, Pascal Leuchtmann, Rudiger Vahldieckhttp://www.mtt.org/symposia/ims/2003

Generalized-scattering-matrix extraction using the Finite-Volume Time-Domain (FVTD) method

©2004 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.In this paper the extraction of the generalized scattering matrix using the finite-volume time-domain (FVTD) method is presented. The extraction scheme takes advantage of the flux-splitting formulation that is inherent to the FVTD algorithm. Thus the incident and reflected waves in a transmission line are immediately known at every time step. A new way to determine the power waves is shown as well as the implementation of the ports and the mode separation in a multimode environment. The ability of the proposed scheme to extract the scattering parameters correctly is illustrated in an example that compares the simulated return loss of a balun to measurements.Dirk Baumann, Christophe Fumeaux, Pascal Leuchtmann, Rudiger Vahldiec

Modeling of dielectric material interfaces for the radial point interpolation time-domain method

Copyright © 2009 IEEEThe Radial Point Interpolation Time-Domain (RPITD) method is a flavor of meshless domain discretization methods applicable to computational electromagnetics. Meshless methods do not require an explicit mesh topology, but rather rely on a representation of a physical model as a node distribution. This is firstly advantageous for modeling of conformal boundaries and multi-scale geometries. But as the most attractive feature, the node arrangements can be adapted on-the-fly. The RPITD method is based on interpolation of the field distribution using radial and monomial basis functions. This paper introduces a technique to model arbitrarily shaped dielectric interfaces in the framework of meshless methods. Using the proposed technique, errors associated to the interpolation of non-smooth fields at material interfaces are reduced, as demonstrated for 2D-TE modes. This allows for accurate modeling of interfaces with dielectric contrast. Unlike previous publications which modify the basis functions at interfaces, a physically motivated correction term is introduced here. Errors in the vicinity of material interfaces decrease significantly and simulation accuracy is generally improved.Thomas Kaufmann, Thomas Merz, Christophe Fumeaux and Rudiger Vahldiec

Developments of finite-volume techniques for electromagnetic modeling in unstructured meshes

©2006 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.This paper provides an overview of the recent developments of finite-volume techniques for time-domain electromagnetic simulations. The distinctive characteristic of finite-volume time-domain (FVTD) algorithms is their applicability in non-Cartesian volume meshes. This allows great geometrical flexibility which is required for most EMC problems. Several aspects of the FVTD method are reviewed, its applications to FMC problems are discussed and illustrated by simulation examplesChristophe Fumeaux, Dirk Baumann, Pierre Bonnet, Rüdiger Vahldiec