Search

The human body’s absorption of electromagnetic fields from communication enabled devices has consistently been a research topic for both researchers from universities and companies in the mobile communication industry. The absorption of electromagnetic fields could mainly result in two consequences: (a) antenna radiation efficiency of the device could deteriorate dramatically; and (b) a large amount of the radiated power could be dissipated into the human body, such as the hand, ear, scalp and brain, which is defined and described by Specific Absorption Rate (SAR). A comprehensive analysis of electromagnetic field absorption by the human body has been carried out to explain and answer some of the key questions in this area.

This paper presents a design methodology of three-dimensional (3-D) passive metallic waveguide-array lens antenna (MWALA) by implementing the Rotman lens concept (RLC) for collinear multi-beam radiations on the same angular plane. The RLC methodology extends the original concept of two-dimensional (2-D) tri-focal Rotman lens into a 3-D one in free space. Thus, the MWALA has a planar aperture facing to the radiation boresight to resemble a planar phased array of waveguide antennas and also has a curved focal surface profile (CFSP) on the opposite side to receive the illumination by the radiations of feed antennas. The three co-planar focal points are specified to define a circular focal arc (CFA) for multiple feed placement to radiate multi-beams through this MWALA. The boundary formed by the CFSP and CFA resembles the shape of Rotman lens equivalently realized in free space. In addition, the shortage of freedoms in conventional MWALA design limited to dual-focus configurations and resulting in narrow scan angles, is relaxed by adopting the phase velocities inside the waveguides as an additional freedom to realize a tri-focal configuration and broaden the scan angles of multi-beam radiation. Theoretical foundation and design guidelines are summarized with numerical and experimental examples presented to validate the feasibility.

Implantable antennas are mandatory to transfer data from implants to the external world wirelessly. Smart implants can be used to monitor and diagnose the medical conditions of the patient. The dispersion of the dielectric constant of the tissues and variability of organ structures of the human body absorb most of the antenna radiation. Consequently, implanting an antenna inside the human body is a very challenging task. The design of the antenna is required to fulfill several conditions, such as miniaturization of the antenna dimension, biocompatibility, the satisfaction of the Specific Absorption Rate (SAR), and efficient radiation characteristics. The asymmetric hostile human body environment makes implant antenna technology even more challenging. This paper aims to summarize the recent implantable antenna technologies for medical applications and highlight the major research challenges. Also, it highlights the required technology and the frequency band, and the factors that can affect the radio frequency propagation through human body tissue. It includes a demonstration of a parametric literature investigation of the implantable antennas developed. Furthermore, fabrication and implantation methods of the antenna inside the human body are summarized elaborately. This extensive summary of the medical implantable antenna technology will help in understanding the prospects and challenges of this technology.

International audience; Antenna characterization using reverberation chamber (RC) has become the new trend in RC measurements. In this work, we compare three antenna characterization methods in RC. These methods are applied in order to determine the radiation efficiency of a patch and a log-periodic antenna. Results are compared and show good coherence. The accuracy of the applied methods is discussed and a solution is proposed in order to enhance the accuracy of reference antenna based methods.

Up to now most limits for radiated emission are given as values for the electrical field strength. Battermann, 2007 has shown that the frequency range extension for radiated emission measurements above 1 GHz generates a lot of problems while performing the test on a classical test site as depicted in Fig. 1. This paper will give a motivation to use an other measurand namely the total-radiated-power than electrical field strength by using alternative test sites like reverberation chambers, TEM-waveguides, Fully Anechoic Rooms (FAR) etc. Nevertheless most of the existing standards still specify electrical field strength limits. This paper will show how to set the parameters in the given algorithm to establish a link between measured total radiated power and equivalent electrical field values.

A double-layer complementary metasurface (MS) with ultra-wideband polarization conversion is presented. Then, we propose two application cases by applying the polarization conversion structures to aperture coupling patch antenna (ACPA). Due to the existence of air-filled gap of ACPA, air substrate and dielectric substrate are used to construct the double-layer MS. The polarization conversion bandwidth is broadened toward low-frequency range. Subsequently, two application cases of antenna are proposed and investigated. The simultaneous improvement of radiation and scattering performance of antenna is normally considered as a contradiction. Gratifyingly, the contradiction is addressed in these two application cases. According to different mechanism of scattering suppression (i.e., polarization conversion and phase cancellation), the polarization conversion structures are utilized to construct uniform and orthogonal arrangement configurations. And then, the configurations are integrated into ACPA and two different kinds of metasurface-based (MS-based) ACPA are formed. Radiation properties of the two MS-based ACPAs are improved by optimizing the uniform and orthogonal arrangement configurations. The measured results suggest that ultra-wideband polarization conversion properties of the MS are achieved and radiation enhancement and scattering suppression of the two MS-based ACPAs are obtained. These results demonstrate that we provide novel approach to design high-performance polarization conversion MS and MS-based devices.

International audience; In this paper, an antenna with reconfigurable radiation pattern in H-plane at 2.45 GHz for high power applications is presented. It is based on a 3-slot array in E-plane covered partially with two mobile metallic flaps in order to reduce their length, and in consequence, they ensure the mechanical reconfiguration pattern in H-plane. The power distribution of the array is ensured with a power splitter in E-plane, and the uniform and in phase field distribution on the slots is ensured with a sectorial horn placed before the splitter. To reduce cost and weight, the power splitter is realized with metalized wood. © 2017, Electromagnetics Academy. All rights reserved.

International audience; This paper investigates the effect of the radius of a Over-The-Air (OTA) multi-probes ring employing half-wavelength dipoles, on the emulated spatial correlation. The Device Under Test (DUT) is considered randomly oriented in the test zone. Based on the correlation error metric, antenna effect on correlation is evaluated for a Clarke's and single cluster scenarios and OTA two-dimensional rings with up to 32 probes. © 2016 European Association of Antennas and Propagation.

International audience; We propose an approach to increase the operating range and matching stability of in-body ingestible or implantable capsule antennas. It involves using high permittivity biocompatible superstrate on a high-Q narrowband microstrip antenna. In this way, the antenna-body coupling can be significantly reduced, resulting in improved detuning immunity, increased radiation efficiency, and reduced power absorption inside the body. To demonstrate the feasibility of the proposed approach, we designed a mid-ISM band (433 to 434.8) MHz low-profile (85 μm) conformal microstrip antenna loaded with high permittivity ceramic superstrate. We achieved a simulated gain of -20.4 dBi. The radiation efficiency reaches 0.6%, which exceeds the counterparts operating within the same band by at least 3.5 times. The bandwidth is 26 MHz (6%), while the antenna remains matched (S11 < -10 dB) at 434 MHz within a wide range of tissue-equivalent phantoms. To validate the numerical results, we manufactured an antenna prototype and characterized it in terms of reflection coefficient S11. © 2016 European Association of Antennas and Propagation.

International audience; We present the performances of new way of using Krylov type algorithms in FETI methods for solving multi-source electromagnetic problems.

We investigate here the capabilities of a 400-element reconfigurable transmitarray antenna to synthesize monopulse radiation patterns for radar applications in $X$ -band. The generation of the sum ( $\Sigma )$ and difference ( $\Delta $ ) patterns are demonstrated both theoretically and experimentally for broadside as well as tilted beams in different azimuthal planes. Two different feed configurations have been considered, namely, a single focal source and a four-element focal source configuration. The latter enables the simultaneous generation of a $\Sigma $ - and two $\Delta $ -patterns in orthogonal planes, which is an important advantage for tracking applications with stringent requirements in speed and accuracy.

Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.

Conference name: 9th European Conference on Antennas and Propagation, EuCAP 2015 Date of Conference: 13-17 April 2015 In this paper we present two antenna designs capable of covering the IEEE 802.11ad (WiGig) frequency band (57-66 GHz and 59-66 GHz respectively). The work below reports the design, microfabrication and characterization of a broadband patch antenna along with the design and microfabrication of multifunction reconfigurable antenna (MRA) in its static form excluding active switching. The first design is a patch antenna where the energy is coupled with a conductor-backed (CB) coplanar waveguide (CPW)-fed loop slot, resulting in a broad bandwidth. The feed circuitry along with the loop is formed on a quartz substrate (at 60 GHz), on top of which an SU-8-based three-dimensional (3D) structure with air cavities is microfabricated. The patch metallization is deposited on top of this structure. The second design is a CB CPW-fed loop slot coupled patch antenna with a parasitic layer on top. The feed circuitry along with the loop is formed on a quartz substrate. On top, the patch metallization is patterned on another quartz substrate. The parasitic pixels are deposited on top of these two quartz layers on top of an SU-8 based 3D structure with air cavities. © 2015 EurAAP.

Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components for Luneburg lenses excited by a linear and circular polarized antenna are analyzed. Co-polarized and cross-polarized field radiation patterns are shown. Reflection from the lens, losses in the lens material, spillover and polarization loss are taken into account for antenna gain calculation. The proposed method significantly reduces computing time for multilayered lens in comparison with the most commonly used in antenna design. © 2015 Radio Society (Mauritius).

In coplanar waveguide (CPW) circuits, printed balanced antennas must be excited through baluns. These baluns often feature coplanar-to-slotline transitions that must be tuned and matched by electromagnetic optimisation, and may interfere with the antenna backward radiation. A new CPW balun for printed balanced antennas is presented and modelled. As its multimodal circuit model makes clear, it integrates an impedance-matching network within its structure that can be analytically designed. The balun has been experimentally tested, exhibiting good agreement with its circuit model and a weak electromagnetic interaction with the antenna radiation.

Plasma antennas constitute a promising alternative to conventional metallic antennas for applications in which reconfigurability with respect to some property is desired. The latter feature can be achieved by tuning the plasma discharge parameters. We use a full-wave numerical tool, ADAMANT (Advanced coDe for Anisotropic Media and ANTennas), based on integral equations, to assess the role played by plasma discharge parameters in shaping the radiation pattern, which is mainly determined by the plasma current distribution. Numerical results for different discharge parameters show that the antenna radiation efficiency can be controlled by adjusting plasma density and magneto-static field.

We report a high-accuracy measurement of the differential static scalar polarizability Δα0 of the 5sS1/22-4dD5/22 transition of the Sr+88 ion. The high accuracy is obtained by comparing the micromotion-induced positive scalar Stark shift to the negative time-dilation shift. Measurement of the trap drive frequency where these shifts cancel is used to determine Δα0 without the need to determine the electric field. Δα0 is a critical parameter for the operation of frequency standards as it determines the blackbody radiation frequency shift coefficient, the largest source of uncertainty in the Sr+88 ion clock. The measured value of Δα0 is -4.7938(71)×10-40Jm2/V2. Taking into account the dynamic correction, the blackbody shift at 300 K is 0.24799(37) Hz. The contribution of the blackbody shift coefficient to the uncertainty of the ion standard has been reduced by a factor of 24, from 2×10-17 to 8.3×10-19. The revised total uncertainty of our reference standard is 1.2×10-17, limited by the blackbody field evaluation. An additional benefit of the low uncertainty of Δα0 is the ability to suppress, by a factor of about 200, the net micromotion frequency shifts. © 2014 Published by the American Physical Society.

We study the applicability of soft interference cancellation in the forward link of commercial multibeam satellite systems with focus on mobile terminals. We adopt a standard currently used in commercial satellite systems as a reference. The multibeam satellite antenna radiation diagram has been generated using a physical optics reflector model, while state-ofthe art channel models have been used for the land mobile satellite (LMS) channel. The interference pattern has been derived through a system simulator developed by the European Space Agency (ESA). Starting from the analysis of the interference pattern we study the application of a low complexity soft interference cancellation scheme. Our results show that, under realistic interference and propagation conditions and for existing standards, a two-colors frequency reuse scheme can be employed while guaranteeing service availability across the coverage and keeping the complexity at the user terminals relatively low.

International audience; The presence of human body has an important influence on the wireless communication systems in indoor environments. The need of efficient prediction for such coverage becomes essential. This paper present an efficient electromagnetic indoor propagation modeling, taking into account the presence of human body and the nature of materials of the complex environment, based on the Finite-Difference Time-Domain method. Numerical results are compared with measurement results and show a good agreement.

The design of substrate integrated waveguide couplers for adaptive receiver applications employing tapered slot antennas is presented. Two different 20 dB couplers are designed on low-permittivity substrate, and their performances are verified by commercially available field solvers. For an incident plane wave, the systems of antenna and couplers are demonstrated to provide the desired operation between 18 GHz and 28 GHz in terms of both received E-field levels and propagation through the components. Antenna radiation patterns are provided. Two different SIW coupler designs are compared with measurements and are found in good agreement, thus validating the design procedure. © 2013 EurAAP., 2013 7th European Conference on Antennas and Propagation, EuCAP 2013, 8 April 2013 through 12 April 2013, Gothenburg

A calculation of the blackbody radiation shift of the B${}^{+}$ clock transition is performed. The polarizabilities of the B${}^{+}$$2{s}^{2}$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e}$, $2s2p$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}{P}^{o}$, and $2s2p$ ${}^{3}\phantom{\rule{-0.16em}{0ex}}{P}^{o}$ states are computed using the configuration interaction method with an underlying semiempirical core potential. The recommended dipole polarizabilities are 9.64(3)${a}_{0}^{3}$, 7.78(3)${a}_{0}^{3}$ and 16.55(5)${a}_{0}^{3}$, respectively. The derived frequency shift for the $2{s}^{2}$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e}$ $\ensuremath{\rightarrow}$ $2s2p$ ${}^{3}\phantom{\rule{-0.16em}{0ex}}{P}_{0}^{o}$ transition at 300 K is 0.0160(5) Hz. The dipole polarizabilities agree with an earlier relativistic calculation [Safronova et al., Phys. Rev. Lett. 107, 143006 (2011)] to better than 0.2$%$. Quadrupole and octupole polarizabilities and nonadiabatic multipole polarizabilities are also reported.

This report provides an electromagnetic characterization analysis in order to ascertain if integrated masts are an effective ship radiofrequency electromagnetic interference mitigation strategy. Free space and fitted antenna radiation patterns, and fitted relative near field power flux densities of a linear array transmitting antenna, and the mutual antenna-to-antenna coupling between a linear array transmit and receive antennas, both fitted on the same mast structure, was determined. Overall, the mast structure can reduce the mutual antenna-to-antenna coupling (up to ~20dB) and can affect the fitted antenna radiation pattern. There is both significantly high (i.e., up to 0 dB) and low (~ -30dB) fitted relative near field power flux density within the vicinity of the transmitting antenna and regions around the mast structure. All this depends on the location and position of the transmit antenna relative to the mast structure, and the location of the receiver antenna relative to the transmit antenna. Both desensitization and third order subharmonic distortions non-linear effects on the receiver antenna system were also assessed due to the fitted relative near field power densities. Depending on the specifications of the receiver system, desensitization (or gain compression) was found to be significant, whereas, third order sub-harmonic distortion was not.. Prepared for: Defense Science and Technology Organization Australia Edinburgh SA 5111, Australia

Three terahertz (THz) GaAs/AlGaAs quantum-well photodetectors with different 1-D metal gratings are fabricated for front-incident detection of THz waves. Photocurrent spectra are acquired and compared with 45 ° incident facet samples (without grating), and peak responsivities are determined with a calibrated blackbody radiation source. The results show that these gratings can couple THz waves into detectors effectively, resulting in good detector responsivities. The modal method is employed to simulate the light coupling efficiency and the optimization conditions of the gratings. © 2011 IEEE.

A system generating 1.8GHz electromagnetic fields for bio-medical and behavioral study on laboratory animals was designed and implemented. The system is based on a reverberation chamber. An input power up to 5W can be sent to an indoor transmitting antenna and an electric field strength (E) more than 90V/m can be reached inside the chamber. The system was characterized at different input powers measuring E in different points by means of a miniature sensor. Then, boxes with 300cc of physiological liquid inside were realized as simple phantoms simulating laboratory animals (rats) and E inside the liquid was measured, performing several simulations by moving the phantoms (1,2) in the chamber and/or putting them still in different positions. On the basis of these measurements, the SAR (Specific Absorption Rate) and the Pe (power efficiency = SAR/input power) were determined at different powers. The actual system is characterized by a low power efficiency with respect to the "in vivo" exposition systems based on transversal electromagnetic (TEM) cells. Its advantage is to have inside the chamber a habitat similar to the usual one for the laboratory animals.