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This work presents the design and realization of four linear arrays of microstrip rectangular patch antennas. This linear array is one of the elements of a passive radar using signals from 4G base stations for UAV detection. The arrays have been validated and operate from 2.62 GHz to 2.69 GHz, with a HPBW of 82° in H-plane and a maximal gain going from 11.1 dB to 12.2 dB in the required bandwidth, with a cosecant squared pattern in the E-plane.

National audience

International audience; In this communication, we present the results obtained within the framework of the Astrid project (DGA-ANR) SAFAS (Self-complementary Surface with Low Signature). The antenna has been designed and optimized using an analytical model of the complete structure. The antenna is able to maintain frequency bandwidth ratios of 4.6: 1 for a scanning capability of up to 60 °. These results were obtained at receiving and the aim of the article is to present the latest advances to take into account the future feeding system.

International audience; Recently the performances of radar absorbing materials have been extended by designing new thin structures with wideband properties and large angles of incidence. In this paper, the design and performances of such ultrawideband microwave absorber of low thickness material developed within the framework of the SAFAS project (self-complementary surface with low signature) are confirmed with complementary quasi monostatic measurements and finite array simulations using Finite Element Tearing and Interconnecting domain decomposition methods (FETI).

International audience

International audience; Using structural composite materials for the fabrication of Radar Absorbing Materials (RAM) allows combining the strong load bearing capability with the radar absorbing functionality in a unique structure. This article shows the possibility to transpose an already existing metamaterial absorber to the domain of composite materials. The dielectric layers of the absorber initially designed with radio-frequency (RF) materials are replaced with fiber-reinforced composite materials and their thickness is optimized again. The working principle of the absorber is explained layer by layer on the Smith chart. The performances of the composite absorber are compared against the initial RF design and against other classical absorbers. The composite design has a total thickness of 8.9 mm and achieves a reflection coefficient below 14 dB within the band 4.6 GHz - 17.2 GHz at normal incidence. The reflection coefficient remains under -10 dB at oblique incidence up to 45°.; L'utilisation de matériaux composites structurels pour la fabrication de matériaux absorbants radar permet de combiner la capacité de charge élevée avec la fonctionnalité d'absorption radar dans une structure unique. Cet article montre la possibilité de transposer un méta matériaux absorbant déjà existant, dans le domaine des matériaux composites. Les couches diélectriques de l'absorbant initialement conçues avec des matériaux radiofréquences (RF) sont remplacées par des matériaux composites renforcés de fibres et leur épaisseur est à nouveau optimisée. Le principe de fonctionnement de l'absorbant est expliqué couche par couche sur la carte de Smith. Les performances de l'absorbant composite sont comparées à la conception RF initiale et à d'autres absorbants classiques. La conception composite a une épaisseur totale de 8,9 mm et atteint un coefficient de réflexion inférieur à -14 dB dans la bande 4,6 GHz - 17,2 GHz à incidence normale. Le coefficient de réflexion reste inférieur à -10 dB en incidence oblique jusqu'à 45 °.

The European Commission Horizon 2020 TWEETHER project will conclude the activity on September 2018 with the release of one transmission hub and three network terminal equipment for enabling the first W -band, 92–95 GHz, point to multipoint system, for high capacity backhaul and fixed access. The ambition of the project is to develop the European technology for a breakthrough in millimeter wave wireless networks, by introducing the use of traveling wave tubes to achieve the required transmission power for covering, by low-gain antennas, wide area sectors with radius longer than 1 km. The lack of transmission power has so far prevented the use of point to multipoint distribution at millimeter waves. At W -band, the 3 GHz bandwidth provides more than 10 Gbps capacity, and 4 Cbps/km2area capacity for small cells backhaul, with flexible allocation of the base stations and low total cost of operation. The TWEETHER system is also designed to provide high throughput fixed access. This paper will describe the latest results and the technological advancements the project generated, bringing Europe at the state of the art for point to multipoint millimeter wave wireless networks.

International audience

International audience

This article presents the results of a design of a forward to backward leaky wave antenna (LWA) based on rectangular waveguide (RWG) technology. This structure combines a snaky wave guide with slots to achieve the required radiation characteristics. The effect of increasing the number of snaky cells has been analyzed to study the effect on the radiation patterns and the S-parameters. The results show that the proposed antenna serves as a suitable candidate for millimeter wave scanning applications in W band. Numerical simulations have been done with a commercial CST Microwave Studio.

National audience; TheHorizon2020TWEETHERprojectaimstobuildapointtomultipointwirelesssystemwithhighcapacityatW-band(92–95GHz)forbackhaulofsmallcellsandfixedaccess.Thepointtomultipointisanattractivesolutionforbackhaul.Itismuchcheaperthanthefibreandneedsonlyhalfoftheequipmentofanequivalentpointtopointbackhaul.TheW-bandwaschosenduetothelightlicensingandthelowcostforoperators.Theuseforthefirsttimeofanovelhighpowertravelingwavetubepermitstocoverwideanglesectorswithrangeofabout1km,providingupto10Gbps/km 2 capacitydensity. The paper will describe the components purposely designed and fabricated for thetransmissionhubandthenetworkterminalequipment.

International audience

International audience; In this article, a dielectric superstrate inspired from transformation optics is presented. When placed over a patch antenna, this superstrate increases the half power beam width (HPBW) of a classical patch antenna. An appropriate spatial transformation relation with spatial compression and refractive index shift factors has been used to derive an expression for a dielectric material profile. The wave front exiting from the transformed space is optimized for a semicylindrical shape. Then, a discretized version of this profile has been used to design a cuboidal superstrate. Full wave simulations have been presented that essentially show a superstrate device capable of producing a 297° of HPBW in H-plane with a peak directivity of 3.2 dBi at the design frequency. The derived solution can be realized using the standard dielectric materials for real-world applications.

A new calibration method of active phased array antennas is presented in this paper. This method can be applied to the antenna arrays of various sizes and various radiating element numbers. It takes into account the edge effects and the coupling between the radiating elements. This method allows avoiding the degradations of the antenna radiation pattern caused by mismatch produced during a scanning and/or a weighting process. HFSS software is used to provide near-field electromagnetic numerical simulations. Matlab is used for far-field calculation from the near-field data; and also for the calculation of the illumination on the antenna surface by back-propagation of far-field data. The calibration process is performed by an optimization process by means of ADS software. An equivalent schematic is built in it in order to obtain desired radiation pattern which corresponds to the illumination on the antenna surface. This method is applied to a concrete case in order to demonstrate its efficiency.

International audience

International audience

The European Horizon 2020 project TWEETHER aims to make a breakthrough in wireless networks to overcome the congestion of the actual mobile networks and foster the new 5G networks. A European Consortium including four universities and five companies from four European countries is devoting a relevant effort to realize novel terminals and transmission hubs to operate in the W-band (93–95 GHz). This paper will describe the advancement of the project.

International audience

International audience; This paper studies the effect of a hybrid reflector on the radiation pattern of an ultra-wide band diamond dipole antenna. The cause of a split radiation pattern in the broadside direction appearing when using a uniform Artificial Magnetic Conductor (AMC) based reflector is investigated and is found to be due to destructive interference in broadside direction produced by surface currents localized in certain areas of the reflector. A hybrid reflector is then proposed to mitigate this problem by using both electrical and magnetic conductors. This solution enhances the gain in the broadside direction of the ultra-wide band antenna. A complete antenna with feeding system and hybrid reflector has been fabricated and measurement results are presented.

International audience

The aim of the present contribution is to show that metasurfaces such as reactive impedance surfaces (RIS) and artificial magnetic conductors can be efficiently used in the design of low-profile circularly polarized L-band antennas. We present the design and simulation of the compact and low-profile antennas. The solution based on RIS will be compared to a circularly polarized microstrip patch antenna using the same materials in order to prove the benefit of metasurfaces. The engineered metasurfaces allow increasing the bandwidths with few modifications on the thickness and the overall antenna size.

International audience

International audience

International audience; This paper presents a low diamond dipole antenna backed with an A Conductor. The paper addresses the proble broadside gain due to the split in the radiati particular frequencies within the operati solution is proposed by using a hybrid A Conductor that can effectively cancel this ef antenna is characterized by an overall thickne corresponds to a tenth of wavelength at th frequency. Index Terms-Wideband diamond dipole Magnetic Conductor, directive antenna.

International audience

n° de priorité : FR1452143 - 2014-03-14; The invention relates to a device (1) for absorbing electromagnetic waves, comprising a plurality of arrays (Ei) each comprising at least one cell (2) for absorbing electromagnetic waves, characterised in that: each array (Ei) has a minimum absorption coefficient valid for given parameters of the waves incident on said array (Ei), said parameters comprising one or more of the following parameters: - a pair of angular ranges ([θi-θ'i],[φi-φi']) of the direction of arrival of the incident waves on the array (Ei), comprising a range ([θi-θ'i]) of angles of incidence and a range of azimuthal angles ([φi-φi']), and - a polarisation of the incident waves, the parameters of the incident waves for which each array (Ei) ensures the minimum absorption coefficient being different from one array (Ei) to the other. The invention also relates to a method for designing and producing an absorbing device.

International audience; This paper discusses the role of extreme material parameters (MP) of a superstrate designed using Transformation Optics (TO), which reorients the radiation of a patch antenna in its azimuthal plane. A MP profile obtained from TO method is compared with a second dielectric MP profile with identical refractive indices to highlight the role of high permittivity and low permeability values.

Based on a common evaluation 5-step methodology, initial performance assessments of the innovative solutions considered within WP4 are carried out. A dozen of radio components and transmission techniques solutions are developed and evaluated through ratio of the Exposure Index.The proposed intermediate performances assessments show a large range of exposure reduction from non-significant to ninety percent reduction, while keeping QoS constant.Despite a large diversity of solutions, the adopted methodology makes possible the comparison of their effectiveness but also allows to highlight some compatibility or at the opposite some conflicts between these solutions.This last point is a mandatory step to prepare solution prioritization and global exposure reduction assessment.

International audience; This paper presents a lightweight microwave absorber suitable for space applications. The absorber is based on a resistive high-impedance surface (RHIS) optimized to achieve reflection under −15 dB in the band (2-2.3 GHz) at oblique incidence for transverse electric (TE) and transverse magnetic (TM) polarizations. A first classical isotropic RHIS structure is shown to be limited to angles of incidence up to 40° for TE polarized waves and up to 35° for TM polarized waves. So the objective of this contribution is to present a second solution based on an anisotropic RHIS structure which presents good absorption of incident waves in TE and TM polarizations for larger angles of incidence. An example is presented for an incidence angle of 65°.

We present the first part of a study supported by the French Ministry of Defense, entitled SAFAS, which aims at developing a low profile self-complementary radiating surface with low signature. This surface concept is intended to be used for antenna and absorber designs. We show some preliminary results for an antenna array required to work for incidences up to 60° over an ultra-wide frequency band with ratio 5:1.

International audience

International audience

This paper presents a simplified model of a terminal mobile where a monopole antenna is associated with three different metamaterials: artificial magnetic conductor (AMC), electromagnetic band gap and resistive high-impedance surface (RHIS). The objective is to evaluate what is the metamaterial which is the best solution to reduce exposure. The exposure has been evaluated using a simplified phantom model. Results show that both AMC and RHIS reduce the exposure preserving the antenna performances. A reduction of 23 % of specific absorption rate 10 g has been obtained when the monopole is associated with an optimized RHIS structure. Antenna with and without metamaterials has been realized. The experimental results confirm the performances given by simulation in terms of impedance matching and radiation.

Exposure Index, evaluation methodology, transmissionThis work proposes hardware design and transmission techniques that are the state-of-the-art in terms of the development of future technologies to reduce human exposure to electromagnetic waves emanating from radiocommunications systems. Based on a detailled State of the Art review, partners have identified promising individual studies to carry on. Each of them is described by detailing the context, the mechanism used to reduce exposure. At last thepratical use of the Exposure Index formula for improvement evaluation is addressed. A classification of the different families of solutions is also proposed. techniques, Components

A Fabry–Perot antenna can be realized by employing a frequency selective surface (FSS), with suitable frequency selective properties, placed at an adequate distance from a perfect electric ground plane, in our case the ground plane is a metamaterial high impedance surface (HIS). The FSS is a multilayer partially reflective surface (PRS) realized by a periodic distribution of metallic elements printed on a dielectric slab. It can almost entirely reflect incident waves. By inserting a patch antenna between the ground plane and the FSS, a highly directive antenna can be obtained. Metamaterials are artificial structures that can be designed to exhibit unusual electromagnetic properties not observed in natural materials. The HIS is a metamaterial structure. The HIS does not support propagating surface waves, and it reflects electromagnetic waves with no phase reversal. Simulated and experimental results are presented. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:981–985, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27531

This article presents a coplanar waveguide-fed wideband bowtie antenna with harmonic suppression using non-uniform cascaded defected ground structure units.The antenna operates between 2 GHz and 5.4 GHz and harmonics are effectively reduced. Its size is only 0.44×0.48 λ02, λ0 being the free-space wavelength at 2 GHz. Simulation and measurement agree very well. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:829–835, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27422

International audience

International audience; This chapter demonstrates that it is possible to design wideband antennas with metamaterials. High Impedance Surfaces (HIS) are used to improve wideband antennas' performances. In particular, the Artificial Magnetic Conductor (AMC) behavior is utilized in order to achieve a reflector which can be located very close to antennas, thereby leading to low profiles. AMC being inherently narrow band, it is shown that this does not necessarily limit the impedance bandwidth of AMC-based antennas. However, some issues regarding the radiation pattern remains when a wide operating band is considered. So this chapter proposes two different approaches to overcome to some extend these limitations. A first approach led to an optimized antenna using an AMC with lumped elements. A second approach is to identify current areas circulating over the AMC's surface which are responsible of radiation pattern degradations. This technique led to a hybrid AMC which largely enhanced antenna's performances over a wide band.

In this communication, Artificial Impedance Surfaces (AIS) based on patches from High Impedance Surface (HIS) are considered. The possibility to use the patch width as an additional degree of freedom for antennas design is investigated. Within the limitation of a single linear polarization, rectangular patches of this AIS allow adjusting the surface impedance value while keeping identical the in-phase reflection property of such metasurfaces on the same frequency range. With this approach, a bandwidth of 17% is achieved by using a dipole antenna over an AIS.

This paper presents the advantages of a Perfect Electric Conductor (PEC) used as a stepped reflector for an Archimedean spiral antenna. Such a configuration is used to improve the broadside gain over a relative bandwidth of 145%.

In this paper we present the design of a CPW-fed wideband bow-tie antenna with harmonic suppression using three non-uniform cascaded bow-tie DGS (defected ground structure) units. The total size of the antenna is 66×73mm2 (0.44×0.48λ 0 2, where λ 0 is the free-space wavelength at the lowest operating frequency). DGS dimensions are optimized to suppress the second and the third harmonics bands. The proposed antenna is matched between 2 GHz and 5.4 GHz (92%), and the band between 7 GHz and 22 GHz (103.5%) is rejected. The antenna has an omnidirectional dipole-type radiation pattern over the whole frequency band.

International audience; A dual-band Artificial Magnetic Conductor (AMC) is presented in this paper. The proposed metasurface is based on a spiral geometry in which an additional resonance has been introduced thanks to a physical understanding of the structure's behavior. The design is compact and the two frequency bands can be adjusted independently. Furthermore, an analytical model is developed which can predict both the frequencies at which the metasurface reflects incident waves in-phase.