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The sixth-generation wireless communication research activities were launched worldwide. A tendency of some researchers to use the sub-terahertz frequency band for 6G is noticed. This frequency band is selected as a candidate for 6G due to its remarkable wide unused frequency bandwidth. In this paper, typical indoor environment material transmission measurements from 2 GHz to 170 GHz are presented. These measurements aim to further understand and compare wavematerial interaction for above and below 100 GHz frequencies by providing a continuous measurement up to 170 GHz of 16 different materials e.g. glass, plasterboard, concrete, and wooden materials. The measurement system is based on a vector network analyzer, with frequency extension modules for frequencies above 50 GHz.

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.

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National audience; Les métasurfaces de Huygens sont des outils puissants pour façonner les fronts d'ondes électromagnétiques. Dans ce travail, nous présentons une cellule multibande et reconfigurable d’une métasurface de Huygens qui permet le dépointage du faisceau dans la bande 5G (3.4-3.8 GHz) sans perturber la phase et la transmission dans les bandes 4G (2.5–2.7 GHz) et Wi-Fi (2.4–2.5 GHz, 5.17–5.83 GHz, 5.93–6.45 GHz). Il est ainsi possible d’obtenir une variation de phase allant jusqu’à 114° dans la bande 5G avec un impact négligeable dans les autres bandes.

International audience

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

National audience; Dans cet article, nous démontrons qu'il est possible de remplacer les couches diélectriques d'un absorbant à métamatériaux initialement conçu avec des matériaux RF par des matériaux composites structuraux, i.e. renforcés de fibres. Ces matériaux, compatibles avec les procédés de fabrication du domaine naval militaire ont été réalisés et mesurés. L'effet des différentes couches de l'absorbant sur la bande passante est détaillé. Après optimisation de l'épaisseur de chaque couche grâce à un modèle analytique, l'absorbant présente un coefficient de réflexion inférieur à-14 dB dans la bande 4.6 GHz-17.2 GHz en incidence normale, pour une épaisseur totale de 8.9 mm. Le comportement de l'absorbant en incidence oblique est aussi discuté.

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 °.

International audience; In this paper, a wideband dual polarized self-complementary connected array antenna with low radar cross section (RCS) under normal and oblique incidence is presented. First, an analytical model of the multilayer structure is proposed in order to obtain a fast and reliable predimensioning tool providing an optimized design of the infinite array. The accuracy of this model is demonstrated thanks to comparative simulations with a full wave analysis software. RCS reduction compared to a perfectly conducting flat plate of at least 10 dB has been obtained over an ultrawide bandwidth of nearly 7:1 at normal incidence and 5:1 (3.8 to 19 GHz) at 60° in both polarizations. These performances are confirmed by finite element tearing and interconnecting computations of finite arrays of different sizes. Finally, the realization of a 28x28 cell prototype and measurement results are detailed.

National audience

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

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

National audience

A compact wideband antenna place above a non-uniform artificial magnetic conductor (AMC) is presented. The antenna is composed of a wideband coplanar waveguide fed antenna, with wideband harmonic suppression characteristic using non-uniform defected ground structure. Besides, a non-uniform wideband AMC is designed. The AMC unit cell is composed of a square patch into which a four arms spiral shape is etched. It exhibits a wider ±90° bandwidth than the spiral unit cell and a smaller size than the square patch unit cell. The antenna is placed above the proposed AMC structure formed by 6 × 5 unit cells. The overall dimensions of the complete structure are 0.7 × 0.6 λ 0 2 , where λ 0 is the free-space wavelength at the lowest frequency. It offers a low-profile configuration with a total thickness of λ 0/14.3, and it is matched between 2.5 and 5.4 GHz (73.5 %). Furthermore, it has a stable main lobe radiation pattern in the E- and H-planes within the operating frequency band. Moreover, compared with the antenna without AMC, the broadside realized gain is significantly increased. A prototype has been realized, and there is a good agreement between simulated and measured results. Furthermore, the proposed structure presents a size reduction of about 34 %, and better radiation characteristics in comparison with the conventional square AMC.

International audience; This paper aims to show the design and performances of a flat superstrate placed above an L-band patch antenna. Obtained from the Transformation Electromagnetics (TE) technique, this superstrate enables to produce an antipodal radiation with a quasi-null radiation in the broadside direction. From the analytical transformations used for the calculation of the constitutive parameters, material permittivity and permeability profiles of the superstrate are deduced. Then, the field distribution and radiation patterns of the whole structure confirm the antipodal radiation behavior.

In this paper, the design methodology of a flat reflector composed with standard dielectric material and using transformation electromagnetics (TE) is presented. First, the mathematical relation between a flat reflector and a parabolic one is described. The TE principle is then described. Some realization issues are highlighted, leading to approximations and compromises in order to design a more realistic structure. In this way, a flat reflector made only with standard dielectric materials is presented, using an original method to achieve the desired spatial permittivity variation. The simulation results of different configurations for the flat reflector are presented and compared to classical solutions in order to prove the thickness reduction and the improvement of radiation characteristics in terms of gain and half-power beamwidth.

This paper presents an analytical model to design a self-complementary connected antenna array above artificial materials like high impedance surfaces (HIS). The objective of this model is to perform parametric studies to facilitate deeper understanding of a complex antenna array with a significantly shorter computation time than with electromagnetic simulators. The model of the complete structure has been designed in receiving mode when structure is illuminated with a plane wave and using transmission line model and ABCD matrix. By applying an interesting property which gives equivalence between the input impedance in transmit mode and the surface impedance in receiving mode, the impedance match of the self-complementary connected antenna array can be quickly calculated. It is also simple to evaluate the influence of the incidence angle on the reflection coefficient of a self-complementary connected antenna array above perfect electric conductor (PEC) or HIS. PEC or artificial materials can modify the antenna array behavior by either increasing the bandwidth or by adding additional bandwidths. All these results have been verified to be accurate by numerical simulations done with Ansys HFSS.

This paper presents the design, realization and measurement of a thin lightweight absorbing material for space applications. Absorber design is based on high impedance surfaces loaded with resistors and known as a resistive high impedance surface (RHIS). The behavior of RHIS is analyzed at normal and oblique incidences for TE and TM polarizations. Prototypes have been realized and measured. Final design has a reflection coefficient less than $$-$$ 15 dB in S-Band (2–2.3 GHz) at normal incidence and till an angular dispersion of 40 $$^\circ $$ for waves in TE polarization, and 35 $$^\circ $$ for waves in TM polarization. Simulation results are validated by measurement.

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.

National audience

National audience

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.

National audience

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