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Purpose The purpose of this sudy is to provide a complete optimization-based methodology to design waveguides with metamaterial walls. The present methodology is based on optimization. Indeed, the inverse problems of design are formulated as nonlinear black-box optimization problems with constraints. Two inequality black-box constraints are taken into account as penalized terms that are added to the objective function when the constraints are not satisfied. The numerical steps are done by using a finite element method solver (GetDP). Thus, different optimization software are tested to solve the nonlinear black-box optimization problems such as IPOPT, NLOPT and NOMAD from the Opti ToolBox in MatLab. Design/methodology/approach In this work, a methodology to design waveguides with metamaterial walls is proposed. The aim is to solve an inverse problem to find the best design where the electric field cartography is the closest to an imposed one. Findings The present methodology is applied to solve inverse problems of design and satisfactory results were provided by the three solvers IPOPT, NLOPT and NOMAD. Those numerical experiments show that NOMAD is the most efficient method to optimize the design of those cylindrical waveguide structures with metamaterial walls. Research limitations/implications The model is set to find solutions using a specific pattern of metamaterials. This is promising to take those geometries as variables of the optimization problems. Moreover, in this exploratory work, no constraint on the fabrication limits has been taken into account. Originality/value The originality is to formulate design problems of waveguide with metamaterial walls into optimization problems. These optimization problems are difficult to solve because the objective function and two inequality constraints are computed via a numerical simulation code based on finite element methods. Thus, an original approach based on penalization is implemented and three optimization software are used. Hence, the authors propose an optimization-based methodology and apply to solve two inverse problems of design.

International audience

International audience; In this paper, a contactless microwave transition is described and characterized. In our "ElectroMagnetic Drive" (EMDrive) measuring setup, it will be dedicated to transmit high Radio Frequency (RF) powers without any mechanical effort. It exhibits very good matching and transmission performances. It is found to transmit 100 W microwave power range at 2.45 GHz without any visible mechanical effect on a 10 mg precision balance, contrary to a previous coaxial cable. This device appears useful to every EMDrive setup and can be easily implemented.

International audience; This paper details the work of the LAPLACE Electromagnetism Research Group to develop an original measuring setup dedicated to the detection of an EMDrive like force. Recent peer-reviewed experimental results [1, 2] were obtained using similar setups based on a torsion pendulum combined with an optical sensor. These very accurate measurement setups are appropriate for measuring such an extremely weak force. They also appear costly, which may discourage other research teams from working on this topic. Our main goal is then to provide an alternative configuration, based on a commercial precision balance, in order to build a measuring setup more affordable, handy, and accurate enough to measure an EMDrive like force. Our experimental system is capable of feeding a truncated cone shaped 2.45 GHz resonant cavity with power up to 140 W. To calibrate the EMDrive force and avoid false positive thrusts, an original setup has been proposed and evaluated. It allows us to really consider that the parasitic effects do not alter the hypothetical force measurement by the use of force direction switching during the measurement.

International audience; In this paper, a detailed study and the optimization of a Negative Impedance Converter (NIC) circuit are presented to increase the bandwidth of a passive metasurface. The design and optimization procedure take into account the biasing and the effect of the transistors. The optimization ensures that the load can be realized with passive components.

This article presents a sensitivity analysis of rectangular waveguides loaded with anisotropic surface impedance boundaries on their vertical walls, by using modal extended theory (MET). Using this method, several dispersion diagrams are computed for various anisotropic impedance boundary conditions of the surface walls of the waveguides in order to assess how the slight changes on the surface impedance can affect on the bandwidth and the fundamental cutoff frequency of the waveguide. The results obtained with MET were validated by comparison with the commercial software ANSYS HFSS. The results show that small anisotropic variations of the surface wall impedances lead to variation on the fundamental cutoff frequency and the bandwidth of the waveguide. Most significantly, and compared to an isotropic metasurface case, the variation of the transverse impedance of the metasurface is the one that have more significant effect over the waveguide parameters. This is an useful information for the metasurface design in order to take into account the fabrication tolerance of these structures and how they can have an influence over the final constructed device.

The modal theory for propagation in structures with constant anisotropic surface impedances as a boundary condition is developed for cylindrical waveguides and rectangular waveguides with vertical anisotropic surfaces. Dispersion diagrams for these waveguides are computed for various sets of surface impedances. The results are then validated by comparison, using commercial software. These results confirm a number of interesting properties of such waveguides with anisotropic surface impedances: the cutoff frequency can be drastically lowered, and left-handed mode propagation in a given frequency band can be obtained. The development of this theory can open the door to the development of new design tools for various applications using guided structures such as small waveguides, filters, positive phase shifters, or horns with excellent radiation properties.

International audience; Dans cet article, la Théorie Modale Elargie (MET) est développée pour les guides d'onde cylindriques à métamatériaux 2D. Un code basé sur la Méthode des Eléments Finis (FEM) calcule les impédances de surface équivalentes des métamatériaux dans la résolution de la MET. Ainsi, les diagrammes de dispersion sont obtenus avec des temps de simulation très réduits par rapport au logiciel commercial HFSS.

International audience;  Abstract-In this article, the Modal Expansion Theory is applied to 2D metamaterial cylindrical waveguides. A new code to compute the surface impedances with 2D Finite Element Method is put forward. The surface impedances depend on the frequency and the incidence angle. The characterization of propagation in a 2D metamaterial waveguide is presented by using the Modal Expansion Theory and 2D Finite Element Method. Comparisons with the software HFSS are carried out in order to validate the new method.

The novelty of this paper is the use of LSE 01 as fundamental mode, and a new modelization based on equivalent circuit method to characterize the substrate integrated non radiative waveguide bandpass filter. Results are validated by comparison with Ansys Electronics HFSS.

International audience; This paper presents a metasurface reflector, characterized with a 0° reflection phase, which can be tuned to operate at any frequency within the band [1.1 – 1.7 GHz] and in two orthogonal polarizations independently. The proposed metasurface, based on a double layer of periodic metallic patches and varactors, behaves like an artificial magnetic conductor (AMC). By varying the capacitance values of the varactors, the positions of the resonant frequencies of the AMC can be tuned in real time. The proposed solution offers the possibility to overcome the narrow band characteristics of AMC structures and to control the two orthogonal polarizations independently.

Static charging of an aircraft surface can lead to electromagnetic disturbances on aircraft radio and avionic systems. This phenomenon is called Precipitation Static. Arc discharges are the main causes, and they often occur when there is a bonding defect on the surface of the aircraft. In order to find these bonding defects, often the whole aircraft has to be scanned. This paper presents a method that aims at reducing the time needed for the search of outer bonding issues. The system is composed of an instrumentation to be used in-flight, that measures the electromagnetic emissions of P-Static sources using several sensors placed on the surface of the aircraft. Then, given several signals measured from sensors and using a time domain location method based on delay estimation, it is possible to compute the source position. The method is validated on a simplified fuselage mock-up with satisfying location performance.

International audience; In this article the Modal Expansion Theory (MET) is developed for 2D metamaterial cylindrical waveguides. A new code based on 2D Finite Element Method (FEM) is implemented to compute conformal surface impedances. The MET using this FEM code is successfully applied to waveguides with different-invariant metamaterials. For such cases, computation time is at least 30 times faster than the commercial software HFSS.

This paper proposes a new modal analysis based on Floquet's theorem which is needful for the study of a 1-D periodic phased array antenna excited by arbitrary located sources. This analysis requires an accurate estimation for calculation of the mutual coupling parameters (for example: mutual impedances or admittances ...) between the array elements and their efiects integrating a large planar radiating structure. Two difierent formulations are suggested, in spectral and spatial domains, to solve the problem and to calculate the coupling coe-cients between the neighbouring elements in a periodic environment. Important gain in the running time and used memory is obtained using Floquet analysis. One numerical method is used for modeling the proposed structures: the moment method combined with Generalized Equivalent Circuit (MoM-GEC).

The hybrid approach based on the coupling of the Wave Concept Iterative Procedure method and the Frequency Domain Transmission Line Matrix method is improved. The proposed method reduces the computation time by solving waves at the planar circuit interface: the volumic method is replaced by an equivalent surface condition. Thanks to this new approach, planar circuits presenting inhomogeneous dielectric substrates are studied. The proposed approach is compared to other methods on several examples.

This article presents the Wave Concept Iterative Procedure (WCIP), an efficient method for characterization of substrate integrated Non-Radiative Dielectric (SINRD) passive circuits based on wave concept formulation and its iterative solution. WCIP simulations are compared to measurements and Finite Element Method simulations. A good agreement is achieved with computation time saving.

Nowadays, met materials with lumped or distributed elements are emerging and it is necessary to develo p new techniques based on the following principles. T he approach should be global and have to be formula ted according to the existing classic formulations. In fact, the Wave Concept Iterative Process (WCIP) is systematically used in such application. On the oth er hand, the periodic medium can have some cells with localized defects that are supposed to be almost pe riodic. Such structures are studied based on the in troduction of auxiliaries’ sources. The study is devoted to th e study of one dimensional then bi dimensional medi um. Simple diffraction phenomenon supports the usefulness of the proposed new approach.

This article focuses on the 2D hybrid technique between the Frequency Domain Transmission Line Matrix Method (FDTLM) and the Wave Concept Iterative Procedure (WCIP). 3D hybridization has already been studied, but results may be improved through a better knowledge of method order. Consequently, developing 2D hybridization aims at understanding the hybridization in simplest problems, especially because Transverse Electric (TE) and Transverse Magnetic (TM) are uncoupled. Our study dwells on accuracy and convergence order of the 2D hybrid method, which will help for 3D mesh use. In this perspective, the scattering nodes and electromagnetic flelds expressions are established in the 2D general case with anisotropic materials. As a result, validation examples are presented to check the approach.

Static charging of an aircraft surface can lead to electromagnetic disturbances on aircraft radio and avionic systems. This phenomenon is called Precipitation Static. Arc discharges are the main causes, and they often occur when there is a bonding defect on the surface of the aircraft. In order to find these bonding defects, in most cases the whole aircraft has to be scanned. This paper presents a novel approach that aims at reducing the time needed for the search of outer bonding issues. The system is composed of an instrumentation to be used inflight, that measures the electromagnetic emissions of P-Static sources using several sensors placed on the surface of the aircraft. Then, given several signals measured from sensors and using a time domain location method based on delay estimation, it is possible to compute the source position. This article is focused on the instrumentation and measurement considerations allowing a proper determination of time delays.

This article presents a new analytical approach to calculate very rapidely the field distribution in rectangular waveguides with anisotropic walls.

Static charging of an aircraft surface can lead to electromagnetic disturbances on aircraft radio and avionic systems. This phenomenon is called Precipitation Static. Arc discharges are the main causes, and they often occur when there is a bonding defect on the surface of the aircraft. This paper presents a method that aims at reducing the time needed for the search of outer bonding issues. The system is composed of an instrumentation to be used in-flight, that measures the electromagnetic emissions of P-Static sources using several sensors placed on the surface of the aircraft. Then, given several signals measured from sensors and using a time domain location method based on delay estimation, it is possible to compute the source position. The method is validated on a reduced fuselage mock-up as well as on an aircraft case, taking into account the possible error sources.

This article presents an e-cient method for characteriza- tion of substrate integrated passive circuits. The analysis is based on the wave concept formulation and the iterative resolution of a system of two equations between incident and re∞ected waves. Simulations ob- tained are compared with analytical references and HFSS simulations. A good agreement is achieved with computation time saving.

The Wave Concept Iterative Procedure is validated for multi-layered substrate with frequency dependent and negative index media. By shifting the plasma frequency, reconfigurable filter design is proposed with a center frequency tunability of 25%. Sensitivity to collisional plasma is proposed.

A new approach to design a metamaterial surface (meta-surface) with the objective of reducing the waveguide's cutoff frequency of the fundamental mode is proposed. From an analytical study of the dispersion diagrams of waveguides with anisotropic walls, a hypothesis for the surface impedances is set up. By means of this new hypothesis, the design of a unit-cell is optimized. Finally, the periodically arranged meta-surface is implemented in a miniaturized waveguide and the simulation results are compared to the ones of a metallic waveguide in order to validate the approach.

This paper presents the use of equivalent parametric circuit models for the investigation of fabrication tolerance sensitivity in substrate integrated waveguide (SIW) components. As the adopted models are parametric, they permit to easily determine the effect of small variations in the geometry of the component, due to the manufacturing process. This feature allows an extremely fast sensitivity analysis and fabrication yield estimate in the case of a mass production. As an example, the sensitivity study of a cavity SIW filter is shown and discussed. Furthermore, the paper presents the comparison of the fabrication tolerance sensitivity between two filters with identical performance, fabricated in SIW and microstrip line technology, respectively. This comparison shows how the sensitivity of scattering parameters is significantly smaller in the SIW filter than in the microstrip counterpart.

With the collaboration of the CNES, a new modeling method for telecommunication devices, presented in this article, has been implemented on any computer. This method combines the variational method, based on electric equivalent circuit representations, and the boundary element method. Results are successfully compared to measurements and those from the previous publications. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 247–258, 2002.

International audience; We aim at coupling a method of moments, the Wave Concept Iterative Procedure, and the Hybridizable Discontinuous Galerkin (HDG) method to study electromagnetic susceptibility of innovative planar circuits in 3-D. Hybridizing the Wave Concept Iterative Procedure with volumic methods such as the Frequency-Domain Transmission Line Matrix method, the finite-element method, and the HDG method in 2-D is a first step for the validation of the proposed coupling technique. The considered problem is Maxwell's equations in the frequency domain. Three test cases in 2-D and a preliminary result in 3-D are provided.

The wave concept iterative procedure (WCIP) is used to analyze a quasi-square open metallic ring frequency selective surface (FSS). The quasi-square open metallic ring FSS is dual-polarized. When the incident plane wave is polarized in a direction parallel to the FSS' coupled parallel strips, it shows two rejecting bands. Moreover, another rejecting band can be obtained if the source plane wave is perpendicularly polarized with respect to the FSS' coupled parallel strips. The three resonant frequencies are inversely proportional to the length of the FSS' coupled strips to provide an easy fine tuning of the FSS structure. The simulated results obtained using WCIP are compared to the measured results, and a good agreement is reported.

International audience; A physically-based preconditioner for the 1d and 2d Wave Concept Iterative Procedure is introduced in this paper. Numerical results are provided to assess the efficiency of this technique.

In this article, modes are analytically expanded for cylindrical waveguide with anisotropic walls. With certain conditions, hybrid modes may appear with fundamental mode cutoff frequency lower than the TE 11 fundamental mode of the equivalent metallic waveguide and/or with a larger single-mode frequency band. In some cases, the E transversal field shape of the fundamental mode can be more linear than the equivalent TE 11 mode. Such properties of guided waves may result in the reduction of waveguide cross section or higher radiation efficiency in antenna applications.

This paper presents an efficient implementation of waves’ concept based on the iterative method algorithm combined with the FFT-2D algorithm adapted to box modes, or Fast Modal Transform (FMT). The advantages of this method are simplicity and the no implication of basic functions and matrices inversion. As used in other calculation’s methods, this work consists of a development of simulation software based on this method for simple layer planar circuits simulation. The simulations of a microstrip line and a low band filter are made. The obtained results have been analyzed and validated by comparison to results obtained by other researchers and by using a EM simulator. Sciences of electronics,technologie of information and telecommunication(2012.

After the presentation of almost periodic structures and their interest in circuits, antennas and diffraction, one focus the study on bidimensional structures which have periodic cells but non periodical patterns inside the cells. The bi-dimensional leaky waves antennas array with a central feed and the circuit in package made up with metallic via in an arbitrary arrangement are particular cases of almost-periodic structures. Two numerical methods are used for modeling the almost periodic planar structures: the method of moments and the wave concept iterative procedure.

Scale-changing technique has been successfully used for the modeling of a passive infinite reflectarray. The obtained results are successfully validated using HFSS simulation results. This technique has proven to be more time-efficient as compared to the conventional full-wave techniques especially for the geometries where greater number of scales can be defined e.g. in case of frequency selective surfaces or structures which utilize active MEMS. The scale-changing technique is intended to be used for the finite array problems in the near future to model the mutual coupling between the cells.

New multilayer configurations for dual and triple-band circularly polarized stacked microstrip antennas (CPSMA) are proposed. More than 7 dB simulated gain for both LHCP frequencies of satellite communication are obtained for the dual-band design and more than 5 dB for both LHCP and GPS RHCP for the triple-band design.

The development of an original method called Scaled Changing Technique (SCT) has led to the fast analysis of planar reconflgurable phase-shifters presenting a great number of phase states. Phase-shifters have been designed for obtaining 360 - phase-shift range and by taking into account the losses. Re∞ectarrays using Radio-frequency Micro-mechanical Switches (RF-MEMS) is an emerging technology for reconflgurable and scanning antennas. In this paper, the planar phase-shifter is composed of 3 metallic patches and 10 RF-MEMS (see Fig. 1). The up and down states of the RF-MEMS control the phase-shift by tuning the slot length. A phase-shifter cell with 10 switches presents 2 10 = 1024 available conflgurations: in order to predict the phase-shift for each conflg- uration, an electromagnetic simulation tool has been developed. This tool has been speciflcally dedicated to the study of these MEMS-controlled planar phase-shifter (1,2). Thanks to this spe- ciflc tool, the fast design of phase-shifter cells covering the overall 360 - phase-shift range has been performed.

International audience; This letter is focused on the design of thinned planar arrays achieving simultaneously the two following requirements: 1) a given beamwidth in the broadside direction and 2) a given peak side-lobe level in a specified sub-domain of the visible region. It is seen that Cantor spiral arrays are excellent candidates. Peak sidelobes of the order of -20 dB and a beamwidth of 0.6 are obtained with only 200 radiating elements.

A new approach, named the scale changing technique, is performed here for the electromagnetic modelling of reflect arrays controlled by radio-frequency micro- electromechanical switches. Based on the partition of the reflectarray surface in planar sub-domains with various scale levels, this technique derives the phase- shift dynamics from the simple cascade of networks, each network describing the electromagnetic coupling between two scale levels. Higher-order modes allow the accurate representation of the electromagnetic field local variation while lower-order modes are used for coupling the various scales.

The original Scale Changing Technique is applied to the electromagnetic modeling of MEMS-controlled phase-shifters used in reconfigurable reflectarrays. The phase shift is derived from the simple cascade of networks, each network describing the electromagnetic coupling between two scale levels. This technique allows computing quasi-instantaneously the 1024 phase-shifts achieved by 10 RF-MEMS switches distributed on the surface of the phase-shifter. Moreover sensitivity as regards of RF-MEMS switches losses are discussed. Experimental data are given for validation purposes.

A proposal is presented for new electromagnetic bandgap (EBG) ground planes in the design of planar antennas with reduced electrical size. Based on the concept of incident and reflected waves (wave concept iterative process $WCIP method) the scattering coefficients are obtained for each ground plane model. The iterative procedure applies the fast modal transform (FMT) to change the analysis between the spatial and spectral domains. The simulation results are compared with measurements and show good agreement. In the analysis of antenna resonance frequency, a reduction in antenna dimensions can be obtained. The decrease in operating resonance frequency is one of the goals in compact transmitter/receiver development.

The fast wave concept iterative process (FWCIP) and the boundary element method (BEM) are combined to evaluate the characteristic impedance of a microstrip filter, which is composed of (8×8) metallic via holes array. Simulations, measurements, and previous publications are in good agreement. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 236–246, 2002.