Sheet Impedance Research Articles

Solution-Processed Metallic Nanowire Network for Wearable Transparent Thermal Radiation Shield.

Heating requirements for residential and commercial dwellings result in significant energy consumption and deleterious environmental effects. Personal radiative thermal management textiles regulate the wearer's body temperature by controlling the material's intrinsic optical properties. Passive heating textiles suppress radiative heat losses and therefore significantly reduce the energy consumption required for building heating systems. Guided by an optical theoretical approach, a transparent radiation shield (TRS) is designed based on silver nanowires (AgNWs) that can suppress human body heat with simultaneous visible light transmittance anticipated for practical fabrics. We experimentally demonstrated a TRS with large infrared light reflectance (low emissivity of 35%) and a visible (VIS) transparency value of 75% (400-800 nm). The results are well corroborated by the Mie scattering theory and the wire-mesh equivalent sheet impedance model, which provide fundamental mechanism understanding and guidance toward higher performance. The TRS is fabricated by a simple, solution-processing method with thermoplastic elastomer protective layers, granting notable stretching capabilities, mechanical robustness, and conformability to any body shape or object. The rigorous theoretical strategy enables the scalable synthesis of low-emissivity and visibly transparent textiles for personal thermal comfort.

FSS based high gain optically transparent MIMO antenna for Sub-6 GHz 5G mid-band applications

A novel optically transparent Multi Input Multi Output (MIMO) antenna design positioned on a Frequency-Selective Surface (FSS) for gain improvement while maintaining a simple fabrication procedure. Transparent conductive materials inherently exhibit higher sheet impedance due to lower conductivity, resulting in decreased antenna gain and radiation efficiency. To address this limitation, an optically transparent FSS is incorporated beneath the MIMO structure to improve radiation characteristics. Utilizing a Malinex substrate and a conductive silver oxide sheet, the 4-element MIMO design achieves both transparency and MIMO operability. The operational bandwidth spans from 3.09 GHz to 3.7 GHz, with a percentage bandwidth of 17.96 %, ensuring port isolation of over 20 dB. With the presence of the FSS, a consistent gain enhancement of approximately 3.46 dBi is achieved, with an average gain within the band reaching 4.56 dBi. The proposed design employs a simplified fabrication process while addressing aesthetic concerns and providing a solution to the existing issue of low gain in conductive metal oxide-based transparent antennas.

Ultrathin MXene film interaction with electromagnetic radiation in the microwave range

The quick progress in communication technologies demands superior electromagnetic interference (EMI) shielding materials. However, achieving a high shielding effectiveness (SE) with thin films, which is needed for microscale, flexible, and wearable devices, through absorption of EM radiation remains a challenge. 2D titanium carbide MXene, Ti3C2Tx, has been shown to efficiently reflect electromagnetic waves. In this paper, we investigated the electromagnetic shielding of ultrathin printed Ti3C2Tx films and recorded absorption up to 50% for 4 nm-thick films. This behavior is explained by impedance matching. Analysis of the sheet impedance in the X-band frequency range allows us to correlate the EMI shielding mechanism with the electrical conductivity measured within the same range. The average bulk in-plane conductivity for 4 to 40 nm-thick films reaches 106 S/m, while the average relaxation time is estimated at around 2.3 ps. Our figures of merit are similar to those reported for ultrathin metal films, such as gold, showing that an abundant MXene material can replace noble metals. We demonstrate that the MXene conductivity mechanism does not change from direct current to THz. The conventional method of reporting EMI SE is correlated with absolute values of transmitted, reflected, and absorbed power, which allows us to interpret previous results on MXene EMI shielding. Considering the easy deposition of thin MXenes films from solution onto a variety of surfaces, our findings offer an attractive alternative for shielding microscale devices and personal electronics.

Bianisotropic Metasurface for Spatial Separation of Multiple Harmonic Waves

An approach to tuning harmonic responses of surface impedance is introduced to spatially separate fundamental, third-harmonic, and fifth-harmonic waves by focusing on the physical implementation perspective. The concept of the bianisotropic metasurface is adopted to refract the wave toward different angles by assigning identical phase gradients at fundamental and third-harmonic frequencies. On the other hand, high-sheet impedance is realized by maintaining the in-phase condition at the fifth harmonic to bypass the incident wave without refraction. The target properties of each unit cell are implemented using I-shaped patterns based on a three-stacked-layer topology. Different sizes and intervals are applied for the I-shaped patterns, and only their horizontal lengths are tuned to achieve the desired sheet impedances. The feasibility of the proposed approach is validated for the fundamental frequency of 10 GHz and two of odd harmonics through far-and near-field measurements. The results confirm that the fabricated metasurface separates the superimposed harmonic waves toward 44 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> , 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> , and 0 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> with the measured refraction efficiencies of 65.6%, 67.2%, and 74% at 10, 30, and 50 GHz, respectively.

A systematic approach for reconfigurable reflecting metasurface synthesis: From periodic analysis to far-field scattering

We present a consistent approach for a systematic design of an intelligent reflecting surface (IRS), based on a new unit cell with efficient reconfigurability functionalities and a three-step electromagnetic methodology for a rigorous IRS synthesis. First, we design and simulate a reconfigurable unit cell, in which the reconfigurability is accomplished by varactor diodes. Next, we model the IRS as a periodic structure of infinite size, according to Floquet theory. By utilizing the theory of anomalous reflection, we arrive at approximate analytical solutions to calculate the set of necessary varactor diodes’ capacitances, which is subsequently fine-tuned by a fast optimization process to achieve enhanced operation. Finally, to arrive at a more realistic design, we properly analyze the IRS as a finite-sized structure. To this end, we employ an efficient finite element method (FEM) analysis, with a properly developed simulation tool, in which the IRS is modeled as an equivalent impedance sheet of zero-thickness. Overall, we extract the far-field scattered pattern of the IRS and evaluate the angular and frequency response of the design for normal and oblique incidence. Our results show that the proposed design exhibits very promising characteristics, both in terms of reconfigurability and frequency response that can be exploited in contemporary and future wireless communication systems.

Impedance models for single and two degree of freedom linings with an improved data base and local non-linearity

Previously developed predictive models for impedance of single-degree-of-freedom and two-degree-of-freedom acoustic linings driven by a broad band acoustic source are reexamined. Two issues are addressed, the first being improvement of the conventional perforate face sheet impedance model. Data correlations based on flow bench measurements of steady flow pressure drop are reevaluated with emphasis on low flow velocity to improve the consistency of the prediction of linear resistance. In addition, for two-degree-of-freedom linings, face sheet mass reactance is modified to account for the presence of the septum. The second issue addresses the implication that for a non-linear lining, with impedance a function of the local sound pressure level, the installed performance of the lining depends on the local impedance, as opposed to impedance based on the source sound pressure level. This is investigated in the benchmarking of the impedance models by comparison of the acoustic transfer function predicted by a propagation code with the imbedded impedance model and transfer function measurements made in a grazing flow duct test facility. The propagation code is extended to make the non-linear behavior of the lining model dependent on the local acoustic spectrum, introducing an additional level of non-linearity and an iterative application of the propagation code. A principal conclusion is that with no grazing flow both the lining model and grazing flow duct transfer function measurements show a significant effect of local variation of the acoustic spectrum. With increasing grazing flow Mach number, this effect is reduced and effectively disappears at the highest Mach number. With increasing grazing flow Mach number the grazing flow contribution to face sheet resistance dominates and tends to mask the non-linear behavior of the component of resistance not related to grazing flow.

Multiple-Beam Steering Using Graphene-Based Coding Metasurfaces.

Recently, the coding metasurface has gained significant attention due to its exceptional potential in controlling electromagnetic (EM) waves with the rapid development of wireless communication systems. Meanwhile, graphene shows tremendous promise for the implementation of reconfigurable antennas due to its high tunable conductivity and its unique property that makes it a very suitable material for realizing steerable coded states. In this paper, we first propose a simple structured beam reconfigurable millimeter wave (MMW) antenna using a novel graphene-based coding metasurface (GBCM). Different from the previous method, its coding state can be manipulated by altering the sheet impedance of graphene instead of bias voltage. Then, we design and simulate several most popular coding sequences, including dual-, quad-and single-beam-generated implement, 30° beam deflection, as well as a random coding sequence for radar cross-section (RCS) reduction. The theoretical and simulation results show that graphene has great potential for MMW manipulation applications, which lay a foundation for the subsequent development and fabrication of GBCM.

Perfectly conducting cylinder covered by two layers of dielectric separated by an infinitely thin impedance layer: multiple suppression of the scattered field harmonics (rigorous approach).

We propose and develop a novel rigorous technique that enables one to obtain the explicit numerical values of parameters at which several lowest-order harmonics of the scattered field are suppressed. This provides partial cloaking of the object, a perfectly conducting cylinder of circular cross section covered by two layers of dielectric separated by an infinitely thin impedance layer, a two-layer impedance Goubau line (GL). The developed approach is a rigorous method that enables one to obtain in the closed form (and without numerical calculations) the values of parameters providing the cloaking effect, achieved particularly in terms of the suppression of several scattered field harmonics and variation of the sheet impedance. This issue constitutes the novelty of the accomplished study. The elaborated technique could be applied to validate the results obtained by commercial solvers with virtually no limitations on the parameter ranges, i.e., use it as a benchmark. The determination of the cloaking parameters is straightforward and does not require computations. We perform comprehensive visualization and analysis of the achieved partial cloaking. The developed parameter-continuation technique enables one to increase the number of the suppressed scattered-field harmonics by appropriate choice of the impedance. The method can be extended to any dielectric-layered impedance structures possessing circular or planar symmetry.

Metasurface Antennas Design: Full-Wave Feeder Modeling and Far-Field Optimization

This article addresses the optimization of the radiation pattern of surface-wave (SW)-based metasurface (MTS) antennas. Those antennas are considered a promising alternative to parabolic reflectors and phased arrays due to their extremely low profile and their ability to provide high gain, shaped beams and multibeams. However, pattern synthesis with MTS antennas is very challenging because of the single active control point and the need to control surface and leaky waves through the MTS. An accurate optimization of the radiation pattern, along with the sidelobe level requires full-wave modeling of the feeding structure, including its coupling with the MTS. MTS synthesis methods existing in the literature usually approximate the feeder model, and neglect its coupling with the MTS. Such approximation may lead to more than 1 dB error in the predicted antenna directivity. This article presents a technique for optimization of the far-field pattern, built on a Method of Moments (MoM) analysis tool in which the MTS coupling with the feeder, a coax probe, is fully considered. The MTS is modeled as an arbitrarily shaped, spatially modulated electric sheet impedance in a layered medium. At each optimization iteration, the complexity of the underlying analysis is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {O}(\text {N}\log \text {N})$ </tex-math></inline-formula> owing to the use of a fast Fourier transforms (FFT)-based acceleration. The effectiveness of the method is demonstrated through the optimization of MTSs radiating a pencil beam and a conical beam with orbital angular momentum (OAM).

Metasurface-Loaded Off-Center Monopoles With Wideband Radiation Performance Using Characteristic Mode Analysis

A metasurface (MTS)-based reactive impedance surface (RIS) is proposed to load an eccentrically placed monopole above a ground plane for controllable wideband omnidirectional radiation. With the off-center placement, the radiation pattern of the monopole is not omnidirectional anymore, with ripples in the H-plane measured by un-roundness. The RIS is introduced above and in parallel with the finite ground plane and the monopole is placed in the center of the RIS. Characteristic mode analysis (CMA) is used to analyze the RIS-loaded monopole and to reveal the mechanism. It is found that two desired modes determine the bandwidth of the omnidirectional radiation together. The resonant frequency of the RIS mode can be easily tuned by changing the sheet impedance of the RIS. A metal-dielectric-metal constructed MTS is proposed to realize the RIS. The grid impedance of the MTS can be tuned easily by changing the size of the patch in the unit cell. For a single monopole placed off-center above a rectangular ground plane (150 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times300$ </tex-math></inline-formula> mm), the impedance bandwidth is increased from 19.6% to 32.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert &lt; -10$ </tex-math></inline-formula> dB at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0} =2.5$ </tex-math></inline-formula> GHz. And the maximum un-roundness is reduced by 66.7% from 4.8 to 1.6 dB over the frequency band of 2.2–2.8 GHz. For a two-monopole antenna system with the same ground plane mentioned above, the loading MTS increases the impedance bandwidth of the monopole from 19.2% to 32.4% with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert &lt; -10$ </tex-math></inline-formula> dB at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0} =2.5$ </tex-math></inline-formula> GHz. When only one monopole is loaded with MTS in the system, the maximum un-roundness is reduced by 65.5% from 5.5 to 1.9 dB in the frequency band of 2.2–2.8 GHz. When both monopoles are loaded with MTS in the system, the maximum un-roundness is reduced by 40% from 5.5 to 3.3 dB in the frequency band of 2.2–2.8 GHz. The antenna prototypes are fabricated and measured.

Electromagnetic Characterization of Thin Films by Using Non-Contacting Waveguides

Surface impedance represents a crucial parameter for the characterization of thin films. Indeed, materials with a sheet impedance varying as a function of their elongation could be used in radio frequency piezoresistive sensors. To estimate this quantity while having the possibility of stretching the sample under test, a waveguide-based non-contact approach is proposed. The absence of contact between the sample under test and the waveguides determines an electromagnetic field leakage, which is prevented by adopting an electromagnetic band gap (EBG) structure. The surface impedance of the sample is retrieved through an inversion procedure exploiting the scattering parameters measured using the proposed setup. The inversion procedure is based on a circuit representation of the waveguide-air-waveguide Section as a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> -junction. The reliability of the proposed measurement method has been experimentally assessed using a WR137 waveguide. The proposed method allows to accurately determine the real part of surface impedance (the sheet resistance), while higher uncertainty is achieved in the estimation of the imaginary part.

Direct Numerical Inversion Methods for the Design of Surface Wave-Based Metasurface Antennas: Fundamentals, Realizations, and Perspectives

A recent synthesis paradigm for tailoring the far-field radiation of leaky wave (LW) radiating metasurface (MTS) antennas is reviewed and experimentally validated. The considered antennas are realized with electrically small patches printed on a planar grounded dielectric slab. The patch layer is modeled as an impedance sheet whose spatial variation is initially designed to provide the desired LW effect from a prespecified surface wave (SW) excitation.

A Combined Machine-Learning/Optimization-Based Approach for Inverse Design of Nonuniform Bianisotropic Metasurfaces

Electromagnetic metasurface design based on far-field constraints without the complete knowledge of the fields on both sides of the metasurface is typically a time consuming and iterative process, which relies heavily on heuristics and ad hoc methods. This paper proposes an end-to-end systematic and efficient approach where the designer inputs high-level far-field constraints such as nulls, sidelobe levels, and main beam level(s); and a 3-layer non-uniform passive, lossless, omega-type bianisotropic electromagnetic metasurface design to satisfy them is returned. The surface parameters to realize the far-field criteria are found using the alternating direction method of multipliers on a homogenized model derived from the method of moments. This model incorporates edge effects of the finite surface and mutual coupling in the inhomogeneous impedance sheet. Optimization through the physical unit cell space integrated with machine learning-based surrogate models is used to realize the desired surface parameters from physical meta-atom (or unit cell) designs. Two passive lossless examples with different feeding systems and far-field constraints are shown to demonstrate the effectiveness of this method.

Multi-Modal Scattering and Propagation Through Several Close Periodic Grids

The presented method describes reflection and transmission of electromagnetic waves at multiple closely stacked metal grids using multimodal S-parameter propagation. For that, the periodic surface admittance curve of every metal layer was determined through a novel semianalytic approach that uses simple Fourier transformations instead of solving an integral equation. The modal components of this surface admittance were used to express the generalized scattering matrices of the individual grids. By applying multimodal propagation techniques to the resulting scattering parameters, it was possible to model the electromagnetic interactions within a multilayer stack of periodic impedance sheets. Resulting reflection and transmission parameters perfectly matched the corresponding full-wave simulations even above the grating lobe regime. In the end, the universal mode propagation method enabled modeling of a layer stack, connected to lumped components.

Conformal and polarization adjustable cloaking metasurface utilizing graphene with low radar cross section for terahertz applications

Metamaterials with precisely chosen negative permittivity and permeability are preferable to cloak the target without scattering. In this work, a metasurface is designed by using graphene as conducting material to cloak a target cylinder under the instancing of TM and TE polarized waves in terahertz range of frequencies. The electric sheet impedance and magnetic sheet admittance played the crucial role to achieve the cloaking with good scattering reduction. Various incident angles are simulated and analyzed for obtaining the good radar cross section (RCS). The proposed metasurface resonates at three different frequencies in terahertz range of 3.8 THz, 9 THz and 13.8 THz and the bandwidth of the three resonating frequencies are 3.5–4.58 THZ, 8.8–9.5 THz and 13–14.98 THz respectively. In addition, the parametric analysis of chemical potential and relaxation time shows effective results in scattering reduction. The monostatic and bistatic RCS are simulated, which results high scattering reduction under different polarizations of different incident angles. The proposed structure is adjustable to various angle of incidence with less than 40 dB scattering reduction for various selected frequencies.

The Design of Dual Band Stacked Metasurfaces Using Integral Equations

An integral equation-based approach for the design of dual band stacked metasurfaces which are invariant in one-dimension is presented. The stacked metasurface will generate collimated beams at desired angles in each band upon reflection. The conductor-backed stacked metasurface consists of two metasurfaces (a patterned metallic cladding supported by a dielectric spacer) stacked one upon the other. The stacked metasurface is designed in three phases. First the patterned metallic cladding of each metasurface is homogenized and modeled as an inhomogeneous impedance sheet. An Electric Field Integral Equation (EFIE) is written to model the mutual coupling between the homogenized elements within each metasurface, and from metasurface to metasurface. The EFIE is transformed into matrix equations by the method of moments. The nonlinear matrix equations are solved at both bands iteratively resulting in dual band complex-valued impedance sheets. In the second phase, optimization is applied to transform these complex-valued impedance sheets into purely reactive sheets suitable for printed circuit board fabrication by introducing surface waves. In the third phase, the metallic claddings of each metasurface are patterned for full-wave simulation of the dual band stacked metasurface. Using this approach, two dual band stacked metasurfaces are designed

An Optically Transparent Metantenna for RF Wireless Energy Harvesting

We propose a novel transparent metasurface antenna (metantenna) based on indium tin oxide (ITO) material for simultaneously achieving wireless energy harvesting (WEH) at radio frequency (RF) bands and efficient transmission of visible light. We adopt the design method of aperture-coupled metantenna to realize broadband and low-profile RF WEH. Then, we replace the conventional opaque metal material with an ITO coating with a sheet impedance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\Omega $ </tex-math></inline-formula> /sq to achieve the transparency of the proposed design. In order to obtain the balance between electrical performance and optical transmittivity (OT), we modify the metasurface structure to further improve the OT of the metantenna. The fabricated transparent metantenna shows an OT of more than 50%. A measured impedance bandwidth of 43.6% from 1.40 to 2.18 GHz is obtained to cover 2G and 3G wireless communication bands. Through designing the broadband rectifying circuit and the energy management circuit, we can obtain the maximum RF-dc efficiency of 65% and a stable dc output voltage of 3.4V, while the overall RF energy harvesting efficiency could reach 14.5% with the power input of 0 dBm. In addition, through the solar energy harvesting test, we can demonstrate the potential of the proposed design to work with solar panels for realizing efficient RF/solar hybrid energy harvesting.

A Metasurface Radar Monopulse Antenna

This article presents the design, fabrication, and testing of a modulated metasurface (MTS) antenna for monopulse radar tracking at Ka-band. The antenna consists of a circular, thin grounded dielectric layer printed by a texture of metallic patches modulated in shape and size. The patch layer can be modeled as a spatially variable capacitive impedance sheet, which together with the grounded slab contribution provides an overall, modulated, inductive boundary condition (BC). The antenna aperture is divided into four identical angular quadrants each of them radiating independent broadside beams when excited by an individual monopole launcher. Each of the four launchers excites a TM cylindrical surface wave (SW), which is progressively converted into a leaky-wave (LW) by the MTS. The four subapertures are virtually separated by properly designing the MTS modulation. To this end, the LW attenuation constant is calibrated for dumping sufficiently each individual SW, thus preventing the interaction between the adjacent regions. Therefore, the printed structure is not delimited by any physical separation, but only by a continuous change of the equivalent BCs. The monopulse-type linearly polarized <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Sigma $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \Delta $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta _{\mathrm{ E}}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta _{\mathrm{ H}}$ </tex-math></inline-formula> beams are obtained by combining the source excitation with a simple phasing scheme. Notably, this solution does not affect the overall lightness, low profile, feed simplicity, and low fabrication cost of the structure, which constitutes an inherent advantage with respect to more traditional waveguide-based solutions.

Efficient Analysis of Planar, Arbitrarily Shaped, and (Bi)-Anisotropic Metasurface Antennas

An efficient method of moments (MoM) scheme is presented for the analysis of planar, possibly cascaded metasurfaces (MTSs) implementing high-impedance surfaces. The MTS can be designed on an arbitrarily shaped domain and is accounted for as a set of cascaded electric sheet impedances. In the proposed method, the shaped MTS is included in a larger rectangular domain meshed with rooftop basis functions, resulting in a Toeplitz–block Toeplitz structure for the substrate impedance matrix, which enables fast Fourier transform (FFT)-based acceleration of matrix–vector products. The basis functions lying in the rectangular domain but outside the MTS are disabled by including zeros in the impedance matrix. The obtained linear system of equations is well conditioned, does not require any specific near-field treatment, and can be solved iteratively using the generalized minimal residual (GMRES) method. It has been demonstrated that the algorithm is able to handle efficiently any MTS antenna shape in single-layer or multilayer configuration with almost linear complexity. It is shown that the high-impedance sheets improve the convergence rate. MTSs with more than 40 wavelengths size, meshed with more than 1 million basis functions, can be analyzed on a conventional computer in less than 15 min. A very good agreement is shown through comparison with results from other software packages.

EBG waveguides for contactless surface impedance measurements

A method for the estimation of sheet impedance of thin sample which does not require a direct contact with the sample under test is proposed. The surface impedance is calculated through an inversion procedure exploiting the scattering parameters obtained through a waveguide measurement setup. An inversion procedure based on the representation of the waveguide-air-waveguide section as a π junction is employed. In order to prevent the field leakage from the air gap created for hosting the thin sheet, an EBG surface is introduced on the flange of the waveguide. It is shown that the introduction of the EBG surface remarkably improves the estimation of the surface impedance of the thin sheet with respect to the case without EBG.