Reconfigurable Dual-Beam Lensing Utilizing an EBG-Based Anisotropic Impedance Surface

Tunable surface waves supported by graphene-covered left-handed material structures

Surface wave distribution over electromagnetic bandgap (EBG) plate is measured and suppression of surface wave propagation over the EBG is investigated. We used a micro current probe that detects Hfield strength of the propagating transverse magnetic (TM) microwave up to 6 GHz. By scanning with the probe over the EBG, we visualized surface wave distribution at various frequencies. This visualized map shows that the EBG plate suppresses the surface wave propagation within the bandgap frequency. We utilized this effect for the antenna reflective shield. By combining the EBG with a microstrip patch antenna, this EBG works as a reflective shield and the front-to-backward radiation ratio of antenna is increased. In this experiment, we fabricated three types of shield board: mushroom type of EBG that has hexagonal textured patches connected with via-holes, textured surface without via-holes, and plane metal. By comparing the surface wave distributions and beam patterns of antenna with various shields, we found that the visualized map of TM surface wave gives us direct and intuitive information and helpful tips in designing the EBG reflective shield for patch antenna.

Anisotropic impedance surfaces have been used to control surface wave propagation, which has benefited applications across a variety of fields including radio-frequency (RF) and optical devices, sensing, electromagnetic compatibility, wireless power transfer, and communications. However, the responses of these surfaces are fixed once they are fabricated. Although tunable impedance surfaces have been introduced by utilizing power-dependent nonlinear components, such a tuning mechanism is generally limited to specific applications. Here we propose an additional mechanism to achieve tunable anisotropic impedance surfaces by embedding transient circuits that are controllable via the type of incident waveform. By switching between the open and short states of the circuits, it is possible to separately control the unit-cell impedances in two orthogonal directions, thereby changing from an isotropic impedance surface to an anisotropic impedance surface. Our simulation results show that a short pulse strongly propagates for both x and y directions at 3GHz. However, when the waveform changes to a continuous wave, the transmittance for x direction is reduced to 26%, although still the transmittance for y direction achieves 77%. Therefore, the proposed metasurfaces are capable of guiding a surface wave in a specific direction based on the incident waveform even with the same power level and at the same frequency. Our study paves new avenues regarding the use of surface wave control in applications ranging from wireless communications to sensing and cloaking devices.

This article implements the high gain superstrate antenna and wideband bandpass microwave filter using a novel uniplanar compact Electromagnetic Bandgap (EBG) structure. The proposed EBG unitcell consists of an outer inductive grid connected to four square loops at corners separated by a center-spitted Jerusalem cross resembled dipole. The design is printed on top of a 0.8 thin Rogers RT Duroid 5880 grounded dielectric substrate. Wide bandgap behavior is observed in the intended EBG from 9.6 GHz to 12 GHz (22.22% FBW). Here, the two different applications of the proposed EBG are presented, which gain the main focus of this work, i.e., EBG loaded microstrip filter and an EBG superstrate for a microstrip patch antenna (MPA) gain enhancement. The unitcell performance is stable for different oblique incidences under Transverse Electric (TE) and Transverse Magnetic (TM) modes. Compared to the reference antenna, the EBG-loaded patch exhibits a gain improvement, and 10.95 dBi is achieved along with bandwidth improvement. The C-band is the intended operating range of a proposed EBG-based wideband filter having less than 1.05 dB Insertion Loss (IL) over the operational range 5.26-13.32 GHz or 86.86%, and its passband BW covers from 5.30 - 13.71 GHz (88.48%).

Electrical failures in avionics systems may result from connector faults. If fault precursors are not detected in advance, they may lead to hard failures such as open and short circuits that could ultimately result in fire or loss of flight critical systems. Therefore, It is crucial to detect, locate, and characterize fault precursors for timely preventive maintenance and mitigation before hard failures occur. In this paper, a physics‐based connector model consisting of multiple coaxial line sections with different characteristic impedances and lengths is proposed. Method of Moments (MoM) analyses were performed using commercial electromagnetic simulation software, FEKO, for transverse electric and magnetic (TEM) wave propagation through a connector. The physical parameters of the connector were optimized to match the measured S parameters for multiple insertion depths. The proposed models represent the connector for multiple insertion depths by varying only two length parameters at a time while other parameters are fixed. Insertion depth‐dependent resonant frequency shifts observed during measurement are also captured by the model over the full range of fully inserted to barely touching contacts. Hence, the models provide accurate representations of the connector and properly detect precursors to partial insertion faults.

Cylindrical and conical ultra-wideband (UWB) dielectric resonator antennas are presented in this paper. The first part of this work is a parametric study of cylindrical and conical dielectric resonator antennas for Ultra-Large Band applications ranging from 3.1GHz to 10.6GHz. The second part of the work consists of creating a reconfigurable rejection band inside this UWB in order to minimize interference between UWB system and some narrowband systems operating in this frequency range (3.1GHz to 10.6GHz), Such as WiMAX and WLAN. To obtain the rejection band, we etch a rectangular ring slot on the micro-strip-line-fed patch. The control of the band notch is made by displacing the cylindrical or the conical resonator. The results obtained showed that the band notch ranges from 3.2GHz to 4.7GHz for the cylindrical resonator and from 3.2GHz to 5.2GHz for the conical resonator. The proposed structures are simulated with the commercial electromagnetic simulation software “Ansoft HFSS.” The numerical results from different simulations are presented in terms of reflection coefficient and radiation pattern.

This paper reports the outcomes of an experimental investigation of the shielding effectiveness (SE) for carbon fibre reinforced polymer (CFRP) composites with varying configurations. It focuses on (1) important parameters affecting the SE of CFRP laminates and (2) applicability of the transmission line (TL) theory to predict their shielding properties. Comparison of the SE profiles showed that quasi-isotropic and cross-ply configurations perform equally well in attenuating the unpolarised radiation and only a modest increase of 10 dB is achieved by doubling the number of plies due to increased absorption. The applicability of the TL model for CFRP composites was found to be limited to thin laminates with quasi-isotropic lay-up, for which the accuracy prediction was within 5 dB in the 150 MHz-1 GHz frequency range. The experimental SE values were also compared to the full wave simulation in a commercial electromagnetic simulation software, demonstrating more accurate predictions than any analytical model.

SummaryThis paper presents a wireless local area network (WLAN) spectrum control system that uses active frequency selective shielding walls to selectively reduce or pass WLAN signals in the 5 GHz band indoors. The proposed system utilizes a well‐known active frequency selective structure based on a rectangular loop with PIN diodes and is thus capable of either reducing or passing the WLAN frequency by using the on/off switching of the PIN diode based on the measured electric field strength in indoor. We designed and simulated the proposed active frequency selective shielding wallpaper by using commercial electromagnetic simulation software and confirmed that the proposed structure can reduce the WLAN signal by switching the PIN diode by applying the manufactured prototype on the exterior of an experimental apparatus containing a WLAN receiver antenna that is capable of measuring the received electric field strength. Extension of the results presented herein can be applied to reduce the wireless signal to enhance the spectrum efficiency of an indoor space.

Breakthrough innovations in electrical machines may be limited by parametric overlays and templates provided in commercial electromagnetic simulation software. Disruptive design spaces must therefore be explored using more flexible open-source software solutions. However, a significant scripting effort is necessary to define some new parametric geometries suitable for design optimization based on open source multiphysics solvers. This article illustrates the use of Pyleecan open-source simulation software under Python to more efficiently model, evaluate and optimize disruptive topologies of 2D or 3D electrical machines. The current status of Pyleecan initiative is first presented. Then, the principle and the advantages of the object-oriented approach of electrical machines are detailed. Some examples of complex innovative topologies that can be generated with Pyleecan are then introduced (e.g. complex winding, uneven slot types, multiple rotor and stators), as well as the optimization possibilities. Finally, the development roadmap of Pyleecan project is given.

A virtually centered broad-wall longitudinal slot antenna have been designed and studied using commercial Electromagnetic Simulation Software (CST Microwave Studio). The result obtained for the S21 of such an antenna has been compared with the measured data to find the accuracy of the software. Also the results obtained for the slot have been compared with the more common offset broad-wall longitudinal slot. Different slot characteristics also have been studied by varying different slot parameters. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.

A novel electromagnetic (EM) decoupling and crosstalk reduction technique applied to hard disk drive is presented. Grooves are introduced with different depths between conductors of the trace suspension assembly interconnects (TSAI). By using commercial EM simulation software, an induced voltage from an unwanted external field on TSAI is reduced in relation with groove depth. As much as 12.5-dB decoupling is observed for 25%-75% groove depths. The crosstalk reduction obtained over 1.0 dB for 1-4 GHz frequency band is achieved and the transmission bandwidth has increased by 20% at 75% groove depth. Hence, additional grooves will strengthen the immunity of TSAI at the reader sensor against external field disturbances as well as offer an improved transmission performance.

A wide-angle, wideband, and polarization-insensitive metamaterial (MM) absorber was studied based on the theoretical concept of uniaxial perfect matching layer (UPML) in the terahertz range. The MM absorber was designed as a multi-layered anisotropic array structure consisting of a conductive VIA, a bi-layered slot-FSS, and a split-ring resonator (SRR) separated by porous silica spacers. Each component is optimized to approach the required macroscopic uniaxial property for satisfying the reflection-less boundary condition. The SRRs and VIAs were found to play an important role in maintaining large absorption when the angle of oblique incidence increases under transverse electric (TE) and transverse magnetic (TM) polarization, respectively. The absorption achieves 90% in the frequency regime of 0.9 to 10.5 THz, corresponding to a bandwidth of 168% to the central frequency, and retains such high performance up to 60° oblique incidence for both TE and TM waves.

This study examines the analytical and numerical solution of electromagnetic surface waves supported by a resistive metasurface-covered grounded metamaterial structure. To simulate the metamaterial, the Kramers–Kronig relation based on the causality principle is used, while the modeling of the resistive metasurface has been done by implementing the impedance boundary conditions. The analytical expressions for the field phasors of surface waves are developed for the transverse magnetic (TM) polarized mode and transverse electric (TE) polarized mode. The characteristic equations are computed for both modes, and the unknown propagation constant is evaluated numerically in the kernel. After computation, the dispersion curves, electric field profiles, effective mode index (N_{eff}), and phase speeds (v_{p}) are presented for both the TM and TE polarized modes. To study the tunability of surface waves, the influence of the thickness of the metamaterial slab (d), effective permittivity of the metamaterial (varepsilon_{1}), thickness of the resistive metasurface (t), and effective permittivity of the metasurface (varepsilon_{r}) on all the numerical results has been studied. However, the geometrical parameters are found to be more sensitive to the effective mode index (N_{eff}) and phase speed (v_{p}) of the surface waves. The results are consistent with the published results, which reflects the accuracy of the work. It is concluded that the appropriate choice of parameters can be used to achieve surface waves with the desired characteristics in the GHz range. The present work may have potential applications in surface waveguide design, surface wave speed controllers, surface communication devices, and light trapping configurations.

A multiband, polarization-controlled energy harvesting metasurface is presented in this article for harvesting electromagnetic energy in the Wi-Fi bands. Inspired by the split-ring resonator (SRR), a metasurface of SRRs is designed by nesting multiple SRRs together. The novelty of the design lies in the controllable multiband polarization and adjustable absorption frequency, so as to achieve the active modulation of energy harvesting on the metasurface at different frequencies. The metasurface is composed of a periodic array of SRRs unit cells, an impedance-matched rectifier, and a load. Metasurface arrays and rectifier integration are proposed to reduce power losses, while the channels formed by the array enhance energy density and improve the ability to capture energy. Moreover, the design for the rectifier is capable of rectifying RF energy from multiple Wi-Fi bands simultaneously at low input RF power density. The finite array of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\times $ </tex-math></inline-formula> 5 SRRs absorber is fabricated and tested. Measurements in an anechoic chamber show that the fabricated prototype reaches the efficiency of 66.5% at 2.4 GHz, 40.6% at 5.2 GHz, 35.6% at 5.8 GHz under transverse electric (TE) polarization, and 38.3% at 5.3 GHz under transverse magnetic (TM) polarization when the incident power density is greater than 66 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

In the paper, we present a straightforward procedure to utilize random rough surfaces with Gaussian probability distribution in commercial full-wave electromagnetic simulation software CST Microwave Studio. Random, two dimensional (2D) matrices with desired size and statistical parameters such as correlation length and root mean square height of the profile are generated in MATLAB®. In order to obtain desired surface parameters, we employ a Gaussian random 2D matrix generator and subsequent filtering with Gaussian 2D filter. A macro in Visual Basic for Application is then developed to convert these matrices into continuous surfaces in CST MWS. Radiation patterns of horizontally and vertically polarized half-wave dipoles are finally evaluated above these surfaces and compared to analytical models.