Showing papers in "Journal of Electromagnetic Waves and Applications in 2009"
TL;DR: In this article, the authors used single negative metamaterials to reduce the electromagnetic interaction between the mobile phone and human head to reduce specific absorption rate (SAR) in the head.
Abstract: In this paper, we use single negative metamaterials to reduce the electromagnetic interaction between the mobile phone and human head. The specific absorption rate (SAR) in the head can be reduced by placing the metamaterials between the antenna and the head. We design the single negative metamaterials from periodic arrangement of split ring resonators (SRRs), spiral resonators (SRs) and open split ring resonators (OSRRs). By properly designing structural parameters of SRRs, the effective medium parameter can be trade negative around 900 MHz and 1800 MHz bands. The design procedure and principle operation of resonators are explained. The performance and size comparison of resonators will be described. Numerical results of the SAR values in the human head with the presence of resonators exhibit SAR reduction. These results can provide useful information in designing safety mobile communication equipments compliant.
73 citations
TL;DR: In this paper, a frequency selective surface (FSS) reflector was used for 4×2 dipole array antenna to reduce radar cross section (RCS) out of operating band.
Abstract: This paper investigates the application of a novel frequency selective surface (FSS) reflector for 4×2 dipole array antenna to reduce radar cross section (RCS) out of operating band. The proposed FSS adopting a regular hexagon quasi-fractal structure has good bandstop characteristic. By replacing the metal reflector with this bandstop FSS sheet, the in-band radiation performance of the proposed array antenna is preserved, while the out-of-band backward RCS is significantly reduced. Due to the good angle stability of the given FSS, the monostatic RCS peaks at oblique angle ( = 60°, ϕ = 0°) are also controlled. The measured results demonstrate the feasibility of antenna RCS reduction by this method.
64 citations
TL;DR: In this paper, a planar zero-index metamaterial, which can be easily fabricated and can be used to enhance the directivity of antennas, was designed and evaluated.
Abstract: In this paper, a planar zero-index metamaterial, which can be easily fabricated, was designed. Both the simulation and experimental results show that a zero index of refraction occurred at 8.75 GHz. The zero index of refraction can be used to enhance the directivity of antennas. We used a dipole antenna embedded in this metamaterial and found that the directivity of the antenna was effectively enhanced compared with the case without this metamaterial.
53 citations
TL;DR: In this article, a novel and simple dual-frequency Wilkinson power divider is proposed, which consists of a section of transmission line and a parallel stub at the input port to satisfy the dual- frequency characteristic.
Abstract: In this article, a novel and simple dual-frequency Wilkinson power divider is proposed. Considering that there is only one section of transmission line linking the input port and the output port directly as a part of the transformer, this power divider is very compact. To satisfy the dual-frequency characteristic, the traditional quarter-wavelength transformer is replaced by the structure which consists of a section of transmission line and a parallel stub at the input port. Besides, in order to obtain the ideal isolation with keeping the ideal matching at the output ports, a resistorr R and series LC components are added. Furthermore, closed-form design equations of this proposed power divider are obtained to simplify the design procedure. The simulation results of four examples indicate that all the features of the power divider can be fulfilled at dual-frequency simultaneously. Furthermore, measurement results of a fabricated power divider operating at 1 GHz and 4 GHz verify the design concept of this ...
53 citations
TL;DR: In this paper, an image reconstruction technique in which conductivity and permeability are calculated by an inverse edge finite element scheme is presented, which can be used to reconstruct all PEP parameters.
Abstract: Magnetic induction tomography (MIT) attempts to image the passive electromagnetic properties (PEP) of an object by measuring the mutual inductances between pairs of coils placed around its periphery. It has been shown that the MIT data contain information that can be used to reconstruct all PEP parameters. In general PEP includes complex conductivity and permeability. This paper presents an image reconstruction technique in which conductivity and permeability are calculated by an inverse edge finite element scheme. The simultaneous reconstruction presented here will enhance scope of application of MIT technique.
50 citations
TL;DR: Simulation of two different coupling mechanisms used in the wireless electricity transfer shows that the resonant near-field coupling is usually more efficient than the inductive coupling for the middle-distance electricity transfer.
Abstract: Wireless electricity transfer is an emerging technology for the future power supply system. In this paper, we simulate two different coupling mechanisms used in the wireless electricity transfer: the inductive coupling and resonant near-field coupling. Equivalent circuits are extracted to simulate their transfer efficiencies. To achieve the maximum transfer efficiency, the optimized frequencies are derived for two mechanisms. There is good agreement between simulation results and measurement results. By comparing their transfer efficiencies, it shows that the resonant near-field coupling is usually more efficient than the inductive coupling for the middle-distance electricity transfer.
45 citations
TL;DR: In this article, a dual-band bandpass filter (BPF) using inverted stepped impedance resonators has been proposed, where the conventional half-wavelength open-circuited stub single-frequency resonators are replaced with dualband simple two-section stepped impedance configurations.
Abstract: This paper presents a new dual-band bandpass filter (BPF) using inverted stepped impedance resonators. In the proposed filter configuration, the conventional half-wavelength open-circuited stub single-frequency resonators are replaced with dual-band simple two-section stepped impedance configurations. Simple equations to design the dual-band stepped impedance resonators are derived using transmission line analysis. The filter structure is investigated using a full wave electromagnetic (EM) simulator and then realized at 2.5 GHz and 3.55 GHz bands. Experiments have also been done to validate the design concept. The distinguished dual-band performance of the proposed design is verified by the simulation and measurement results.
38 citations
TL;DR: In this paper, a miniaturized Wilkinson power divider (WPD) using nonuniform transmission lines theory is presented, where the normalized width w(z)/h function of the NTLs which is expanded in a truncated Fourier series is used for optimization.
Abstract: A miniaturized Wilkinson power divider (WPD) using nonuniform transmission lines theory is presented in this letter. In the proposed design, we use nonuniform transmission lines instead of uniform transmission lines (UTLs) in each arm of WPD. The normalized width w(z)/h function of the NTLs which is expanded in a truncated Fourier series is used for optimization. A 500-MHz power divider is designed, fabricated and measured. The measurement results are in good agreement with the simulation results. The proposed divider's size has been reduced up to 52% in comparison with that of the conventional WPDs.
35 citations
TL;DR: In this article, a novel method is proposed to design wideband bandpass filters with compact size, combining half mode substrate integrated waveguide (HMSIW) and periodic dumbbell-shaped defected ground structure (DGS).
Abstract: In this paper, a novel method is proposed to design wideband bandpass filters with compact size. Combining half mode substrate integrated waveguide (HMSIW) and periodic dumbbell-shaped defected ground structure (DGS), two compact wideband bandpass filters with different HMSIW-microstrip transitions are fabricated and measured. The filters are found to possess wide passband bandwidth and compact size. Good agreement between the measured and simulated results demonstrates the validity of this technique.
35 citations
TL;DR: In this article, a theoretical analysis of optical reflection for a dielectric chirped distributed Bragg reflector (DBR) is presented, which is modeled by several sub-DBRs stacked successively with differ optical reflectors.
Abstract: A theoretical analysis of optical reflection for a dielectric chirped distributed Bragg reflector (DBR) is presented The chirped DBR is modeled by several sub-DBRs stacked successively with differ
34 citations
TL;DR: From the simulation results, spatial diversity and polarization diversity are found to be better than all other aforementioned approaches.
Abstract: Radio-frequency identification (RFID) blind spots are the regions within the maximum operating range of the RFID system where the RFID reader fails to read the RFID tag. The existence of blind spots have troubled supply chain management and RFID system engineers because any failed or omitted reading of RFID tag would slow down the inventory tracking process. This paper studies the potential locations of blind spots as well as the effectiveness of several blind spots remedy methods such as frequency diversity, spatial diversity, polarization diversity, and antenna beam steering. Using the blind spots creation approach introduced in this paper, the locations of the blind spots can be calculated and visualized. From our simulation results, spatial diversity and polarization diversity are found to be better than all other aforementioned approaches.
TL;DR: In this paper, a 3 dB power divider based on dual-composite right/left handed transmission line (D-CRLH TL) is proposed for the first time.
Abstract: A novel 3 dB power divider based on dual-composite right/left handed transmission line (D-CRLH TL) is proposed for the first time. The D-CRLH TLs are applied as artificial transmission lines. The wideband compact D-CRLH power divider is with low insertion loss and excellent amplitude and phase balance. The experimental results show that |S 11| is below −15 dB; the isolation is higher than 15 dB; and the insertion loss is less than 1 dB from 0.85 GHz to 4.3 GHz. The two output ports achieve the same amplitude and phase. The amplitude balance is below 0.3 dB, and the phase balance is less than 3°. The simulation results agree well with the measurements. The power divider has good application prospects in microwave systems.
TL;DR: The design and analysis of a dual-band equal-split Wilkinson power divider, which fulfills all the features of a conventional Wilkinson powerdivider, such as an equal power split and impedance matching at ports is presented.
Abstract: The design and analysis of a dual-band equal-split Wilkinson power divider are presented in this paper. The structure of the power divider and the formulas used to determine the design parameters have been given. The divider has two output ports shifted away from the isolation resistor to the open stub. As a result, the bandwidth can be enhanced obviously for small band-ratios. Closed-form design equations are derived using even- and odd-mode formulation. For verification, a microwave power divider operating at 1 and 2 GHz is fabricated, the experimental results show that the designed power divider fulfills all the features of a conventional Wilkinson power divider, such as an equal power split and impedance matching at ports.
Abstract: This paper studies optical solitons by the method of Lie group analysis. The stationary 1-soliton solution is obtained for the nonlinear Schrodinger's equation with parabolic and dual-power law nonlinearity.
TL;DR: An improved method for estimating 2D DOA with L-shaped array based on shift invariance property is presented, which has much better 2D-DOA estimation performance than conventional ESPRIT algorithm, and it can identify more DOAs thanventional ESPR IT algorithm.
Abstract: In this paper, we address the problem of bind 2D Direction Of Arrival (DOA) estimation with L-shaped array. Based on shift invariance property, an improved method for estimating 2D DOA is presented. The algorithm uses the array geometries to construct a matrix and then obtain the required signal subspace via the eigen decomposition of the constructed matrix. This algorithm works well without spectral peak searching. Our algorithm has much better 2D-DOA estimation performance than conventional ESPRIT algorithm, and it can identify more DOAs than conventional ESPRIT algorithm.
TL;DR: In this paper, a planar Artificial Magnetic Conductor (AMC) based on a Frequency Selective Surface (FSS) for frequencies in the SHF RFID band is presented.
Abstract: A novel design of planar Artificial Magnetic Conductor (AMC) based on a Frequency Selective Surface (FSS) for frequencies in the SHF RFID band is presented. A discussion about design parameters and the influence of dielectric substrate thickness on the operating band and on the bandwidth is analyzed. The designed AMC shows polarization angle independency. Its angular margin when operating under oblique incidence is also tested. The discussion is supported by a FEM simulation and measurements in anechoic chamber of the manufactured prototype, with a good agreement between simulations and measurements.
TL;DR: Differential Evolution is employed to optimize the geometric parameters of Yagi-Uda antennas to show that the DE is a robust and useful optimization tool for designing antennas.
Abstract: Differential Evolution (DE) can solve multi-objective optimization problem in an extremely efficient manner. Based on thin wire modeling, method of moments code is developed for evaluating the antenna designs. DE is employed to optimize the geometric parameters of Yagi-Uda antennas. The length and spacing of Yagi-Uda antennas are optimized variables. The results clearly show that the DE is a robust and useful optimization tool for designing antennas.
TL;DR: In this paper, it is shown that the required feeding networks can be further simplified by keeping the elements at the edges of the array with common excitations for both sum and difference patterns.
Abstract: Given a linear antenna array with an excitation distribution affording an optimal sum pattern, subarray weighting allows the same array also to generate a difference pattern, with minimal alteration of the signal feed circuitry. In this approach, it is not necessary to consider the whole array for subarraying: We report that the required feeding networks can be further simplified by keeping the elements at the edges of the array with common excitations for both sum and difference patterns.
TL;DR: In this paper, the spatial characteristics of the ionospheric clutter in a planar array are analyzed, then a new orthogonal projection method with eigenvalue decomposition (EVD) is proposed.
Abstract: The ionospheric clutter has been proved to be one of the dominant clutters degrading the performance of the HF surface-wave radar (HFSWR) severely, so suppressing the ionospheric clutter is a vital part of radar signal processing sequence. In this paper, the spatial characteristics of the ionospheric clutter in a planar array are analyzed, then a new orthogonal projection method with eigenvalue decomposition (EVD) is proposed. The real data results are given to confirm that the proposed method is efficient in ionospheric clutter suppression and can enhance the capability of target detection dramatically.
TL;DR: In this paper, the authors derived high frequency field expressions for a cylindrical reflector, which is composed of a chiral nihility layer backed by perfect electromagnetic conductor (PEMC), based on Maslov's method.
Abstract: High frequency field expressions for a cylindrical reflector, which is composed of a chiral nihility layer backed by perfect electromagnetic conductor (PEMC), have been derived. The treatment is based on Maslov's method. Dependence of co-polarized and cross-polarized field components for different values of admittance parameter of PEMC has been studied.
TL;DR: In this article, the guiding properties of a periodically corrugated metal wire at microwave frequencies are studied theoretically, and it is shown that if the grooves of the wire are filled with a dielectric with high permittivity, the strong field confinement of spoof surface plasmon polaritons can be achieved even at frequencies smaller than the asymptotic frequency, for which the SPP losses are quite low.
Abstract: The guiding properties of a periodically corrugated metal wire at microwave frequencies are studied theoretically. The outer radius of the corrugated wire is of subwavelength size, and it seems difficult for spoof surface plasmon polaritons (SPPs) in the wire to be confined highly, even if the set of the geometric parameters of the wire structure is optimized. However, if the grooves of the corrugated wire are filled with a dielectric with high permittivity, the strong field confinement of spoof SPPs can be achieved even at frequencies smaller than the asymptotic frequency, for which the SPP losses are quite low. It is also shown that for this type of wire structure, the subwavelength microwave guiding is available for a certain frequency range.
TL;DR: In this article, a Yagi-Uda antenna constructed of three Koch fractal elements is presented with a half-power beamwidth of 64° achieved with dimensions below a third of a wavelength.
Abstract: A Yagi-Uda antenna constructed of three Koch fractal elements is presented. Simulated and measured characteristics of the antenna shows a half-power beam-width of 64° achieved with dimensions below a third of a wavelength. Furthermore, the Koch dipole and its size miniaturization capabilities are investigated.
TL;DR: In this paper, the subspace-based optimization method was extended to two-dimensional electric impedance tomography (E2E tomography) for the purpose of solving inverse scattering problems.
Abstract: This paper extends the application of the subspace-based optimization method, which was originally proposed to solve inverse scattering problems, to two dimensional electric impedance tomography (E...
TL;DR: Based on the quarter-wave dielectric mirror (Bragg reflector), a chirp scheme to enhance the bandwidth is proposed in this paper. But the chirping scheme is limited to a single channel.
Abstract: Based on the quarter-wave dielectric mirror (Bragg reflector), a chirp scheme to enhance the bandwidth is proposed. We model the chirped mirror by successively cascading a number of sub-Bragg refle...
TL;DR: In this article, an electromagnetic pulse coupling to a device from a wire penetrating a cavity aperture by applying the transient electromagnetic topology (TEMT) method was studied. But the results obtained by the TEMT method are compared with those obtained numerically by using the FDTD method only and experimentally.
Abstract: This paper studies an electromagnetic pulse coupling to a device from a wire penetrating a cavity aperture by applying the transient electromagnetic topology (TEMT) method. The computation process is divided into two steps: The three dimensional finite-difference time-domain (FDTD) method is used to compute the excitation fields of the wire, and then the SPICE model of the wire is used to compute the current response of the device. The results obtained by the TEMT method are compared with those obtained numerically by using the FDTD method only and experimentally. And good agreement has been obtained. All the calculations are done in the time domain, and the TEMT method can be used to directly analyze nonlinear or time-varying loads. The wire does not have to be meshed in the TEMT method, so the TEMT method is more efficient than the FDTD method only.
TL;DR: In this article, the authors presented a new design for a circularly-polarized (CP) microstrip patch antenna with switchable polarization sense, where the antenna has a circular radiating patch and it is excited by a microstrip feed line through the coupling of a fullwavelength annular ring slot in the ground plane.
Abstract: This paper presents a new design for a circularly-polarized (CP) microstrip patch antenna with switchable polarization sense. The antenna has a circular radiating patch and it is excited by a microstrip feed line through the coupling of a full-wavelength annular-ring slot in the ground plane. First, it is found that the antenna polarization can be switched between vertical and horizontal polarizations when two PIN diodes are used to reconfigure the coupling slot and the open stub of the feed line, respectively. Such a linearly-polarized reconfigurable microstrip antenna can be converted to a switchable CP antenna by embedding a cross slot with unequal lengths into the radiating patch. Details of the designs are described, and both simulated and measured results are presented.
TL;DR: In this article, a resonant transmission of an electrically small aperture with a ridge in a conducting plane was analyzed and it was found that the transmitted power at the resonance condition converges to the transmission cross section of the aperture regardless of its size or shape.
Abstract: A resonant transmission of an electrically small aperture with a ridge in a conducting plane is analyzed. It is an example of resonant transmission and the ridge inserted at the center line of the electrically small aperture resonates it by increasing an equivalent capacitance of the aperture. At resonance condition, the transmitted power through the aperture can be significantly enhanced compared to that at off-resonance. It is found that the transmitted power at the resonance condition converges to the transmission cross section of the aperture regardless of its size or shape. In addition, the electric and the magnetic fields distributions on the aperture with and without the ridge are compared to facilitate the understanding of the resonant behavior.
TL;DR: In this paper, the authors proposed a Frequency-Dependent Crank-Nicolson Finite Difference Time Domain (FD-CN-FDTD) scheme for Debye media and numerical tests are performed with two widely used sparse iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalized Minimal Residual (GMRES), for comparison.
Abstract: Unconditional stability of the Crank-Nicolson Finite Difference Time Domain (CN-FDTD) method permits us to use time steps over the Courant-Friedrich-Lewy (CFL) limit of conventional FDTD method. However, in this work it was realized that, when the time step is set above CFL limit the coefficient matrix arising from Crank-Nicolson method is no longer diagonally dominant and iterative solvers require longer solution time in each FDTD iteration. Frequency dependent CN-FDTD (FD-CN-FDTD) scheme for Debye media is formulated and numerical tests are performed with two widely used sparse iterative solvers, Bi-Conjugate Gradient Stabilised (BiCGStab) and Generalised Minimal Residual (GMRES), for comparison. BiCGStab outperforms GMRES in every aspect of the study.
TL;DR: In this article, three fractional dual solutions between the original and dual to original solutions are determined inside the chiral nihility slab and corresponding fields outside the nihile slab are determined and analyzed.
Abstract: Inside the chiral nihility slab, three fractional dual solutions between the original and dual to original solutions are determined. Chiral nihility slab is backed by perfect electric conductor. Corresponding fields outside the nihility slab are determined and analyzed. It is noted that in only one case outside field is also fractional dual while for other two cases corresponding fields are not fractional dual.
TL;DR: In this article, the authors present the first study of the multipactor effect in a circular waveguide, demonstrating its existence and providing a susceptibility chart for such a structure, which will be of great interest for the better understanding of multipactor physical phenomena.
Abstract: This paper mainly focuses on demonstrating that a multipactor discharge can occur within a circular waveguide operating under the fundamental TE 11 circular mode. Circular waveguides are widely used in the fabrication of many passive components, in order to implement resonant cavities as well as irises to connect adjacent guides for both application domains, particle accelerators and satellite subsystems applications. Thus, we present the first study of the multipactor effect in a circular waveguide, demonstrating its existence and providing a susceptibility chart for such a structure, which will be of great interest for the better understanding of multipactor physical phenomena.