Showing papers in "Electromagnetics in 2013"
TL;DR: In this article, a multicore photonic crystal fiber-based 1 × 8 two-dimensional splitters were proposed, where an optical signal at a wavelength of 1.55 μm inserted into the central core is equally divided into eight other cores, each with 12.5% of the total power.
Abstract: This study uses the beam propagation method to propose a new design of multicore photonic crystal fiber-based 1 × 8 two-dimensional splitters. An optical signal at a wavelength of 1.55 μm inserted into the central core is equally divided into eight other cores, each with 12.5% of the total power. In addition, the physical behavior of the coupling characteristics is obtained using coupled mode analysis. Numerical simulations demonstrate that the optical signal can be divided equally in a photonic crystal fiber structure having dimensions of 60 μm × 60 μm × 5.35 mm.
26 citations
TL;DR: In this paper, the problem of evaluating the electromagnetic field of a perfectly electrical conductor wedge located over stratified media is solved through Fredholm integral equations derived by using the generalized Wiener-Hopf technique.
Abstract: The problem of evaluating the electromagnetic field of a perfectly electrical conductor wedge located over stratified media is solved through Fredholm integral equations derived by using the generalized Wiener–Hopf technique. The numerical solution of the integral equation is efficiently accomplished by a simple quadrature method. Numerical simulations that illustrate the validity of the proposed method as well as some applications are presented.
18 citations
TL;DR: A novel method combining time-domain reflectometry and the electromagnetism-like mechanism is developed and applied to wiring network diagnosis and was successfully applied to diagnose two faulty wiring networks of different configurations.
Abstract: In this article, a novel method combining time-domain reflectometry and the electromagnetism-like mechanism is developed and applied to wiring network diagnosis. The proposed method consists of two steps. In the first step, the propagation along the cables, i.e., the time-domain reflectometry, is modeled using an RLCG circuit model. In the second step, the electromagnetism-like mechanism is combined with the developed wire propagation model to solve the inverse problem in order to deduce physical information about the defects in the wiring network from its measured time-domain reflectometry. Using experimental data, the proposed method was successfully applied to diagnose two faulty wiring networks of different configurations.
15 citations
TL;DR: In this paper, the hybrid boundary element method, based on the equivalent electrodes method and the boundary element methods, is applied on several examples for calculating the characteristic impedance of transmission lines, and the results for the observed transmission lines are compared to corresponding ones obtained by the finite element method.
Abstract: The hybrid boundary element method, based on the equivalent electrodes method and the boundary element method, is presented in this article. This method is applied on several examples for calculating the characteristic impedance of transmission lines. It should be emphasized that the combination of the equivalent electrodes method and a new variant of the boundary element method can be efficiently implemented in quasi-transverse electromagnetic analysis of transmission lines without loss of accuracy. All results for the characteristic impedance of the observed transmission lines are compared to corresponding ones obtained by the finite-element method.
14 citations
TL;DR: In this paper, a computer-aided design oriented cavity model is proposed to predict the effect of composite and suspended substrates on the characteristics of an equilateral triangular patch antenna.
Abstract: A computer-aided design oriented cavity model is proposed in this article to predict the effect of composite and suspended substrates on the characteristics of an equilateral triangular patch antenna. The present model is very simple, fast, accurate, and valid for an entire range of permittivities and thicknesses of composite and suspended substrates as well as a single-substrate patch antenna. No design guide line or experimental results are available in the open literature to predict the characteristics of an equilateral triangular patch antenna on composite substrate. Also, the effect of a suspended substrate on input impedance, bandwidth, and gain of an equilateral triangular patch antenna has not yet been investigated, so commercial softwares (HFSS [Ansoft Corp., 2012] and CFDTD [Artech House, 2004]) was employed to validate the present model for a suspended and composite substrate triangular patch antenna. The computed values of a triangular patch on single substrate are compared with diffe...
14 citations
TL;DR: The proposed power divider thus has controllable bandwidth, exactly the same as the conventional Gysel power Divider, as well as simple structure, wide frequency band ratio, good isolation and return loss, and high-power handling capability advantages over the Wilkinson powerdivider.
Abstract: In this article, a new design for an equal and unequal dual-band Gysel power divider with a novel dual-band transformer has been proposed. This transformer is replaced with two conventional quarter-wavelength transmission lines between the isolation resistors. The proposed power divider thus has controllable bandwidth, exactly the same as the conventional Gysel power divider, as well as simple structure, wide frequency band ratio, good isolation and return loss, and high-power handling capability advantages over the Wilkinson power divider.
12 citations
TL;DR: This power divider has a simple structure that enables an easy circuit design and analysis and is based on using microstrip open stubs to suppress the second to sixth harmonics simultaneously.
Abstract: This article presents a power divider with a simple technique for harmonics suppression. This technique is based on using microstrip open stubs to suppress the second to sixth harmonics simultaneously. This power divider has a simple structure that enables an easy circuit design and analysis. The simulated and experimental results are shown for the proposed 0.9-GHz power divider, which is implemented in microstrip technology. The design equations are derived using the odd- and even-mode formulations.
12 citations
TL;DR: In this article, a simple and fast semi-analytical approach for magnetic interaction force calculations based on fictitious magnetization charges and the discretization technique was proposed, and the results for the interaction magnetic force obtained by the proposed approach are compared with the finite-element method.
Abstract: This research includes a simple and fast semi-analytical approach for magnetic interaction force calculations based on fictitious magnetization charges and the discretization technique. Two different examples are analyzed: (1) calculation of the interaction magnetic force between laterally displaced cylindrical permanent magnets made of the same magnetic material and magnetized uniformly along their axes of symmetry (opposite direction) and (2) determination of the attraction force between a “horseshoe” permanent magnet of circular cross-section and an infinite linear magnetic plane with relative magnetic permeability μr. The results for the interaction magnetic force obtained by the proposed approach are compared with the finite-element method.
9 citations
TL;DR: In this article, a fast numerical algorithm is proposed for calculating the difference field radar cross-section of an object above a rough surface, which is solved by an iterative solver.
Abstract: A fast numerical algorithm is proposed for calculating the difference field radar cross-section of an object above a rough surface. The electric-field integral equation of the difference of the induced current on the rough surface and the induced current on the object is derived, which is solved by an iterative solver. The characteristic basis functions are used to calculate the induced current on the rough surface, which is part of the right-hand side of the system. It is observed that the coupling matrices (nonself-block interactions of the rough surface and the interactions between the object and the rough surface) are rank deficient. The matrix decomposition algorithm is used and extended to compress the coupling matrices. Numerical examples show that the characteristic basis functions method combined with the matrix decomposition algorithm can greatly reduce the CPU time and memory cost. The accuracy and efficiency are discussed by numerical examples.
9 citations
TL;DR: In this paper, the design, simulation, and realization of an L-band axial-mode 1 × 2 short helical antenna array are presented, where the antenna array has a compact size and is lightweight.
Abstract: In this article, the design, simulation, and realization of an L-band axial-mode 1 × 2 short helical antenna array are presented. The antenna array has a compact size and is lightweight. To improve array performance, special attention is paid to important parameters, such as gain, impedance matching, axial ratio, and mutual coupling. Impedance matching is achieved by optimization of the helix wire radius and the feed length. Axial ratio is improved by adding the optimized incorrect turn at the end of the helix. Finally, to reduce the mutual coupling between the elements, split-ring resonators are designed and installed between the two antennas.
9 citations
TL;DR: The low-frequency results demonstrate the capability to correctly describe the topology of this type of wiring structure, including realistic and complex installation configurations, and the importance of taking into account losses much larger than the usual skin effect wire loss models in order to reach good agreement with measurements.
Abstract: This article describes the approach developed to model the topology of a complex harness. The modeling is based on the multi-conductor transmission line network theory. The topological model of the complex harness was validated using S-parameter simulations compared with measurements. The low-frequency results demonstrate the capability to correctly describe the topology of this type of wiring structure, including realistic and complex installation configurations. The results also show the importance of taking into account losses much larger than the usual skin effect wire loss models in order to reach good agreement with measurements.
TL;DR: In this article, a printed slot antenna with circular polarization characteristics for X-band applications was proposed, where a modified L-shaped ring radiating stub and a U-shaped strip with an open stub inside it protruded on the ground plane were inserted.
Abstract: This article proposes a novel printed slot antenna with circular polarization characteristics for X-band applications. By using a modified L-shaped ring radiating stub, and also by inserting a U-shaped strip with an open stub inside it protruded on the ground plane, additional resonances are excited and, hence, much wider impedance bandwidth can be produced, especially at the higher band. By using these structures, very good axial-ratio bandwidth is obtained. The operating frequencies of 8.213 to over 11.87 GHz with circular polarization characteristics 8.32–10.79 GHz. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the X-band frequency range. The designed antenna has a small size of 20 × 20 mm2.
TL;DR: In this article, a dual-band circularly polarized multi-layer microstrip antenna for 3.5-5.2-/5.8-GHz applications is presented.
Abstract: A novel dual-band circularly polarized multi-layer microstrip antenna for 3.5-/5.2-/5.8-GHz applications is presented. A stacked-patch configuration is used for the compact dual-band antenna design, and good circular polarization performance is achieved by adjusting the size of truncated corners and inserted slits of the hexagonal patches. The antenna generates circular polarization radiation at 3.49 and 5.18 GHz with good return loss and broadside radiation patterns. The measured peak gains of the antenna are 3.5 and 5.1 dBi at the lower and upper bands, respectively. In addition, the antenna occupies a small radiating area of 15.6 × 16 mm2.
TL;DR: The size-reduced system is constructed in the marching-on-in-degree time-domain integral equation solver with the aggregative basis function method to analyze transient electromagnetic scattering of conducting objects.
Abstract: The aggregative basis function method for a marching-on-in-degree time-domain integral equation solver can significantly reduce the matrix size and storage and make the reduced system easily manageable and solvable. In the conventional generation of an aggregative basis function, a repeated solution of the matrix equation is required with various excitations, and hence, an efficient approach to generate the aggregative basis function is proposed in this article. The singular value decomposition is performed on multiple right-hand sides, which are linearly dependent or rank deficient, and after the singular value decomposition truncation, fewer matrix equation solutions are necessary with the retained excitation to generate the aggregative basis function. The size-reduced system is then constructed in the marching-on-in-degree time-domain integral equation solver with the aggregative basis function method to analyze transient electromagnetic scattering of conducting objects. Several numerical exam...
TL;DR: In this article, a method based on the invasive weed optimization algorithm is described for synthesizing a point source doubly curved reflector antenna with a shaped pattern in an elevation plane and a narrow beam in a perpendicular plane.
Abstract: In this article, a method based on the invasive weed optimization algorithm is described for synthesizing a point source doubly curved reflector antenna. The proposed method is for designing a reflector with a shaped pattern in an elevation plane and a narrow beam in perpendicular plane. By determining two basic curves, the doubly curved reflector surface can be produced. The central vertical curve approximately produces a shaped elevation pattern. It can be expressed by a well-defined function, and the function parameters will compose a solution space to be explored by invasive weed optimization. The transverse section curve is known to be a part of a parabolic reflector for producing a narrow beam in that plane. The validity of the proposed method is verified by an example of a shaped elevation pattern reflector antenna; the example is a flat-topped elevation pattern. The simulation results based on physical optics further prove the validity and versatility of this technique for solving reflect...
TL;DR: In this article, an electromagnetic boundary value problem dealing with a slit surrounded by rectangular grooves on the exit surface in a conducting plane is rigourously solved based on the Fourier transform, eigenfunction expansion, and mode-matching method.
Abstract: Directional emission from a slit surrounded by rectangular grooves on the exit surface in a conducting plane is investigated. An electromagnetic boundary-value problem dealing with a slit surrounded by rectangular grooves on the exit surface in a conducting plane is rigourously solved based on the Fourier transform, eigenfunction expansion, and mode-matching method. The radiation pattern from the slit is represented in a series and computed to illustrate the radiation behaviors in terms of the groove geometry.
TL;DR: In this article, a modified microstrip-monopole antenna with four small circular patches at the top of the microstrip was proposed, which reduced the thickness of the antenna to only 45.9% of the original microstrip.
Abstract: A novel low-profile broad-beamwidth circular polarization antenna, named modified microstrip-monopole antenna is presented in this article. Four small circular patches are loaded at the top of the microstrip-monopole antenna. Applying this simple method, the thickness of the proposed antenna can be reduced to only 45.9% of the microstrip-monopole antenna. The low profile characteristics of microstrip antenna can be kept. The 3-dB beamwidth of the proposed antenna is 134° at the central frequency, which is 1.81 times of the classical microstrip antenna. Measured and simulated results are demonstrated, and good agreement is obtained.
TL;DR: In this article, the authors present analyses of and design procedures for a compact quintuple-resonance aperture-backed ultra wideband bandpass filter, which has a structure that is both horizontally and vertically symmetrical, simplifying the analysis to a quarter of the structure while enabling the stepped-impedance feed lines to be designed analytically.
Abstract: This article presents analyses of and design procedures for a compact quintuple-resonance aperture-backed ultra-wideband bandpass filter. First, a one-wavelength H-ring resonated at 6.85-GHz center frequency is coupled with open stubs at both sides to produce a triple-resonance filter characteristic. To increase the resonances of the filter to five, stepped-impedance feed lines are then implemented to introduce two extra transmission poles at each side of the center frequency. The filter, which has a structure that is both horizontally and vertically symmetrical, simplifies the analysis to a quarter of the structure while enabling the stepped-impedance feed lines to be designed analytically. A wide aperture is then etched on the ground plane directly below each interdigital line to achieve strong coupling. This results in wider coupling gaps to enable in-house fabrication. A floating strip conductor is then added at the center of each ground aperture to suppress the spurious harmonic appearing at...
TL;DR: In this paper, the effect of incident wave properties on the resonance that occurs when the target size is close to the wavelength was investigated and the laser radar cross-section of a conducting target was calculated using a boundary value method with a beam wave incidence and H-wave polarization.
Abstract: The main concern of this study is the effect of incident wave properties on the resonance that occurs when the target size is close to the wavelength. In doing that, the laser radar cross-section of a conducting target is calculated using a boundary value method with a beam wave incidence and H-wave polarization. Therefore, the effect of creeping waves, produced with H-wave incidence, on the backscattering enhancement would be clarified. A comparison with a similar scattering problem using a plane wave incidence is considered.
TL;DR: In this paper, a miniaturized fourth-order direct-coupled bandpass filter with good stopband responses using hexagonal stepped-impedance resonators is presented.
Abstract: A miniaturized fourth-order direct-coupled bandpass filter with good stopband responses using hexagonal stepped-impedance resonators is presented. Based on the odd- and even-mode equivalent circuits, the resonance characteristics of the hexagonal stepped-impedance resonators with mixed electric/magnetic coupling are investigated. Multiple finite-frequency transmission zeros are realized in the stopband but without introducing either cross-coupling between nonadjacent resonators or source-load coupling between input/output ports. The frequency-dependent coupling matrix of the proposed filter is presented. A new bandpass filter centered at 2.45 GHz with 6.5% fractional bandwidth has been designed and fabricated to verify the validity of the proposed method. The measurement result shows four finite transmission zeros in the stopband, located at 0.98 GHz with 73.14-dB rejection, 2.10 GHz with 48.18-dB rejection, 2.75 GHz with 53.80-dB rejection, 3.12 GHz with 57.08-dB rejection, respectively. The cir...
TL;DR: A novel design method for miniaturized tri-band Wilkinson power dividers with independently controllable center frequencies and a simple structure, which consists of three-section coupled lines and three isolation resistors is proposed.
Abstract: The purpose of this article is to propose a novel design method for miniaturized tri-band Wilkinson power dividers with independently controllable center frequencies and a simple structure. Different from the traditional circuit of tri-band power dividers using three-section transmission-line transformers, this proposed structure consists of three-section coupled lines and three isolation resistors. Due to flexible even- and odd-mode parameters and inherent small size features of parallel coupled lines, this compact divider not only provides arbitrary tri-band operation but also increases the degrees of freedom in determining isolation performances. Furthermore, the simplified design equations for electrical parameters are obtained, and several ideal examples are demonstrated for initial theoretical verifications. As a remarkable example, a compact microstrip power divider operating at three industrial, scientific, and medical bands, namely, (0.92, 2.45, and 5.8 GHz), is designed, fabricated, and...
TL;DR: In this paper, the electromagnetic scattering of an arbitrarily polarized plane wave obliquely impinging on the edge of anisotropic impedance half-planes and planar junctions featuring inclined anisotropy axes is analyzed.
Abstract: The electromagnetic scattering of an arbitrarily polarized plane wave obliquely impinging on the edge of anisotropic impedance half-planes and planar junctions featuring inclined anisotropy axes is analyzed. Exact spectral representations for the total field are derived when the wedge faces are characterized by a set of specific homogeneous anisotropic impedance boundary conditions exhibiting an impedance matrix with no vanishing diagonal terms, as implied by the arbitrary orientation of the principal anisotropy axes with respect to the edge. The proposed solutions, which extend previous formulations valid for direction of the anisotropy axes either parallel or perpendicular to the edge, are derived by resorting to the Sommerfeld–Maliuzhinets method and exploiting the properties of the special function χΦ, originally introduced in the study of the scattering from wedges in gyroelectric media. Explicit uniform asymptotic expressions for the fields are provided along with samples of numerical resul...
TL;DR: In this paper, an improved augmented electric field integral equation method for modeling micro-scale structures is proposed, where a normalization factor is proposed to make the system stable for electrically small structures, especially for small structures working at several GHz.
Abstract: An improved augmented electric field integral equation method for modeling micro-scale structures is proposed in this article. The scaling property of the matrix systems of the original electric field integral equation method and the corresponding augmented electric field integral equation method are analyzed in detail. It is found that though the augmented electric field integral equation method works well for ordinary structures at very low frequencies, the matrix is ill conditioned for micro-scale structures with very dense mesh. Different balancing techniques are studied to alleviate this problem. A normalization factor is proposed to make the system stable for electrically small structures, especially for micro-scale structures working at several GHz. Numerical results are presented to demonstrate the accuracy and stability of this method.
TL;DR: In this paper, a dyadic Green's function of a wedge with anisotropic impedance faces, excited by an electric dipole source, is derived for the paraxial region where the source and observation points are in proximity to the apex but widely separated.
Abstract: A dyadic Green's function of a wedge with anisotropic impedance faces, excited by an electric dipole source, is derived for the paraxial region where the source and observation points are in proximity to the apex but widely separated. The principal anisotropy axis is the edge axis, and surface impedances parallel and transverse to this axis are considered. Following a “separation of variables” derivation, final dyadics involve eigenfunction solutions over an angular wave number and a longitudinal spectral integral, which is evaluated asymptotically assuming that k|z – z′| is large. It is observed that derived forms reveal three distinct scattering mechanisms: edge-guided waves, surface waves, and guided waves in the classical sense. Numerical simulations limited to paraxial region show that edge-guided and guided-wave terms are dominant at points away from the wedge surface, whereas surface waves are dominant near impedance surfaces. Both capacitive, inductive, and mixed (one face capacitive and ...
TL;DR: In this paper, the capacitance of two coupled metallic funnels was evaluated using the method of moments using pulse functions as basis functions and delta functions as testing functions, and the validity of the analysis has been presented by comparison of data presented on capacitance considering a case study published in open literature.
Abstract: This article presents the evaluation of capacitance of two coupled metallic funnels. Two cases have been considered: (1) two skewed funnels and (2) two coaxial funnels. Integral equations are formed by relating the unknown charge density on the cylinders to the corresponding potential on the conductors. The integral equations are solved using the method of moments using pulse functions as basis functions and delta functions as testing functions. The numerical data on capacitance for both configurations have been presented. The validity of the analysis has been presented by comparison of data presented on capacitance considering a case study published in open literature.
TL;DR: In this article, a subwavelength aperture antenna with multiple corrugations and a superstrate layer was investigated based on Fourier transform and mode matching, demonstrating a rigorous and fast convergent series solution.
Abstract: In this study, a subwavelength aperture antenna with multiple corrugations and a superstrate layer was investigated based on Fourier transform and mode matching, demonstrating a rigorous and fast convergent series solution. The aperture antenna with a corrugated conducting flange and a dielectric superstrate was fabricated in the X-band frequency range to demonstrate the validity of the derived series solution. The measured reflection coefficient and radiation pattern of the proposed antenna are also presented and compared to the computational results to assess the effect of the dielectric superstrate. A maximum gain enhancement of 5.19 dB was achieved by employing the superstrate.
TL;DR: In this paper, the effects of roughness on the upper and lower surfaces are studied by using the perturbation technique, which consists of a few recalling steps to evaluate the Sommerfeld integral with the aid of the complex image theory.
Abstract: Propagation of electromagnetic waves in flat or rough surfaces is and will continue to play one of the most important roles for long-range communications and in various applications. In this article, scattering electromagnetic waves from three-layered media (air, seawater, and ground) separated by rough boundaries (variable interfaces) is investigated theoretically by using the imaging space of Hankel transformations. The effects of roughness on the upper and lower surfaces are studied by using the perturbation technique. The reversal of Hankel transformations produces an integral representation of the interfering field, which was very tedious and complicated because they involved Sommerfeld integrals. As a result, the technique that consists of a few recalling steps to evaluate the Sommerfeld integral is developed with the aid of the complex image theory to obtain the closed-form expressions for the far field in the ground (third layer), which radiated from a vertical magnetic dipole located in ...
TL;DR: In this article, a stronger smooth condition of the surface is added to ensure the convergence of the vertical improper integral to ensure that the surface current density should be zero at the point.
Abstract: The tangential scattered magnetic field of a perfectly electric conducting surface is usually expressed as an improper integral. However, the improper integral is divergent. Hence, the field is expressed as a limit of an integral in some references. In this article, the limit of the integral is called a vertical improper integral. A stronger smooth condition of the surface is added to ensure the convergence of the vertical improper integral. The relationship between the vertical improper integral and the Cauchy principle value integral is established. An example shows that the tangential scattered magnetic field is infinite at a first-order smooth point if it is assumed that the surface current density is non-zero at the point. By the boundary condition, it is obtained that the surface current density should be zero at the point. A numerical example is given to demonstrate the effectiveness of the vertical improper integral method. The numerical result also shows that singular integrals need not ...
TL;DR: In this article, the theory and experiment of a probe-fed conformal antenna with a conducting parasitic element mounted on a spherical multilayer structure are presented in a mixed-potential integral equation formulation.
Abstract: The theory and experiment of a probe-fed conformal antenna with a conducting parasitic element mounted on a spherical multilayer structure are presented in this article. Linear Rao–Wilton–Glisson triangular basis functions are applied in a mixed-potential integral equation formulation. Current distributions on coaxial probe and conformal radiating elements are computed by using the proper spatial domain electrical dyadic Green's function and its asymptotic approximation. A prototype of such an antenna is fabricated and tested. The effect of the parasitic element on the input impedance, gain, and radiation patterns of the antenna is investigated. It is shown that the antenna characteristics are improved significantly with the presence of the stack. Good agreement is achieved between the results obtained from the proposed methods and measurement results.
TL;DR: In this article, a printed antenna is proposed, fabricated, and tested for an ultra-wideband LTE/GSM/UMTS WWAN wireless USB dongle attached to a laptop computer.
Abstract: In this article, a novel printed antenna is proposed, fabricated, and tested for an ultra-wideband LTE/GSM/UMTS WWAN wireless USB dongle attached to a laptop computer. With a chip capacitance (1.0 pF) embedded to improve the desired impedance matching in the design, a fundamental resonant mode at about 750 MHz is successfully excited to cover LTE700/GSM850/900 operating bands, while the big radiating plate can generate two resonance frequencies to meet the bandwidth of DCS1800/PCS1900/UMTS2100/LTE2300/2500. Owing to its simple structure and configuration, the presented antenna, having an evident compact size of 20 × 19 mm2, can be integrated easily in the USB dongle together with the other functional modules. These measurement results (antenna gain and radiation efficiency are better than 1.3 dBi and 45%, respectively) demonstrate that this antenna achieves a good agreement with those of the simulations as well as good omni-directional characteristics within its operating frequency bands, making ...