A novel ortho-mode transducer (OMT) for dual-band dual-polarized communication systems is proposed in this letter. The OMT is loaded with five posts in reasonable positions of the waveguides and a shorted circuit piston in the branch waveguide. Compared with the septum loaded traditional one, the presented OMT is more flexible, simple and easy to fabricate. Both simulations and measurements indicate that the impedance bandwidths of VSWR<1.15 ranging from 6.50 to 7.20 GHz and 8.80 to 10.2 GHz can be obtained. The low insertion losses indicate that the presented OMT can be used in actual project. Moreover, good isolation performance between the two input ports in both bands are obtained because of the inherent existence of cross polarization.

A typical magnetic resonance coupling based wireless Electric Vehicle (EV) charging system consists of a transmitting coil at the charging station and a receiving coil in the vehicle. In order to maintain good energy transfer efficiency of the wireless charging system, the effect of the proximal metallic object in the vicinity of the receiving coil has been investigated. Both from the theoretical simulation and experimental measurement, it has been observed that the resonance based wireless energy transfer system is very sensitive to the nearby metallic objects, leading to significant deterioration in energy transfer efficiency. This effect on the energy transfer efficiency is also seen to be different for different physical spacing between the transmitting and receiving coils. It is also found that the operating resonant frequency for optimum energy transfer efficiency changes with the metallic object in close proximity to the receiving coil. The theoretically simulated results well agree with the experimental results. The analysis will provide future guidelines for designing an efficient resonance coupling based wireless charging system for EVs even in the presence of metallic objects.

The rigorous evaluation of the NRCS (Normalized Radar Cross Section) of an object above a one-dimensional sea surface (2D case) needs to numerically solve a set of discretized integral equations involving a large number of unknowns. Thus, the direct solution of the impedance matrix equation via LU decomposition becomes the most expensive step in the MoM (Method of Moments) procedure. So, in order to minimize the computation cost, the iterative domain decomposition method called EPILE (Extended Propagation-Inside-Layer Expansion) was used and then was combined with the FBSA (Forward-Backward with Spectral Acceleration) to calculate the local interactions on the rough sea surface. The resulting fast method is called EPILE+FBSA. In this paper, we take advantage of the rank-deficient nature of the coupling matrices, corresponding to the object-surface interactions, to further reduce the complexity of the method by using the ACA (Adaptive Cross Approximation). Thus, the coupling matrices are strongly compressed without a loss of accuracy and the memory requirement is then strongly reduced. For a cylinder above a rough sea surface, the results show the efficiency of the accelerated EPILE+FBSA+ACA method.

A simple microstrip circular disc antenna to excite circularly polarized radiation is presented. In a single-probe fed circular disc sector patch, the corners are further truncated to obtain circular polarization characteristics. The truncation helps to reduce the ground plane dimensions making the antenna more compact with overall dimensions of 50 mm x 50 mm x 1.6 mm. The lengths of truncation necessary to achieve circular polarization are mathematically expressed. The simulated and experimental results are compared and are found to be in good agreement. Axial ratio bandwidth of 1.3% is obtained. The overall size reduction is 55% in comparison with the original disc sector antenna. The antenna resonates in the UMTS 1900-2170 MHz band and can be employed for Mobile Communication applications.

Small ultra high frequency (UHF) radio frequency identification (RFID) tags of fragment-type structure can be designed for broadband operation and for versatile impedance matching to different chips. The fragment-type tag structure can be optimized by using genetic algorithm. In our design, multi-objective evolutionary algorithm based on decomposition combined with enhanced genetic operators (MOEA/D-GO) is used for optimization searching. The multiple objectives are defined in terms of power transmission coefficients for operation in multiple RFID bands and for impedance matching to several prevailing RFID chips. For demonstration, a fragmented tiny square UHF tag of dimensions of 5.5 mm * 5.5 mm is designed for multi-band operation over the 433 MHz, 869 MHz and 915 MHz RFID bands, and a fragmented round tiny RFID tag of radius of 4.5 mm is also designed for versatile connection to five prevailing RFID chips at 915 MHz. The tiny round versatile tag is tested by connecting two chips, the IMPIMJ Monza-4 chip (11-143j) and ALIEN Higgs-3 chip (27-195j), respectively. Effects of input impedance and adjunct fragments on versatility of the design are further discussed.

A dual-band capacitive coupled planar inverted F antenna is presented. The antenna operates in two bands centered around 1.5 GHz and 2.4 GHz with nearly omnidirectional radiation pattern in the entire operating band. It offers a peak gain of 2.4 dBi at 1.5 GHz and 7 dBi at 2.4 GHz with an average efficiency of 82%, 97% respectively. Effects of key design parameters such as the distance between feed strip and radiator patch, the dimensions of the feed strip on the input characteristics of the antenna and length of slot have been investigated and discussed. The antenna is compact and simple to fabricate. The antenna posses an overall dimension of 10×40×6 mm³ when fabricated on substrate of dielectric constant 4.4 and thickness 1.6 mm.

3D integration using through-silicon-vias (TSVs) is gaining considerable attention due to its superior packaging efficiency resulting in higher functionality, improved performance and a reduction in power consumption. In order to implement 3D chip designs with TSV technology, robust TSV electrical models are required. Specifically, due to the increase of signal speeds into the gigahertz (GHz) spectrum, a high frequency electrical characterization best describes TSV behavior. In this letter, 5x50 μm TSVs are manufactured using a via-mid integration scheme and characterized using S-Parameters up to 65 GHz. At 50 GHz, the measured attenuation constant is 0.35 dB/via with a time delay of 0.7 ps/via.

The purpose of this paper is on the behavioural modelling of surge voltage pulses used in Atom Probe Tomography. After brief description of the atom probe functioning principle, we examine the excitation electrical pulse signal integrity along the electric pulser (E-pulser) feeding line modelling with respect to the IEC1733/04 standard. This feeding electric line is ended by cylindrical via ground to control the ion emission. By using the transmission line (TL) ultra-broadband RLCG model, the propagating pulsed signals degradation is predicted. The signal propagation was analysed in both frequency and time domains by taking into account the substrate dispersion. The wideband frequency behaviours of the surge signal along the feeding line were examined from DC-to-2 GHz. In addition, by considering pulse surge signals with pulse-width and rise-/fall-time parameters (T₁=9 ns, t_r1=t_f1=1.6 ns) and (T₂=30 ns, t_r2=4 ns/t_f2=18 ns), the transient responses from 5 cm to -20 cm length TL are characterized. It was shown that the excitation pulse was significantly distorted. It was emphasized that the operated signal delay varies from 0.3 ns-to-1.5 ns in function of the via capacitor value. The time-dependent radiated E-field on the performance of the atom probe system which enables to characterize the nature of tested materials (ions or atoms) is discussed. The presented analysis approach is particularly useful for E-pulser integrated in measurement scientific instruments as Atom Probe Tomography time of flight optimisation, a nano-analysing technique that uses ultra-sharp high vacuum pulse to induce controlled erosion of samples. In this application, the excitation voltage pulse integrity during the propagation is required in order to improve the measurement instrument performances.

A novel broadband planar rotated cross monopole antenna, which consists of a vertical patch (area A) and a rotated horizontal patch (area B), is proposed. By rotating the horizontal patch, the bandwidth of the proposed antenna can be significantly enhanced. The effect of the rotated angle of the horizontal patch on the bandwidth has been deeply studied. The measured results show that the proposed antenna with compact size of 50×50 mm² can achieve a wide impedance bandwidth (10-dB reflection coefficient) as large as 8.76 GHz (2.33-11.09 GHz) or about 130%, which is nearly two times of what the corresponding conventional cross monopole antenna was.

A Coplanar Waveguide(CPW)-fed monopole loaded with Composite Right/Left Handed Transmission Line (CRLH-TL) unit cell is presented in this letter. Multiband is achieved due to the nonlinear dispersion relation of the CRLH-TL unit cell. The CRLH-TL unit cell supports a fundamental LH wave (phase advance) at lower frequencies and a RH wave (phase delay) at higher frequencies. By loading CRLH-TL unit cells with a conventional monopole, the resonant frequency of higher order mode can be decreased and zeroth-order mode or even negative-order mode can be achieved. As a result, the proposed antenna operates at 1.43 GHz, 2.58 GHz, 3.31 GHz and 4.4 GHz. Finally the modified antenna is fabricated and measured; measurements and EM simulations are in a good agreement that confirms the proposed theory.

A compact ultra wide band (UWB) antenna with dual band notch characteristics is proposed. The antenna consists of a coplanar waveguide (CPW) fed bevelled rectangular patch and a modified rectangular ground plane. A Z-shaped meander line parasitic element and a pair of symmetrical L-shaped quarter-wavelength stubs are employed to realize band-notched functions at WiMAX and WLAN bands respectively. By optimizing the dimensions and positions of these notch structures, the desired notch-bands of WLAN and WiMAX are achieved. Unlike other dual band-notched antennas reported in literature this antenna has a merit of regulating the centre frequency as well as the bandwidth of both the notched bands easily and independently. The measured -10 dB S₁₁ covers the bandwidth from 2.5 to 11.5 GHz, with two notched bands from 3.3 to 3.6 GHz and 5.2 to 5.75 GHz. The proposed antenna exhibits nearly omni-directional radiation patterns with moderate gain and small group delay variations less than 0.5 ns over the entire operating bandwidth except at the notched bands. Moreover, by using antenna transfer function, the time domain characteristic of the antenna is also studied to confirm its suitability for UWB pulse communication.

This work is devoted to a theoretical investigation of the current crowding problem in flat conductors bent at arbitrary angles. Using conformal mapping techniques, we succeed in obtaining an analytical expression for current density distributions in such conductors. It is shown that the current density increases in a small vicinity of the corner and approaches to infinity at its top. In order to eliminate the infinity, the vertex is replaced by an arc of a circle with a small radius. The method has been developed for an arbitrary angle; several specific examples are considered.

A pattern synthesis approach based on a modified alternating projection method for large planar arrays is presented in this paper. In the alternating projection method, pattern synthesis problem is considered as finding the intersection between two sets: the specification set and the feasible set. The former contains all the patterns that want to be obtained, while the latter contains all the patterns that can be realized. An element belongs to both sets is a solution to the problem. In this paper, a modified projection operator which varies with the iteration number is introduced because the conventional alternating projection method is known to suffer from low convergence rate and/or trapping on local optimum depending on the starting point. When the planar array has a nonuniform element layout, the unequally spaced elements are interpolated into virtual uniform elements with an interpolation of the least square sense. Then the synthesis problem is converted to the problem of a uniform array. Finally, several examples are presented to validate the advantages of the proposed method. Results show that the modified method is fast and obtains better results than the conventional one.

A new design for a low-reflection inhomogeneous microwave lens based on periodically loaded one-dimensional transmission lines is proposed and experimentally tested. The inhomogeneous effective refractive index of this flat-profile lens is achieved by loading the transmission lines comprising the lens with different inductive elements.

A cylindrical metallic plasmonic nano-antenna consisting of a shell supporting a disk, named capped shell, is proposed and studied by frequency domain finite element analysis. This new topology is shown to be weakly dependent on the radius of the structure and is therefore suitable for fabrication by parallel processes such as island lithography which generates a pseudo-random array with a distribution of diameters. Furthermore, compared to similar resonators such as rods, disks and shells, the capped shell generates a larger volume with high fields, and is hence useful as a nano-antenna for light-matter interaction.

This paper presents a novel method for the two-dimensional direction of arrival (DOA) estimation based on QR decomposition. A configuration with two uniform linear antenna arrays (ULA) is employed for the joint estimation of elevation (θ) and azimuth (φ) angles. Q data matrix will estimate the azimuth angle while R data matrix will estimate the elevation angle. The proposed method utilizes only a single snapshot of the received data and constructs a Toeplitz data matrix. This reduces the computational complexity of the proposed method to O((N+1)²) from O(N³) for SVD based methods. The structure of the data matrix also favors the 2D DOA estimation for both coherent and non-coherent source signals. Simulation results are presented, and performance of the proposed method is compared with the Matrix Pencil method for 2D DOA estimation of multiple incident source signals.

In this paper, magnetic material was applied in the design of a UHF-RFID metal tag to increase the reading distance. The influence of the electromagnetic properties, especially the electromagnetic loss, of magnetic substrate on the gain of the tag antenna is discussed by analyzing the reflection and the surface current distribution. As to folded antenna, the loss of energy caused by the magnetic substrate tends to occur in the folding edge of the antenna. Both simulations and experiments indicate that electromagnetic loss markedly reduces the gain rapidly when both the dielectric loss tangent (tanδ) and the magnetic loss tangent (tanδm) are between 0 and 0.3. The reading distance drops from 3 m to 1.5 m when the tanδm of the magnetic composite substrate increases from 0.009 to 0.023. And tanδm should be less than 0.1 for the antenna working excellently. The conclusion offers meaningful guidance for future studies of magnetic substrate folded metal tag.

We discuss the ab initio rendering of four-dimensional (4-d) spacetime of Maxwell's equations on random (irregular) lattices. This rendering is based on casting Maxwell's equations in the framework of the exterior calculus of differential forms, and a translation thereof to a simplicial complex whereby fields and causative sources are represented as differential p-forms and paired with the oriented p-dimensional geometrical objects that comprise the set of spacetime lattice cells (simplices). We pay particular attention to the case of simplicial spacetime lattices because these can serve as building blocks of lattices made of more generic cells (polygons). The generalized Stokes' theorem is used to construct discrete calculus operations on the lattice based upon combinatorial relations depending solely on the connectivity and relative orientation among simplices. This rendering provides a natural factorization of (lattice) 4-d spacetime Maxwell's equations into a metric-free part and a metric-dependent part. The latter is encoded by discrete Hodge star operators which are built using Whitney forms, i.e., canonical interpolants for discrete differential forms. The derivation of Whitney forms is illustrated here using a geometrical construction based on the concept of barycentric coordinates to represent a point on a simplex, and the generalization thereof to represent higher-dimensional objects (lines, areas, volumes, and hypervolumes) in 4-d. We stress the role of the primal lattice, the barycentric dual lattice, and the barycentric decomposition lattice in achieving a complete description of the lattice theory. Lattice Maxwell's equations based on the exterior calculus of differential forms and on the use of Whitney forms as field interpolants inherits the symplectic structure and discrete analogues of conservation laws present in the continuum theory, such as energy and charge conservation. This framework also provides precise localization rules for the degrees of freedom associated with the different fields and sources on the lattice, and design principles for constructing consistent numerical solution methods that are free from spurious modes, spectral pollution, and (unconditional) numerical instabilities. We also brie y consider the relationship between lattice 4-d Maxwell's equations and some incarnations of discretization schemes for Maxwell's equations in (3+1)-d, such as finite-differences and finite-elements.

Mathematical frameworks for representing fields and waves and expressing Maxwell's equations of electromagnetism include vector calculus, differential forms, dyadics, bivectors, tensors, quaternions, and Clifford algebras. Vector notation is by far the most widely used, particularly in applications. Of the more sophisticated notations, differential forms stand out as being close enough to vectors that most practitioners can readily understand the notation, yet at the same time offering unique visualization tools and graphical insight into the behavior of fields and waves. We survey recent papers and book on differential forms and review the basic concepts, notation, graphical representations, and key applications of the differential forms notation to Maxwell's equations and electromagnetic field theory.

A novel hybrid simulation based on the coupled Maxwell-Schrödinger equations has been utilized to investigate, accurately, the dynamics of electron confined in a one-dimensional potential and subjected to time-dependent electromagnetic fields. A detailed comparison has been made for the computational results between the Maxwell-Schrödinger and conventional Maxwell-Newton approaches, for two distinct cases, namely, characterized by harmonic and anharmonic electrostatic confining potentials. The results obtained by the two approaches agree very well for the harmonic potential while disagree quantitatively for the anharmonic potential. This clearly indicates that the Maxwell-Schrödinger scheme is indispensable to multi-physics simulation particularly when the anharmonicity effect plays an essential role.