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.

Fragment structure should find its application in acquiring high isolation between multiple-input multiple-output (MIMO) antennas. By gridding a design space into fragment cells, a fragment-type isolation structure can be constructed by metalizing some of the fragment cells. For MIMO isolation design, cells to be metalized can be selected by optimization searching scheme with objectives such as isolation, return losses, and even radiation patterns of MIMO antennas. Due to the exibility of fragment-type isolation structure, fragment-type structure has potentials to yield isolation higher than canonical isolation structures. In this paper, multi-objective evolutionary algorithm based on decomposition combined with genetic operators (MOEA/D-GO) is applied to design fragment-type isolation structures for MIMO patch antennas and MIMO PIFAs. It is demonstrated that isolation can be improved to different extents by using fragment-type isolation design. Some technique aspects related to the fragment-type isolation design, such as effects of fragment cell size, design space, density of metal cells, and efficiency consideration, are further discussed.

This article proposes a new design of wideband wide beam microstrip like antenna (MLA) in X-band (8-12 GHz) overcoming the limitations of conventional MLA design. The waveguide is filled with a dielectric material, which is shaped beyond the waveguide aperture as a pyramidal structure. This helps in achieving the size reduction of the waveguide and matching of aperture admittance over the complete operational band. Also a vertical electric dipole feed design is proposed to excite MLA and match the source and load admittances. The input reflection coefficient observed over the complete band is better than -10 dB. The measured gain and cross polarized levels of antenna achieved are better than 3 dBi and -18 dB across the bandwidth, respectively. The measured and simulated results are in good agreement.

This article presents a comprehensive review of the research carried out on Dielectric Resonator Antennas (DRAs) over the last three decades. Dielectric resonator antennas (DRAs) have received increased attention in various applications due to their attractive features in terms of high radiation efficiency, light weight, small size and low profile. Over last decades, various bandwidth enhancement techniques have been developed for DRAs. In this article, the attention is focused on a type of DRAs that can offer multi-resonance frequencies and these frequencies can be merged into a broad band. In order to effectively review design techniques, DRAs in this article are categorized into three types, broadband, ultra-wideband (UWB) and multiband. The latest developments in DRAs are discussed in the limited scope of this article.

A Multiple Input Multiple Output (MIMO) antenna consisting of two 90° angularly separated semicircular monopoles with steps for Bluetooth, Wi-Fi, Wi-MAX and UWB applications is proposed. Initially, an array of two coplanar circular monopoles with element separation of 25 mm is investigated. In this configuration, mutual coupling is < -5 dB and < -10 dB over 2 GHz-3 GHz and 3 GHz-10.6 GHz, respectively. Mutual coupling is reduced by using 90° angularly separated semicircular monopoles. With semicircular configuration, though the mutual coupling is improved, impedance bandwidth is reduced due to reduction in electrical length. A step like structure is introduced in the semicircular monopoles, and ground plane is modified and extended between the two elements to improve the impedance bandwidth and mutual coupling. Impedance bandwidth from 2.0 GHz-10.6 GHz with S₂₁ < -20 dB and -14 dB is achieved over 3.1 GHz-10.6 GHz and 2.0-3.1 GHz, respectively. The antenna is fabricated using 46 mm × 37 mm RT Duroid substrate. Measurement results agree with the simulation os. Radiation patterns are stable, and correlation coefficient is < 0.02 over 2.0-10.6 GHz.

A novel method of the aerosolized gene delivery is proposed, and its feasibility is computationally analyzed. Aerosolized DNA or siRNA attached to magnetic particles can be accelerated using ponderomotive force to high velocities in a pulsed magnetic field of a solenoid and efficiently delivered to cell culture or to the lung epithelium. The proposed noninvasive method of intra-cellular gene delivery can be considered as a combination of principles of classical high-pressure air jet gene delivery with magnetophoresis.

The visibility distribution, which is related to the configuration of stations, can be categorized into different features, each having different levels of data number density. A computationally efficient multi-feature image reconstruction algorithm, well adapted for next-generation telescopes, is proposed based on this observation, which is more flexible to handle massive amount of visibility data expected in the future. In reconstructing the M87 image with the visibility data simulated on the Low-Frequency Array (LOFAR), this algorithm turns out to be a few hundreds to one thousand times faster and is more resilient to noises than the conventional algorithms.

Decoupling networks (DNs) have frequently been used to obtain high isolation performance between coupled antennas in multiple-input multiple-output (MIMO) systems due to their advantage of spatial efficiency, which is particularly important for mobile devices. However, conventional DNs suffer from narrowband limitations. In this paper, a broadband decoupling technique is proposed that broadens the isolation bandwidth using a parallel resonant point. A 1.95 GHz MIMO antenna system with 460 MHz of bandwidth (fractional bandwidth, FBW = 23.6%) is designed and measured using the scattering parameters. The isolation is found to be better than -15 dB, while the reflection coefficient is better than -6 dB. Furthermore, the antenna efficiency and envelope correlation coefficient (ECC) are evaluated in a reverberation chamber.