In this paper, a general design of an equal-split N-way power divider, similar to Bagley polygon power divider, but with an even number of output ports is proposed. A circularshaped 4-way divider is designed and simulated using two different full-wave simulators. Very good matching at the input port is achieved, and good transmission parameters are obtained. After that, the same circular-shaped divider is redrawn in a rectangular form to save more circuit area, and to align the four output ports together. For verification purposes, the 4-way rectangular-shaped Bagley power divider is simulated, fabricated and measured. Both simulation and measurement results prove the validity of the design.

In this paper, different topologies of dual-frequency modified 3-way Bagley polygon power dividers are designed and analyzed. Equal split power division is achieved at arbitrary design frequencies. In the first structure, two-section transmission line transformer is used to realize the dual-frequency operation. In the second and third structures, dual-frequency T-shaped and π-shaped matching networks are used. For the sake of simplicity, closed form design equations are presented for each matching network. To validate the design procedure, three examples are designed, simulated, and fabricated. The three matching networks are explored through these three examples. The design frequencies are chosen to be 0.5 GHz and 1 GHz.

The present contribution is concerned with an exact frame-based pulsed-beams expansion of planar aperture time-dependent electromagnetic fields. The propagating field is described as a discrete superposition of tilted, shifted and delayed electromagnetic pulsed-beam waveobjects over the frame spectral lattice. Explicit asymptotic expressions for the electromagnetic pulsed-beam propagators are obtained for the commonly used pulsed-quadratic windows.

This paper presents an efficient hybrid simulation technique for analysis of the electromagnetic field interactions between multi-transmitters and receivers located within a closed environment. The Method of Moments/circuit method is first used for modeling of the transceivers and their nearby surrounding to obtain the equivalent sources/receivers. Then, an approach that combines the asymptotic method and the ray tracing technique is deployed to calculate the long-distance coupling between a pair of transmitter and receiver. The acceleration algorithms for ray tracing have been developed to deal with more complex scenarios. The seamless combination between the circuit, numerical, and asymptotic approaches is the key to get accurate simulation results. Several numerical examples and experimental results are presented to demonstrate the efficiency of the proposed technique.

Accurate and effective system-level modeling has become necessary to address electromagnetic compatibility (EMC) issues in modern circuit and system design. Model order reduction (MOR) techniques provide a feasibility to approximate complex circuit models with compact reduced-order models. In this paper, an effective MOR technique entitled multi-point moment matching (MMM) is implemented for the partial element equivalent circuit (PEEC) modeling. Moment information at multiple frequency points is used in this method in order to accurately estimate a given system over an entire frequency range of interest, and for each frequency an enhanced asymptotic waveform evaluation (AWE) is applied to obtain a reduced-order model by constructing a pole-residue representation of the original transfer function. The improvements of conventional AWE in aspects of both moment computation and moment matching can avoid ill-conditioned moment matrices and unstable dominant poles. The complex frequency hopping (CFH) technique is employed to select the multiple expansion points by using a newly developed upwardsearch algorithm. Numerical simulations of coupled microstrip lines in both frequency and time domain indicate the effectiveness of the proposed method.

The Wave Concept Iterative Procedure is validated for multi-layered substrate with frequency dependent and negative index media. By shifting the plasma frequency, reconfigurable filter design is proposed with a center frequency tunability of 25%. Sensitivity to collisional plasma is proposed.

The broadband microstrip antenna is realized by cutting the slot inside the patch. The slot introduces a resonant mode near the fundamental resonance frequency of the antenna and realizes broadband response. The compact variations of circular microstrip antenna are realized by placing the shorting posts along the zero field line at the fundamental mode. These shortened antennas have narrower bandwidth. In this paper, a compact half U-slot cut shorted sectoral microstrip antenna is proposed. The detailed analysis has been carried out to study the effect of the slot on various modes of the Sectoral patch. It has been observed that the half U-slot does not introduce any additional mode, but reduces the resonance frequency of the higher order mode of the shorted Sectoral patch and along with its fundamental mode realizes broader bandwidth. The bandwidth of more than 700 MHz, at the center frequency of approximately 2700 MHz, has been realized.

In this work, we theoretically investigate the tunable photonic band gap (PBG) in a semiconductor-dielectric photonic crystal made of highly doped n-type silicon (Si) layers alternating with silicon oxide layers. The tunable characteristic is studied by changing the donor impurity concentration in Si layer. The PBG is numerically analyzed in the near infrared frequency region from the reflectance calculated by the transfer matrix method. The effect of filling factor in Si layer on the photonic band gap is also illustrated. These tunable properties in such a photonic crystal provide some information that could be of technical use to the semiconductor optoelectronics, especially in communication applications.

The present study deals with a novel approach for fractional space generalization of the differential electromagnetic equations. These equations can describe the behavior of electric and magnetic fields in any fractal media. A new form of vector differential operator Del, and its related differential operators, is formulated in fractional space. Using these modified vector differential operators, the classical Maxwell equations have been worked out for fractal media. The Laplace, Poisson and Helmholtz equations in fractional space are derived by using modified vector differential operators. Also a new fractional space generalization of the potentials for static and time varying fields is presented.

This paper studies the excitation of a physical leaky mode in a covered microstrip structure at low frequencies. We calculate the current excited in the line by a delta-gap voltage source via a full wave analysis based on a mixed potential integral equation scheme. The current in the line is decomposed into its bound mode and continuous spectrum components. The bound mode component is associated with the propagation effects whereas the continuous spectrum component is associated with reactive and/or radiative effects and contains the contribution of the leaky mode. Our analysis also includes a detail study of the dispersion relations of the bound and leaky modes along with their corresponding electric fields. At low frequencies, in the covered microstrip structure with a low top cover height, we have found that the bound mode role is superseded by the leaky mode, in the sense that it is the leaky mode which partially or totally carries the signal energy. Therefore, the spurious effects associated with the excitation of a leaky mode, which usually appear at high frequencies in open microstrip lines, appear here in the low frequency range. This effect may have very relevant practical consequences in the performance of such systems.

Power transformers in service are subjected to a wide variety of electrical, mechanical and thermal stresses capable of producing insulation faults. This type of failure figures amongst the most costly faults in distribution networks since it produces both machine outage and electrical supply interruption. Major research effort has therefore focused on the early detection of faults in the insulating systems of large high voltage power transformers. Although several industrial methods exist for the on-line and off-line monitoring of power transformers, all of them are expensive and complex, and require the use of specific electronic instrumentation. For these reasons, this paper will present the On-Line analysis of transformer leakage flux as an efficient alternative for assessing machine integrity and detecting the presence of insulating failures during their earliest stages. An industrial 400 kVA-20 kV/400V transformer will be used for the experimental study. Very cheap, simple sensors, based on air core coils, will be used to measure the leakage flux of the transformer, and non-destructive tests will also be applied to the machine in order to analyse pre- and post-failure voltages induced in the coils.

This paper proposes a novel approach for the spatial microwave power combining. Anisotropic metamatierials are employed to trim the combined electrical fields and form a single beam radiation pattern. The radiation characteristics of a binary horn antennas array are investigated both numerically and experimentally at 12 GHz. The results show that much higher combining efficiency can be achieved. Given a designed combining efficiency, the strict relative position requirements in each transmission unit are reduced in this scheme.

Recent research into very large, regularly shaped, geological structures has shown that in the 100 kHz to 10 MHz frequency range electromagnetic waveguide behaviour is observed when the material forming the structure is not too lossy (conductivity σ<0.0001). While mode formation and modal behaviour in electromagnetic waveguides is very well understood, much of the literature describes high frequency structures for which it can generally be assumed that the loss tangent of the wave guiding medium (tanδ) is very much less than unity. In this case wave attenuation is small and can generally be considered to be insignificant. This is not true for large low frequency waveguides, such as those formed by geological strata, and little seems to have been reported in the literature on the nature of modes in waveguides of this description. The paper takes the form of a parametric study aimed at ascertaining the limitations to modal formation in waveguides, for which tand is greater than unity, by revisiting the basic equations describing electromagnetic wave propagation in lossy media. The theoretical predictions are supported by modelling studies on large waveguide strata formed from material layers with dimensions typical of a geological structure such as a coal seam or oil-wet, strata-bound, petroleum reservoir.

Great accuracy and reasonable computational time are desirable in a deterministic ray tracing model for an efficient radio frequency planning. An algorithm to speed up a ray tracing engine is described which allows to select arbitrary areas around transmitters and receivers by dividing the scene in a voxel chessboard. The reliability of the algorithm has been evaluated by comparing measured and predicted path losses in real urban scenarios while the algorithm performance is expressed in terms of computational time reduction.

We experimentally characterize the pulse-shortening phenomena in traveling-wave field effect transistors (TWFETs). When a decreasing voltage pulse is applied to the gate line and an increasing voltage pulse is simultaneously applied to the drain line, a sinusoidal wave supported by an exponential edge is developed in the drain line. In order to make the velocity of the sinusoidal wave coincident with that of the exponential edge, the wavenumber of this sinusoidal wave must be considerably increased. Moreover, the small-amplitude parts of the wave disappear with the shorter propagation while the large-amplitude ones remain in the drain line. The input pulse is considerably shortened owing to these two properties. This paper validates the pulse-shortening phenomena by performing several measurements using a breadboarded TWFET.

A printed broadband planar inverted-F antenna (PIFA) with zeroth-order resonator (ZOR) loaded is proposed whose shorting strip of the PIFA is replaced by an inter-digital capacitor and thin inductive strip in series. The loaded inter-digital capacitor and thin inductive strip act as a shorting strip at the 3.1 GHz, which allows the antenna to maintain its regular performance. Around 2.0 GHz, the antenna with the inter-digital capacitor and thin inductive strip works on the zeroth-order resonance mode, which makes the physical size be independent of the wavelength. By merging the two modes, a broadband performance can be achieved. The size of the antenna is only 12.5 mm×7.81 mm×1.6 mm with single layer. The measured antenna bandwidth is 1.63 GHz (about 65%), total gain is above 2.5 dBi and the simulated radiation efficiency is over 90% in the working band. Especially the antenna has same direction of the radiation patterns in the broadband. In the end, the antenna with lumped elements loading is also discussed.

The dielectric pyramid loaded and the dielectric cone loaded diagonal horn working at 150 GHz are investigated by using Gaussian beam mode analysis. With extremely low cross-polarized and axially symmetrical field distribution in the horn aperture, the calculated fundamental Gaussian mode coupling achieves about 98%. The far field radiation patterns of the two antennas are analyzed using fundamental Gaussian mode aperture-field distribution model whose results agree with high-accuracy CST^TM software computations, indicating that the dielectric loaded horns radiate fine Gaussian beams. The dielectric loaded geometry may be used to modify the diagonal horns with distorted beam.

This paper presents a novel compact suspended double side millimeter bandpass filter (BPF) with wide stopband using Suspended Compact Microstrip Resonant Cell (SCMRC). For SCMRC exhibit slow-wave band-stop characteristics, two distributed SCMRC structures are designed to achieve wide stopband characteristic. By apply SCMRC structure and double side design, this novel BPF is size reduced. Back-to-back rectangular waveguide to suspended microstrip probe transitions at different millimeter bands are designed and fabricated to verify transmission characteristics of novel SCMRC bandpass filter. Experimental results show low insertion loss (< 1.2 dB) in the passband and sharp, wide rejection in the stopband with about 150% bandwidth (below -15 dB, from 50 GHz to 100 GHz), make good agreement with simulated results.

Metamaterial covers exhibit inimitable electromagnetic properties which make them popular in antenna engineering. A traditional metamaterial cover has an identical transmission phase for a normally incident plane wave regardless of its polarization state. The purpose of this research is to show the possibility of using a polarization dependent metamaterial cover to change the polarization state of the incident plane wave. Novel polarization-dependent metamaterial (PDMTM) covers, whose transmission phases for two principal polarizations are different, are presented. A full-wave FDTD numerical technique developed by the authors is adopted for the simulations.

A simple and efficient joint algorithm of finite difference time domain (FDTD) and periodic boundary condition (PBC), called as the direct spectral FDTD method, has been investigated to study three-dimensional (3D) periodic structures with oblique incidence, where both the azimuth angle φ and the elevation angle θ are varying. The number of sampling points for the horizontal wave number can be determined by using an adaptive approach. As numerical results, the transmission and reflection coefficients from split-ring resonators (SRRs) and a dielectric grating slab are computed to validate the accuracy and efficiency of the direct spectral FDTD method. The computed results are in good agreement to the published ones obtained by other methods.