This paper introduces a new configuration for a two phase field assisted hybrid switched reluctance generator, which can operate in motoring mode as well. This concept allows higher output power production compare to standard SRG. The proposed novel generator consists of two magnetically independent stator and rotor sets (layers), where each stator set includes four salient poles with windings wrapped around them, while the rotor comprises of two salient poles with different arc lengths and no windings. There is a stationary reel, which has the field coils wrapped around it and is placed between the two-stator sets. In this format, the developed magnetic field from the stator poles travels to the rotor then to the rotor shaft and finally completes its path via the generator housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. The analysis is carried out for the machine in self exited generator mode as well as field assisted mode. In the numerical analysis, the finite element analysis is employed, whereas in the experimental study, a proto-type generator has been built and tested.

We report on the modeling of light reflection in disordered chirped mirrors with a photonic band gap in the visible. The stop band limits have a threshold-like behavior as a function of disorder and sustain a certain amount of disorder before changing. We determine the disorder value that leads to a substantial broadening of the total reflection range.

This work presents a novel design for high-impedance surface (HIS) embedded dielectric resonator (DR) structures to efficiently control bandwidth of suppressing simultaneous switching noise (SSN) in high speed digital printed circuit boards (PCBs). The proposed structure is designed by periodically embedding high dielectric constant materials into the substrate between a continuous power plane and a middle patch. A conventional HIS structure has only one resonance frequency to produce stopband while the proposed structure has two resonances to widen the suppression bandwidth. The -30 dB stopband of the proposed structure is about two times wider than that of a conventional HIS structure. The excellent SSN suppression behavior was verified by measurements and simulations.

In traveling wave tube (TWT) amplifiers, an axial focusing magnetic field is required to keep electrons traveling in a narrow, pencil-like beam over the considerable length of the circuit. Conventionally, this focusing has been accomplished by using a periodic permanent magnet system housing axially polarized ring magnets. Making the structure to this point has been a complicated process consisting of brazing multiple metals together and honing the piece to the desired specifications. We present a new method of fabricating this housing structure monolithically using iron, developing magnetically oversaturated housing regions, and saving processing time and effort.

In this paper, the wave propagation and the cutoff frequencies of a rectangular metallic waveguide, partially filled the metamaterial multilayer slabs have been studied. The equations of the TMM method are not complex and the numerical examples show that we can easily obtain the characteristics of the metamaterial multilayer's rectangular waveguide satisfyingly. The cutoff frequencies of the metamaterial waveguide show very different characteristics compared with the usual waveguide.

Strong visible green upconversion emission in nanocrystalline BaZrO₃:Yb³⁺ powder, obtained by a hydrothermal process at 100ºC, is reported. The unconverted emission has a quadratic dependence on the pump intensity with a lifetime around half that of the NIR lifetime. Results suggest cooperative upconversion as the mechanism responsible for the green fluorescence. This efficient Yb³⁺-based cooperative up-conversion process allows the development of novel emitting materials in the UV-VIS range.

This paper demonstrates a novel way to enhance the temperature sensitivity in one-dimensional (1D) photonic band gap (PBG) material by using a ternary periodic structure (i.e. three material layers constituting a period of lattice). The temperature sensitive wavelength band shift of (Si/SiO₂) periodic structure was significantly enhanced when the structure was modified by sandwiching a thin layer of Bi₄Ge₃O₁₂ between every two layers, constituting a period of lattice. When the thickness of sandwiched layer was increased further enhancement in temperature sensitivity was observed. These 1D ternary PBG structures can be substituted in place of 1D binary PBG for enhancing the temperature sensing performance.

In this work, we present a novel DC-bias network for multiharmonic microwave circuits based on an arbitrarily width-modulated microstrip line. The arbitrary shape of the width-modulated microstrip line is obtained by using multiple microstrip taper sections. The method is illustrated through the design of four different DC-bias networks blocking from 1 to 4 harmonic components of a 2.5 GHz signal. The designs with an optimum shape for the arbitrarily widthmodulated microstrip line have been manufactured and measured, obtaining a good agreement between the simulated and measured behavior.

Photonic band structure and reflection properties of one-dimensional magnetic star wave-guide (MSWG) structure composed of a backbone (or substrate) waveguide along which a finite side branches grafted periodically have been investigated. The dispersion relation and hence the photonic band gaps (PBGs) of the magnetic SWG structure have been obtained by applying the Interface Response Theory (IRT). Investigation of dispersion characteristics shows that the existence of band gaps in magnetic SWG structures does not require the contrast in the wave impedance of the constituent materials, which is unlike the usual magnetic photonic crystal structure, where there must be the contrast in the wave impedance for the existence of the band gaps. Moreover, magnetic SWG structures have wider reflection bands in comparison to normal magnetic photonic crystal (MPC) structure for the same contrast in the wave impedance. Analysis shows that the width of forbidden bands for MSWG structure changes with the change in permittivity and permeability of the backbone, and side branches materials even the ratio of wave impedance is the same, but it remains the same in case of MPC structure. In addition to this, we have studied the effects of variation of number of grafted branches and substrates i.e., number of nodes on the reflection bands of magnetic SWG structure.

In this paper, inhomogeneous planar layers are optimally designed as reflection wave polarizers in a desired incidence angles range. First, the electric permittivity function of the structure is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The validation and the performance of the proposed structure are verified using some examples.

In this paper, the effective skin depth which provides a useful evaluation for field penetration in multilayer coated conductor is proposed. The reflection on the interface between the adjacent conductors is considered in theoretical derivation. It is found that the effective skin depths of the gold and gold-nickel coated copper rapidly vary with the thickness of the outer layer (gold) when the gold thickness is less than twice gold skin depths and achieve stabilization as the gold thickness increases to five times gold skin depths.

The generalized forward-backward and novel spectral acceleration (GFB/NSA) method is applied to capacitance extraction problems of finite planar periodic structures. In the GFB method, the interaction within a unit cell can be calculated and stored beforehand. The interactions between relatively far-separated unit cells are however calculated by the GFB/NSA method to further accelerate the calculation speed. The contributions to a receiving element on finite planar periodic structures are separated into weak and strong source contributions by an appropriate separation index, which is conveniently specified by an amount of unit cells rather than a distance. The strong source contribution is performed by the standard matrix-vector multiplication in the GFB method, while the weak source contribution is computed using the NSA algorithm. Numerical examples show comparisons of the GFB/NSA method with a commercial software, including the efficiency of the method. With the array increment in one direction, the GFB/NSA method shows O(N) in the calculation time per iteration, while its memory requirement for a very large problem also tends to be O(N), where N is the number of unknowns.

A novel approach for logic state dependent generation of polarized photon is proposed, where the logic states '0' and '1' are represented by two sub-spaces in the Hilbert space of the hyperfine states of rubidium atom (⁸⁷Rb). Each subspace consists of a ground state, an intermediate state and an excited state. The atom is placed at the center of a two-mode cavity, and the cavity modes correspond to frequencies of the generated photon. Photon generation process involves raising the atom to the excited state within the corresponding subspace and letting it decay back to the initial (ground) state, emitting thereby a photon of logic state dependent polarization. In order to keep the driving laser frequencies far off from the cavity mode frequencies, the atom is raised to the excited state in two steps --- first from the ground state to the intermediate state and then from the intermediate state to the excited state. Polarization states of the photon represent the logic states, and can be used to transport logic from one node to another of the quantum network.

A compact circularly polarized (CP) microstrip antenna with inserted nine cross slots is proposed to reduce the size and widen the beamwidth. The antenna is operated at 1.268 GHz, and built by using a substrate with a coaxial probe feed. The impedance bandwidth (VSWR < 2) is 1.5% and the 3 dB axial ratio bandwidth is 0.52%. The measure gain is 4.5 dBi and beamwidth is about 110^o. The measured results for the compact CP antenna with embedded cross slots size shows that the resonate frequency is significantly lowered from 1.951 GHz to 1.268 GHz, corresponding to a 35% antenna size reduction compared with the one without any slot.

This paper investigates a miniaturized resonant antenna that comprises a meandered monopole and a partial ground plane. A bandwidth enhancement is found using the ground plane on the back side of the circuit board where the entire communication system resides. The meandered monopole together with the ground plane forms a wideband dipole antenna. The design shows over 25% 10 dB impedance bandwidth at 2.5 GHz ISM band with a monopole area of 300 mils by 166 mils on a small circuit board and a backside ground plane 1500 mils by 600 mils. The wire length is about one third and the Q factor is about twice as compared against the case of using a straight quarter-wave microstrip monopole. The antenna Q factor as a function ground plane area is characterized. The use of circuit ground as a part of an antenna should find useful applications in portable wireless systems. Good agreements are found between simulated and measured antenna gain patterns and return loss.

In this article, we demonstrate that in the case of a positive group velocity left-handed nonlinear (LH-NL) transmission line with series nonlinear capacitances, the spatial derivative of the voltage distribution satisfies the nonlinear Schrödinger (NLS) equation. Consequently, it will shown that a LH-NL transmission line with series varactors can be used to generate both bright and dark solitons similar to a composite right-left-handed (CRLH) transmission line periodically loaded with shunt varactors. The paper also discusses the conditions for generation of bright and dark solitons.

Leakage fields are one of the main issues in design of electromagnetic systems. Some of these fields close their paths through the core and air, giving rise to non-ideal behavior of the magnetic systems. This paper explains a novel concept of active shielding which consists of two compensation coils in series and generates a counter field opposite to the leakage fields leaking from an iron-core system. As the method is based on physical reasoning of electromagnetic coupled circuit theory, the design criterions for the compensating coils parameters, their number of turns and their adaptation to the systems, were considered. The state of the art is presented by a model which is verified by roots of system characteristic equations, using state equations. In a case study, this method was investigated in a 25kA (125kVA) current injection transformer (CIT) system delivering a secondary current as closely proportioned to the primary current as possible, using finite element method (FEM) simulation. This paper will also push the state of the art by reducing the age effect of the CIT through mechanical force reduction.

Microwave imaging is one of the most promising emerging imaging technologies for breast cancer detection. Microwave imaging exploits the dielectric contrast between normal and malignant breast tissue at microwave frequencies. Many UWB radar imaging techniques require the development of accurate numerical phantoms to model the propagation and scattering of microwave signals within the breast. The Finite Difference Time Domain (FDTD) method is the most commonly used numerical modeling technique used to model the propagation of Electromagnetic (EM) waves in biological tissue. However, it is critical that an FDTD model accurately represents the dielectric properties of the constituent tissues and the highly correlated distribution of these tissues within the breast. This paper presents a comprehensive review of the dielectric properties of normal and cancerous breast tissue, and the heterogeneity of normal breast tissue. Furthermore, existing FDTD models of the breast are examined and compared. This paper provides a basis for the development of more geometrically and dielectrically accurate numerical breast phantoms used in the development of robust microwave imaging algorithms.

In this paper, we describe a new full-wave integral equation model to tackle electromagnetic scattering problems arising from objects buried in layered media. Such a model is a rewriting of the usually adopted Contrast Source integral equation and is named Contrast Source-Extended Born (CS-EB) owing to this circumstance and to the relationship existing among its linearization and the Extended Born approximation. By means of this alternative formulation, it is possible to modify the relationship among the scatterer permittivity and the field it scatters, thus possibly reducing the degree of non-linearity of this latter relationship. Accordingly, in these cases, the adoption of the CS-EB model may be convenient with respect to traditional ones in both forward and inverse scattering problems.

This paper presents the 3-D dispersion analysis of finite-difference time-domain (FDTD) schemes for doubly lossy media, where both electric and magnetic conductivities are nonzero. Among the FDTD schemes presented are time-average (TA), time-forward (TF), time-backward (TB) and exponential time differencing (ETD). It is first shown that, unlike in electrically lossy media, the attenuation constant in doubly lossy media can be larger than its phase constant. This further calls for careful choice of cell size such that both wavelength and skin depth of the doubly lossy media are properly resolved. From the dispersion analysis, TF generally displays higher phase velocity and attenuation errors due to its first-order temporal accuracy nature compared to second-order ETD and TA. Although both have second-order temporal accuracy, ETD has generally lower phase velocity and attenuation errors than TA. This may be attributed to its closer resemblance to the solution of first-order differential equation. Numerical FDTD simulations in 1-D and 3-D further confirm these findings.