According to the derived transfer function using different orders of approximation, stability and signal transmission analysis of a driven metallic single-walled carbon nanotube (SWCNT) bundle interconnect are performed. It is shown that as the length of SWCNT bundle interconnect increases, the poles will be closer to the imaginary axis, which causes the transmitted signal response tends to be more damping. Using the fourth-order approximation of the transfer function, the transmitted pulse waveform along the SWCNT bundle interconnect is captured accurately, with signal overshoot and time delay examined. Further, a complete physical model for the transient response of carbon nanotube bundle interconnect is derived, which can also accurately predict the transient response of carbon nanotube bundle interconnect including time delay and crosstalk.

Medical implants in the form of linear conductive structures partially insulated along their length are especially prone to induced heating when subjected to the radiofrequency field used during magnetic resonance imaging (MRI). Leads or similar structures are often implanted near the skin and we have analyzed such implants when the implantation depth is varied in steps from 3 mm to 9 mm or more. Current, electric field, and induced temperature rise distributions in tissue have been obtained. The results have been validated by laboratory measurements.

A Modular Toroidal Coil (MTC) is composed of several solenoidal coils (SCs), which are connected in a series and distributed in the toroidal and symmetrical form. This paper presents analytical equations of mutual inductance and electromagnetic torque of the MTC applicable to Tokomak reactors. These equations are based on those formulated by Neumann. The numerical analysis of the integrations resulting from these equations is solved using the extended three-point Gaussian algorithm. The results obtained from the numerical simulation agree with the empirical results, the experimental results, and the virtual work theorem, which indicates the reliability of the presented equations. The behavior of the mutual inductance of the coil shows that the maximum stored energy is obtained when the electromagnetic torque is zero, and vise versa.

This paper presents a fast and effective electromagnetic reconstruction algorithm with phaseless data under weak scattering conditions. The proposed algorithm is based on the phaseless data multiplicative regularized contrast sources inversion method (PD-MRCSI). We recast the weak scattering problem as an optimization problem in terms of the undetermined contrast and contrast sources. Using the conjugate gradient iterative method, the problem is solved by alternately updating the contrast sources and the contrast. Additionally, this method can combine with the PD-MRCSI method. Taking advantage of the properties of fast convergence of this algorithm and stable convergence of PD-MRCSI method, the combined technique makes image reconstructions more fast and effective. Although the method is derived from weak scattering situation, it is also useful for the case which weak scattering approximation is not satisfied. The synthetic numerical reconstruction results, as well as experimental reconstruction results, presented that the proposed method is a very fast and effective reconstruction algorithm.

Microwave inverse scattering approaches have shown their effectiveness in imaging inaccessible regions. Unfortunately, the problem at hand is strongly non-linear and ill-posed and therefore it is often solved by seeking for the global minimum of a proper functional. Nevertheless, it is also necessary to introduce suitable regularizations in order to improve the convergence of the reconstruction process toward a reliable solution. In this context, the paper presents a method that exploits an energetic constraint to define a regularization term of the cost functional. A numerical validation with single and multiple inhomogeneous lossless targets demonstrates that an improvement of the reconstruction accuracy is achievable without introducing significant computational complexity to the inverse scattering problem.

Novel complementary split ring resonator (CSRR) is introduced to increase the stop bandwidth. Despite of their exotic behavior due to negative permittivity, their performance is limited by their stop bandwidth. The orientation of CSRR etched on the ground has strong coupling that can be altered for the increased stop bandwidth. The proposed design has measured stop band from 4~7.25 GHz whereas conventional CSRR of same dimension has stop band from 4.1~5.0 GHz.

In this paper, an innovative method for obtaining a pencil beam pattern is presented. Planar arrays of parasitic dipoles are used to modify the pattern of an active dipole above a ground plane, in order to obtain a pencil beam of moderate gain and bandwidth. Only one feed point and one active element provides a very simple feeding network that reduces the complexity of the antenna. The correct configuration of the elements of the parasitic arrays allows to obtain the desired pencil beam pattern. Three designs that use parasitic arrays fed by a λ/2-dipole and synthesize pencil beam patterns are shown: 1) an antenna designed at 1.645 GHz and composed by one layer of 49 parasitic elements; 2) an antenna designed at the same frequency but composed by two layers of 49 parasitic elements; 3) an antenna designed at 5 GHz, composed by one layer of 49 parasitic elements, and taking into account the dielectric substrate and teflon screws.

To analyze resonances in an axisymmetric inhomogeneous cavity, a higher-order finite element method (FEM) is developed. Mixed higher-order node-based and edge-based elements are applied to eigenvalue analysis for the azimuthal component and meridian components of the field, respectively. Compared with the lower-order FEM, the higher-order FEM can improve accuracy with the same number of unknowns and can reduce the CPU time and memory requirement for specified accuracy. Numerical results are given to demonstrate the validity and efficiency of the proposed method.

Analytical formula for the cross-spectral density matrix of a twisted electromagnetic Gaussian Schell-model (TEGSM) beam propagating through an astigmatic ABCD optical system in gain or absorbing media is derived based on the unified theory of coherence and polarization. Generalized tensor ABCD law in media is derived. As an application example, the evolution properties of the degree of polarization of a TEGSM beam in a Gaussian cavity filled with gain media are studied numerically in detail. It is shown that the behavior of the degree of polarization depends on the parameters of the gain media and the TEGSM beam. Our results will be useful for the spatial modulation of polarization properties of stochastic electromagnetic beam.

Electrically small oblate spheroidal and spherical antennas in confocal shells with negative permittivity represent perspective antenna design to combine moderately small size, wide bandwidth, high e±ciency and power of radiation. However, optimization of the antennas performance parameters imposes contradictory restrictions on permittivity of the shells, electrical size of the antennas, shape of the antennas and shells. Simulation results based on method of eigen-functions have shown that the antennas can be tuned on resonance for small magnitudes of negative permittivity of the shells and antiresonance for higher magnitudes. Optimal combination of power and efficiency of radiation of the antenna and the quality factor is obtained in an intermediate range of negative permittivity by combining merits of resonance and antiresonance of the antenna. Antiresonant range of the oblate spheroidal antenna emerges for lower permittivity magnitudes as compared with the spherical antenna. As a result, the optimal size of the shell of oblate spheroidal antenna is comparatively small. However, more gradual emerging of antiresonant properties of the spherical antenna makes spherical design more suitable for higher level of inherent absorption of the shell medium with negative permittivity.

A compact dual-mode open stub-loaded resonator and bandpass filter (BPF) is proposed in this paper. The resonator, which is formed by attaching a disc-shaped open stub and circular open stubs in pairs to a high impedance microstrip line, generates two operating modes in the desired band, and the even-mode resonance frequency can be flexibly controlled by the disc-shaped open stub at central plane, whereas the odd-mode one is fixed. The four transmission zeros are created to sharpen the rejection skirt, suppress two high harmonic resonant modes and deepen upper-stopband, respectively. Experimental results of the dual-mode filter which incorporates this resonator with parallel-coupled feed line with tuning stub at 5.8 GHz show good agreement with the simulated ones. The size for the resonator is only 4.7 × 3.4 mm (0.29λg×0.21λg in which λg is the guided wavelength of 50 Ω microstrip at 5.8 GHz).

This paper proposes a novel compact dual-band bandpass filter (BPF) using four spiral resonators for application in GSM and IEEE 802.11b WLANs for the first time. Since the two passbands can be tuned individually, the filter has more design freedoms. The symmetry coupling structure is realized to achieve a isolation higher than 30 dB between the lower and higher passbands. The full-wave simulator IE3D is used to design the spiral resonators and calculate the coupling coefficients of the basic coupling structures. The designed BPF is fabricated and measured. Good agreement between the simulated and measured results verifies our design concept.

This paper proposes magnetostatic analysis of Switched Reluctance Motor (SRM) under angular misalignment fault to evaluate the performance of the motor under different operating conditions. In this analysis three-dimensional finite element method (FEM) is used to simulate reliable and precise model by considering the complex motor magnetic geometry, end effects, axial fringing effects as well as nonlinear properties of the magnetic materials. The FE analysis is performed to obtain the static magnetic characteristics of SRM including flux density, flux linkages, terminal inductance and mutual inductance profile under different rotor positions for different varying degree of faults. Consequently, it presents assessing the features of mutual inductance in inactive phases to study the variations of diagnosis index. The results obtained present useful information regarding the detection of fault and its direction as well as the amount of angular misalignment fault in the motor. To the best knowledge of the authors, such an analysis has not been carried out previously.

The work is devoted to the problem of scattering of monochromatic electromagnetic waves on heterogeneous dielectric inclusions of arbitrary shapes. For the numerical solution of the problem, the volume integral equation for the electric field in the region occupied by the inclusion is used. Discretization of this equation is carried out by Gaussian approximating functions. For such functions, the elements of the matrix of the discretized problem are calculated in explicit analytical forms. For a regular grid of approximating nodes, the matrix of the discretized problem proves to have the Toeplitz structure, and the matrix-vector product with such matrices can be carried out by the Fast Fourier Transform technique. The latter strongly accelerates the process of the iterative solution of the discretized problem. Electric fields inside a spherical inclusion and its differential cross-sections are calculated and compared with the exact (Mie) solution for various wave lengths of the incident field. Internal electric fields and the differential cross-sections of a cylindrical inclusion are calculated for the incident fields of various directions and wave lengths.

In this paper, a novel compact quintuple-mode UWB bandpass filter (BPF) with sharp rejection skirt and wide upper-stopband performances is realized using stub-loaded multiple-mode resonator (MMR). The proposed resonator is formed by attaching two pairs of circular impedance-stepped open stubs in shunt and a pair of short-circuited stubs to high impedance microstrip line. By simply adjusting the radius of circular impedance-stepped open stubs and the lengths of short-circuited stubs, the first five resonant modes of the resonator can be roughly allocated within the 3.1--10.6 GHz UWB band meanwhile the high resonant modes in the upper-stopband can be suppressed. The short stubs in pairs can generate two transmission zeros near the lower and upper cut-off frequencies, leading to sharper rejection skirt outside the desired passband. Finally, a quintuple-mode UWB BPF is designed and fabricated, and the measured results demonstrate the feasibility of the design process.

In this paper, some common misconceptions in several papers dealing with the optimal design of multilayer microwave absorbers are indicated. Specifically, it is emphasized that Chew's recursive formula for the reflection coefficient of multilayer media for the TM polarization corresponds to the magnetic field, not the electric field. It is also emphasized that both TM and TE polarizations should have the same magnitude of the reflection coefficient for the case of normal incidence. Numerical optimal results are also presented and ompared with those existing in the literature.

Reverberation chambers are widely used in electromag-netic compatibility test facilities because they provide a large working volume and are cheaper than other types of test facilities. In addition, they provide a statistically uniform field and generate a high maximum electric field within a relatively large volume. The volume of the cavity, the structure of the stirrer, and high tested frequency must be used in the reverberation chamber appropriately. Changing a volume of cavity dimensions and test frequency can be difficult in the reverberation chamber because they were determined already in the design process. In these cases, the stirrer should be changed. We investigated of the effects of various stirrer angles and heights on a reverberation chamber. The optimization of the stirrer with respect to various stirrer parameters was investigated; these parameters are related to field uniformity, the quality factor, stirred efficiency, and electric field polarity. Our results suggest that a reverberation chamber can be successfully operated if careful decisions are made regarding the stirrer design.

The study of a planar circular slot antenna for Ultrawideband (UWB) communications is presented. The integration on this antenna of a notch filter, to reduce the possible interferences with the 5 GHz WLAN communications, has been discussed in detail. Four different structures, achieved by etching a suitable pattern on the antenna circular stub, have been considered, and their features have been compared. The antenna with symmetrical and inverted-L cuts shows the best performance, and it has been therefore realized and fully characterized. It shows very good matching features over the UWB band, and notable rejection of the 5 GHz WLAN band.

This paper proposes a novel multi-band monopole antenna for PDA phone. A simple inverted-U-shaped driven element operates frequency bands centered at 1710 and 2350 MHz, which achieve a bandwidth based on 6-dB return loss from 1550 to 2490 MHz sufficient for DCS, PCS, UMTS, and WLAN applications. A low frequency meander path and an impedance matching stub with a truncated slit located at ground plane operates frequency band centered at 910 MHz. The bandwidth from 868 to 995 MHz covers the GSM 900 application band. The design procedures and both simulated and measured results are presented and discussed in this paper.

The paper aims at solving the problem of plane electromagnetic waves scattered by N dielectric coated conducting strips. The method used is based on an asymptotic technique introduced by Karp and Russek for solving scattering by wide slit. The technique assumes the total scattered field from each coated strip as the sum of the scattered fields from the individual element due to a plane incident wave plus scattered fields from factious line sources of unknown intensity located at the center of every element. The line sources account for the multiple scattering effect. By enforcing the boundary conditions, the intensity of the line sources can be calculated. Numerical examples are introduced for comparison with data published in the literature.