The modular toroidal coil (MTC) is composed of several solenoidal coils (SCs) connected in series and distributed in toroidal and symmetrical forms. In this paper, we present an accurate approach for calculation of the mutual and self-inductance between all the SCs of MTC with any arbitrary section. We use Biot-Savart's and Neumann's equations to calculate the self- and mutual inductance between two filamentary circular rings with inclined axes that lie in the same plane, respectively. Their centers are either displaced along the axis of one coil or displaced along one axis of the first coil and then displaced sideways. We use the extended three-point Gaussian algorithm to solve the numerical analysis of the integrations resulting from these equations. Additionally, we apply the filament method to calculate the inductance of the MTC coil. Moreover, the finite element method (FEM) is employed to obtain SC inductance. The results obtained using the FEM confirms the analytical and empirical results. Furthermore, the comparison of the behavior of SC inductance, when the dimensional parameters of the SC are changed, with the FEM results shows an error of less than 0.2%. In this approach, we clarify how the presented equations have to be used for different coil combinations in the filament treatment. Thus, the presented approach can be easily used to calculate the mutual and self-inductance of a MTC between any two MTC rings in three dimensions.

Two different approaches for compensating the probe positioning errors in a near-field-far-field transformation with cylindrical scanning using a nonredundant number of measurements are presented and experimentally validated in this paper. In order to evaluate the uniformly distributed samples from the irregularly spaced ones, the former makes use of the singular value decomposition method, whereas the latter employs an iterative technique. In both the cases, the near-field data needed by a standard nearfield-far-field transformation are efficiently evaluated via an optimal sampling interpolation algorithm.

A simple field analysis was developed for helical slow-wave structure symmetrically supported by rectangular shaped discrete dielectric support rods partially embedded in the metal segments projecting radially inward from a metal envelope for wideband traveling-wave tubes. The tape helix model was used for the prediction of the dispersion relation and the interaction impedance characteristics. The closed form simplified expressions are obtained by combining the tape model dispersion relation for free-space helix and the dielectric loading factor obtained for the loaded helix in the sheath model. The dispersion characteristics and the interaction impedance characteristics obtained by the present analysis were compared with other more involved analytical method reported in the literature for the similar helical slow-wave structure and found to be in close agreement. The present analytical results were also validated against HFSS simulation with an agreement within 5% for both the characteristics for a wide range of structure parameters. An appropriate choice of the structure parameters (helix thickness, height of the metal segments, material of the dielectric support rods, wedge segments angle and helix pitch) provided the phase velocity varying with frequency corresponding to flat to negative structure dispersion with an appreciable interaction impedance values over a wide frequency band. The present analysis enjoys simplicity and establishes the potential of theproposed helical interaction structure for its employment in wideband traveling-wave tubes.

Intelligent compression is important to image transmission in real time over bandlimited channels for synthetic aperture radar (SAR) payloads deployed on unmanned aerial vehicles (UAV), where target areas are encoded with high fidelity, while background data are encoded with lesser fidelity. A target-aided SAR image intelligent compression (TAIC)system is presented in this paper, which utilizes robust fixed-rate trellis-coded quantization (FRTCQ) to encode target sequences and FRTCQ to encode background sequences. Multiresolution constant false alarm rate (CFAR) detector in wavelet domain using db4 based on the multiscale model of target is embedded. Generic region of interest (ROI) mask is created. In order to achieve better quality of target areas decoded, ROI mask is modified. The improved performance using TAIC system by compressing target chips from training set and testing set in Moving and Stationary Target Acquisition and Recognition (MSTAR) database is demonstrated.

This paper describes a study on RF attenuation path loss behavior in suburban coverage within Cyberjaya and Putrajaya areas, located in Selangor State in Malaysia. The objective of this study is to develop and optimize a path loss model based on the existing Hata path loss model and outdoor measurement using frequency range from 400 MHz to 1800 MHz. The optimized model had been used and validated at places within Putrajaya area to find the relative error in order to assess its performance. The values for modified empirical parameters of Hata model were developed and presented in this paper. From the simulation result, the optimized model is found to best fit into the base station located at Putrajaya with smaller mean relative error. The smaller mean error shows that the optimization has been done successfully and thus, this optimized model can be useful to telecommunication providers in Malaysia in order to improve their service for mobile user satisfaction.

In this paper, two-dimensional time-stepping finite-element (TSFE) method is performed for modeling and analyzing of a salient pole synchronous generator with different degree of dynamic eccentricity (DE) fault. TSFE analysis is used to describe the influence of DE fault on the flux distribution within the generator and no-load voltage profiles at low and high field current is obtained for healthy and faulty cases. Comparing the magnetic flux distribution of healthy and faulty generators helps to detect the influence of DE fault. Also, it can be seen at no-load condition with low excitation current, the effect of the eccentricity is considerable compared to that of the rated excitation current. Since the calculation of inductances of the machine is the most important step for fault analysis and diagnosis, the self- and mutual-inductances of the stator phases and rotor windings are calculated in the eccentric generator. Double periodic phenomenon is observed in inductances profile of stator phases due to the DE fault. Finally, spectrum analysis of stator current of two generators with different design parameters is used to diagnosis the significant harmonics in the presence of DE fault.

In this paper, a novel microstrip structure is developed to realize a dual-band bandpass filter. The proposed bandpass structure uses a microstrip resonator with two independently controlled resonance frequencies producing two frequency bands of interest controlled by adjusting the dimensions of the resonator. Parametric analysis is performed on the structure to determine the optimum dimensions to obtain the desired frequency response and is explained in the paper. The dual-band bandpass filter developed in this paper exhibits dual operating frequencies at 1390 MHz and 2520 MHz with 9.85% and 9.92% fractional bandwidths respectively. We achieved a compact second-order dual-band bandpass filter with controllable resonance frequencies and low insertion losses in the passband with high selectivity. The measured results are in good agreement with simulated results. Additionally, it can be easily fabricated and can be used in applications where miniaturization and compatibility with microstrip technology are of primary concern.

This paper presents an approach to the design of a novel dual-band power divider with variable power dividing ratio. To achieve dual-band operation, a novel dual-band quarter-wave length transformer based on coupled-lines is proposed, which is used to replace the quarter-wave length transformer in Wilkinson power divider. The proposed dual-band power divider features a simple compact planar structure with wide bandwidth performance for small frequency ratio. Closed-form design equations with one degree of design freedom are derived using even- and odd-mode analysis and transmission line theory. For verification purpose, power dividers operating at 2.4/3.8 GHz with dividing ratios of 2:1 and 1:1 are designed, simulated and measured. The simulated and measured results are in good agreement.

In this paper, a novel double-printed trapezoidal patch dipole antenna suitable for UWB applications with band-notched characteristic is presented and investigated. The band -notched characteristic is achieved by inserting T-shape slots on the trapezoidal radiating patches. The impedance characteristic, radiation patterns and the transfer function are studied. Experimental results show that the proposed antenna covers the entire UWB band (3.1-10.6 GHz) while it has a notched band for the IEEE 802.11a frequency band (5.15-5.825 GHz). Measured group delay, transmission characteristics and Time domain characteristics indicate that the proposed antenna satisfies the requirement of the current wireless communications systems.

In this paper, the designed of triple-band printed dipole antennas are incorporated with single-band artificial magnetic conductor (AMC). The single-band AMCs are designed to resonate at 0.92 GHz, 2.45 GHz and 5.8 GHz using TLC-32 dielectric substrate. The four important parameters in AMC high impedance surface (HIS) design are also described in this paper. By simulating a unit cell of the AMC structure using a transient solver in Computer Simulation Technology (CST) software, the characteristic of the AMC can be characterized. The AMC condition is characterized by the frequency or frequencies where the magnitude of the reflection coefficient is +1 and its phase is 0°. It has high surface impedance (Z_s) and it reflects the external electromagnetic waves without the phase reversal. This characteristic of AMC enables the printed dipole to work properly when the antenna with AMC ground plane (GP) is directly attached to the metal object. The performances of the antenna with and without AMC structure as a ground plane to the antenna such as return loss, realized gain, radiation efficiency, radiation pattern and directivity are studied. Reported results show that the performances of the antenna are improved. Hence, the designed dipole tag antenna can be used for metal object identifications when the AMC structure is introduced as a ground to the antenna. The properties of the antenna are also remained well when the size of metal plate attached to them is increased.

A method to diagnose on-off faults in a planar antenna arrays using far field radiation pattern is presented. A systematic approach is suggested for detecting location of faulty elements using Artificial Neural Networks (ANN). Radial Basis Function neural network (RBF) and Probabilistic neural network (PNN) are considered for performance comparison.

Electromagnetic (EM) problem model for anisotropic plasma in kDB coordinates system is set up. And the model includes almost all the respects of EM-problems for anisotropic plasma. Based on shift-operator finite difference time-domain (SO-FDTD) method, Maxwell equations and EM-field constitutive equations are solved and discrete difference scheme of each EM-field component is obtained. Then the propagation characteristics of eigen wave are expressed by the two components of electric displacement vector as well. Lastly, three typical examples are calculated by SO-FDTD method, and the results verify the effectiveness and exactness of SO-FDTD method in kDB coordinates system.

This paper presents SPICE models to analyze the radiated and conducted susceptibilities of multiconductor shielded cables in the time and frequency domains. These models, which can be used directly in the time and frequency domains, take into account the presence of both the transfer impedance and admittance, and allow the transient analysis when the termination is nonlinear or time-varying. The radiated and conducted susceptibilities are studied by using an incident plane-wave electromagnetic field and an injection current on the cable shield as the source, respectively. Results obtained by these models are in good agreement with those obtained by other methods.

We propose a hybrid finite-difference frequency-domain method to study the perpendicular crossing waveguide, dielectric and microwave, TE and TM modes, by exploiting built-in structural symmetries in these waveguide devices. In the plus (+) symmetry model, the complete solution is obtained by solving two rectangular-shaped quarter structures each with two transparent boundaries and two symmetry boundaries. For the cross (x) symmetry model, solutions of four triangular-shaped quarter structures are needed but each with only one transparent boundary. Numerical results are verified by comparison between these two models and with the power conservation test. We show the total and the fundamental-mode, coupling coefficients of the reflected, cross and through power in the crossing waveguide as functions of the normalized frequency.

A novel DOA finding method for conformal array applications is proposed. By using sub-array divided and interpolation technique, ESPRIT-based algorithms can be used on conformal arrays for 1-D and 2-D DOA estimation. In this paper, the circular array mounted on a metallic cylindrical platform is divided to several sub-arrays, and each sub-array is transformed to virtual uniform linear array or virtual uniform planar array through interpolation technique. 1-D and 2-D direction of arrivals can be estimated accurately and quickly by using LS-ESPRIT and 2-D DFT-ESPRIT algorithms, respectively. This method can be applied not only to cylindrical conformal array but also to any other arbitrary curved conformal arrays. Validity of this method is proved by simulation results.

Electromagnetic shields are designed to optimize the performance for shielding effectiveness and reflectivity. Multilayered laminates of different materials are developed to achieve excellent results in terms of not only in shielding effectiveness but also for reflectivity. In this paper, a three layered laminate is considered for estimation of the required parameters in the X-band frequency range. A sandwich of conductive polymer between a conductor and microwave absorber yields very good performance. Several investigations were carried out for the estimation of shielding effectiveness and reflectivity of the three layered laminate structure at different thickness of each layer and for a combination of different materials.

A double-side radiating leaky-wave antenna based on composite right/left-handed (CRLH) coplanar-waveguide (CPW) is proposed. Dispersion diagram of the unit cell is investigated, and balanced property is confirmed. Thus, the CRLH leaky-wave antenna can have backfire radiation due to the left-handed property of the CRLH structure and broadside radiation at the balancing frequency point. The measured results show that the proposed antenna can offer a scanning angle covering almost backfire-to-endfire directions.

A combined method of the non-uniform fast fourier transform (NUFFT) migration and the least-square based matching pursuit decomposition (MPD) algorithms is proposed to obtain better discrimination and interpretation for subsurface from ground penetrating radar (GPR) signals. By using the modified NUFFT migration algorithm, a fast and high resolution GPR reconstruction can be obtained with an additional reduction in storage and computation requirements. By incorporating the MPD algorithm into a migration method, denoised reconstructions are obtained to enhance objects detection, including the identification of objects' geometries and the estimation of their sizes and locations. Several examples from synthetic data and field data are demonstrated to establish the effectiveness of the synergic effect by comparing it with the conventional migration methods.

A theoretical analysis of the properties of the defect modes in a one-dimensional defective photonic crystal (PC) is given. Two defective PCs stacked in symmetric and asymmetric geometries are considered. The defect modes are investigated by the calculated wavelength-dependent transmittance for both TE and TM waves. It is found that there exists a single defect mode within the photonic band gap (PBG) in the asymmetric PC. There are, however, two defect modes within the PBG in the symmetric one. The dependences of defect modes on the angle of incidence are illustrated. Additionally, the effect of defect thickness on the number of defect modes is also examined.

The modeling of quasi-static optimization problems often involves divergence-free surface current densities. In this paper, a novel technique to implement these currents by using the boundary element method framework is presented. A locally-based characterization of the current density is employed, to render a fully geometry-independent formulation, so that it can be applied to arbitrary shapes. To illustrate the versatility of this approach, we employ it for the design of gradient coils for MRI, providing a solid mathematical framework for this type of problem.