In this paper, a fast method is proposed to calculate wide- band frequency responses of complex radar targets on a personal computer. When frequencies are low, the frequency factor can be separated from space parameters by Chebyshev polynomial approximations of Green's function. Then, matrices from MoM at different frequencies can be rapidly filled, and monostatic RCS can be soon calculated. If frequencies are relatively high, a fast high-order MoM (HO-MoM), in which matrices products are in place of multi- dimension numerical integrations, is presented. That will reduce the CPU time requirement. Lastly, Numerical results are given for various structures and compared with other available data.

Two novel structures for high-Q MEMS tumble capacitors are presented. The proposed designs include full plate as well as the comb structured capacitors. They can be fabricated employing surface micromachining technology which is CMOS-compatible. The structures do not require the cantilever beams which introduce considerable series resistance to the capacitor and decrease the quality factor. Therefore, our proposed structures achieve better Q in a smaller die area. The simulated results for 1 pF full plate capacitor shows a tuning range of 42% and a Q of 47 at 1 GHz. However, with the same initial capacitance, but the comb structure, the tuning range is increased to 43% but the Q is decreased to 45 at 1 GHz. The simulated Pull-in voltage with no residual stress is 3.5 V for both capacitors. The S11 responses are reported for a frequency range from 1 up to 4 GHz.

This paper presents the study of a circular slot antenna for ultrawide-band (UWB) applications. Antenna is fed by a circular open ended microstrip line. The frequency band considered is from 4 to 14 GHz, which has approved as a commercial UWB band. The proposed antenna has a return loss less than 10 dB, phased linear, and gain flatness over the above a frequency band.

Based on the strict and delicate analogue relation between the magnetic moment of rotational charged bodies and the rotation inertia of rigid bodies, a new concept of charge moment tensor I which is different from the existent electric multiple moment is introduced in this paper. And by means of eigenvalue theory of tensor I , the concept of principal axes and principal-axis scalar charge moment are constructed, and further the scalar charge moment of a charged body and the magnetic moment of a rotational charged body around an arbitrary direction are attained. The relationship between the scalar charge moment distributive law of quadric camber and the positive or negative definiteness of tensor I are discussed. Meanwhile Some principles or theorems are extended, generalized, illustrated, and enumerated.

In this paper we show, theoretically, that total omnidirec- tional reflected frequency band is enlarged considerably by using one- dimensional photonic crystal (PC) structure composed of alternate lay- ers of ordinary material (OM) and left handed material (LHM). From the analysis it is found that the proposed structure has very wide range of omnidirectional total frequency bands for both polarizations in com- parison to the normal PC structure, which consists of alternate layers of ordinary material having positive index of refraction. The proposed structure also has an absolute band gap that can be exploited to trap the light.

This paper presents a simple and alternative approach for the analysis of inductive waveguide microwave components. The technique uses a surface integral equation formulation, in which the contours of the waveguide walls and of the inner obstacles are all discretized using triangular basis functions. In order to avoid the relative convergence problem of other techniques based on mode matching, an alternative port treatment is used. The technique is based on the application of the extinction theorem using the spatial representation of the Green's functions in the terminal waveguides. In addition, the Fast Multipole Method is proposed in order to reduce the computational cost for large problems. Different complex structures are analyzed, including microwave bandpass filters with elliptic transfer functions, waveguide bends and T-junctions. Results show the high accuracy and versatility of the technique derived.

Broken rotor bars and end-ring are common faults in three-phase squirrel-cage induction motors. These faults reduce the developed toque and increase the speed fluctuations of the motor. Meanwhile, developed unsymmetrical magnetic generates noise and vibration in the motor. Local heat around the broken bars may gradually break the adjacent bars and the motor will be finally out of service. Finite element method (FEM) is the most accurate technique for diagnosis and analysis of induction motor, because it can include all actual characteristics of the healthy and faulty induction motors. However, current density is generally considered as input for performance computation process, while fault can inject a large harmonics to the stator current. These harmonics may not be ignored in the fault diagnosis of the motor. In addition, all FE applications consider the steady-state mode of operation. In this paper, a three-phase voltage-fed squirrel-cage induction motor with rotor broken bars is proposed and analyzed for the starting period of the motor. Both no-load and on-load cases are considered. Also, concentrated rotor broken bars under one-pole and the distributed rotor broken bars under different poles are studied and compared.

In this paper, rain statistics of 10 years record in Taiwan area was used to investigate the transmission performance of the Ka- band LMDS system with QAM modulation. Emphasis was placed to investigate the effects of rain fading under M-QAM modulation schemes. It is found that for LMDS cellular network, M-QAM modulation is difficult to provide an effective and reliable high speed transmission for the case of 6 km radius of cell coverage unless the frequency and polarization diversities are applied; otherwise, the cell coverage of service should be shrunk.

This paper presents an approach for the design and optimization of pseudo-gradual transitions in circular waveguides using the genetic algorithm (GA). The characterization of these transitions is carried out by the mode-matching method. This method, associated with the generalized scattering matrix technique, leads to determine the reflection coefficient on the useful band of the studied structures and to observe their frequential behavior. The GA is employed to optimize the choice of geometrical parameters by minimizing a cost function, corresponding to the maximum magnitude of the reflection coefficient in the band. The selection of the most relevant parameters allowed an improvement of the performances for the optimized components. Results of optimization are given for both two and four-section transformers.

The coupled mode approach is applied to the ferrite circular waveguide magnetized through a rotary four-pole transverse bias magnetic fields. The plausible mathematical model of the ferrite waves propagation in the guide is developed which includes gyromagnetic interaction of two orthogonal TE11 isotropic modes. The importance of the birefringence effect in determining of phase shift and polarization phenomena are thereby demonstrated. As a result basic design consideration of the circular polarizer applied as a "half-wave plate" in rotary-field phase shifter are provided.

The classical soft-and-hard surface boundary conditions have previously been generalized to the form a · E = 0 and b · H = 0 where a and b are two complex vectors tangential to the boundary.A realization for such a boundary is studied in terms of a slab of special wave-guiding anisotropic material. It is shown that analytic expressions can be found for the material parameters and thickness of the slab as functions of the complex vectors a and b. Application of a generalized soft-and-hard boundary as a polarization transformer is studied in detail.

An effective computational method based on a conventional modal-expansion approach is presented for solving the problem of diffraction by a deep grating. The groove depth can be the same as or a little more than the grating period. The material can be a perfect conductor, a dielectric, or a metal. The method is based on Yasuura's modal expansion, which is known as a least-squares boundary residual method or a modified Rayleigh method. The feature of the present method is that: (1) The semi-infinite region U over the grating surface is divided into an upper half plane U₀ and a groove region UG by a fictitious boundary (a horizontal line); (2) The latter is further divided into shallow horizontal layers U₁, U₂, ···, U_Q again by fictitious boundaries; (3) An approximate solution in U₀ is defined in a usual manner, i.e., a finite summation of up-going Floquet modal functions with unknown coefficients, while the solutions in U_q (q = 1, 2, ···, Q) include not only the up-going but also the down-going modal functions; (4) If the grating is made of a dielectric or a metal, the semi-infinite region L below the surface is partitioned similarly into L₀, L₁, ···, L_Q, and approximate solutions are defined in each region; (5) A huge-sized least squares problem that appears in finding the modal coefficients is solved by the QR decomposition accompanied by sequential accumulation. The method of solution for a grating made of a perfect conductor is described in the text. The method for dielectric gratings can be found in an appendix. Numerical examples include the results for perfectly conducting and dielectric gratings.

In this paper we use optical power control to support multirate transmission over temporal optical CDMA networks. We apply the centralized power control algorithm to set the transmit power of the users' optical sources in order to satisfy a given target QoS. In addition, optical amplifiers are included to enhance the overall system performance while the Amplified Spontaneous Emission (ASE) is considered as the main noise source. The objective function defined as the sum of the transmitted optical power from all nodes is minimized subject to a signal-to-interference (SIR) constraint. Moreover, the network feasibility, defined as the ability to evaluate a power vector that satisfy the target SIR, is discussed in terms of the spectral radius of the network interference matrix. Next, the spectral radius of the network interference matrix is investigated and modeled as a truncated Gaussian distribution. Last, a rate reduction algorithm, categorized in terms of the number of nodes involved in the process of rate reduction, is proposed to increase the network feasibility. As more nodes are added to the rate reduction campaign, the network feasibility is significantly enhanced. For typical network parameters we find by simulating 10⁴ random network realizations that a threenode rate reduction results in 99% network feasibility.

Propagation environment and antenna array configuration have significant effect on spatial correlation properties of multipleinput multiple-output (MIMO) wireless communications channels. In this paper the effect of different antenna array geometries on MIMO channel properties is investigated in urban city street grid propagation environment. Four antenna array geometries with the same number of antenna elements and fixed inter-element spacing are considered, namely, uniform linear array (ULA), uniform circular array (UCA), uniform rectangular array (URA) and uniform cubic array (UCuA). The effect of ULA orientation in azimuthal plane on MIMO channel ergodic capacity is also investigated. Varying orientation angle from 0 to π at the two communication ends is considered. The investigation is carried out based on three dimensional (3D) spatial multi-ray realistic propagation channel model covering different propagation types. It is shown that the antenna array geometry have significant impact on MIMO channel properties. Under different propagation scenarios the ULA shows superiority to the other considered geometries in terms of the ergodic channel capacity and number of spatial parallel channels. However, this superiority depends largely on the array azimuthal orientation.

In this paper fault diagnosis of induction motor under mixed fault is carried out using precise analysis of the air-gap magnetic field based on time stepping finite element method. By feeding voltage instead of current density to the finite element computation part, the drawbacks of the application of finite element method in fault diagnosis of induction motor are overcome. Normally static eccentricity and broken rotor bars faults have been individually diagnosed in the published papers. Here diagnosis of the mixed fault,including static eccentricity and broken rotor bars,is introduced which is considered as a novel part of the present work. Precise analysis of magnetic field in the air-gap of a faulty induction motor is carried and performance of the motor is predicted. Taking into account the magnetic core saturation is another advantage of the present work. This is required in the transient analysis of a faulty motor.

This paper presents the analysis of linear tapered waveguide. Voltage-standing-wave-ratio (VSWR) is obtained from transmission matrix of the taper waveguide. Taper section is divided into number of section having uniform length. Transmission matrix of taper waveguide is found by multiplication of transmission matrix of each section. Transmission matrix of each section is obtained as the product of three matrices. One is of the initial length of transmission line,second one is due to discontinuity and third one is of the final length of transmission line. Transmission matrix of discontinuity is obtained by two methods. One is by equivalent circuit of step discontinuity and another is by moment method. The results are seen to be in good agreement with [1,2] and [3].

Broadband planar and non-planar negative refractive index (NRI) metamaterial (MTM) designs consisting of a periodically arranged split ring resonator and wire structures are developed in the terahertz (THz) frequency regime using the Finite-Difference Time- Domain (FDTD) method. The novel MTM designs generate a broad negative index of refraction (NIR) passband approximately two and a half times higher than those of the conventional SRR/wire structures, by using the same dimensions. Numerical simulations of wedgeand triangle-shaped metamaterials are used to prove the negative refractive index of the models. The fabricated MTMs exhibit passband characteristics which are in good agreement with the model results. The parametric studies of correlated factors further support these outcomes.

A theoretical modal dispersion study of a new unconventional Bragg waveguide having hypocycloidal core cross-section and surrounded by Bragg cladding layers is presented using a very simple boundary matching technique [1]. An attempt has been made to determine how the modal characteristics of a standard Bragg fiber change as its circular shape is changed to the hypocycloidal shape. It is seen that in the case of a hypocycloidal Bragg waveguide single mode guidance is possible when V ≤ 10.0 where V is the normalized frequency parameter.

In the Part I of this work general introduction to the transient impedance assessment of simple grounding systems has been presented. Part I also deals with the analysis of the vertical grounding electrode, while this paper analyses a more demanding case of the horizontal electrode.The mathematical model is based on the thin wire antenna theory featuring the Pocklington integro-differential equation. The Pocklington equation is solved using the Galerkin-Bubnov indirect Boundary Element Method. The details are available in Appendix. The formulation of the problem is posed in the frequency domain, while the corresponding transient response of the grounding system is obtained by means of the inverse Fourier transform. Some illustrative numerical results are shown throughout this work.

The paper deals with the transient impedance calculation for simple grounding systems. The mathematical modelmodel is based on the thin wire antenna theory. The formulation of the problem is posed in the frequency domain, while the corresponding transient response of the grounding system is obtained by means of the inverse Fourier transform. The current distribution induced along the grounding system due to an injected current is governed by the corresponding frequency domain Pocklington integro-differential equation. The influence of a dissipative half-space is taken into account via the reflection coefficient (RC) appearing within the integral equation kernel. The principal advantage of the RC approach versus rigorous Sommerfeld integral approach is simplicity of the formulation and significantly less computational cost. The Pocklington integral equation is solved by the Galerkin Bubnov indirect boundary element procedure thus providing the current distribution flowing along the grounding system. The outline of the Galerkin Bubnov indirect boundary element method is presented in Part II of this work. Expressing the electric field in terms of the current distribution along the electrodes the feed point voltage is obtained by integrating the normal field component from infinity to the electrode surface. The frequency dependent input impedance is then obtained as a ratio of feed-point voltage and the value of the injected lightning current. The frequency response of the grounding electrode is obtained multiplying the input impedance spectrum with Fourier transform of the injected current waveform. Finally, the transient impedance of the grounding system is calculated by means of the inverse Fourier transform. The vertical and horizontal grounding electrodes, as simple grounding systems, are analyzed in this work. The Part I of this work is related to the vertical electrode, while Part II deals with a more demanding case of horizontal electrode.