We propose an exact synthesis method which allows the design of dual-band transformers with an arbitrary even number of uniform sections giving equi-ripple impedance matching in two separate bands centered at two arbitrary frequencies. This method is a generalization of the exact Collin-Riblet synthesis of Chebyshev single-band transformers. As compared to a single-band Collin-Riblet transformer encompassing both required passbands, the proposed design yields significantly better performance in terms of passband tolerance and width.

A low complexity wavelet packet transform-based least mean square (LMS) adaptive beamformer is presented in this paper. This beamformer uses wavelet packet transform as the preprocessing, reduces the signal dimension in wavelet packet domain for low complexity and denoising, and employs least mean square algorithm to implement adaptive beamformer. Theoretical analysis and simulations demonstrate that this algorithm with better beamforming performance converges faster than the conventional adaptive beamformer and the wavelet transform-based beamformer. Finally, our proposed algorithm has the low complexity, and it can be easy to implement.

The problem of diffraction of a plane electromagnetic wave by a slot in a planar perfectly conducting screen of arbitrary thickness in the presence of a half-infinite dielectric arranged at a distance from a screen is solved rigorously on the bases of eigenfunction expansion and mode matching technique. The calculation algorithm for various components of the electric and magnetic field vectors in the entire space is presented, and a simple computation method for corresponding diffraction integrals is described. Just one more method of field visualization is demonstrated, which utilizes a picture of the energy-flux lines.

Making use of the Toeplitz structure of the mutual coupling matrix of the Uniform Linear Array (ULA), estimating the direction-of-arrival (DOA) of the sources as well as the mutual coupling coefficients of the array can be formulated as a linear inverse problem, where the solution is given by the Kronecker product of the vectors with respect to the DOAs and the mutual coupling coefficients. Through mathematical manipulation, these solution vectors can be decoupled. Estimation of the DOAs is cast into the framework of sparse solution finding. To derive the solution, an alternating minimization technique is presented. The proposed method is firstly developed based on the noise free observation covariance matrix, and can be generalized to directly using the snapshots. Using the proposed method, DOA estimation is feasible even in single snapshot case. The performance of the proposed methods with covariance matrix, single snapshot and multiple snapshots are illustrated by computer simulations. Their ability to resolve closely spaced targets and the applicability to correlated sources have also been demonstrated.

Method of Moments (MOM) combining with the Kirchhoff Approximation(KA) for analysis of the problem of optical wave scattering by a stack of two one-dimensional Gaussian rough interfaces is solved. The scattered field from the upper interface is solved by MOM and the transmitted field from the lower one is expressed from the Kirchhoff approximation where the multiple scattering phenomenon is neglected. The advantage of this hybrid method is that it is more exact than Kirchhoff approximation. The two rough interfaces separate three lossless and homogeneous media. The bistatic scattered field and the scattering coefficient are derived in this paper for vertical and horizontal polarizations. The influence of the relative permittivity, the height rms and the correlative length, the average heights between the two interfaces on the bistatic scattering coefficient is discussed in detail. The application of this work is the study of electromagnetic modeling of oil slicks on ocean surfaces.

This paper presents an improved method for microwave nondestructive dielectric measurement of layered media using a parallel-plate waveguide probe. The method bases on measuring the S parameter S11 or reflection coefficient from the N-layer media over the range of 1 to 10 GHz. Formulation for the aperture admittance is presented which allows the solving of the inverse problem of extracting the complex permittivity for two cases of the media, (1) one that terminates into an infinite half-space, (2) one that terminates into a sheet conductor. Our theoretical analysis allows the study of the effects of air gaps and slab thickness on the probe measurements. Through numerical simulations, the ability to use the proposed method for dielectric spectroscopy and thickness evaluation of layered media is demonstrated.

This study includes three parts: First is fuzzy modeling of scattered field from unloaded dipole antenna. In second step a fuzzy model for scattered field from a linearly loaded thin dipole antenna is introduced. In both parts, knowledge bases of diameter and load impedance are separately extracted and saved as very simple curves. It is shown that the behavior of scattering dipole antenna is well approximated with the single transmitting dipole antenna obtained in our previous study. In the third step, using the concept of spatial membership functions, two obtained knowledge bases are combined so that the spatial knowledge base including simultaneous effects of diameter and load impedance is extracted. As a result, these spatial knowledge base as well as the behavior of single transmitting dipole antenna are used instead of time consuming and repetitive computations in accurate methods. With the use of this spatial knowledge and behavior of single transmitting dipole antenna, the scattered field from dipole antenna for any load impedance and diameter is predicted. Comparing the predicted results with accurate ones shows an excellent agreement. Moreover the computation time is considerably reduced.

The electrodynamical rigorous solution of Maxwell's equations related to the microwave pulse propagation inside a threedimension heart model is presented here. The boundary problem was solved by using the singular integral equations' method. The carrier microwave frequency is 2.45 GHz. The pulse durations were always equal to 20 ms. The modulating signals are triangular video pulses with the on-off time ratio equal to 5 and 100. The model heart was limited by a non-coordinate shape surface and it consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood with the permittivity ε₂ = 58 − i19 and the walls of the heart consisted of myocardium tissue with the permittivity ε₁ = 55 − i17. Microwave electric field distributions were analysed at four longitudinal cross-sections of the heart model.

This paper links joint direction of arrival (DOA) and frequency estimation problem to the trilinear model and derives a novel blind joint angle and frequency estimation algorithm. The proposed algorithm has better performance than ESPRIT algorithm. Our proposed algorithm is thought of as a generalization of ESPRIT. The useful behavior of the proposed algorithm is verified by simulations.

Based upon developed radial FDTD-method, used for solution of Maxwell equations in cylindrical coordinates and implemented in Matlab-7.0 environment, we simulated focusing of the annular Gaussian beam with radial polarization by conical microaxicon with numerical aperture 0.60. It is shown that the area of focal spot (defined as area where intensity exceeds half of its maximum) can be 0.096λ², and focal spot diameter equals to 0.35λ.

A He's Energy balance method (EBM) is used to calculate the periodic solutions of nonlinear oscillators with fractional potential. Some examples are given to illustrate the effectiveness and convenience of the method. We find this EBM works very well for the whole range of initial amplitudes, and the excellent agreement of the approximate frequencies and periodic solutions with the Exact or other analytical solutions has been demonstrated and discussed. Comparison of the result obtained using this method with that obtained by Exact or other analytical solutions reveal that the EBM is very effective and convenient and can therefore be found widely applicable in engineering and other science.

In this paper,a novel compact monopole ultra-wideband (UWB) antenna with a notched ground is presented. To increase the impedance bandwidth,a notched ground is introduced. The parameters and the characteristics of the antenna are given. It shows good characteristics for UWB,and it satisfies the VSWR requirement of less than 2.0 in the frequency band from 2.55 GHz to more than 13 GHz. The measured radiation patterns show good omnidirectional performance and antenna gains across the operation bandwidth.

The speedy dissemination of digital consumer electronics devices within personal area causes increments of multimedia communication and advent of entertainment networking. This feature of communication requires high data-rate transmission. In order to meet the demand, in this paper, we apply multiple antenna schemes to MB-OFDM UWB system. And to use the UWB system with multiple antennas for various channel environment, some adaptive MIMO schemes are considered for multiple antenna MB-OFDM system. The first investigated technique is adaptive antenna selection which selects the proper number of transmitting antennas using estimated SNR. And the second technique is adaptive modulation which can be used after the adaptive antenna selection is executed. By using these adaptive techniques, the reliable and high data-rate communications which are well adapted to the various user's demands and channel conditions are achieved.

The efficient algorithm is presented for the analysis of electromagnetic scattering from composite structures with coexisting open and closed conductors. A hybrid combined-field integral equation-the improved electric-field integral equation (CFIE-IEFIE) formulation with the incomplete LU factorization (ILU) preconditioner is proposed. Numerical results are given to demonstrate that the efficiency of our algorithm can be significantly improved when compared with the conventional EFIE formulation and the hybrid CFIE-EFIE formulation.

In this paper, a fast and efficient method based on MOM is proposed for the analysis of antenna and array mounted on bodies of revolution. An attachment mode is introduced to ensure the continuity of current density at the junction region between wire antenna and cylindrical surface. A method based on suitable changes of coordinates and domains is presented to extract singular point of the self-impedance element calculation at junction region and accurate impedance can be obtained. Taking the antennas and array mounted on a finite solid conducting cylinder as an example, the impedance characteristics and radiation pattern are calculated. The good agreement between the results obtained by using the analysis method presented in this paper and those of CST and NEC software reveals the accuracy and high efficiency of this method.

This paper is addressed to a design of K-band dual mode radar used in traffic information collection. The radar can work in both Frequency Modulate Continual Wave (FMCW) mode and Continual Wave (CW) mode. As VCO is seldom used as the oscillator in CW radar for velocity measurement, this paper studied the effect of phase noise and detecting distance on velocity error in CW mode in VCO design. The analysis shows that the effect of phase noise on velocity error can be reduced by shortening the detecting distance. There's little difference in short-range velocity measurement between the dual mode radar with MMIC VCO and the CW radar with low phase noise oscillator.

Off-axis ellipsoid reflector based off-focus configuration for deastigmatism and circularization of an elliptical Gaussian beam is proposed. Mostly used off-axis ellipsoid reflector based conventional configuration is constructed by aligning the incident direction directed to one focus of the ellipsoid, which reflect the output beam to the another focus of the ellipsoid. However, such configuration is unavailable to deastigmatize and circularize an elliptical Gaussian beam. Therefore, the coupling efficiency between the reflected beam and an essentially circular beam is not well satisfied. In this case, an off-axis ellipsoid reflector based off-focus configuration is proposed to obtain better coupling efficiency. Different from the conventional configuration, in the proposed off-focus configuration, the incident beam direction is diverged from one focus of the ellipsoid. As a result, the coupling efficiency of no less than 99.9% (as compared with coupling efficiency of about 94.2% based on conventional configuration) can be obtained, which is verified with numerical calculations.

Electromagnetic scattering of two or more incident plane waves has been investigated for a perfect electromagnetic conductor (PEMC) circular cylinder, coated with a metamaterial havingneg ative index of refraction. The incident waves are considered for both the TM and TE cases in the analysis. The scattered fields are calculated by the application of appropriate boundary conditions at the interfaces between the different media. It is assumed that both the PEMC cylinder and the coatingla yer are infinite alongthe cylinder axis. The numerical results are compared with the published literature, and are found to be in good agreement.

Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, the effects of a two-dimensional electromagnetic bandgap (EBG) Structures on the performance of microstrip patch antenna arrays are investigated using the Ansoft High Frequency Selective Simulator (HFSS^TM). A mushroom-like EBG structure is compared with 2-DEBG Structures. HFSS^TM is employed to determine the effects of different Structures on two element microstrip patch antennas array. Two element microstrip patch antenna array on a uniform substrate suffer from strong mutual coupling due to the pronounced surface waves. Therefore, diverse forms of 2-DEBG Structures like: little number of holes, large number of holes, defect mode and different number of mushroom-patches columns structure are discussed. The two element microstrip patch antennas array placed on a defect in the electromagnetic (EBG) substrate that localizes the energy under the antennas. The excitation frequency of the two element microstrip patch antennas array near the resonance frequency of the defect mode can be used to control the coupling between antennas that are placed in an array. The mutual coupling improved by using large number of mushroom-patches columns structure.

A no-load induction motor under static eccentricity is modeled using time stepping finite element (TSFE) method; current, torque, and speed signals of the motor are obtained by finite element method (FEM) and used for static eccentricity fault diagnosis and analysis. The frequency spectrum analysis of the stator current around fundamental frequency component is used to predict the static eccentricity. Noise, unbalanced magnetic pull (UMP) and arc occur during the starting of the faulty motor, therefore, performance of the motor over the period of starting up to the steady-state is investigated. It is shown that the rate of obtained signals from the constant permeability based analysis is very larger than that of the real case. It is indicated that in order to obtain accurate results the saturation must be taken into account in the analysis of the motor. Simulation results for a 3 hp, three-phase, 230 V, 36 stator slots induction motor with 28 rotor slots are given in this paper. Experimental results for the motor confirm the simulation results very well.