This paper presents a method of antenna impedance measurement for RFID tag antenna based on a differential probe. The importance of accurate impedance measurement in optimal design of tag antenna, especially for the metal tags, is first addressed. Afterwards, an overview of the existing methods based on the singleended probe and the balun probe is presented. The proposed method using the differential probe is explained based the well-known two port network model. Experiments for both balanced and unbalanced tag antenna measurement demonstrate the differential probe can provided better agreement with simulated results.

We have investigated the scattering of the Magnetic Resonance Imaging (MRI) radiofrequency (RF) field by implants for Deep Brain Stimulation (DBS) and the resultant heating of the tissue surrounding the DBS electrodes. The finite element method has been used to perform full 3-D realistic simulations. The near field has been computed for varying distances of the connecting portion of the lead from the air-tissue interface. Dissipated powers and induced temperature rise distributions have been obtained in the region surrounding the electrodes. It is shown that the near proximity of the air-tissue interface results in a reduction in the induced temperature rise.

In this paper, we present a novel technique to reduce the size of edge-fed microstrip patch antenna. By etching the patch as the Sierpinski carpet, the resonant frequency can be lowered to lower values, and this property can be employed to reduce the size of the conventional patch antenna. The measurement results show, the patch achieved a maximum 33.9% size reduction by the edge-fed Sierpinski Carpet microstrip patch antenna (SCMPA) of the second iteration order, and other performances, such as return loss bandwidth and radiation patterns, were virtually unchanged.

This paper is concerned with a new time-domain modeling topology for signals which is appliedto OFDM systems. This model is a more accurate based on Wiener approach. Also the memory effect will be shown using two-tone intermodulation distortion (IMD) measurement with different tone frequency spacing and power levels. Next adaptive predistorter to counterbalance the AM/AM andAM/PM nonlinear effects of the transmitter power amplifier is proposedb y Hammerstein approach. Finally we consider the effectiveness of proposedmetho don performance of OFDM signal as the wideband system by reduction of distortion. It is confirmed by computer simulation that proposedapproac h produces a faster convergence speed than the previous adaptive predistortion technique.

In this paper, the Haar wavelets basis functions are applied to the method of moments to calculate the radar cross section of the resistive targets. This problem is modeled by the integral equations of the second kind. An effective numerical method for solving these integral equations is proposed. The problem is treated in detail, and illustrative computations are given for several cases. This method can be generalized to apply to objects of arbitrary geometry.

This paper shows the efficiency of neural networks (NN), coupled with the finite element method (FEM), to evaluate the broadband properties of dielectric materials. A characterization protocol is built to characterize dielectric materials and NN are used in order to provide the estimated permittivity. The FEM is used to create the data set required to train the NN. A method based on Bayesian regularization ensures a good generalization capability of the NN. It is shown that NN can determine the permittivity of materials with a high accuracy and that the Bayesian regularization greatly simplifies their implementation.

In this paper, we consider the resistances and inductances extraction from finite conducting metals. To remedy the weakness of volume integral equation, we extend the usage of a surface integral equation method from analyzing finite conducting rectangular wire strip to analyzing arbitrarily shaped geometry. Moreover the multilevel Green function method (MLGFIM) with a complexity of O(N) is employed to accelerate the matrix-vector multiplications in iterations. The numerical results shows the efficacy of the proposed method.

A three dimensional plano-convex lens which is placed at a certain distance from a plane uniaxial interface has been considered. High frequency fields refracted by the geometry are derived. The treatment is based on Maslov's method. The method combines the simplicity of asymptotic ray theory and generality of the transform method to remedy the problem of geometrical optics around the caustic point of a focusing system. Field patterns are obtained which includes the observation points around the caustic region. The results are found in good agreement with obtained using Huygens-Kirchhoff Principle.

Inspired by the requirement of proper link simulation methods in performance analysis of communication systems, we present in this paper a recipe for channel implementation in simulation environments. Our focus here is the indoor applications of wireless local-area networks (WLANs). Specifically, we describe a procedure that beginning with statistical description of the channel impulse response leads to an efficient multi-input multi-output (MIMO) channel simulating method for arbitrary antenna configurations at both ends. A sample set of distributions for model parameters are also provided at the 5-GHz band, which is the operating frequency band of IEEE 802.11a, HIPERLAN/2, and the emerging IEEE 802.11n standards, and the corresponding software implementation of the simulator is addressed for public use.

This paper presented a novel dual band transmitter which operates as power amplifier or frequency doubler with the stop band characteristic of defected ground structure (DGS). It works as a power amplifier at 2.4GHz which satisfies the 802.11b/g wireless LAN standard or performs as an active frequency doubler at 6.8GHz which depends on the input frequency and. The equivalent circuit and the stop band characteristic of the proposed microstrip DGS are analyzed and simulated. For the proposed transmitter, second harmonic suppression is below -52.6dBc in the amplifier mode, and fundamental suppression is below -41dBc in the frequency doubler mode with the stop band characteristic of DGS. The designed transmitter used GaAs InGaP Heterojunction broadband MMIC. It achieves 13.7dBm of P_1dB and its gain is 16.5dB in amplifier mode, and its maximum output power is 7.8dBm at 6.8GHz in frequency double mode.

In the present work the radiation of sound from a bifurcated circular waveguide formed by a semi-infinite rigid duct inserted axially into a larger infinite tube with discontinuous wall impedance is reconsidered through an alternative approach which consists of using the mode matching technique in conjunction with the Wiener-Hopf method. By expressing the total field in the appropriate waveguide region in terms of normal modes and using the Fourier transform technique elsewhere, we end up with a single modified Wiener-Hopf equation whose solution involves an infinite system of algebraic equations. This system is solved numerically and the influence of some parameters on the radiation phenomenon is shown graphically. The equivalence of the direct method described in [1] and the present mixed method are shown numerically.

The diffraction by a finite parallel-plate waveguide with four-layer material loading is rigorously analyzed by means of the Wiener-Hopf technique for the H-polarized plane wave incidence. Taking the Fourier transform for the unknown scattered field as well as the Helmholtz equation and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations. The Wiener-Hopf equations are solved via the factorization and decomposition procedure together with the use of rigorous approximation procedures leading to an efficient approximation solution. The scattered field in the real space is evaluated explicitly by taking the inverse Fourier transform. Illustrative numerical examples on the radar cross section (RCS) are presented and the far field scattering characteristics of the waveguide are discussed.

The plane wave diffraction by a finite parallel-plate waveguide with four-layer material loading is rigorously analyzed for the case of E polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved via the factorization and decomposition procedure together with a rigorous asymptotics. The scattered field is evaluated explicitly by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the radar cross section (RCS) are shown for various physical parameters and the far field scattering characteristics are discussed in detail.

A series of N identical periods of pairs of isotropic and biisotropic layers with defect in j-th basic element is investigated. The universal method that simultaneously allows to taking into account different types of defects in the structure is proposed. The problem is solved using the circuit theory and the transfer matrix methods. The analysis of the dynamic of electromagnetic properties of the investigated structure was carried out for different types of defects.

Main intension is to calculate admittance and radiation pattern of longitudinal shunt slot in rectangular waveguide using Method of Moments (MoM) technique. Resonant length calculation of the slot is a critical parameter in the design of waveguide slot array antenna. All computed results are compared with simulated results. CST Microwave studio is used for the simulation and is totally based on FIT techniques. For computation purpose MATLAB 7.0 is used. The numerical data on transmission and reflection coefficient are evaluated. Method of moment solution is used to calculate resonant length versus slot offset for given waveguide dimension and frequency. E and H field radiation pattern are calculated for different offset in different frequencies.

In this paper, the characteristics of an L probe fed planar rectangular patch antenna mounted on a cylindrical surface for circular polarization is investigated. To obtain a large bandwidth an L probe feed is used which is in the shape of a fork attached to a coaxial cable and is placed under a corner of the patch antenna. Simulation results, obtained via HFSS, on the return loss and radiation pattern of the antenna for circular polarization are presented. Results show an impedance bandwidth of 74.6%, an average gain of 7.5 dBi with stable radiation patterns across the entire passband and a bandwidth of 58% for AR< 3 dB.

Peak to Average Power Ratio (PAPR) is one of the serious problems in any wireless communication system using multi carrier modulation technique like OFDM, which reduces the efficiency of the transmit high power amplifier. In this paper, proposed scheme will be introduced that combine interleaving method with peak windowing. Simulation results show that our technique simultaneously decrease Bit Error Rate (BER), reduce the PAPR by 3.5 dB and improve out-of- band radiation, in presence of nonlinear power amplifier model.

Electromagnetic fields and media can be compactly represented by applying the four-dimensional differential-form formalism. In particular, classes of linear (bi-anisotropic) media can be defined in terms of the medium dyadic mapping between the electromagnetic two-forms. As a continuation to the process started by medium dyadics satisfying linear and quadratic algebraic equations, the class of biquadratic (BQ) media is defined by requiring that the medium dyadics satisfy the bi-quadratic algebraic equation. It is shown that the corresponding four three-dimensional medium dyadics are required to satisfy only two dyadic conditions. After studying general properties of BQ media, a special case is analyzed in detail as an example.