This paper presents a multiband slot antenna with modifying fractal geometry fed by coplanar waveguide (CPW) transmission line. The presented antenna has been designed by modifying an inner fractal patch of the antenna to operate at multiple resonant frequencies, which effectively supports the digital communication system (DCS 1.71-1.88 GHz), worldwide interoperability for microwave access (WiMAX 3.30 - 3.80 GHz), IMT advanced system or forth generation mobile communication system (3.40-4.2 GHz), and wireless local area network (WLAN 5.15 - 5.35 GHz). Manifestly, it has been found that the radiation patterns of the presented antenna are still similarly to the bidirectional radiation pattern at all operating frequencies. The properties of the antennas, for instance, return losses, radiation patterns and gain are determined via numerical simulation and measurement.

Due to the special structure of current carrying planar spiral coils, precise calculation of the forces between them is complicated and time-consuming. To overcome these problems, in this paper a new and fast method is proposed for calculation of the magnetic forces between planar spiral coils. The advantage of the proposed method is that just by having the external dimension of coils and their number of turns, the force between them at different distances and with different currents can be calculated. The results obtained by direct and proposed calculation methods show the efficiency of the latter in simplicity and calculation time. The precision of the proposed method has been confirmed by experimental tests done on constructed coils.

We are developing prototype free electron maser (FEM) that is compact, tuneable and efficient for potential industrial use. Therefore we define the characteristics for the construction of a novel X-band rectangular waveguide pre-bunched free electron maser (PFEM). Our device operates at 10 GHz and employs two rectangular waveguide cavities (one for velocity modulation and the other for energy extraction). The electron beam used in this experiment is produced by thermionic electron gun which can operate at 3 kV and up to 5 mA. The resonant cavity consists of a thin gap section of height 1.5 mm which reduces the beam energy required for beam wave interaction. The prototype design, engineering and construction process are reported in this paper.

In this paper, a time stepping two-dimensional FEM is performed for modeling and analysis of a IM with insulation failure inter-turn fault. FEM analysis is used for magnetic field calculation and the magnetic flux density and vector potential of machine is obtained for healthy and faulty cases. Comparing the magnetic flux distribution of healthy and faulty machines helps to detect the influence of turn fault. The machine parameters (self and mutual inductances) are obtained for IM with inter-turn fault. Finally, the FEM machine model is used for studying the machine under different fault condition. Study results including phases and fault currents express the behavior of machine with inter-turn faults. The symmetrical current components of IM with different fault severity are obtained by FE study and studied. The machine torque in healthy and faulty condition is also obtained and compared. The torque vibration increase upon to degree of fault.

A uniform geometrical theory of diffraction (UTD) enhanced physical optics and time domain integral equation (PO-TDIE) hybrid algorithm is proposed. UTD is applied to calculate the edge effect and to compensate the calculation error made by the PO current approximation. This method can improve the accuracy while maintaining the computational complexity, compared to PO-TDIE. Numerical result illustrates the validity and efficiency of the proposed method.

Focal region fields of perfect electromagnetic conductor (PEMC) paraboloidal reflector placed in homogenous and reciprocal chiral medium are analyzed. Maslov's method is used to derive the expressions for the focal region fields because the geometrical optics (GO) fails at these points. The results obtained by this method are solved numerically, and line plots for the reflected field of the paraboloidal PEMC reflector are obtained for di®erent values of admittance of the PEMC reflector and chirality parameter of the medium.

a small tapered slot antenna with a notched band for wireless applications is proposed in this paper. A modified transition from microstrip to slotline is used to introduce a notched band from 4.90 to 6.34 GHz. Corrugated edges on the ground is also used to improve the radiation patterns at the lower frequency band. Relatively stable radiation patterns and consistent group delay except the notched band have been obtained as proved experimentally.

The characteristics of an ultra-wideband (UWB) planar monopole antenna with multiple simple slots is presented. By placing a pair of symmetrical horizontal slots on the sides of the monopole antenna a tune-able notch characteristic can be obtained. The length, width and height of the slot can be used to tune the centre frequency, bandwidth and reflection coefficient of the notch. Placing two pairs of horizontal slots on the sides of the monopole antenna two tune-able notched characteristics can be obtained. Based on slot length and slot position an approximate formula for the notch centre frequency is given. The results of simulation and measurement are presented and discussed.

This paper presents a Fisher information based Bayesian approach to analysis and design of the regularization and preconditioning parameters used with gradient based inverse scattering algorithms. In particular, a one-dimensional inverse problem is considered where the permittivity and conductivity profiles are unknown and the input data consist of the scattered field over a certain bandwidth. A priori parameter modeling is considered with linear, exponential and arctangential parameter scalings and robust preconditioners are obtained by choosing the related scaling parameters based on a Fisher information analysis of the known background. The Bayesian approach and a principal parameter (singular value) analysis of the stochastic Cramer-Rao bound provide a natural interpretation of the regularization that is necessary to achieve stable inversion, as well as an indicator to predict the feasibility of achieving successful reconstruction in a given problem set-up. In particular, the Tikhonov regularization scheme is put into a Bayesian estimation framework. A time-domain least-squares inversion algorithm is employed which is based on a quasi-Newton algorithm together with an FDTD-electromagnetic solver. Numerical examples are included to illustrate and verify the analysis.

This paper presents a design of Wide-Band Microstrip Yagi-Uda antenna with high gain and high front to back (F/B) ratio. Numerical and measured results of our design show more than 18dB front to back ratio at 5.5 GHz and no backward radiation at 5.2 GHz. An impedance bandwidth of 22.05% was achieved around 5.5 GHz. The antenna gain (10-12.4 dBi) can be varied to be suitable for various applications. Measured return loss and radiation pattern of this antenna is presented to validate the results of simulations by two methods. The first method based on finite element method (FEM) and the second one based on finite integral technique (FIT) were used to analyze antenna structure, and subsequently the Genetic Algorithm (GA) was applied by using HFSS simulator to obtain the optimized parameters. In order to find the best design method for this antenna, the effect of distance between the parasitic elements of proposed antenna was studied. Finally two microstrip Yagi-Uda array antennas were combined to increase the gain of antenna. To demonstrate the major benefits, a comparison of our initial and final designs of Yagi-Uda antenna is provided.

In this paper, a simple and effective method for Through-The-Wall (TTW) life signs detection is introduced and discussed. To this aim, a Continuous Wave (CW) Microwave Transceiver working in X-Band is adopted. The detection procedure is based on the evaluation of correlation function in frequency domain between the measured and model signals. In order to ensure the reliability, proper background removal strategies are introduced. The effectiveness of the proposed approach is shown by processing experimental data collected in a realistic TTW scenario.

A novel printed top-loaded monopole antenna with a pair of sleeves on the ground plane for multiband wireless local area network (WLAN) applications is presented. This antenna is composed of a top-loaded monopole and two sleeves on a ground plane. Both the antenna and the ground plane are printed on the same side of an inexpensive FR4 substrate. This antenna has light weight and compact size of only 29×45×0.5 mm³. The operation bandwidth of this proposed antenna covers 2.4 GHz/5.2 GHz/5.8 GHz WLAN bands and 7.4 GHz~8.8 GHz for UWB application, which perfectly meet the requirement of multiband working. The measured and simulated results agree well with each other.

A fiber loop mirror (FLM) with two-stage high birefringence (Hi-Bi) fibers is theoretically and experimentally studied for various rotation angles and Hi-Bi fiber lengths. The experimental spectra are observed to be in good agreement with the theoretical spectra, verifying our theoretical model. The wavelength interval of the comb filter depends on the Hi-Bi fiber lengths and rotation angles. By varying the rotation angle from 0^ο to 90^ο, a comb-like transmission spectrum with small wavelength spacing is evolving into an exotic but periodic transmission spectrum and eventually become a larger wavelength spacing transmission spectrum. The FLM is useful in many applications such wavelength division multiplexing power equalization and management, switchable multi-wavelength fiber laser, optical switch and etc.

This paper deals with an inverse source problem starting from the knowledge of the radiated field in Fresnel and near zone. In particular, here we are concerned with a 2D geometry characterized by a rectilinear magnetic source and measurement rectilinear domains in Fresnel and near zone. The effect of the added knowledge of the radiated field over a second observation domain is investigated via the Singular Values Decomposition of the radiation operator and we point out how the addition of a second observation domain allows us always to achieve a better noise rejection. Also, we determine conditions under which the knowledge of the field over the second domain increases the information content (as the number of singular values of the radiation operator before their asymptotic decay) for both the Fresnel and near zone cases. Finally reconstruction examples with noise-free and noisy data are presented.

In this work, a design method of an Ultra-Wideband (UWB), low-noise amplifier (LNA) is proposed exerting the performance limitations of a single high-quality discrete transistor. For this purpose, the compatible (Noise F, Input VSWR V_i, Gain G_T) triplets and their (Z_S, Z_L) terminations of a microwave transistor are exploited for the feasible design target space with the minimum noise F_min(ƒ), maximum gain G_Tmax(ƒ) and a low input VSWR V_i over the available bandwidth B. This multi-objective design procedure is reduced into syntheses of the Darlington equivalences of the Z_Sopt(ƒ), Z_Lmax(ƒ) terminations with the Unit-elements and short-circuited stubs in the T-, L-, Π- configurations and Particle Swarm Intelligence is successfully implemented as a comparatively simple and efficient optimization tool into both verification of the design target space and the design process of the input and output matching circuits. A typical design example is given with its challenging performance in the simple Π- and Π-configurations realizable by the microstrip line technology. Furthermore the performances of the synthesized amplifiers are compared using an analysis programme in MATLAB code and a microwave system simulator and verified to agree with each other.

In this paper, a quasi-elliptic bandpass filter was designed, simulated, and fabricated using four-pole cross-coupled stepped impedance resonators (SIR). Using a special type of stepped impedance resonators, a great increase in rejection band width of the filter was obtained. In order to perform the mentioned design practically, we utilized a compound sandwich model of two substrates (in strip line form). Furthermore, we used Defected Ground Structure (DGS) in order to omit the first spurious resonant frequency and increase bandwidth of the filter. The fabricated sample was measured, and the results showed a good agreement with simulated results.

Carbon nanotubes are characterized by slow wave propagation and high characteristic impedance due to the additional kinetic inductive effect. This slow wave property can be used to introduce resonant dipole antennas with dimensions much smaller than traditional half-wavelength dipole in Terahertz band. However, this property has less effect at lower frequency bands. This paper introduces the physical interpretation of this property based on the relation between the resonance frequency and the surface wave propagation constant on a carbon nanotube. This surface wave propagation is found to be characterized by high attenuation coefficient at low frequency bands which limits using carbon nanotube as an antenna structure at these frequencies.

A Computer Aided Design (CAD) approach based on Artificial Neural Networks (ANN's) is successfully introduced to determine the characteristic parameters of Circular-shaped Microshield and Conductor-Backed Coplanar Waveguide (CMCB-CPW). ANN's have been promising tools for many applications and recently ANN has been introduced to microwave modeling, simulation and optimization. The Multi Layered Perceptron (MLP) neural network used in this work were trained with Levenberg-Marquart (LM), Bayesian regularization (BR), Quasi-Newton (QN), Scaled Conjugate gradient (SCG), Conjugate gradient of Fletcher-Powell (CGF) and Conjugate Gradient backpropagation with Polak-Ribiere (CGP) learning algorithms. This has facilitated the usage of ANN models. The notable benefits are simplicity & accurate determination of the characteristic parameters of CMCBCPW's. The greatest advantage is lengthy formulas can be dispensed with.

This paper presents a graphics processing based implementation of the Finite-Difference Frequency-Domain (FDFD) method, which uses a central finite differencing scheme for solving Maxwell's equations for electromagnetics. The radar cross section for different structures in 2D and 3D has been calculated using the FDFD method. The FDFD code has been implemented for the CPU calculations and the same code is implemented for the GPU calculations using the Brook+ developed by AMD. The solution obtained by using the GPU based-code showed more than 40 times speed over the CPU code.

This paper presents a comparison of cylindrical and plane air gap magnetic couplings in which the tile permanent magnet polarizations can be either radial or tangential or axial. The expressions of the torque transmitted between the two rotors of each coupling are determined by using the coulombian approach. All the calculations are performed without any simplifying assumptions. Consequently, the expressions obtained are accurate and enable a fast comparison between the structures presented in this paper.