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.

In this research paper, we propose an amplitude-only method for unique thickness evaluation of medium- and low-loss materials. The method is based on using amplitude-only measurements at different frequencies to evaluate the unique thickness. Main advantages of the method are a) it eliminates the necessity of repetitive measurements of different-length materials to evaluate the unknown thickness of the same type material and b) it determines the thickness at any desired frequency in the band. Because the method uses amplitude-only measurements and enables the thickness evaluation at any frequency, it can be a good candidate for thickness evaluation of materials in industrial-based applications.

To efficiently solve large dense complex linear system arising from electric field integral equations (EFIE) formulation of half-space electromagnetic scattering problems, the multilevel fast multipole algorithm (MLFMA) is used to accelerate the matrix-vector product operations. The two-step spectral preconditioning is developed for the generalized minimal residual iterative method (GMRES). The two-step spectral preconditioner is constructed by combining the spectral preconditioner and sparse approximate inverse (SAI) preconditioner to speed up the convergence rate of iterative methods. Numerical experiments for scattering from conducting objects above or embeded in a lossy half-space are given to demonstrate the efficiency of the proposed method.

Based on an analytical expression for the integration of the free-space Green's function involving any combination of basis and test functions, an accurate and highly efficient method to determine the Method of Moments matrix has been developed. A full analytical expression is obtained through direct integration of the Taylor's series expansion of the free-space Green's function. Based on the distance between the source and observation points, a criterion is established to reduce the full expression to a much-simplified expression, which speeds up the computational efficiency to fill up the Method of Moments matrix without compromising the solution accuracy.

In this paper, we present a low cost RF oscillator design incorporating a folded parallel coupled resonator. The oscillator is designed on FR4 substrate to achieve low cost. FR4 is a low cost substrate but has a poorly controlled dielectric constant and high loss tangent thereby challenging the design of higher performance circuits. This oscillator operates in 900 MHz band, delivers an output of -3.13 dBm and has phase noise 101.8 dBc/Hz at 10 kHz offset. The size of the folded parallel coupled resonator is 16% smaller than the conventional parallel coupled resonator, thereby making the overall circuit more compact. The power output and phase noise results are better than the oscillator designed with conventional resonator. Open loop analysis method has been adopted for the oscillator design and analysis. The measured data shows good agreement with the simulated results. The performance parameters of this oscillator make it suitable for use in low cost wireless communication solutions in 900 MHz band.

Practical antenna array designs generally require that the elements are separated by electrically short distances. The resultant mutual coupling often adversely affects the achievable performance. Various methods are available to quantify the effects of mutual coupling in arrays and improve performance through mutual coupling compensation. Mutual coupling is often described by a coupling matrix that relates the coupled and uncoupled quantities. Unfortunately, the accuracy with which the coupling matrix can be calculated is highly dependent on both the method selected and the frequency. This is a significant limitation for wideband analysis where the coupling matrix needs to be calculated accurately at all frequencies of interest. This paper introduces a novel method for the precise calculation of the coupling matrix at any frequency of interest. It is an extension of the induced EMF method to multiple array elements. The method has the important practical advantage of being independent of the numerical technique used in the analysis. Since the coupling matrix is calculated by exciting the elements in the transmission mode, the method resembles well-known network analysis. However, as outlined in the paper, there are subtle differences between the two approaches, which lead to more accurate results with the new proposed method. It is also demonstrated that antennas with arbitrary geometries and illuminations are handled accurately by the method.

High-order modes of spoof surface plasmon polaritons (SPPs) on the periodically corrugated metal surfaces are investigated theoretically with the modal expansion method. An analytical expression for the condition of existence of high-order modes is presented. The properties of high-order modes such as dispersion and field pattern are analyzed detailedly, from which it seems that the propagation of spoof SPPs along the corrugated metal surface is mainly based on the coupling between the open groove cavities.

The dispersion equation for free electromagnetic waves guided by an anisotropically conducting open tape helix is derived from the exact solution of a homogenous boundary value problem for Maxwell's equations without invoking any apriori assumption about the tape-current distribution. A numerical solution of the dispersion equation for a set of typical parameter values reveals that the tape-helix dispersion curve is virtually indistinguishable from the corresponding dominant-mode sheath helix dispersion curve except within the tape-helix forbidden regions.

This paper presents a theoretical model for the propagation of a hollow Gaussian electromagnetic beam [HGB], propagating in a plasma with dominant relativistic-ponderomotive nonlinearity. A paraxial like approach has been invoked to understand the nature of propagation; in this approach all the relevant parameters correspond to a narrow range around the irradiance maximum of the HGB. The critical curves for the propagation of various order HGBs have been discussed, and the dependence of the beam width parameter on distance of propagation has been evaluated for three typical cases of steady divergence, oscillatory divergence and self focusing of the HGB.

The optical properties of birefringent Bragg fiber with a fiber core of 2-dimension (2D) elliptical-hole photonic crystal structure has been study. Elliptical air holes are introduced into the fiber core to form a normal 2D photonic crystal structure with a hole pitch (center-to-center distance between the air holes) much smaller than the operation wavelength of the Bragg fiber. The elliptical-hole photonic crystal structure acts as an anisotropic medium with different effective indices for transmission light of different polarization, which inevitably results in high birefringence (up to the order of magnitude of 0.01) of the Bragg fiber. The proposed Bragg fiber possesses different band-gaps for differently polarized mode. Besides the periodic alternating layers of high/low refractive indices, the bandwidth of the band-gap is also dependent on the effective index of the fiber core, which can be controlled by the area of the elliptical air holes.

Focal region fields of a perfect electromagnetic conductor (PEMC) paraboloidal reflector placed in homogenous and reciprocal chiral medium are analyzed under the effect of high chirality parameter. The chiral medium supports both negative phase velocity (NPV) and positive phase velocity (PPV) modes simultaneously under strong electromagnetic coupling. The geometrical optics (GO) fields have singularities at the focal region. Therefore, to avoid these singularities Maslov's method is used for the focal region fields. The results obtained using this method are solved numerically, and line plots for the reflected field of the paraboloidal PEMC reflector are obtained for different values of admittance of the PEMC paraboloidal reflector and chirality parameter of the medium.

The response of a two-layer structure of orthogonal coupled microstrip transmission lines illuminated by an external electromagnetic field has been studied. A simple model for the crosstalk region using lumped capacitance and inductance elements is used. The effect of the external EM field on the microstrip lines field in order to reach transmission line equations along the lines. The model is finally validated using the full wave analysis simulator, HFSS. Voltage and current along the lines obtained by the present method are in good agreement with the results of the full wave analysis (HFSS). The proposed model has been used for voltage and current in terminal ports up to 10 GHz. This method can be developed simply for multilayer structures.