The effect of cold plasma beam on electromagnetic whistler wave with perpendicular AC electric field has been studied by using the unperturbed Lorentzian (Kappa) distribution in the Earth's atmosphere for relativistic plasma. The cold plasma has been described by a simple Maxwellian distribution where as Lorentzian (Kappa) distribution function has been derived for relativistic plasma with temperature anisotropy in the presence of a perpendicular AC electric field to form a hot/warm background. The dispersion relation is obtained by using the method of characteristic solutions and kinetic approach. An expression for the growth rate of a system with added cold plasma injection has been calculated. Results for representative values of parameters suited to the Earth's magnetosphere has been obtained. It is inferred that in addition to the other factors, the relativistic plasma modifies the growth rate and it also shifts the wave band significantly. The relativistic electrons by increasing the growth rate and widening the bandwidth may explain a wide frequency range of whistler emissions in the Earth's magnetosphere.

Forward scattering from a finite, right-circular cylinder is analyzed as a function of size. Both axial and broadside incidence are treated. Predictions based upon combinations of Physical Optics, Wu's series, and empirical formulas are compared with numerical results from the moment method. The analysis examines cylinders that vary between 1 to 20 wavelengths in radius and 0 to 20 wavelengths in length. Approximate formulas accurately model the RCS of cylinders as small as one wavelength in radius. Accuracy of predictions improves with increase in cylinder size.

In this paper two-dimensional problem of plane-wave diffraction by a "fractional strip" is studied. "Fractional strip" is introduced as a strip with fractional boundary conditions (FBC) involving fractional derivatives of the field components. FBC describe intermediate boundary between perfect electric conductor (PEC) and perfect magnetic conductor (PMC). It is shown that "fractional strip" has scattering properties similar to the well-known impedance strip. For one important case of fractional order equal to 0.5 the solution of the wave diffraction problem by a "fractional strip" can be found analytically. Detailed comparison analysis of the physical characteristics of the scattered fields for both fractional and impedance strips is presented. The relation between the fractional order and the value of impedance is derived. It is shown that in a wide range of input parameters the physical characteristics of the "fractional strip" are similar to the strip with pure imaginary impedance.

In this paper we evaluate the potential of a 5-element monopole array incorporated into a handheld device for beamforming in the 5.0-GHz band. The geometry of the handset consists of a 5-element array: four elements located at the handset corners and the fifth-element located at the center. Also, the interaction of the antenna array, mounted on a mobile handset, with a human head phantom is investigated. Firstly, the spatial peak specific absorption rate (SAR) values of 5-element array antennas for mobile handsets in the vicinity of a spherical phantom of a human head are evaluated numerically as a function of the distance between the handset and the head phantom for two different scenarios. Next, the effect of the human head on the handset radiation pattern is studied. The effect of different handset positions on the radiation pattern is also considered. The particle swarm optimization (PSO) algorithm is used to optimize the complex excitations of the adaptive arrays elements in a mutual coupling environment for beamforming synthesis. All numerical simulations are performed using the FEKO Suite 5.3 software. To validate the numerical simulations, we first perform two validation tests and compare the numerical results with published simulated and measurement results.

A new multi-layer planar array architecture to achieve multi-polarized radiation is developed in this paper. The design concept is based on embedding U-shaped coupling slots in the ground plane to extend the bandwidth. The proposed antennas have two feed ports, by adjusting the feeding properly, the antennas can transmit arbitrary elliptic polarized signal theoretically. Return loss and radiation patterns are measured for the 1-element, 2-element, 4- element, 16-element antenna arrays at 12.5 GHz. Radiation patterns of the antenna arrays show close agreement to the predicted ones in the shape of the main beam. By further incorporating properly designed feed networks, the -20 dB return-loss bandwidth of the proposed antenna arrays can cover the 12.5 GHz frequency band (12.25-12.75 GHz). Design details and experimental results are presented and discussed.

This work is aimed at presenting a methodology that exploits the scattered electromagnetic radiation collected on a measurement region outside the area under investigation to locate and characterize multiple unknown profiles. In many practical cases, an accurate quantitative imaging of the scenario under test is required and it can be reached by using a high resolution representation of the dielectric profile of the scatterers. Towards this aim, an enhanced iterative multi-resolution procedure that exploits a morphological processing for detecting and focusing on different non-connected regions-of-interest is developed. A suitable set of representative numerical results is presented for demonstrating that the proposed approach is able to efficiently detect the objects located in the test domain and to enhance the accuracy in reconstructing multiple scatterers.

In our earlier work we introduce a numerical analysis to investigate the excess noise and performance factor of double carrier multiplication homojunction avalanche photodiodes (APDs) considering the nonlocal nature of the ionization process. In this paper we investigate the gain,breakdo wn voltage and carrier injection breakdown probability of homojunction avalanche photodiode in the wide range of multiplication region width. Also in our calculations the effects of dead space has been considered. Our analyses based on the history dependent multiplication theory (HDMT) and width independent ionization coefficient.

Employing Lorentz reciprocity and the Stratton-Chu formalism it is shown that the Poincare-Steklov or admittance operator can be interpreted as a complex symmetric operator mapping the tangential electric field (instead of the equivalent magnetic current) onto the equivalent electric current. We show that the pertinent block Calder´on projectors can be reformulated as operators with a block Hamiltonian structure. This leads to an explicitly complex symmetric Schur complement expression for both the interior and exterior admittance operators.

It is well known that under certain conditions, one dimensional photonic crystal (1D-PC) displays total omni-directional reflection (ODR) band gaps. The enhancement of total omnidirectional reflection band gap in 1D-PC is calculated theoretically. Using Transfer Matrix Method (TMM) and Bloch theorem, the reflectivity of one dimensional periodic structure for TEand TM-modes at different angles of incidence has been calculated.

This article presents a new approach based on artificial neural networks (ANNs) to calculate the characteristic parameters of elliptic and circular-shaped microshield lines. Six learning algorithms, bayesian regularization (BR), Levenberg-Marquardt (LM), quasi-Newton (QN), scaled conjugate gradient (SCG), resilient propagation (RP), and conjugate gradient of Fletcher-Reeves (CGF), are used to train the ANNs. The neural results are in very good agreement with the results reported elsewhere. When the performances of neural models are compared with each other, the best and worst results are obtained from the ANNs trained by the BR and CGF algorithms, respectively.

In this paper, He's energy balance method is applied to nonlinear oscillators. We illustrate that the energy balance is very effective and convenient and does not require linearization or small perturbation. Contrary to the conventional methods, in energy balance, only one iteration leads to high accuracy of the solutions. It is predicted that the energy balance method can be found wide application in engineering problems.

A novel planar bow-tie aperture antenna is proposed for ultra-wide band (UWB) application in this paper. Beveling technique is employed to increase the impedance bandwidth, and slot loading is introduced to improve the impedance matching. The measured impedance bandwidth is from 2.7 to 12 GHz for S₁₁ < -10 dB, proving the effectiveness of these two techniques. The measured radiation patterns are relatively stable almost over the entire ultra-wide band of 3.1 to 10.6 GHz with low cross-polarization levels of at least -10 dB. Moreover, the proposed antenna maintains the advantages of ease of fabrication and relatively small electrical size.

We have studied the optical properties, band structures and group velocities, of one dimensional photonic crystal (1-D PC) containing negative index materials using translational matrix method (TMM). The 1-D PC containing negative index materials is a periodic arrangement of positive index material (PIM) and negative index material (NIM). The observed group velocity of such structure is larger than the speed of light in certain range of normalized frequency which shown abnormal behaviors. The group velocity of the PC containing negative index materials have found larger than the speed of light. The values of the group velocity become zero, negative and positive for normalized frequencies. The structure containing negative index materials can be used to trap the photons inside the PC i.e., light localization occurs without introducing the defects.

The discrete complex image method stands as one of the most efficient techniques that is able to represent the Green's functions of multilayered structures accurately in the near- and intermediate-field regions. In order to extend the validity of the method to the far region, the surface waves are extracted. Although the extraction process yields accurate results in the intermediate and far-field regions, erroneous results are observed in the near-field region. In this paper, this problem is treated by extracting the contribution of an additional number of artificial poles. Using this scheme, the discrete complex image method can provide accurate representation of Green's functions in both the near- and far-field regions.

Electromagnetic ion cyclotron (EMIC) waves have been studied in the presence of AC electric field perpendicular to ambient magnetic field in the ionosphere with observed superthermal electrons. The presence of 4 eV-50 eV superthermal electrons have been recently seen by Indian SROSS-C2 satellite, Lorentzian Kappa distribution has been used to derive dispersion relation and growth rate using method of characteristics and kinetic approach. The free energy source like anisotropy in temperature, AC electric field and presence of superthermal electrons affect the growth rate. Lorentzian kappa distribution plays important role in giving the wide spectrum range of emitted frequencies.

To investigate the effect of microwave emitted by mobile phones on the rat central nervous system (CNS), in vitro cultured cortical neuronal cells and in vivo rat's brain were exposed to the electromagnetic waves emitted by a microwave transmitter that mimics the working frequency of mobile phones. Trypan blue staining and terminal deoxynucleotidy transferase-mediated dUTP nick-end labeling (TUNEL) were used to determine the survival state of neuronal cells while immunohistochemistry method was used to determine the expression level of Bcl-2 and Bax. Our results show that microwave lead to significant cell death in culture and more in vivo brain neuronal cells were stained positive for TUNEL, Bax and Bcl-2 in rats with cranial defect after exposure than that for control groups (with intact cranium, or had no microwave exposure) (P < 0.01). However, no significant differences were observed in the ratio of Bax/Bcl-2 among the groups studied. Therefore, microwave emitted from mobile phones is harmful to both in vitro cultured cortical cells and in vivo brain neuronal cells from rat with cranial defect. The integrity of cranium is important in protecting the CNS against apoptotic injuries inflicted by the microwaves from mobile phones.

An expression for the eddy current loss in solid rectangular cores is obtained using linear electromagnetic field analysis. Wherefrom text book formula for eddy current loss is derived highlighting various assumptions involved. To get an insight into the current interruption phenomena, electromagnetic fields in a composite rectangular core are analyzed. It is concluded that the reduction in eddy current loss in a laminated cores is basically due to the insertion of distributed capacitors in eddy current paths. Presence of these capacitors increases the impedance of the eddy current path, reducing eddy currents and eddy current loss.

In this paper, a compact waveguide bandpass filter is proposed. The proposed structure consists of some inductive diaphragms in a rectangular waveguide and the regions between them have been filled fully by dielectrics. The relations between the physical and electrical parameters of the existed asymmetrical impedance invertors are obtained. The usefulness of the proposed structure and its performance are verified by designing and simulating an equal-ripple X-band bandpass filter.

In this paper, optimum code rates for a number of channel codes which are used in the coded direct-sequence spread-spectrum (DS-SS) and coded code-division multiple-access (CDMA) communication systems operating in the presence of narrow-band interference (NBI) are investigated. The criteria in obtaining the optimum code rates is based on maximum tolerable NBI power to signal power ratio. First, we consider Optimum Codes, Super Orthogonal Codes (SOC), and Repetition Codes for a single-user DS-SS system and then, the optimum rates for the Optimum Codes in CDMA system using single-user and multi-user detection methods are obtained. In the latter case, we will consider evaluating the optimum code rate for two different multi-user detection schemes, namely, a detection method using joint coding/decoding and a detection method using successive interference cancellation.