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.

The performance of capacitive interdigital sensors involved with anisotropic and inhomogeneous nematic liquid crystal (LC) film is investigated. These sensors have potential applications in chemical and biological systems. The theory for modeling the permittivity tensor of the LC film as a function of the molecular orientation is presented. The LC film is handled as inhomogeneous material where molecules are assumed to have different orientations with respect to the frame axes. Under these conditions, fringing field capacitances as functions of the molecular deformations are calculated. Examples of modeled capacitive interdigital sensors in the present of different inhomogeneous distributions of LC films will be studied and discussed.

The three-dimensional Gaussian beam scattering from the bounded periodic sequence of one-to-one composed isotropic magnetodielectric and bi-isotropic layers are investigated. The beam field is represented by an angular continuous spectrum of plane wave. The problem of the partial plane wave diffraction on the structure is solved using the circuit theory and the transfer matrix methods. It is found that after reflection from the structure, the circular Gaussian beam becomes, in general, an elliptical Gaussian beam, in addition to a displacement of the beam axis from the position predicted by ray optics.

This paper presents some new techniques for high resolution (HR) image processing and compares between them. The paper focuses on two main topics, image interpolation and image superresolution. By image interpolation, we mean extracting an HR image from a single Degraded low resolution (LR) image. Polynomial based image interpolation is reviewed. Some new techniques for adaptive image interpolation and inverse image interpolation are presented. The other topic treated in this paper is image super-resolution. By image super resolution, we mean extracting a single HR image either from multiple observations or multiple frames. The paper focuses on the problem of image super resolution using wavelet fusion and presents several super resolution reconstruction algorithms based on the idea of wavelet fusion.

The aim of the present paper is to reveal the effect of motion on the scattering by an edge. To this end one considers a canonical structure formed by a perfectly conducting half-plane illuminated by a time-harmonic and uniformly moving infinitely long line source. The relevant line source is located parallel to the edge and moves with a constant velocity which is also parallel to the half-plane. This is the dual of a previously studied problem in which the halfplane was moving uniformly. The present problem is first reduced into a Wiener-Hopf problem in the sense of distribution and then solved by an ad-hoc method. The edge-diffracted field is discussed in detail.

This paper is intended to the analysis of adaptive radar detectors for partially correlated χ² targets. This important class of targets is represented by the so-called moderately fluctuating Rayleigh targets, which, when illuminated by a coherent pulse train, return a train of correlated pulses with a correlation coefficient in the range 0 < ρ < 1 (intermediate between SWII and SWI models). The detection of this type of fluctuating targets is practically of great importance. Since the CFAR detectors represent an attractive class of schemes that can be used to overcome the problem of clutter by adaptively setting their threshold based on local information of total noise power, they are commonly used to decide the presence or absence of the radar target of interest, which is of partially correlated χ² type. In addition, the OS based algorithms are chosen to carry out this task owing to their immunity to outlying targets which may be present amongst the contents of the reference window. Moreover, since the large processing time of the single-window OS detector limits its practical applications, our scope here is to analyze the performance of OS modified versions for moderately fluctuating Rayleigh targets in nonideal situations. This analysis includes the single-window as well as the double-window OS detection schemes for the case where the radar receiver postdetection integrates M square-law detected pulses and the signal fluctuation obeys χ² statistics with two degrees of freedom. These detectors include the mean-level (ML-), the maximum (MX-) and the minimum (MN-) OS algorithms. Exact formulas for their detection probabilities are derived, in the absence as well as in the presence of spurious targets. The primary and the secondary interfering targets are assumed to be of the moderately fluctuating Rayleigh targets. Swerling's well known cases I and II represent the cases where the signal is completely correlated and completely decorrelated, respectively, from pulse to pulse. Under the multiple-target operations, the ML-OS detector has the best homogeneous performance, the MN processor has the best multitarget performance when a cluster of radar targets appears in the reference window, while the MX scheme doesn't offer any excessive merits, neither in the absence nor in the presence of outlying targets, as expected.