Radiation from a superstrate loaded cylindrical-rectangular microstrip patch antenna with an air gap between the substrate and the superstrate, is analyzed using the full-wave approach and the electric surface current model. Results are presented in the form of normalized radiation patterns for various thicknesses of the air gap and also for superstrates made of lossy dielectric material, to show the effects of these on the radiation from the antenna. Both axialand azimuthal current elements are considered.

The scattering of a plane electromagnetic wave by a perfectly conducting prolate or oblate spheroid is considered analytically by a shape perturbation method. The electromagnetic field is expressed in terms of spherical eigenvectors only, while the equation of the spheroidal boundary is given in spherical coordinates. There is no need for using any spheroidal eigenvectors in our solution. Analytical expressions are obtained for the scattered field and the scattering cross-sections, when the solution is specialized to small values of the eccentricity h = d/(2a), (h<<1), where d is the interfocal distance of the spheroid and 2a the length of its rotation axis. In this case exact, closed-form expressions, valid for each small h, are obtained for the expansion coefficients g⁽²⁾ and g⁽⁴⁾ in the relation S(h) = S(0)[1 + g⁽²⁾h² + g⁽⁴⁾h⁴ + O(h⁶)] expressing the scattering cross-sections. Numerical results are given for various values of the parameters.

The problem of determining the Green's function of an electric line source located in a permeable, anisotropic (Ëœμ_xx, Ëœμ_xy, Ëœμ_yx, Ëœμ_yy and Ëœε_zz nonzero interacting parameters) half-space above a Perfect Magnetic Conductor (PMC) ground plane (called the TM^z case herein) for the case where image theory cannot be applied to find the Green's function of the PMC ground plane system has been studied. Monzon [2, 3] studied the Green's function TE^z problem dual to the present one for two cases; (1) when the system was unbounded, anisotropic space where Ëœε_xx, Ëœε_xy, Ëœε_yx, Ëœε_yy and Ëœμ_zz were the nonzero interacting parameters; and (2) when the scattering system was an anisotropic half-space located above a Perfect Electric Conductor (PEC) ground plane and where Ëœε_xx, Ëœε_yy and Ëœμ_zz were the nonzero interacting parameters and Ëœε_xy = Ëœε_yx = 0. Monzon [2] referred to the latter ground plane case as the case where "usual image" theory could be used to find the Green's function of the system. The Green's function for the TM^z-PMC case studied herein was derived by introducing and using a novel, linear coordinate transformation, namely Ëœx = (σ_P /Ï„)Ëœx + σ_MËœy, Ëœy = Ëœy, (Eqs. (6c,d), herein). This transformation, a modification of that used by [2, 3], reduced Maxwell's anisotropic equations of the system to a non-homogeneous, Helmholtz wave equation from which the Green's function, G, meeting boundary conditions, could be determined. The coordinate transformation introduced was useful for the present PMC ground plane problem because it left the position of the PMC ground plane and all lines parallel to it, unchanged in position from the original coordinate system, thus facilitating imposition of EM boundary conditions at the PMC ground plane. In transformed (or primed) coordinates, for the TMz-PMC and TE^z-PEC ground plane problems, respectively, the boundary conditions for the Green's functions G_TM ≡ E_z and G_TE ≡ H_z were shown to be [α*(∂G/∂˜x) + (∂G/∂˜y) |_Ëœy=0 = 0, where G = G_TM or G_TE, α = α_TM or α_TE, where α_TM and α_TE are complex constants (dually related to each other by Ëœμ ↔ Ëœε), and where Ëœy' = 0 is the position of the ground plane. An interesting result of the analysis was that the constant αTE (as far as the author knows) coincidently turned out to be the same as the first of two important constants, namely S₁(dl_v/dl) and S2(dl_v/dl), which were used by Monzon [2, 3] to formulate integral equations (based on Green's second theorem) from which EM scattering from anisotropic objects could be studied. Spatial Fourier transform (k-space) techniques were used to determine the Green's function of the Helmholtz wave equation expressed in transformed coordinates which satisfied the mixed-partial derivative boundary condition of the system. The Green's function G was expressed as a sum of a "free space" Green's function gf (proportional to a Hankel function H⁽²⁾₀ and assumed excited by the line source in unbounded space) and a homogeneous Green's function g whose spectral amplitude was chosen such that, when g was added to g_f , the sum G = g_f + g, satisfied boundary conditions. The k-space, Sommerfeld integrals making up g turned out to converge slowly, and so, using contour integration in the complex plane (Appendix B), g was expressed in a rapidly convergent form, and thus one leading to its practical numerical evaluation. Extensive numerical testing of how well the Green's functions G = g_f + g satisfied boundary conditions and how well the homogeneous Green's function g satisfied Green's second theorem was performed. Excellent verification of the numerical and analytical procedures were found and displayed in the error tables of Tables 1-4 of the paper. Plots illustrating the novel coordinate transformation introduced were presented and several numerical plots of the Green's function developed herein were presented. The application of the present work to find the Green's function for the case when a negative-index, anisotropic metamaterial is adjacent to a conducting ground plane is discussed. Application of the Green's function theory developed herein to multi-layer anisotropic systems is discussed.

This paper aims at developing a technique to calculate the reflection, absorption, and transmission of electromagnetic waves by a bounded plasma region. The model chosen for this study is a magnetized,steady-state, two-dimensional,non uniform plasma slab, which is presented by a number of parallel flat layers. It is assumed that the electron density is constant in each layer such that the overall electron density profile across the slab follows any prescribed distribution function. The proposed technique is referred to as Scattering Matrix Model (SMM). The fields in each layer are written in the form of summation of the appropriate eigen functions weighted by unknown scattering coefficients. These coefficients are determined via the application of the appropriate boundary conditions at each interface. The effect of varying the wave frequency and the plasma parameters on the reflected,transmitted,and absorbed powers are presented and discussed.

In this paper, finite difference frequency domain (FDFD) formulation has been developed for the analysis of electromagnetic wave interaction with chiral materials, and the validity of the formulation for three dimensional scattering problems has been confirmed by comparing the numerical results to exact or other numerical solutions. The influences of the chirality on the scattered field components are investigated. Numerical results for bistatic radar cross section (RCS) are presented and compared to reference solutions and it is found that the proposed FDFD method shows good agreement. It is realized that the presented method is relatively easy to program and can be applied to a wide variety of problems of complex and composite structures efficiently.

In this paper, a tabusearc h tracker with adaptive neurofuzzy inference system (TST-ANFIS) is presented for multiple target tracking (MTT). First, the data association problem, formulated as an N-dimensional assignment problem, is solved using the tabu search algorithm (TSA), and then the inaccuracies in the estimation are corrected by the adaptive neuro-fuzzy inference system (ANFIS). The performances of the TST-ANFIS, the joint probabilistic data association filter (JPDAF), the tabusearc h tracker (TST), Lagrangian relaxation algorithm (LRA), and cheap joint probabilistic data association with adaptive neuro-fuzzy inference system state filter (CJPDA-ANFISSF) are compared with each other for six different tracking scenarios. It was shown that the tracks estimated by using proposed TST-ANFIS agree better with the true tracks than the tracks predicted by the JPDAF, the TST, the LRA, and the CJPDAANFISSF.

A novel structure for the capacitive micromachined switches with low actuation voltage is proposed. In this structure both contact plates of the switch are designed as displaceable membranes. Two structures with similar dimensions and conditions, differing on only the number of the displaceable beams are analytically investigated as well as simulated using ANSYS software. The obtained results indicate about 30% reduction in actuation voltage from the conventional single beam to our proposed double beam structure. The stress on the beam due to the actuation voltage is also reduced increasing the switching life time. The dynamic simulation results in switching time of 6.5 μsec compared to the 8.9 μsec of the analytical results. It can be implemented by the well established surface micromachining for RF applications.

The focusing characteristics of 2D-Cylindrical Electromagnetic Band Gap (CEBG) structures constituted of metallic wires and with defects are analyzed numerically for directive antennas application. The introduction of defects into the periodic structures consists of removing one or multiple wires. The simulations were carried out with a Finite Difference Time Domain (FDTD) code, where the excitation is a line source and the CEBG structure is considered infinite in the vertical direction. Numerical results showing the effects of the number of cylindrical layers and of the number of defects are presented and discussed. These results allow to determine the structures giving best focusing performance and to obtain the frequency band for directive radiation.

Aclosed-form formula, the discrepancy parameter, which has been defined as the ratio of the modal expansion coefficients between the electromagnetic field obtained from the image approximation and the incident electromagnetic field, has been proposed for the evaluation of the validity of the image approximation in the electromagnetic wave propagation, i.e., Love's equivalence principle, and the electromagnetic wave scattering, i.e., the induction equivalent and the physical equivalent, in the cylindrical geometry. The discrepancy parameter is derived through two equivalent methods, i.e., the vector potential method through the cylindrical addition theorem and the dyadic Green's function method, for both the TE and TM cylindrical harmonics. The discrepancy parameter justifies the fact that the image approximation approaches the exact solution for the cylindrical surface of infinite radius. For the narrow-band field with limited spectral component in k space, the cylindrical modal expansion of the electromagnetic wave into the TE and TM cylindrical harmonics can be separated into the forward-propagating wave that propagates forward and the back-scattered wave that is back-scattered by the PEC surface, within the image approximation. The discrepancy parameter shows that the validity of the image approximation depends on the property of the incident field and the radius of the cylindrical surface, i.e., the narrow-band field and the surface of a large radius are in favor of the image approximation, which has also been confirmed by the numerical result.

In this paper, the higher order hierarchical basis functions are employed to solve the electric field integral equation for computing electromagnetic scattering from three-dimension bodies comprising both conducting and dielectric objects. In higher-order methods of moments (HO-MoM), the equivalent surface electric and magnetic currents are usually expanded by the same basis functions, which are not appropriate in our problem here. The pointwise orthogonal basis functions respectively for electric and magnetic currents are proposed in our improved HO-MoM. Quadrilateral patches are used in curvilinear geometry modeling since they result in the lowest number of unknowns. Numerical solution procedure is particularly analyzed, and numerical results are given for various structures and compared with other available data lastly.

In this paper we investigate the effect of replacing the ordinary rectangular microstripp atches in a linear antenna array with fractal patch elements. It is shown that using fractal patches substantially decreases the Mutual Coupling between elements. The effects of fractal type, spacing between elements, feed point location and number of parasitic elements on array performance has been studied.

In this paper, we present a comparison study between phase-only and amplitude-phase synthesis of symmetrical dual-pattern linear antenna arrays using floating-point or real-valued genetic algorithms (GA). Examples include a sum pattern and a sector beam pattern. In the former, phase is only optimized with predetermined Gaussian amplitude distribution of fixed dynamic range ratio (|^amax / ^amin|) and in the latter, both are optimized with less dynamic range ratio than the former and yet share a common amplitude distribution.

This paper presents an icosahedron-based spherical antenna array for phase mode processing. In this topology, the interelement spacing is almost identical. This feature is useful for threedimensional beam scanning and for reducing the effects of mutual coupling. The use of directional elements in this array for wideband synthesis is discussed, and our results show that the use of such elements can overcome the limitations of rapid variations in the amplitude of the far-field mode over a wide frequency band and enable such array to synthesize wideband patterns.

A novel method is introduced to synthesize microstrip Nonuniform Transmission Lines (NTLs) for matching between two arbitrary complex frequency dependent impedances in a wideband or multi-band frequency range. First, stripwidth or the characteristic impedance function of the microstrip NTL is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimization approach. The usefulness of the proposed method is verified using some examples.

In this paper, new circuit models are used to calculate the induced fields in biological media exposed to an incident plane wave in the two-dimensional cases. These models represent the induced fields in the medium using the lossy long transmission line model [1]. The voltages and currents in the circuit model simulate the electric and magnetic fields in the medium. The response of the medium to the incident wave is represented by equivalent conduction and polarization current sources in the medium. These currents are used as the excitation sources in the circuit model from which the required induced fields are obtained. An accurate absorbing impedance boundary condition for open boundaries is used which considerably reduces the matrix dimensions. The validity of these models is tested in the problem of absorption of E- and H-waves by biological multilayered cylinders. Results are compared with available analytical and numerical solutions.

The far-field radiation characteristics of an infinitesimal dipole embedded between two partially reflective surfaces (PRS) to obtain high directivity are studied analytically. The analysis is based on integral summation of spectral radiation fields of the source in cylindrical coordinate, so that we can find the effects of transmission and reflection coefficients of PRS on all components of primary radiation source. The analysis shows that due to the existence of TE_z and TM_z modes for horizontal dipole source, the effects of PRSs are different for each mode. Also, this study shows that by adjusting the spacing of the plates, it is possible to achieve high directive multibeam patterns.

In this paper a Polarized Optical Orthogonal Code (Polarized-OOC) is proposed by exploiting the polarization property of the fiber and the chip's polarization state. The polarized-OOC code is generated using the concept of Mark Position Difference (MPD) set. Polarized-OOC code cardinality is shown to be two times that of the conventional OOC which reflects an increase in the number of supported users. Furthermore, since the correlation properties of the constructed code are the same as that of conventional OOC, error rate performance is evaluated in the same way as in conventional OOC. Also, a simple procedure for fiber-induced polarization rotation compensation is introduced. We then use simulations to show that relative polarization axis misalignment between the desired user and interfering users leads to violation of the correlation properties of the proposed code.

The properties of a grounded dielectric slab with double negative (DNG) metamaterials are investigated in this paper. Dramatically different dispersion curves of evanescent surface modes (electromagnetic fields exponentially decay both in air and inside the slab) are observed. They are highly dependent on the medium parameters. As the counterpart of the improper complex leaky modes in a double positive (DPS) medium, the complex modes in a DNG medium are proved to be exclusively proper. They have exponentially decaying fields in the air region and are termed complex surface modes. It is found that there are an infinite number of complex surface modes and they cannot be suppressed. The Poynting vectors of complex surface modes are studied and it is proved that their integrals along the transverse direction are simply zero. The complete mode spectrum of the dielectric slab for both DPS and DNG media are tabled and compared. Surface wave suppression is discussed and its necessary and sufficient conditions are presented.

Based on a generalized Helmholtz's identity, definitions of an irrotational vector and a solenoidal vector are reviewed, and new definitions are presented. It is pointed out that the well-known uniqueness theorem of a vector function is incomplete. Although the divergence and curl are specified, for problems with finite boundary surfaces, normal components are not sufficient for uniquely determininga vector function. A complete uniqueness theorem and its two corollaries are then presented. It is proven that a vector function can be uniquely determined by specifyingits divergence and curl in the problem region, its value (both normal and tangential components) on the boundary.

In this paper, a conceptual schematic for calibration of large phased array antenna is presented. Derived from an earlier work by the authors, the presentation demonstrates a simple yet innovative schematic of inserting time delay units with each element in the array which can be used to generate both SUM and DIFFERENCE pattern. Both these patterns are electronically steerable. The calibration is done using SUM-DIFFERENCE pattern. PIN switches are used to insert proper time delay units. Thus the schematic is completely programmable using a microcontroller to control the insertion of time delay. The details of the schematic is presented along with the generated antenna patterns.