The complex permeability of ferromagnetic thin films is measured up to 10 GHz by using shorted microstrip method combining with conformal mapping. The S-parameters are measured by vector network analyzer (VNA), and the effect of thin film placed both upwards and downwards in the fixture are investigated. The experimental results show that the complex permeability of the thin films is measured accurately from 500 MHz to 10 GHz, and loading the samples with thin film placed downwards can avoid the electromagnetic resonance effectively.

The scattering of an arbitrary electromagnetic wave by a thin disk located in free space is formulated rigorously in terms of coupled dual integral equations (CDIEs) for the unknown images of the jumps and average values of the normal to the disk scattered-field components. Considered are three cases of the disk: (1) zero-thickness perfectly electrically conducting (PEC) disk, (2) thin electrically resistive (ER) disk and (3) dielectric disk. Disk thickness is assumed much smaller than the disk radius and the free space wavelength, in ER and dielectric disk cases, and also much smaller than the skin-layer depth, in the ER disk case. The set of CDIEs are "decoupled" by introduction of the coupling constants. Each set of DIEs are reduced to a Fredholm second kind integral equation by using the semi-inversion of DIE integral operators. The set of "coupling" equations for finding the coupling constants is obtained additionally from the edge behavior condition. Thus, each problem is reduced to a set of coupled Fredholm second kind integral equations. It is shown that each set can be reduced to a block-type three-diagonal matrix equation, which can be effectively solved numerically by iterative inversions of the two diagonal blocks and 2×2 matrix.

The efficiency of different ways for controlled changes of spectral characteristics of open electrodynamic resonant structures are studied and evaluated in the paper.

Image reconstruction in electrical impedance tomography (EIT) is an ill-posed nonlinear inverse problem. Regularization methods are needed to solve this problem. The results of the ill-posed EIT problem strongly depends on noise level in measured data as well as regularization parameter. In this paper we present trust region subproblem (TRS), with the use of Lcurve maximum curvature criteria to find a regularization parameter. Currently Krylov subspace methods especially conjugate gradient least squares (CGLS) are used for large scale 3D problem. CGLS is an efficient technique when the norm of measured noise is exactly known. This paper demonstrates that CGLS and TRS converge to the same point on the L-curve with the same noise level. TRS can be implemented efficiently for large scale inverse EIT problem as CGLS with no need a priori knowledge of the noise level.

This paper deals with the design and numerical analysis of a reconfigurable antenna implemented according to the total geometry morphing approach. The reconfigurable antenna is designed so to resemble a reference bowtie antenna, suitable for a stepped frequency Ground Penetrating Radar (GPR) applications, with geometry variable in order to work in different operative conditions. In particular, the good agreement between the reference antenna and the reconfigurable one is tested within the work frequency band 0.3-1 GHz for both the free-space and half-space geometry. Finally, a trial of the reconfigurability of the proposed solution is shown for operative conditions with antenna in contact with different dielectric media.

The coupled mode theory (CMT) is used to analyze uniform Fiber Bragg gratings. The multi-mode CMT is expressed as the first-order vector ordinary differential equations (ODEs) with coefficients depending on the propagation distance. We show in this paper that by changing variables, the original couple mode equations (CMEs) can be re-casted as constant coefficient ODEs. The eigenvalue and eigenvector technique (EVVT), the analytic method for solving constant coefficient ODEs, is then applied to solve the coupled mode equations. Furthermore, we also investigate the application of Runge-Kutta method (RKM) to the calculation of the global transfer-function matrix for CMEs. We compare the transmission and the reflection spectra obtained by EVVT with those by RKM. Both results agree within machine accuracy. Numerical simulations conclude that solving constant coefficient ODEs improves the speed and accuracy of solutions to the original CMEs.

In this work, source equivalence and computation of the reflected (induced) electromagnetic field in geophysical situations are studied. It is shown that the application of Huygens' principle allows for full generalization of Fukushima's equivalence theorem that applies only for magnetic field. The source equivalence is revisited for a vertical line current element, and it is shown that the equivalent charge required to replace the original source by a planar equivalent source together with the surface charge associated with the reflected field generates a purely vertical total electric field on the ground. Consequently, if the magnetic field and horizontal components of the total electric field on the ground are of interest, only equivalent currents need to be considered. The classical Complex Image Method (CIM) is derived from exact image theory for planar impedance surfaces. The classical CIM is extended by considering a divergence-free source current that may have components also perpendicular to the ground plane. The extension is seen to generate a complex image charge not present in the classical CIM. Further, a generalized application of the extended CIM to geophysical situations having divergence-free volume source currents is introduced. The application involves decomposition of the source into line current elements and rotations, translations and reflections of the electromagnetic field expressions associated with each element. The validity of the new approach is verified for an example of external current system and ground model setup by means of comparisons to results obtained from exact formulation by~[18].

Solutions of the homogeneous 2D scalar wave equation of a type reminiscent of the "splash pulse" waveform are investigated in some detail. In particular, it is shown that the "higher-order" solutions relative to a given "fundamental" one, from which they are obtained through a definite "generation scheme", come to involve the relativistic Hermite polynomials. This parallels the results of a previous work, where solutions of the 3D wave equation involving the relativistic Laguerre polynomials have been suggested. Then, exploiting a well known rule, the obtained wave functions are used to construct further solutions of the 3D wave equation. The link of the resulting wave functions with those analyzed in the previous work is clarified, the pertinent generation scheme being indeed inferred. Finally, solutions of the Klein-Gordon equation which relate to such Lorentzian-like solutions of the scalar wave equation are deduced.

In this paper, a study is made of the electrostatic potential and field of an electric dipole located in the interface between two dielectric regions. When the dipole is oriented perpendicular to the interface, the detailed position of the charges of the dipole relative to the location of the interface has a significant effect on the value of the field produced away from the dipole, unlike the case of a dipole parallel to the interface. It is shown that it is the total dipole moment (due to both free and bound charges), rather than simply the impressed (free) dipole moment that is important in determining the field in this case. Based on these results, the question of defining and determining the electric polarizability of a perfectly conducting object partially embedded in a dielectric interface is examined. The example of a conducting sphere embedded halfway in the interface is studied as a demonstration of our general formulation. The results of this paper are important for the proper modeling of arrays of scatterers embedded in an interface, such as frequency-selective surfaces (FSSs) and metafilms.

In this paper we derived the formula for calculating the mutual inductance between circular filaments with lateral and angular misalignment by using the approach of the magnetic vector potential. The results obtained correspond to those of F. W. Grover, although the latter used the general formula given by the Neumann integral instead of a vector potential approach. However, the major purpose of this paper is to clarify some confusion introduced in previous works regarding the mutual inductance calculation between thin filamentary circular coils with parallel axes in air. This problem has been solved by Kim et al. (1997) using the magnetic vector potential, but unfortunately it leads to erroneous results, even for slight misalignments of the coils' center axes. This is why we chose to use the approach of the magnetic vector potential to show that, when properly derived, the results must indeed reduce to the well known F.W. Grover's formulas.

A method based on adaptive-network-based fuzzy inference system (ANFIS) is presented for the analysis of conductor-backed asymmetric coplanar waveguides (CPWs). Four optimization algorithms, hybrid learning, simulated annealing, genetic, and least-squares, are used to determine optimally the design parameters of the ANFIS. The results of ANFIS models are compared with the results of conformal mapping technique, a commercial electromagnetic simulator IE3D, and the experimental works realized in this study. There is very good agreement among the results of ANFIS models, quasi-static method, IE3D, and experimental works. The proposed ANFIS models are not only valid for conductor-backed asymmetric CPWs but also valid for conductor-backed symmetric CPWs.

Conjugately characteristic-impedance transmission lines (CCITLs) implemented by lossless periodic transmission-line structures have found various applications in microwave technology, and the T-chart was developed to perform the analysis and design of CCITLs effectively. Originally, the normalization factor used in defining normalized impedances of the T-chart is the geometric mean of characteristic impedances of CCITLs, which is not only one possible choice. By using other normalization factors based on characteristic impedances, different graphical representations can be obtained; i.e., T-charts for CCITLs with passive characteristic impedances are not unique, and it depends on the associated normalization factor. In this study, three more possible normalization factors related to characteristic impedances of CCITLs are investigated. It is found that all T-charts for each normalization factor are strongly dependent on the argument of characteristic impedances of CCITLs in a complicated fashion. The original T-chart based on the geometric mean of characteristic impedances is found to be the most convenient graphical representation for solving CCITL problems.

It is known that the conventional algorithm (CA) of hybrid finite element-boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA) usually suffers the problem of slow convergence, and the decomposition algorithm (DA) is limited by large memory requirement. An efficient twofold iterative algorithm (TIA) of FE-BI-MLFMA is presented using the multilevel inverse-based incomplete LU (MIB-ILU) preconditioning in this paper. It is shown that this TIA can offer a good balance of efficiency between CPU time and memory requirement. The tree-cotree splitting technique is then employed in the TIA to further improve its efficiency and robustness. A variety of numerical experiments are performed in this paper, demonstrating that the TIA exhibits superior efficiency in memory and CPU time to DA and CA, and greatly improves the computing capability of FE-BI-MLFMA.

A printed compound air-fed array antenna with hexagonal configuration is developed, which consists of a stacked-patch radiator, an FSS-cover an AMC-base both with square elements arranged as a hexagonal grid respectively. By means of optimal option for all the structural parameters individually, a broadband prototype is designed at 10 GHz, the peak-gain of 17.11 dBi is performed by hexagonal aperture with side-length of 45 mm (1.5 wavelength); a common frequency bandwidth of 8.20 % for VSWR ≤ 2.0:1 and gain-drop ≤ 2 dB and SLL ≤ −15 dB is obtained by simulation. They are verified by measured results as 16.59 dBi peak-gain and 7.54 % common bandwidth.

The effect of copper on the microwave absorption, conductivity and complex permittivity of fritless Ni_(1-x)Cu_xMn₂O₄ (x=0,0.4,0.8,1) thick film on alumina have been investigated in the 8-18 GHz frequency range. The structural changes have been identified by scanning electron microscope (SEM), FTIR and RAMAN scattering spectroscopy. The microwave conductivity and permittivity increase as copper content increases. The fritless Ni_(1-x)Cu_xMn₂O₄ (0≤x≤1) thick film with x=0.4 shows best absorption properties, though all the other compositions also show good absorption in a large frequency range. The microwave conductivity increases from 1S/cm to 951 S/cm due to copper and the dielectric constant (ε) increases from 7 to 19.5.

Scattering of electromagnetic waves by periodic stripe grating backed with a layer of metamaterial is considered. The distinguished feature of the structure is the association of periodicity of two scales: Micro scale that is the scale characteristic to metamaterial of the layer, and the scale of periodic metal stripe grating that is of the scale of wavelength of incident electromagnetic field. Such association gives rise to new type of resonant phenomena such as "crowding" of resonant transmission/reflection peaks in the vicinity of characteristic frequencies of the structure. The study of the problem is performed on the base of rigorous and accurate solution to the diffraction and spectral problems, which guarantees the robustness of numerical algorithm; and allows asymptotical analytical analysis of the problem and prediction of various resonant phenomena.

In this paper, the Matrix-Pencil method is used to retrieve the radiation pattern of several antennas measured in different semianechoic scenarios using low directive probes, where the existence of reflected contributions can severely disturb the measurement. Starting from data measured in the frequency domain, this method allows the direct path to be identified and the radiation pattern of the antenna to be retrieved with good accuracy in all the cases under study.

In this paper, models of metallic absorbers for electromagnetic waves in the infrared to microwave frequency range are reported and discussed. The Hadley's formalism (1D model) of transmission, reflection and absorption for semi-infinite layers, which allows to design all configurations of unstructured absorber films and dielectrics is generalized. To make the micro-fabrication of the metallic absorbers easier (that means to have layers thick enough), the metallic layers need to be structured (grid for example). We developed a model that allows us to consider the structure of metal as a homogeneous layer, where the diffraction is negligible. This new layer can be used with the previous model. When diffraction effects must be taken into account, we modified an electrical model made by Ulrich. We further developed it for the configuration of a dielectric before the metallic grid. The results showed the importance to take into account all the dimensions of the grid, the dielectric layer parameters and the wavelength to design the best absorber.

We investigate the dispersion properties of both TE and TM surface polariton modes formed at the surfaces of a bilayer composed of a single-negative materials. The dispersion curves of surface polaritons modes is found to consist of two branches, and it is shown that TE and TM surface polaritons may have a simultaneous mode. The characteristics of TE and TM surface polaritons modes (the frequency, localization position, ...) are shown to depend on the relative thicknesses of two single-negative layers of the bilayer. We find that the TE and TM surface polariton modes propagate in the same directions along the interfaces of the bilayer in the most cases. Nevertheless, the TE and TM surface polariton modes may have opposite directions of propagation for appropriate thicknesses of two single-negative layers. This can be interesting especially in the case of simultaneous TE and TM surface polariton mode, for which the structure acts as a polarizing beam splitter.

In this paper, a low-cost multiband printed-circuit-board (PCB) antenna that employs Koch fractal geometry and tunability is demonstrated. The antenna is fabricated on a 1.6 mm-thick FR4-epoxy substrate with dimensions 4 cm × 4.5 cm, is microstrip-line fed and has a partial ground plane flushed with the feed line. The proposed antenna is simulated using the Finite-Element Method for three different switching cases and the return loss is measured for each case. It is shown that the antenna can cover the bands of several applications including 3G, WiFi, WiMAX as well as a portion of the UWB range. The radiation patterns are satisfactorily omnidirectional across the antenna's operation bands.