This paper presents the results of profile inversion of multi-frequency electromagnetic scattered field data, measured by the Institute Fresnel, Marseille, France, from cylindrical objects, both for TM and TE illuminations. The reconstructions are obtained by applying the Multiplicative Regularized Contrast Source Inversion (MR-CSI) method. The results show that the MR-CSI method successfully performs 'blind' inversion of a wide class of scattered field data. Further, we also show that by inverting both TM and TE data simultaneously, a more accurate reconstructed image can be obtained.

Circularly symmetric patch antennas tuned by transversely magnetized lossy ferrite are studied. The circular and ring patch geometries printed on ferrite substrate or tuned by ferrite post and ferrite toroid are studied. Both saturated and partially magnetized ferrite are considered. Strong effects on the dispersive properties of modes propagating under the patch and in turn on the antenna resonant frequency and input impedance are observed when the ferrite losses are taken into account. The patch antennas resonance at a novel mode propagating in the traditionally assumed switch-off frequency range of negative effective permeability constitutes an essential original contribution of this work. In all cases the dynamic control of the patch resonant frequency through the DC-biasing field is investigated. The "perfect magnetic walls approximation" was employed in the analysis since it offers a valuable physical insight as well as simplified closed form expressions for the resonant conditions. These are used as engineering design formulas for an initial antenna design, which is in turn fine tuned with the aid of a numerical simulation-optimization scheme. The validity of the present method was verified through comparisons with published experimental results and numerical simulations.

Combined volume scattering with rough surface scattering effects in passive microwave remote sensing of wet snow is studied in this paper. The dense medium radiative transfer (DMRT) theory with quasicrystalline approximation (QCA) is used to describe the volume scattering model for densely distributed sticky coated dielectric particles. The Numerical Maxwell Model of 3D simulations (NMM3D) is used to simulate the rough surface bistatic scattering and emission, and the bistatic scattering coefficients and emissivity of the rough surfaces are utilized as the boundary conditions for the DMRT. Full multiple scattering solutions are calculated by solving the DMRT numerically. Wet snow model is adopted in this paper, the results are illustrated for a layer of wet snow over a moist rough ground at 18.7 GHz and 38.5GHz.

Abstract-Electromagnetic Interference (EMI) is becoming a crucial issue in the era of modern electronic systems. For EMI measurement, it is required to place a sensor to receive the radiation from the equipment in a suitable test environment. The performance of the sensor depends on its Antenna Factor, which is the ratio of the incident electric field on the antenna surface to the received voltage at the load end. Here, a Method of Moment-based numerical technique has been used to evaluate the performance of a sensor in different test environments with different wave impedances. The evaluation of the sensor has been performed in terms of the Antenna Factor. The results are presented for free space environment of impedance 377Ω and Gigahertz Transverse Electromagnetic (GTEM) Cell of characteristic impedance 50Ω. The results show well agreement with experimental data.

In present paper, a novel and effective hyperthermia applicator utilizing an elliptically bent conformal array of longitudinal slots in narrow wall of rectangular waveguide is analyzed by two different approaches, viz., the vector potential method and Fresnel- Kirchhoff scalar diffraction field theory. The agreement between two theories is reasonably very good. This configuration is mainly intended as a specialized and very effective applicator for hyperthermia treatment of tumor within curved portions of human body such as abdomen, neck, chest etc. Each slot of the conformal array is excited by a coaxial line probe. It is proposed that the interior of the waveguide be filled with water to provide a good impedance match with the bio-medium. The contour distribution of specific absorption rate (SAR) in x-z plane, SAR distribution in y-direction and parameters such as penetration depth, power absorption coefficient, effective field size (EFS) due to the conformal array as well as single slot are evaluated and compared at 433 MHz. The results for contour SAR distribution at 433 MHz for elliptically bent conformal array are also compared with those for other array configurations such as circularly bent conformal array and planar array. The effect of change in phase and amplitude excitation of each slot of the array on SAR distribution is also examined. The results demonstrate that slotted waveguide conformal array offers marked improvement in SAR distribution and penetration depth over single slot. It also has better focusing ability as compared with planar array for controlled amplitude and phase excitations of the elements.

The technology of adaptive antennas is rapidly growing during the last years. It is true that switched beam antennas, the simplest type of smart antennas, may provide substantial benefits when implemented in a cellular mobile telephony system. The performance of a six-beam switched parasitic planar array, in terms of bit error rate (BER) measurement, is presented in this paper. The switched parasitic planar array is designed with the aid of genetic algorithms method. The antenna system is evaluated in a radio environment where interfering signals are present. The results obtained from the simulation are compared with respect to the ones when an omni directional antenna is used instead of the switched beam array, revealing that the performance of such a telecommunication system can be improved.

Artificial boundary conditions, which can be identified as Robin boundary conditions positioned at a complex space coordinate, are introduced in order to obtain pertinent approximations for the Green's functions in grounded layered media. These artificial boundary conditions include perfectly matched layers backed by perfectly electric or magnetic conductors. As a first result, we obtain analytical expressions for the differences of Green's functions sub ject to different boundary conditions. Since weighted sums of Green's functions are again Green's functions, the need arises to solve an optimization problem, in the sense of obtaining the optimal weighted mixture of Green's functions, as compared to the exact Green's function. Comprehensive eigenexpansions for the Green's functions are given in the general case, and a few examples illustrate the goodness of fit between the approximate Green's functions and the exact Green's function.

A Nyström method with edge condition (EC) is developed for electromagnetic scattering by two-dimensional (2D) open structures. Since EC correctly describes the edge behavior of currents on the scatterers, the use of it in Nystr ̈om method can dramatically coarsen the discretization near the edges. In the implementation of the scheme, we derive the closed-form expressions for the singular or near- singular integrations of Hankel functions multiplied by the polynomials with or without EC. This allows us to control the numerical errors efficiently by approximating the Hankel functions with more series terms and selecting higher-order polynomials to represent the currents in the local correction. The numerical results illustrate that the solutions with the use of EC converge much faster than without the use of EC. Also, EC is more essential in TM polarization than in TE polarization due to the singular behavior of current near edges.

The limited-memory quasi-Newton optimization method with simple bounds has been applied to develop a novel fully threedimensional (3-D) magnetotelluric (MT) inversion technique. This nonlinear inversion is based on iterative minimization of a classical Tikhonov-type regularized penalty functional. But instead of the usual model space of log resistivities, the approach iterates in a model space with simple bounds imposed on the conductivities of the 3-D target. The method requires storage that is proportional to n_cp×N, where the N is the number of conductivities to be recovered and ncp is the number of the correction pairs (practically, only a few). This is much less than requirements imposed by other Newton type methods (that usually require storage proportional to N×M, or N×N, where M is the number of data to be inverted). Using an adjoint method to calculate the gradients of the misfit drastically accelerates the inversion. The inversion also involves all four entries of the MTimp edance matrix. The integral equation forward modelling code x3d by Avdeev et al. [1, 2] is employed as an engine for this inversion. Convergence, performance and accuracy of the inversion are demonstrated on a 3D MTsyn thetic, but realistic, example.

In this paper a new technique for the evaluation of the Green's functions of filament sources in layered media, is presented. The technique is based on the annihilation of the asymptotic and singular behaviors of a spectral Green's function. The remaining function, after annihilation, is treated using a two levels discrete complex image method (DCIM). The application of the proposed technique, provides a complete analytical expression for the spatial Green's function, in terms of the iterative value of the propagation constant. This expression consists of the annihilating functions and a number of complex images. In order to validate the proposed technique, microstrip lines and slotlines are analyzed and the obtained results are found to agree very well with those obtained using a commercial software.

In this paper, we introduce a first order accurate resonance model based on a second order Padé approximation of the reflection coefficient of a narrowband antenna. The resonance model is characterized by its Q factor, given by the frequency derivative of the reflection coefficient. The Bode-Fano matching theory is used to determine the bandwidth of the resonance model and it is shown that it also determines the bandwidth of the antenna for sufficiently narrow bandwidths. The bandwidth is expressed in the Q factor of the resonance model and the threshold limit on the reflection coefficient. Spherical vector modes are used to illustrate the results. Finally, we demonstrate the fundamental difficulty of finding a simple relation between the Q of the resonance model, and the classical Q defined as the quotient between the stored and radiated energies, even though there is usually a close resemblance between these entities for many real antennas.

An approach is proposed to obtain some exact explicit solutions in terms of elliptic functions to the Novikov-Veselov equation (NVE[V(x, y, t)] = 0). An expansion ansatz V → ψ = Σ²_j=0 a_jf^j is used to reduce the NVE to the ordinary differential equation (f')² = R(f), where R(f) is a fourth degree polynomial in f. The wellknown solutions of (f')2 = R(f) lead to periodic and solitary wave like solutions V. Subject to certain conditions containing the parameters of the NVE and of the ansatz V → ψ the periodic solutions V can be used as start solutions to apply the (linear) superposition principle proposed by Khare and Sukhatme.

It has been observed that localized solution modes provide sparse factored representations of the discrete integral equations encountered in the simulation of electromagnetic phenomena at low frequencies. This paper extends these results by incorporating overlapped localizing modes. For TM_z scattering from a rectangular array of perfectly conducting obstacles, it is observed that the complexity scaling of the resulting factorization is significantly reduced relative to previously reported results. The memory complexity of the resulting factored representation scales approximately as O(N) for electrically small arrays. Limitations and possible extensions of these results are discussed.

n this paper, we measured what influence the sinusoidal transmission characteristics of the electric power line with various forms gave to the transmission characteristic of OFDM (Orthogonal Frequency Division Multiplexing) signal through PLC (power line communication system) modem. The electric power line transmission line with various forms in a real environment is classified into two basic elements, which are an outlet type branch and a switch type branch. Next, PHY rate (Physical rate) is measured for each basic element connected with the PLC modem. At this time, the transmission characteristics of the electric power line are simulated from measured data. OFDM sending and receiving systems are composed on the computer, and the PHY rate is simulated. By comparing with measured and calculated values, it is revealed that PHY rate of PLC modem is most affected in the case of the power line transmission characteristics having broad band and high level attenuation and is not affected in the case of that having narrow band group delay variation.

Oblique coordinates are introduced into the method of lines. For the purpose of analysis, suitable equations are derived. The formulas are applied to compute the transmission in a waveguide device consisting of straight waveguides connected by a tilted one. Furthermore, the band structure of a hexagonal photonic bandgap structure was computed using these oblique coordinates.

This paper presents the design and implementation of an Active Integrated Antenna (AIA) using a Voltage Controlled Oscillator (VCO) for applications in the Industrial Scientific Medical band (2.4 ÷ 2.4835 GHz). Surface Mounting Device (SMD) technology has been applied in the realization of the passive and active components, and low cost FR-4 dielectric slabs have been employed for the integration of the antenna and the active/transmissive circuits, residing, respectively, on the opposite faces of a Personal Computer Memory Card International Association (PCMCIA) card. The proposed layout makes use of a properly corrugated ground plane, i.e., a High Impedance Ground Plane (HIGP), to improve the antenna performances and to minimize the coupling between the radiating component and other possible radiating elements and/or electronic circuits residing nearby. The analysis and the design of the radiating element with the HIGP are based on a rigorous full wave Method of Moment (MoM) formulation developed in the Spectral Domain (SD), while the design of the active circuitry is developed through the commercial tool AWR Microwave Office. The final design of the component is obtained hybridizing the two methods and applying a Genetic Algorithm (GA) optimization tool in order to take advantage of the HIGP, while keeping the geometrical dimensions of the antenna suitable for mounting on a PCMCIA card, and maintaining the antenna performances acceptable. The measured results show the performances of the VCO, an antenna gain of 19.4 dBi and an increased front-to-back radiation ratio compared to the one of the same antenna mounted on a standard Perfect Electric Ground Plane (PEGP). This result, thus, demonstrates the minimization of the interferences between the designed antenna and other possible radiating and transmissive devices residing nearby.

A new methodology has been developed, based on moment method; for analyzing a class of rectangular waveguide based circuits and radiators. The methodology involves in modeling the given structure using tetragonal bricks or cavities and then replacing all the apertures and discontinuities with equivalent magnetic current densities so that the given structure can be analyzed using only the Magnetic Field Integral Equation (MFIE). As it is necessary to use a number of such cavities in order to study these complicated waveguide structures, the present method is named as Multiple Cavity Modeling Technique (MCMT). The ma jor advantage for using the MCMT in rectangular waveguide based structures is the fact that since only the magnetic currents present in the apertures are considered the methodology involves only solving simple magnetic field integral equations rather the coupled integral equation involving both the electric and magnetic currents. Further it is possible to consider both co and cross polarization and also the thickness of the waveguide discontinuities like diaphragm thickness or window thickness in the analysis. Due to this, it is possible to get highly accurate result. It is also possible to extend the method to any number of resonators, cavities or irises regardless of the polarization. To demonstrate, the methodology has been applied to analyze an open end of a waveguide with dielectric plug, both in transmitting and receiving mode, and a waveguide step discontinuity. Even mode and odd mode admittances of interacting identical inductive diaphragms have also been calculated using this methodology. Data obtained using this technique has been compared with measured, CST microwave studio simulation and literature available data. The theory has been validated by the reasonable agreement obtained between experimental data, simulated data and literature available data with numerical data

In this paper, the effect of Electromagnetic Bandgap (EBG) Superstrates on return loss of the Probe-Fed Microstrip Antenna (PFMA) has been examined. Originally the EBG superstrate layer made by Frequency Selective Surface (FSS) layers is used to increase the directivity of the PFMA, but to increase the efficiency of the whole structure including the PFMA and EBG superstrate it is necessary to have suitable impedance matching. In this paper the EBG superstrate as a resonance load to the primary radiation source (PFMA) and then by choosing the appropriate geometrical parameters of the structure we can obtain suitable impedance matching beside the directivity enhancement of the primary radiation source.

In this paper, the theoretical foundations of near-field-far- field transformations with spiral scannings are revisited and a unified theory is provided. This is accomplished by introducing a sampling representation of the radiated electromagnetic field on a rotational surface from the knowledge of a nonredundant number of its samples on a spiral wrapping the surface. The obtained results are general, since they are valid for spirals wrapping on quite arbitrary rotational surfaces, and can be directly applied to the pattern reconstruction via near-field-far-field transformation techniques. Numerical tests are reported for demonstrating the accuracy of the approach and its stability with respect to random errors affecting the data.

Abstract-The backscattered field of an illuminated sphere with diameter Ø = 30.5 cm above a perfect conducting plate is measured in an anechoic chamber at different heights for a varying incidence angle φ in the range 5° to 75°. A high frequency field λ « Ø is transmitted, so that two significant transitions from lit to shadow regions are given over the entire incidence angle range for the considered ray field. The polarimetric behavior of the measured scattering matrix [S] is investigated by using the common coherent and incoherent decomposition theorems used by the radar polarimetry scientific community. Close to the shadow boundaries the polarimetric behavior of the sphere significantly changes. Representing the different decomposition parameters used in radar polarimetry over the incidence angle range, the transition zones are related to local maxima or minima. Hence, the extreme values of the polarimetric parameters give information about the geometrical parameters e.g target size and its height above the plate.