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A program for analysing spherical patch antennas by means of the moment method in spectral domain is adapted to the analysis of frequency-selective surfaces (FSS). In the new model, a plane wave is impinging on a dipole array lying in free space. The plane wave is expanded into a series of spherical harmonics while the Green's functions of the spherical structure are found with the aid of the GIDMULT...
Frequency selective surfaces' (FSS) representation with an equivalent circuit composed of lumped elements is very useful in the design stage, where it is desirable to know in a quick way if a FSS is able to give a fixed frequency response. The final aim will be to obtain an equivalent circuit that fits the simulated FSS response with the proposed LC circuit. The method will be validated with a metallic...
Summary form only given. This paper presents an innovative phased array antenna that can provide a variable number of beams for simultaneous satellite contacts. It has many operational advantages over conventional reflector dish antennas in capacity, responsiveness, throughput and flexibility for satellite operations support. A review of satellite operations support was used as the framework to identify...
Numerical simulations of large periodic structures, such as metamaterials or phased arrays, can be excessively time consuming because of the large number of unknowns involved. This paper presents a technique based on a MoM simulation code and the array scanning method which allows to compute efficiently induced currents in periodic structures excited by a single source. Moreover, by combining this...
The idea of objective, computer based methods for testing audio quality is introduced in this work. Including some basic of perceptual coding, international standards and description of new measurement algorithm. With described algorithm PEAQ we have measured a characteristics of four different codecs and have shown the results in this paper
In this paper we present a low-profile directional UWB antenna with improved radiation efficiency when operating in close vicinity to a biological tissue. This antenna is intended for the use in UWB wireless body area network (WBAN) applications, between 3 and 6 GHz. A novel design is based on a UWB slot antenna structure with an added radiator/reflector element in order to achieve directional radiation...
Fractals are geometric structures which exhibit invariance property with respect to a change of scale. They can be obtained by repeating a basic operation (generator) on a smaller and smaller scale. Optical Cantor fractal multilayers are structures obtained by applying the fractal Cantor construction to the optical length of the layers of two different dielectrics. Their transmission spectrum can...
In order to improve quality of a medical image, obtained by magnetic resonance, several factors can be modified, in particular the homogeneity of the value of the static field, the technique of acquisition with its parameters, the sensitivity of the reception antenna. On this last factor there remains progress very significant to achieve. In order to calculate with more precision the signal collected...
This paper highlights the problem of quality estimation of speech signal transformed into digital form and the problem of impairments introduced by transmission system. These issues could be analyzed by using adequate quality measuring methods. Quality measuring methods have been classified according to their main characteristics and application field. This paper introduces most commonly used subjective...
This paper reports results obtained by propagation modeling for WLAN applications. A multi-ray model is proposed and tested through analytical calculations, neural network simulation, and measurements. As the case used a corridor of university building in Dubrovnik, for which calculation, simulation and measurement of signal strength were obtained. Calculation is based on ray-tracing method with neglecting...
The paper deals with the boundary element modeling of the human body exposed to extremely low frequency (ELF) electric fields. Two models are presented throughout this work; a multidomain body of revolution and the realistic representation of the human body. The formulation of the problem is based on the quasi-static approximation and the related Laplace equation variant of the continuity equation...
A procedure for the assessment of the maximal power frequency magnetic flux density from a power substation is proposed in the paper. The present technique is based on a multiquadric approximation of magnetic flux density obtained using the discrete measured data. The approximation sufficiently handles multidimensional multiextreme functions by interpolating their scattered values accurately. Subsequently,...
Introducing leaky loss transmission line theory, a novel design method of circularly polarized antenna is proposed. The principle of this method is that two summations that are perpendicular to a complex vector component of currents are placed on the small strip conductors, of which each set represents an antenna structure, have equal amplitude and different phase by 90 degrees. To achieve efficient...
A unique solution for H-scattering from a roughness (boss or indentation) on a PEC ground plane in the two-dimensional case is obtained making use of a new method that combine the Galerkin MoM on entire-domain basis and the Rayleigh's method expansion of a solution in terms of the eigensolutions of Helmholtz equation in cylindrical coordinates. This method uses the dividing of upper space into two...
An effective procedure for the computation of the antenna directivity from a nonredundant number of voltage data acquired via a bi-polar scanning in the near-field region is developed in this work. It can be applied whenever the power radiated by the antenna in the backward half-space is negligible and the total radiated power coincides practically with that radiated in the forward one. It makes use...
In this contribution, we propose the analysis of a planar hexagonal spiral microstrip element for ultra wide band antenna arrays. The antenna is mounted on a low cost and light dielectric substrate and is backed by a ground plane. The spiral element consists of a single arm and it is fed by a simple coaxial probe. The shape of the radiating element fits very well in array configurations with a triangular...
In this paper a new effective optimization algorithm suitably developed for electromagnetic applications called genetical swarm optimization (GSO) will be presented. This is an hybrid algorithm developed in order to combine in the most effective way the properties of two of the most popular evolutionary optimization approaches now in use for the optimization of electromagnetic structures, the particle...
The analysis of an array of waveguide openings placed at a conformal ground plane and covered with a multilayer radome is approached using the moment method in spectral domain. The main disadvantage of the spectral domain method lies in numerical problems appearing when the structures with large radii are analyzed. We have developed a hybrid spectral domain-UTD method in order to overcome these difficulties...
A UTD (uniform theory of diffraction) solution is presented for the electromagnetic field diffracted at the truncation of dielectric screens. The formulation is heuristically derived from a revisited exact solution, obtained for the electromagnetic problem of edges illuminated at skew incidence, with surface impedance boundary conditions. The heuristic modification, and a suitable asymptotic evaluation...
Three small multi-band planar inverted-F antennas (PIFAs) are presented. They have been developed to be used in future small multi-standard handsets. Mobile communication (GSM1800, UMTS), wireless local area network (WLAN) (IEEE 802.11b, HiperLAN2) and wireless personal area network (WPAN) (Bluetooth) standards have been envisaged. Prototypes have been designed, fabricated and tested. Good agreement...
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