Stefano Bertini

Analysis of Realistic Ultrawideband Indoor Communication Channels by Using an Efficient Ray-Tracing Based Method

A fundamental step in ultrawideband (UWB) communication system design involves the characterization of the indoor propagation channel. In this paper, we show that the UWB propagation channel parameters can be accurately predicted by employing ray tracing (RT) simulation carried out at various frequencies over the signal bandwidth. It is important to note that the determination of the rays reaching a given location is made only once, as the RT algorithm is independent of frequency. A parallel ray approximation (PRA) is used to significantly improve the computational efficiency of the RT based method. Moreover the accuracy of the approximation is verified through a measurement campaign.

An Efficient Interpolation Scheme for the Synthesis of Linear Arrays Based on Schelkunoff Polynomial Method

A novel approach to the synthesis of linear arrays is presented in this letter. It is based on the Schelkunoff method and an efficient interpolation scheme which provides a clever reduction of the optimization variables, maintaining, at the same time, a sufficiently large degree of freedom. The optimization procedure is, therefore, employed into a Genetic Algorithm (GA) which reveals very efficient and with a strongly improved convergence rate. Some examples of linear arrays exhibiting very narrow beamwidth and low side lobe level (SLL) are reported to show the effectiveness of the procedure.

An acceleration technique for Ray Tracing simulation based on a shadow volumetric binary and line space partitioning

Ray tracing (RT) techniques are widely employed to estimate the field levels both in urban areas and within building (indoor propagation). The radio propagation is modeled as a set of plane waves, approximated by rays which, undergoing multiple scattering phenomena (reflection, diffraction, transmission), link the transmitting to receiving antennas. Typically, the computational time of RT tools quickly increases as the complexity of the scenario and the maximum order of bouncing allowed grow. Several acceleration techniques have been proposed based on a reduction of the total number of ray-facet intersection tests [1-2-3]. In order to reduce the allowed rays, one can resort to algorithms typically employed in computer graphics: to this end, an evaluation of visibility relations between pair of facets and between facets and transmitting/receiving antennas is needed (two objects - antenna or facets - are visible if and only if a not occluded direct ray can be traced between them).

Efficient Design of Horn Antennas by Hybridizing Mode Matching/FEM with MoM

A full wave hybrid numerical technique is presented for the analysis of horn antennas with general cross section interior taper and arbitrarily shaped outer surface. A mode matching (MM)/ edge based two-dimensional finite element (FE) method is employed for the generalized scattering matrix (GSM) of the stepped-waveguide model of the inner horn taper. The exterior problem is solved by employing a Method of Moments (MoM) procedure with Rao-Wilton-Glisson (RWG) basis functions, to evaluate the Generalized Scattering Matrix (GSM) of the radiating aperture. Inner and outer GSMs are therefore connected to obtain a full wave solution for the overall radiating structure.

A Spectral Rotation Approach for the Efficient Calculation of the Mutual Coupling Between Rectangular Apertures

In this letter, a procedure based on the spectral rotation is introduced that allows us to calculate the mutual coupling between apertures in the spectral domain without evaluating any convolution products (reaction integral) directly. A numerical evaluation of the computational cost is presented to show the efficiency of the method for electrically large problems. Numerical examples are given to highlight the agreement between the spatial and spectral rotation methods. Finally, the procedure is applied for the de sign of a horn antenna array with rotated apertures.

Modeling realistic wide-band indoor propagation channels by using an efficient ray-tracing simulator

This paper proposes a novel procedure to extract the wide-band propagation channel parameters, that employs a RT simulation carried out at different frequencies and followed by a proper processing of the simulated data. In particular, a RT-based tool suitable to be used for accurate and reliable site-planning in the framework of wide-band indoor wireless systems has been implemented, which shows an excellent agreement between simulation results and measured data

A remotely distributed ray tracing for the analysis of electromagnetic propagation in complex indoor and outdoor environments

Communication engineers are nowadays facing an increasing amount of problems which require versatile and valuable tools able to provide a reliable prediction of signal propagation in complex environments. Moreover, the increase of data rate and the growing demand of mobility have determined an increment in the number of the base stations. As a matter of fact, an optimal network planning requires to both cover the widest area and provide high data-rate services; to this end, mobile phone companies and wireless internet service providers demand efficient predictions about signal strength and channel characterization. The involved scenarios can also be indoor and/or mixed indoor and outdoor, with applications spanning from the case of a wireless indoor network, to the analysis in a hazardous working area to check the respect of the legal requirements dictated by the electromagnetic compatibility standards, or else a mobile-phone planning for base station placement, to quote a few.

An Efficient Ray Tracing Propagation Simulator for Analyzing Ultrawideband Channels

A fundamental step in ultrawideband (UWB) communication systems involves the characterization of the indoor propagation channel. In this paper, we show that UWB channel parameters can be predicted accurately by ray tracing (RT) simulation carried out at various frequencies over the signal bandwidth. Our RT algorithm is independent of frequency, therefore the determination of the rays reaching a given location is made only once. Moreover, a parallel ray approximation is used to improve significantly the computational efficiency of the RT based approach. The excellent agreement between simulation results and measured data proves that our RT-based tool can be used successfully for accurate and reliable site-planning in UWB systems.

Analysis of large aperture antenna arrays using a hybrid mode matching/characteristic basis functions method

Finite arrays of waveguides and horn antennas are widely used both as direct radiators as well as feed clusters for reflector antennas. Accurate and efficient numerical simulation techniques represent a powerful tool for the design of such antennas. Many approaches have been proposed in the literature that employ hybrid techniques to efficiently analyze both the interior waveguide problem and as well as their coupling to the outer free space [1]–[3]. The mode matching (MM) is used to compute the generalized scattering matrix (GSM) for the inner waveguide problem, whereas the Method of Moments (MoM) evaluates the GSM for the outer free space coupling. When the array is electrically large in terms of number of elements or radiating apertures dimensions, the applicability of this approach is limited because the associated MoM matrix is large. Some novel approaches have been proposed in the literature to reduce the matrix size [4]. Recently the Characteristic Basis Function method (CBFM) [5] has been proposed to solve electrically large problems by using a set of high-level basis functions, called CBFs, that are physics-based and tailored to the problem.

Design of horn antennas by hybridizing mode matching with a spectral domain procedure

A hybrid MM/spectral domain based approach for the analysis of horn antennas has been presented. It has been show that the choice of TE and TM waveguide modal eigenvectors as basis functions, permits to resort to an efficient spectral domain procedure for the calculation of the admittance matrices. A numerical example involving an horn antenna with rectangular cross section has been presented. The proposed approach is well suited for solving problems involving analytically transformable modes; anyway if the analytical transforms of the modes are not available, a DFT procedure can be used. Thus, problems involving not-conventional shaped horn antennas can be addressed too. Moreover, the spectral domain procedure can be easily extended to the calculation of the mutual coupling when aperture array problems are encountered, even when dealing with not coplanar apertures.