Search

In this paper, we derive the backscattering coefficient/forward propagation equation for frequency-modulated waves of high-frequency radar over the sea. Numerical simulations have been performed in order to compare the characteristics of a constant frequency and frequency-modulated electromagnetic wave in the function of sea state and index profile. From these simulations, we have drawn some conclusion on the differences in the Doppler spectrum observed for the two waveforms. [ABSTRACT FROM PUBLISHER]

Abstract: Use of large-eddy simulation (LES) data in electromagnetic wave propagation modeling is not very common because of the high computational cost involved. A new phase-screen method is proposed to model radio wave propagation, in the atmospheric turbulence, using the resolved scale refractivity obtained from LES. The proposed method offers the same level of accuracy, as the one already existing in the literature, at much cheaper cost. [Copyright &y& Elsevier]

Abstract: The paper describes a new efficient method for finding and simulation of electric and magnetic fields in homogeneous non-dispersive electrically anisotropic materials. Electromagnetic wave propagation in these materials is descried by the time-dependent Maxwell’s system which implies initial value problems (IVPs) for electric and magnetic fields. Our method essentially uses matrix symbolic calculations in MATLAB and allows us to compute explicit formulae of electric and magnetic fields. These formulae are used for generating images of electric and magnetic fields inside different materials. A collection of electric and magnetic field images is presented in the paper. [Copyright &y& Elsevier]

This paper presents a ray-tube tracing method to simulate waves propagating in curved road tunnels from base stations for mobile communications. Ray tubes are traced by including multiple reflections in the curved tunnels and diffractions from wedges of the tunnel structures, together with the direct path. To verify this ray-tube tracing approach, field measurements of 900 MHz signals in two curved road tunnels from GSM base stations were performed for comparisons with the ray-tube tracing simulations. By tracing ray tubes reflected and diffracted from the curved structures of the tunnels, the effects of the curvature on wave propagations in large guiding structures can be evaluated. Good agreement between simulations and measurements has been obtained. A parametric study of the influence of the tunnel geometry and the signal frequency on the path loss is also presented by applying this ray-tube tracing method. Curved tunnels for different radii of curvature in the tunnel cross-section and horizontal plane and also lengths of the curved part are compared, together with rectangular tunnels. Simulations of the field distribution over the cross-section of the curved tunnel away from the transmitting antenna are demonstrated as well. The ray-tube tracing program can be applied to determine the deployment of the base-station antennas for improving signal coverage in tunnels, which may have curved structures. [ABSTRACT FROM AUTHOR]

In this paper, the simulation of general frequency-dependent magnetoelectric material properties in time-domain TLM is described. The formulation is developed from Maxwell's equations and the constitutive relations using bilinear 𝒵-transform methods leading to a general Padé system. The approach is applicable to all frequency-dependent linear materials including those displaying anisotropic and bianisotropic behaviour. The method is validated by the example of a chiral slab having an analytic solution. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Indoor propagation is conducted in an experimental room, in order to estimate the setting absorber for an improved wireless LAN communication environment. Comparison of well reflected environment, replacing of one side wall to the developed absorber makes the average delay profile half, and further replacing of ceiling makes that 1/4. Simulation using the ray-tracing method is also performed to confirm the effectiveness. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 226–228, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20425 [ABSTRACT FROM AUTHOR]