In this paper transmission line matrix method is used to simulate the WAVE PROPAGATION through window structures. In this analysis a single window with precise dimensions and also a group of windows are considered. The effect of window’s dimension, window’s material, and angle of incidence are all evaluated in details and in each case, the method has been compared with other numerical results, such as FDTD, ray tracing, and finite element methods. Furthermore, in one case the implementation of TLM method was shown to have a good agreement with the measured values.

In this study, absorption of high frequency RADIO WAVEs in the ionospheric plasma have been investigated. The WAVE equation was obtained in terms of ionospheric parameters. The numerical values of the absorption have been calculated for 4 MHz, 4.5 MHz and 5 MHz WAVEs. The necessary parameters for calculation have been obtained using an International Reference Ionosphere (IRI) Model. The altitudinal, diurnal, seasonal and the variations of absorption with frequency have been examined. The calculations show that the highest absorption occurs in the D-region. The absorption is higher in summer than in other seasons and is maximum at daylight. In addition, absorption decreases with the increase of frequency.

To simulate the effects of rain on the WAVE PROPAGATION, refractive index, size, and pattern of the rain drops should be characterized. By finding these parameters through the measurements, one is able to calculate scattering parameters from a particle and then extend it to a group of particles. In this study, attenuation, polarization changes, and phase shift are calculated by considering rainfall distribution and moment method. Based on the comparison of the simulation results and ITU recommendations, it is shown that ITU recommendations model is general and approximately presents average attenuation.

In this paper, the parabolic equation method is applied to analyze RADIO WAVE PROPAGATION through window structures. By this method, a typical window PROPAGATION situation is simulated for different window sizes and frame types. The simulation results are represented for both normal and oblique incident cases of uniform and non-uniform plane WAVE. Results from the implementation of the parabolic equation method show good agreement with FDTD reported simulations. Base on this study, as the parabolic equation method needs less memory size and CPU time against FDTD method, it can be used as an efficient algorithm to analyze this kind of problems.

With the rapid growth of INDOOR wireless communication systems, the need to accurately model RADIO WAVE PROPAGATION inside the building environments has increased. Many site-specific methods have been proposed for modeling INDOOR RADIO channels. Among these methods, the ray tracing algorithm and the finite-difference time domain (FDTD) method are the most popular ones. The ray tracing approach as a high frequency technique is efficient for calculating the received field at a small number of receiver locations. Application of FDTD method as a full WAVE technique for INDOOR PROPAGATION modeling is time consuming and requires large amounts of memory. The parabolic equation method (PEM) is a fast full-WAVE technique which allows accurate modeling of the PROPAGATION environment and its electrical parameters. This paraxial version of the WAVE equation can be solved by marching techniques which need far less computation resources than a full elliptic equation. The PEM has been extensively used as an efficient algorithm for outdoor PROPAGATION modeling. In this paper we propose an unprecedented application of PEM for INDOOR PROPAGATION problems. Depending on the required speed and accuracy of computations, two and three-dimensional versions of the PEM can be used for INDOOR problems. Without loss of generality, we restrict ourselves to the two-dimensional problems and use two-dimensional approximation of the parabolic equation for fast and accurate RADIO WAVE PROPAGATION modeling in INDOOR environments. The parabolic equation has been derived for lossless media where the refractive index is very close to unity. To the authors' best knowledge the paraxial version of the WAVE equation has not yet been derived for PROPAGATION in general lossy dielectric media. In this paper, we first derive the general form of the parabolic WAVE equation for lossy dielectric media where it can be used for modeling the RADIO WAVE PROPAGATION through walls. The special form of the parabolic equation for modeling WAVE PROPAGATION in free space can be derived from this general form. We then apply PEM to model PROPAGATION of RADIO WAVEs through a row of windows, reinforced concrete walls and typical corridors inside buildings. As windows are one of the most prevailing architectural elements in buildings, the phenomenon of plane WAVE transmission through them is of interest. In this paper PEM is used to model the RADIO WAVE PROPAGATION through windows. The numerical simulation results are presented for both normal and oblique incidence and compared with some reported results. The transmission and reflection characteristics of inhomogeneous walls have been studied by many numerical and analytical methods such as the finite-element method (FEM) and FDTD. In this paper, we use PEM to characterize reflection and transmission properties of reinforced concrete walls under plane WAVE incidence. The effect of several parameters namely wall thickness, bar diameter and spacing on the transmission coefficients of reinforced concrete walls will be analyzed. Corridors are also popular elements of buildings, so that the analysis of RADIO WAVE PROPAGATION in corridors has involved many researchers. The PEM is an effective method for modeling WAVE PROPAGATION in these environments. The effect of obstacles such as cupboards and cabinets inside a corridor can be modeled by PEM. This method is also able to model the effects of variations of the corridor direction on the WAVE PROPAGATION. The numerical simulation results will be presented and compared with the available data in the literature.

The RADIO blackout occurring in hypersonic spacecraft re-entry is a very fundamental problem, primarily because of the relatively long (several minutes) blackout period. In this research, the role of injected solid dielectric particulate into the plasma sheath formed around the spacecraft in mitigating the RADIO communication cut-off between the ground-based station and the space vehicle is studied analytically. Considering the PROPAGATION dynamics of RADIO WAVEs in the dusty plasma formed by solid particle injection and using Fresnel’s formulae, the effect of dust particle number density and its dimension is investigated in the frequency range of 1-20GHz. In addition, the effect of the incident angle of the WAVE with the hypersonic shuttle nose surface has also been studied.

Inclination of the ground plane and large terrain irregularities may cause beam broadening of the scattered field patterns. The conventional formulation of the parabolic equation method (PEM) is not feasible and straightforward for the analysis of scattered fields. It is proposed to formulate the parabolic equation method in such a way as to be capable of considering the beam broadening of field patterns, so that PEM may be able to treat the analysis of RADIO WAVE PROPAGATION over the ground with large irregularities. In this paper, we intro introduce a new formulation for the analysis of RADIO WAVE PROPAGATION over smooth inclined ground planes by PEM. Contrary to the available formulations for the analysis of RADIO WAVE PROPAGATION over irregular terrains, in the proposed PEM method, the PROPAGATION of scattered WAVEs from the ground plane is considered and accounted for in a separate manner from the incident WAVEs. It will be observed that the PEM procedure is capable of analyzing the RADIO WAVE PROPAGATION over irregular ground planes with large slopes.

This paper introduces a new model for predicting the tropospheric scintillation path loss with respect to Iranian climate. Tile variance, probability density function (PDF), and attenuation scintillation are predicted based on the new model and using measurement data obtained from Iranian metrological department for different parts of Iran. Applying this model and corresponding data, the variance of scintillation, scintillation pathl loss and scintillation ,standard deviation predicted for different Iranian cities. The results reveal that scintillation variance PDF shows a long normal behaviour in Iran. Moreover, the path loss due to scintillation phenomenon in satellite- ground communication links cannot be ignored particularly in microWAVE and higher frequency ranges. Therefore, it is necessary to take into account these effects when designing satellite- ground and microWAVEs communicational links.

In this paper, PROPAGATION of an electromagnetic beam wrapped around the axis of a thin axisymmetric WAVE guide embedded in a square law medium, depending on a b2 parameter small enough to make the b2n terms negligible for n  ³ 2 has been analyzed. To solve Maxwell's equations in this WAVE guide, a paraxial approximation of the WAVE equations, satisfied by the electric and magnetic components of the electromagnetic field, has been used. The solutions of the corresponding paraxial WAVE equations describe beam PROPAGATION by a series expansion of Gaussian modes.

This paper introduces a method of INDOOR positioning where multipath PROPAGATION exists due to reflective obstacles. In this method the fingerprint pattern is yielded by analyzing PROPAGATION delay data. Unlike received signal strength (RSS) level data needed for conventional RSS fingerprint method, PROPAGATION delay data needed in this method is not altered by reflection from obstacles, meaning: while conventional RSS method requires actual measurements, using the proposed method, one can construct finger print pattern by mere analysis. Furthermore, the results from this method are more accurate and less ambiguous than those of RSS. This is due to the fact that whereas the signal strength level data is received at one instance, the PROPAGATION delay data as its nature suggests is received at a number of separate instances meaning it contains more information. The paper also provides an example to demonstrate the simplicity of the method and the accuracy of its results, which for the mentioned problem are of an average error of less than 3. 7cm and a variance of less than 6. 5cm.