Gokhan Apaydin

Numerical Investigations of and Path Loss Predictions for Surface Wave Propagation Over Sea Paths Including Hilly Island Transitions

Surface wave propagation along multi-mixed-paths with irregular terrain over spherical Earth in two-dimension (2D) is discussed. For the first time in the literature, sea-land-sea (island) transition problem including non-flat (hilly) islands is investigated systematically. A finite element method based multi-mixed path surface wave virtual propagation predictor tool FEMIX is developed for this purpose. FEMIX, tested and calibrated against analytical ray-mode reference models accommodated with the Millington curve fitting approaches, is shown to be capable of modeling propagation along sea surface having multiple hilly islands over MF (300 kHz - 3 MHz) and HF (3 - 30 MHz) bands.

The Split-Step-Fourier and Finite-Element-Based Parabolic-Equation Propagation-Prediction Tools: Canonical Tests, Systematic Comparisons, and Calibration

Powerful propagation-prediction tools, based on the split-step Fourier-transform and the Finite-Element-Method (FEM) solutions of the parabolic equation (PE) are discussed. The parabolic equation represents one-way propagation, and is widely used in two-dimensional (20) groundwave propagation modeling. It takes the Earths curvature, the atmospheric refractivity variations, non-flat terrain scattering, and the boundary losses into account. MA TLAB-based numerical split-step parabolic-equation and Finite-Element-Method parabolic-equation routines were developed. These were used in canonical tests and comparisons to illustrate that the parabolic equation accounts for all of these effects. Both tools were calibrated against an analytical exact solution.

FEM-Based Surface Wave Multimixed-Path Propagator and Path Loss Predictions

A finite element method (FEM)-based surface wave propagation prediction simulator is developed. The simulator is tested and calibrated against analytical ray-mode models that also take into account the Millington recovery effects. It successfully calculates path losses over multimixed propagation paths at MF and HF frequency bands where the surface wave contribution is significant.

Wedge Diffracted Waves Excited by a Line Source: Method of Moments (MoM) Modeling of Fringe Waves

Method of moments (MoM) simulation of fringe waves generated by a line source that excites a perfectly reflecting wedge is introduced and compared with the exact physical theory of diffraction (PTD) fringe waves.

A Novel Two-Way Finite-Element Parabolic Equation Groundwave Propagation Tool: Tests With Canonical Structures and Calibration

A novel two-way finite-element parabolic equation (PE) (2W-FEMPE) propagation model which handles both forward and backward scattering effects of the groundwave propagation above the Earths surface over irregular terrain paths through inhomogeneous atmosphere is introduced. A Matlab-based propagation tool for 2W-FEMPE is developed and tested against mathematical exact and asymptotic solutions as well as the recently introduced two-way split-step PE model through a canonical validation, verification, and calibration process for the first time in literature.

A Canonical Test Problem for Computational Electromagnetics (CEM): Propagation in a Parallel-Plate Waveguide [Testing Ourselves]

This paper aims to provide a tutorial on computational electromagnetics (CEM), and simple MATLAB codes for sophisticated investigation of analytical and well-known numerical models. The problem of propagation inside a parallel-plate waveguide is used for this purpose.

Two-Way Propagation Modeling in Waveguides With Three-Dimensional Finite-Element and Split-Step Fourier-Based PE Approaches

Two-way, three-dimensional finite element and split-step Fourier-based parabolic equation (PE) wave propagation prediction algorithms are developed, and MATLAB-based simulators are introduced. The simulators are calibrated against analytical exact data derived from modal summation through tests inside rectangular waveguides.

Double Tip Diffraction Modeling: Finite Difference Time Domain vs. Method of Moments

Discontinuities such as tips and edges cause diffracted fields when electromagnetic waves interact with objects. Two-dimensional (2D) wedge with non-penetrable boundaries is a canonical structure which has long been investigated analytically and numerically for the understanding and extraction of diffracted waves. Multiple-diffraction has also been investigated. Here, double tip diffraction is modeled with both finite-difference time-domain and method of moments and reference data are generated.

Two-way fourier split step algorithm over variable terrain with narrow and wide angle propagators

Helmholtzs wave equation can be approximated by means of two differential equations, corresponding to forward and backward propagating waves each of which is in parabolic wave equation (PWE) form. The standard PWE is very suitable for marching-type numerical solutions. The one-way Fourier split-step parabolic equation algorithm (SSPE) is highly effective in modeling electromagnetic (EM) wave propagation above the Earths irregular surface through inhomogeneous atmosphere [1–4]. The two drawbacks of the standard PWE are: (i) It handles only the forward-propagating waves, and cannot account for the backscattered ones. The forward waves are usually adequate for typical long-range propagation scenarios. However, the backward waves become significant in the presence of obstacles that redirect the incoming wave. Hence, this necessitates the accurate estimation of the multipath effects to model the tropospheric wave propagation over terrain. (ii) It is a narrow-angle approximation, which consequently restricts the accuracy to propagation angles up to 10°-15° from the paraxial direction. To handle propagation angles beyond these values, wide-angle propagators have been introduced [5–6].

Matlab-based fem ¿ parabolic-equation tool for path-loss calculations along multi-mixed-terrain paths [wireless corner]

A novel Finite-Element Method ¿ Parabolic-Equation (FEMPE) based MATLAB tool is developed. This calculates the electromagnetic field strength and path loss for one-way, forward propagation over multi-mixed irregular terrain paths through an inhomogeneous atmosphere, recommended by the ITU. The well-known smooth-Earth Millington curve-fitting model, based on analytic ray and mode approaches, is also included.