Çağatay Uluışık

Radar cross section (RCS) modeling and simulation, part 1: a tutorial review of definitions, strategies, and canonical examples

Modeling and simulation strategies for radar cross section (RCS) prediction are reviewed, and a novel FDTD-based virtual RCS prediction tool is introduced in this two-part paper. Part 1 is reserved for a tutorial review. Concepts and definitions related to RCS modeling are outlined. Analytical approaches, i.e., high-frequency asymptotics (HFA), as well as powerful time- and frequency-domain numerical methods, are given. Canonical examples using the finite-difference time-domain (FDTD) Method, the method of moments (MoM), and physical optics (PO) are presented.

A MATLAB-based visualization package for planar arrays of isotropic radiators

This article introduces a simple MATLAB antenna package (ANTEN/spl I.bar/GUI) for the visualization of the radiation patterns, beamforming, and beam-steering capabilities of user-designed planar arrays of isotropic radiators. The package can be used as an educational aid, especially in antennas and propagation lectures.

A MATLAB-based transmission-line virtual tool: finite-difference time-domain reflectometer

This article introduces a simple virtual tool, TDRMeter, for the investigation and visualization of time-domain pulsed voltage/current, traveling along a terminated finite-length transmission line, without and with faults somewhere between the source and the load. The package can be used as an educational tool in various undergraduate lectures to aid in teaching electromagnetics as well as transmission lines

A Tutorial on Bessel Functions and Numerical Evaluation of Bessel Integrals

This paper aims to provide a tutorial on Bessel functions, and especially on the numerical evaluation of Bessel integrals. Bessel integrals are asymptotically evaluated using high-frequency methods, such as the stationary-phase method, steepest-descent path evaluations, and uniform asymptotics. Concepts such as saddle points and their contributions, and integration over the steepest paths are emphasized. A MATLAB simulation package, BESSEL_GUI, was prepared to compare each method with the other, and also with the MATLAB built-in function besselj (v, z). The tool also allows plotting the magnitude of the complex integrand of the Bessel integral in three dimensions. The user can thus visualize the locations of the saddle points and the steepest-decent paths.

A MATLAB-based visualization package for complex functions, and their mappings and integrals

This paper aims to provide a tutorial on the visualization of complex functions. The MATLAB-based package ComplexGUI was prepared to illustrate mappings by elementary complex functions. The tool shows how user-defi ned curves and regions are transformed by some elementary functions. Concepts such as branch points, branch cuts, the principal branch of multivalued functions, and Riemann surfaces are emphasized. The package also enables asymptotic evaluation of Bessel integrals along user-specifi ed contours, and compares the result with the built-in function in MATLAB. The tool allows deforming the integration contour to a path through the saddle points in the direction of the steepest-decent path to obtain a better result.

A LabVIEW-Based Analog Modulation Tool for Virtual and Real Experimentation

This tutorial discusses analog-modulation techniques with the LabVIEW-based AnalogMod package, developed for the illustration of different modulation types in undergraduate labs. The tool can generate and display the time- and frequency-domain behaviors of modulated signals. All the modulation parameters can be specified by the user. The package also enables adding noise to a modulated signal, and selecting among different types of baseband pulse-shaping filters. Examples presented here may be partially built in a virtual LabVIEW environment, and partially on circuit boards, to enhance the practical skills of undergraduate students. The transition between the virtual and the real world is accomplished via data-acquisition cards, installed in PCs.

Time-Domain Investigations of Periodic Rectangular Dipole Arrays

Radiation from large arrays of finite one-and two-dimensional periodic, linearly phased, electric current dipoles is investigated. The classical element-by-element summation representation is modified to speed up the convergence. A synthetic aperture type approach is applied in the Floquet domain for modeling finite arrays. Numerical results for the radiated field are presented both in frequency and also in time domains.

Numerical Modeling and Simulation Studies of 2D Propagation over Non-flat Terrain and Through Inhomogeneous Atmosphere

This paper introduces Matlab-based two dimensional (2D) virtual propagation tools (VT) which can be used to investigate EM propagation over user-specified nonflat terrain through inhomogeneous atmosphere. The VTs can be used for both engineering (GSM coverage planning, digital site survey, etc.) and educational purposes (e.g., in EM Theory, Wireless Communication, Antennas and Propagation lectures).

A Matlab-Based virtual propagation tool: surface wave mixed-path calculator

A new Matlab-Based, user-friendly virtual propagation tool (VPT) that can be used for multi-mixed path surface wave path loss calculations has been designed. Any multi-mixed-path surface wave propagation scenario may be specified by the user together with all the necessary input parameters, and path loss vs. range plots may be produced. The effects of multi-mixed paths, electrical parameters of each propagation section, as well as the frequency can be observed and extra path losses can be predicted. The VPT can be used both for design and training purposes.

Modeling and simulation strategies in wireless propagation and coverage planning

This paper presents two-dimensional (2D) user-friendly, tailored with attractive and useful graphical user interfaces (GUI), Matlab propagation packages based on the classical knife-edge model and the parabolic equation method that can handle realistic propagation scenarios with non-flat, arbitrarily-designed and user-selected terrain profiles. Any 2D propagation scenario may be built by the user, and field vs. range and/or height profiles can be simulated.