Modeling of the Scattering Field of an FGM-148 Javelin Anti-Tank Missile in Altair Feko

Introduction. Computer-aided design systems for microwave devices are an effective tool for assessing the backscattering characteristics of complex-shaped objects. However, these calculations are often associated with significant computational costs, especially at large values of the ratio of the characteristic dimensions of the object to the wavelength. The use of asymptotic methods in combination with the mesh coarsening of object partition can significantly reduce these costs. However, in each practical case, this leads to a deterioration in the accuracy of the estimates obtained, which is hard to predict.Aim. Comparative assessment of the results of modeling the scattering field in the CAD of microwave devices using various methods for calculating and detailing the object model in the decimeter and centimeter wavelength ranges.Materials and methods. The research object was an anti-tank guided missile FGM-148 Javelin. The scattering field of Altair FEKO microwave devices was modeled in CAD using the methods of moments and physical optics in the frequency range from 1 to 10 GHz and angles from 0 to 180°. A comparison of one-dimensional backscatter diagrams and radar images obtained using these methods was carried out.Results. For the class of objects under consideration, the method of physical optics provides acceptable accuracy at frequencies of 5 GHz and higher with a step of partitioning the model surface of the order of one centimeter and a total calculation duration of the order of several minutes (Intel Core i5-4460 PC / 3.2 GHz / 8 MB RAM). At lower frequencies, acceptable accuracy and a similar calculation duration are achieved when calculating by the method of moments and a partitioning step of about 20 cm. The possibility of using the Altair FEKO CAD system for modeling radar images of objects with a resolution of at least 20 cm is demonstrated.Conclusion. The results obtained complement the well-known studies in the field of comparative assessment of the time and accuracy characteristics of various methods for calculating the scattering field of objects in the CAD of microwave devices.

Download Full-text

Influence of multiple reflections in simulation of scattering electromagnetic wave by objects of complex shape

Achievements of Modern Radioelectronics ◽

10.18127/j20700784-202109-02 ◽

2021 ◽

Author(s):

V.V. Razevig ◽

A.S. Bugaev ◽

A.I. Ivashov

Keyword(s):

Electromagnetic Wave ◽

Electromagnetic Waves ◽

Spatial Configuration ◽

Scattering Problem ◽

Physical Optics ◽

Reconstruction Algorithms ◽

Multiple Reflections ◽

Radar Images ◽

Real Objects ◽

Concealed Weapon Detection

Microwave imaging technique allows obtaining images of hidden objects in structures and media using microwaves. This technique has various applications such as: nondestructive testing, medical imaging, concealed weapon detection, through-the-wall imaging, etc. Obtaining radar images in these applications is based on processing phase and amplitude of the reflected signal recorded over an aperture (a microwave hologram). To design and evaluate the effectiveness of modern radars, to test the developed reconstruction algorithms, microwave holograms of various objects obtained under different conditions are required. Obtaining microwave holograms by experimental methods is associated with measuring the scattering fields of real objects. Such experiments are rather laborious and expensive. Therefore, the problem of modeling the processes of scattering of electromagnetic waves by the objects of study is very important. Since the implementation of rigorous methods for solving the scattering problem is associated with large computational costs, it is sometimes advisable to use various simplifications and assumptions to analyze scattering fields on objects of complex spatial configuration. One of these methods is the physical optics method, which is a very common method for calculating fields scattered from objects of various shapes. The physical meaning of the approximation of the physical optics approach is that the field on the surface of the scattering object is taken to be equal to the field in the absence of the object. In other words, multiple reflections of an electromagnetic wave between different parts of the object are not taken into account. The aim of this work is to study the influence of the effects of re-reflection of an electromagnetic wave and to reveal the dependence of the accuracy of the calculation of the scattered field, performed by the physical optics method, on the shape of scattering objects. A comparison of microwave holograms obtained by the physical optics method with the results of calculations using the computational electromagnetic software product FEKO is carried out. It was found that for objects consisting of separate elements, spatially separated in a plane parallel to the registering plane, rereflections have the strongest effect on the recorded microwave hologram of an object if a distance between the elements equal to about 65% of the wavelength. In general, for such objects, the degree of influence of multiple reflections is small, and they can be ignored when modeling microwave holograms. For objects consisting of separate elements spatially spaced in a direction perpendicular to the registering plane, the influence of multiple reflections is approximately five times greater than for the previous case. The greatest effect is observed when the distance between the elements is equal to 30% of the wavelength. Under such conditions, ignoring re-reflections when modeling microwave holograms can lead to incorrect results when reconstructing them. When modeling scattering by spatially extended solid objects, the degree of influence of re-reflections depends on the shape of the object: if the side of the object oriented to the registering plane of the microwave hologram is convex, then the influence is minimal, and if it is concave, re-reflections must be taken into account.

Download Full-text

ASYMPTOTIC METHODS OF ANALYSIS IN ELECTRODYNAMICS

ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА ◽

10.36622/vstu.2021.15.5.011 ◽

2021 ◽

pp. 79-84

Author(s):

И.А. Баранников ◽

К.А. Бердников ◽

Е.А. Ищенко ◽

С.М. Фёдоров

Keyword(s):

High Efficiency ◽

Integration Method ◽

Asymptotic Methods ◽

Analysis Procedure ◽

Physical Optics ◽

Antenna Element ◽

Final Integration ◽

Sbr Method ◽

Grid Division ◽

Simulation Time

Рассматривается метод геометрической дифракции и физической оптики, который является одним из самых точных и эффективных для решения крупных электродинамических задач. Для анализа характеристик процесса приводится его математическое описание, а также для сравнения с ним приведено описание метода конечного интегрирования, который является наиболее популярным и эффективным для малых объектов. Так показано, что применение метода МКИ невозможно для крупных объектов, так как в процессе сеточного разбиения происходит создание слишком большого числа ячеек для расчета, что значительно усложняет процедуру анализа. Для оценки эффективности и точности метода было произведено моделирование антенного элемента, который установлен на корабле-носителе. Так, характеристики излучателя рассчитывались с использованием метода конечного интегрирования, после чего характеристики диаграмм направленности передавались в проект с кораблем, затем производилось моделирование с использованием метода SBR. Итоговые результаты моделирования показали высокую эффективность и точность метода, а возможность установки шага сканирования позволяет управлять временем моделирования, однако стоит учитывать, что слишком большой шаг приводит к снижению точности анализа The article discusses the method of geometric diffraction and physical optics, which is one of the most accurate and effective for solving large electrodynamic problems. To analyze the characteristics of the process, we give its mathematical description and, for comparison, a description of the final integration method, which is the most popular and effective for small objects. Thus, we show that the application of the MCI method is impossible for large objects since in the process of grid division, too many cells are created for the calculation, which significantly complicates the analysis procedure. To assess the effectiveness and accuracy of the method, we simulated the antenna element, which is installed on the carrier ship. We calculated the characteristics of the emitter using the method of finite integration, after which we transferred the characteristics of the radiation patterns to the project with the ship, then we carried out the simulation using the SBR method. The final results of modeling showed high efficiency and accuracy of the method, and the ability to set the scanning step allows you to control the simulation time, however, it should be borne in mind that too large a step leads to a decrease in the accuracy of the analysis.

Download Full-text

Comparative Assessment of the Accuracy of the Elevation differences obtained from different Geomatics Techniques and Instruments

Nigerian Journal of Environmental Sciences and Technology - March 2018 ◽

10.36263/nijest.2017.01.0021 ◽

2017 ◽

Vol 1 (1) ◽

pp. 136-145

Author(s):

H. A. P. Audu ◽

M. Y. Tijjani

Keyword(s):

Comparative Assessment ◽

Linear Measurements ◽

Third Order ◽

Total Station ◽

Acceptable Accuracy ◽

Reconnaissance Survey ◽

Instruments And Techniques ◽

The Difference ◽

Automatic Level

This study carried out the comparative evaluation of the accuracy of elevation differences determined from two Geomatics instruments and techniques in part of University of Benin, Ugbowo Campus. Reconnaissance survey was carried out and the two Geomatics instruments (Total station instrument and the Automatic level instrument) used for this study were tested and found to be in good working conditions. In line with the survey regulation, the position of the control stations (UB GPS101and UB GPS102) where the survey commenced were checked for disturbance and the obtained angular and linear measurements proved that the control stations were in situ. The perimeter traversing, using the total station instrument, with closed traverse technique and the perimeter levelling using the trigonometric levelling method and the level instrument with flying level both commenced from the GPS control stations and terminated at the same control stations. The known coordinates of UB GPS102, when compared with those determined with the total station instrument, have some millimetres differences. The difference in the elevation of the GPS control station and the elevation determined for the same control station with the total station instrument was in millimetre. These values were within the specified and acceptable accuracy limits. The accuracy of the tertiary traverse survey, which has satisfied the allowable accuracy limits for tertiary traverse survey, was 1: 41,428.043. The allowable accuracy for third order levelling for the study area was 26mm. Their computed accuracies using the total station and level instruments were 21mm and 13mm respectively. Although the elevations determined from the two Geomatics instruments met the standard accuracy limits for tertiary levelling, the accuracy of the elevations obtained with the level instrument is higher than those obtained with the total station instrument. These results are in conformity with the findings of some researchers on the related subject matter.

Download Full-text