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The study aim was to validate that dielectric permittivity measurement using the open-ended coaxial probe can be reliably modeled using electromagnetic modeling and simulations, followed by the postprocessing calculations based on the simple capacitive-load model. Saline solutions with various NaCl concentrations were used as materials under test (MUTs) to investigate how ionic conductivity affects the model validity. Two different solvers and simulation methods were used: FEKO for the frequency domain and CST for the time domain. Furthermore, we performed physical experiments with the same probe and MUTs, again implementing the capacitive-load model on the measurement data to observe the model validity. Relative error of the capacitive-load model with respect to the reference permittivity values, both in measurements and simulations, was within 10% for all cases except for the measured ε r ′ of 1M solution at the lowest frequencies. The model yielded average relative errors well below 1% for the physiological saline, which is relevant for biological materials. The error increased for higher concentrations and for the lowest simulated frequencies but was within the declared measurement accuracy of the probe itself. This makes the simple capacitive-load model valid for all analyzed concentrations in the microwave frequency range from 0.5 to 18 GHz. [ABSTRACT FROM AUTHOR]

This study investigates a means through which commercially available computational electromagnetic modeling software can be used to predict radar cross sections (RCSs) of airborne organisms of interest as a preliminary step toward enabling detection and tracking of these organisms. This work aims to analyze this framework for the specialized case of the honey bee (Apis mellifera), given its critical role in food security as a major pollinator of agricultural crops. A Method-of-Moment (MoM) solver made available by Altair’s FEKO is used to conduct the analysis over varying frequencies, illumination angles, and polarizations. A high degree of correlation between measured and modeled cross sections is noted. Maximum RCS root-mean-square errors (RMSEs) between the two are approximately 4 and 5 dB relative to 1 $\text{m}^{2}$ (dBsm) for Horizontal polarization (H-pol) and Vertical polarization (V-pol) X-band measurements, respectively. Findings of this study also highlight the sensitivity of both modeled and measured RCS estimates to the dielectric properties of honey bees and the corrupting effects that this may have if not accounted for accurately, where errors are shown to increase from 2 to 5 dBsm, but without significantly corrupting the overall RCS azimuth profile. [ABSTRACT FROM AUTHOR]

This paper assesses the feasibility of finding a time bin of optimum onset to improve the robustness of the resonance modes of a midsized aircraft target in the context of radar target identification subject to bistatic and polarization diversities. The approach utilizes the frequency data (noncoherent) to determine a reference onset and a reference resonant frequency set of interest and then employs the time data (coherent) to determine an optimum onset that leads to a minimum error between the reference and extractable mode frequencies. Both sets of data are subject to a qualitative assessment to investigate the impact of the bistatic and polarization radar configurations on the optimum onset to improve the mode extraction. The results show that an optimum onset, compared to the reference onset, is more immune to noise perturbation and has a better discriminative ability for same-class targets.

Ultra-wideband (UWB) patch antenna for Ku/K band applications is presented. In this paper, a microstrip line feed has been modified to an elliptical gradient structure, and the conventional radiator patch has been developed through the use of the symmetrically circular slots. These modifications have been used to improve the performance of the antenna significantly. Upper and lower frequency ranges achieve UWB antenna performances start from 11.57 GHz to 21.45 GHz. Proposed antenna exhibits good impedance matching, which makes it convenient to work in various applications. Besides that, the reflection coefficient is reduced attained to -31.81 dB over the operating band. The antenna is developed and analyzed using the commercially available software FEKO simulator based on the method of moments (MoM). Other parameters results such as sidelobe level (SLL) and beamwidth (half power - 3 dB) are added and discussed significantly. The proposed design is fabricated and tested experimentally, and the results show that a satisfying agreement with the simulation results.

We discuss two methods for measuring the bistatic scattering characteristics of 2D samples of various materials. Experiments and numerical simulations were performed to determine the specular reflection coefficient as a function of wave angle of incidence for a 2D sample of material using a bistatic experimental design (in which the receiving and transmitting antennas rotate) as well as a monostatic design using a dihedral corner reflector (in which the object rotates). The characteristics of a flat magnetodielectric sample were measured at the ITAE RAS using two test stands and an appropriate experimental design. The procedural measurement errors were determined by performing numerical simulations of measurements to determine the specular reflection coefficient of the test specimen; these simulations were performed using the FEKO software and integral equations (solved using the method of moments) following two experimental designs. The results were compared with one another and with the results from calculations of the specular reflection coefficient performed in closed form using the Fresnel formulas under the assumption of an infinite flat layer of material. These calculations enabled comparison of the procedural measurement errors in the reflection coefficient determined using the two aforementioned experimental designs. The corner-reflector measurements were shown to have 1–2 dB higher procedural measurement error (deviation from the calculation in closed form) than the measurements using a bistatic test stand. The experimental results are consistent with the numerical simulations. The conclusions reached in this paper are valid with respect to any experimental facilities for studying 2D materials. [ABSTRACT FROM AUTHOR]

The far-field pattern of a geometrically large and complex antenna used in low-frequency radio astronomy is computationally expensive to simulate on electromagnetic simulators, such as FEKO. For example, one station of the Square Kilometer Array, which consists of 256 log-periodic antenna elements, will take years to simulate using the full CAD model for the full operational frequency band. This paper focuses on reducing the simulation time for a single antenna element by simplifying the simulation model, thus decreasing the number of unknowns that have to be solved in a simulation. An iterative process for optimizing the simplification of such an element is described, while keeping the reflection coefficient within 1 dB absolute mean deviation of the measured data. After four iterations, the amount of unknowns to be solved, which includes the number of triangles and segments, was reduced from 29,307 to 11,991. This decreased the computation time by 86.5%, making array simulations feasible. Using the techniques described in the paper, other antenna constructions can benefit from it and be simulated more efficiently. [ABSTRACT FROM AUTHOR]

In this study, we analyze the coupled signal for various cable parameters when a high-altitude electromagnetic pulse(HEMP) is incident on a cable connected to an EMP protection shelter. The structural conditions or operating environments vary depending on the purpose of use, such as to supply power or transmit communication signals to the internal devices of the shelter. Using the cable equivalent model and simulations, we interpret the coupled signal that is induced in the cable according to the presence or absence of a shielding layer, number and thickness of inner core wires, braiding conditions of the shielding layer, cable length, height from the ground plane, and whether the input terminal is grounded. We compare and analyze the induced current according to the cable parameters based on an RG58 coaxial cable. [ABSTRACT FROM AUTHOR]

An efficient method is presented to take into account the radiation pattern deformation due to the presence of a finite ground plane lying under an antenna array and above a layered dielectric medium. The interactions between the antennas and the ground plane are computed using two main algorithms: on one hand, the near-field interactions are carried out using inhomogeneous plane waves, and on the other hand, a new formulation based on an analytical Hankel transform is derived to handle the intermediate-field interactions. This formulation expresses the electric field as a finite series of Hankel functions and associated Anger–Weber functions. The method is validated here for the second version of the square kilometer array (SKA) log-periodic Antenna (SKALA2) and then applied to an SKA low-frequency station (SKA1-LOW). [ABSTRACT FROM AUTHOR]

Ultra-wideband (UWB) patch antenna for Ku/K band applications is presented. In this paper, a microstrip line feed has been modified to an elliptical gradient structure, and the conventional radiator patch has been developed through the use of the symmetrically circular slots. These modifications have been used to improve the performance of the antenna significantly. Upper and lower frequency ranges achieve UWB antenna performances start from 11.57 GHz to 21.45 GHz. Proposed antenna exhibits good impedance matching, which makes it convenient to work in various applications. Besides that, the reflection coefficient is reduced attained to -31.81 dB over the operating band. The antenna is developed and analyzed using the commercially available software FEKO simulator based on the method of moments (MoM). Other parameters results such as sidelobe level (SLL) and beamwidth (half power - 3 dB) are added and discussed significantly. The proposed design is fabricated and tested experimentally, and the results show that a satisfying agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Inductively-coupled wireless power transfer (WPT) system is broadly adopted for charging batteries of mobile devices and electric vehicles. The performance of the WPT system is sensitively dependent on the strength of electromagnetic coupling between the coils, compensating topologies, loads and airgap variation. This paper aims to present a comprehensive characteristic analysis for the design of the WPT system with a numerical simulation tool. The electromagnetic field solver FEKO is mainly used for studying high-frequency devices. However, the computational tool is also applicable for not only the analysis of the electromagnetic characteristic but also the identification of the electrical parameters in the WPT system operating in the nearfield. In this paper, the self and mutual inductance of the wireless transfer windings over the various airgaps were inferred from the simulated S-parameter. Then, the formation of the magnetic coupling and the distribution of the magnetic fields between the coils in the seriesparallel model were examined through the near-field analysis for recognizing the efficient performance of the WPT system. Lastly, it was clarified that the FEKO simulation results showed good agreement with the practical measurements. When the input voltage of 10 V was supplied into the transmitting unit of the prototype, the power of 5.31 W is delivered with the transferring efficiency of 97.79% in FEKO. The actual measurements indicated 95.68% transferring efficiency. The electrical parameters; Vin, Vout, Zin, θ, Iin, and Iout, had a fair agreement with the FEKO results, and they are under 8.4% of error. [ABSTRACT FROM AUTHOR]

The wind farm and high-frequency radar station inevitably produce more and more prominent electromagnetic interference problem. The key to solve the interference problem is to study the electromagnetic scattering characteristics of wind turbines in high-frequency area and obtain the scattering centres of the wind turbine. Here, the wind farms model established by FEKO is used to calculate the far-field scattering data. A two-dimensional scattering centre model of the wind turbine with small turning angle is established, and the two-dimensional radar imaging of the wind turbine is achieved. Using the non-parametric method to set the appropriate threshold, the two-dimensional scattering centre of the wind turbine is obtained. Theoretical analysis and simulation results show that this modelling method can reflect the target electromagnetic scattering accurately and effectively, which has certain significance in the radar identification of wind turbine and obtaining the scattering centres of wind turbine. For the parametric method, extraction of wind turbine scattering centres and analyse the Doppler effect generated when the wind turbine rotates to do the preliminary work.

The wind farm and high-frequency radar station inevitably produce more and more prominent electromagnetic interference problem. The key to solve the interference problem is to study the electromagnetic scattering characteristics of wind turbines in high-frequency area and obtain the scattering centres of the wind turbine. Here, the wind farms model established by FEKO is used to calculate the far-field scattering data. A two-dimensional scattering centre model of the wind turbine with small turning angle is established, and the two-dimensional radar imaging of the wind turbine is achieved. Using the non-parametric method to set the appropriate threshold, the two-dimensional scattering centre of the wind turbine is obtained. Theoretical analysis and simulation results show that this modelling method can reflect the target electromagnetic scattering accurately and effectively, which has certain significance in the radar identification of wind turbine and obtaining the scattering centres of wind turbine. For the parametric method, extraction of wind turbine scattering centres and analyse the Doppler effect generated when the wind turbine rotates to do the preliminary work. [ABSTRACT FROM AUTHOR]

Nowadays we are living in the ages of expansion of communication. The young generation depends on the online communications with other. Each of the devices is purposed to communication. Cloud data storage systems are available only with stable connection. Requirements are growing up to date. The answer on these requirements: the high speed of transmission, high level of security and wide bandwidth are optical communication systems. This system offers comparable features as optical system with physical optical fibers. But it has one big drawback. It is sensitivity to weather changes. We have to make backup link for case of outages. One part of design FSO/RF system in our case contains selection of appropriate type of RF antenna. We are looking for appropriate candidate. This paper is focused on analysis of helix antenna operating in non-licensed frequency range on 9.2GHz. The point of this paper is the examination of the impact of the height of helix designed antenna. [ABSTRACT FROM AUTHOR]

Passive corner reflectors and active transponders are often used as man-made reference targets in Synthetic Aperture Radar (SAR) radiometric calibration, With the emergence of new radar systems and the increasing demand for greater accuracy, wide-band and wide-beam radars challenge the hypothesis that the Radar Cross Section (RCS) of reference targets is constant. In this study, the FEKO electromagnetic simulation software is used to obtain the change curve of the target RCS as a function of frequency and aspect angle while incorporating high-resolution point-target SAR simulation, and quantitatively analyzing the effect of the modulation effect on SAR images. The simulation results suggest that the abovementioned factors affect the SAR calibration by more than 0.2 dB within a fractional bandwidth greater than 10% or azimuth beam width of more than 20°, which must be corrected in the data processing.

Electromagnetic waves emanating from the transmitter can reach to the receiver by reflection, direct or diffraction mechanism. In urban areas, dominant mechanism is diffraction. Thanks to using of high frequency, the obstructions can be modeled as a knife-edge. Coverage prediction is vital to install reliable and high-quality communication systems. In this study, a triple diffraction coefficient is derived for Uniform Theory of Diffraction (UTD) model and used for coverage problem. Coverage problems could be solved by the developed program in MATLAB computationally. Simulation results obtained in developed program are compared with FEKO electromagnetic wave propagation simulation software. [ABSTRACT FROM AUTHOR]

The compressive sensing (CS) is a new sampling paradigm that promises to accurately reconstruct compressible signals from much fewer measurements than nominal number of data points. To apply the attractive properties illustrated above, a new method named CS-FEKO is proposed in this paper, which introduces the ideas from CS into commercial software field computations involving bodies of arbitrary shape (FEKO) to improve the efficiency of FEKO in solving multistatic scattering problems. In performing a multistatic scattering analysis with CS-FEKO, the far-zone scattered fields in one scattering angle over all excitations are viewed as the signal of interest. The CS is first utilized as a preprocessing of FEKO, which modifies the conventional plane incident waves to the excitations that the CS needed. Then, FEKO is applied to solve the scattering problems under the new set of excitations to get the measurements of the scattered fields. Finally, the CS is secondly introduced as a postprocessing of FEKO, where CS inversion is employed to recover the desired far-zone multistatic scattered fields. To make a full use of the high efficiency and the deep optimization benefits of FEKO in solving wide-angle scattering problems, two forms of measurement matrixes are introduced, which have a more concise expression, and can reduce the simulating runtimes dramatically. The multistatic scattering radar cross section for different objects obtained from CS-FEKO are presented and compared with those derived from FEKO to illustrate the accuracy and efficiency of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper discusses the benefits but also challenges of GPU accelerated electromagnetic solvers from a commercial point of view, namely using FEKO as example. Specifically, the effects of some of the complex interdependencies between different components are presented. It is shown that despite the advances made in the field of GPGPU computing, and impressive speedups for parts of a program or simplified problems, there are a number of factors to consider before these techniques can be applied to a commercial product that is expected to be robust and, most importantly, to always give trustworthy results for a wide variety of problems. [ABSTRACT FROM AUTHOR]

A new fractal structure of a circular microstrip patch antenna (CMPA) for multi-band frequencies is proposed. To obtain multi-band characteristics, several techniques can be applied such as fractal geometry, defected ground structure (DGS) and making a slot in the patch. Fractal is one of the methods used to reduce the size of the antenna due to is space-filling ability. The proposed antenna operates at different resonant frequencies, at 3.32 GHz, 4.12 GHz, 4.82 GHz, 5.45 GHz, 6.02 GHz, 6.52 GHz, 6.97 GHz, 7.4 GHz and 7.76 GHz, with the return loss of less than -10 dB, VSWR < 2. The relative permittivity of the substrate used in this model is 1.01, and the face medium of the patch is made up of a perfect electric conductor (PEC). The fractal antenna is designed and simulated using the FEKO comprehensive software version 7.0 that is based on a method of moment (MOM) for solving electromagnetic structures. The performance of the antenna shows good radiation characteristics that makes it suitable for the current wireless communication systems for the S-and C-band applications. [ABSTRACT FROM AUTHOR]

Radars demand low profile and light weight antenna subsystems. Microstrip antennas possess these characteristics and serve as an alternative to the bulky and heavy weight reflector/slotted waveguide array antennas, thus an ideal choice for radars. Here, a single line fed microstrip antenna with pierced corners is designed. This antenna has improved parameters compared to the conventional square microstrip antenna. The main problem encountered is in designing the patch antenna with optimum values for various antenna parameters. In order to solve this problem, an alternative solution used is Artificial Neural Networks (ANN). The antenna is also optimized using Particle Swarm Optimization (PSO). The parameters considered in all the cases are return loss (S11) and VSWR which was designed using FEKO software. The designed antennas are found to radiate in the C-band, which covers frequencies in the range 5-8GHz, applicable in most of the modern radars. The simulation design is carried out using CADFEKO suite. [ABSTRACT FROM AUTHOR]

Communication technologies are growing for day to day because demand on data sharing is unstoppable. Users require availability of approach to network at all time. Implementation of smart technologies allows communication of all type of devices. Capacity of data flow have to grow. Video formats HD or 4K require transmit on high data speed. Based on the demands many types of different communication systems which are suitable for these speeds were designed. One of these systems is FSO (Free Space Optics). FSO system is based on transmission of optical beams which carry the information. This system allow high data speed comparable with standard optical fiber in range to 10km. One of drawbacks of this system is LOS (Light of Sight) between communication points. The other drawback is sensitivity to weather changes. Optical beams interfere with water particles and cause attenuation on transmission path. The solution is in implementation using hybrid FSO/RF system which combines optical communication system with RF (Radio Frequency) backup link. We realized FSO communication link on Technical University of Košice. Our research is focused on design of appropriate type of antenna for our RF backup link. Our results in this area were published. [ABSTRACT FROM AUTHOR]

Free space electromagnetic wave propagation is an excessively pretty simple. However, in the reality, there are obstructions like buildings and hills blocking the electromagnetic waves and leading diffraction and reflection, and these obstructions can be modeled as a knife edge or wedge due to using of UHF. Hence, the vital problem is how an electromagnetic wave propagates in multiple diffraction scenario including buildings, trees, hills, cars etc. In order to estimate the field strength or relative path loss of the waves at the receiver, so many electromagnetic wave propagation models have been introduced throughout the century. Ray tracing and numerical integration based propagation models are introduced. In this paper, detailed information is provided about S-UTD-CH (Slope UTD with Convex Hull) model. Particularly, in the transition zone, the S-UTD-CH model can be applied to multiple diffraction scenarios. In addition, Fresnel zone concept, convex hull and slope UTD models are fundamentals of the S-UTD-CH model. Moreover, in terms of computation time and accuracy, the S-UTD-CH model is conceived an optimum model. Furthermore, verification of S-UTD-CH model is made by means of FEKO, which is a comprehensive electromagnetic simulation software tool by Altair. [ABSTRACT FROM AUTHOR]

This work presents a method based on quantum particle swarm optimization (QPSO) for the synthesis of a linear array of non-uniformly spaced parallel unequal length very thin dipole antennas for impedance matching of all the antenna elements in the array. This technique is used along with the generation of the radiation pattern with low side lobe level and main lobe tilting including uniform null filling (NF) which is generally useful for broadcasting applications. Mutual coupling effect exists between the parallel dipole antennas and it is analyzed using induced electro-motive force (EMF) method, assuming the distribution of the current on each and every dipole to be sinusoidal. To obtain the desired results, current excitation, length of the antenna and spacing between the antennas are taken as the optimizing parameters and QPSO as the optimizing algorithm. Two examples are presented to show the effectiveness of the proposed method. The performance of this algorithm for impedance matching is validated by duly comparing it with a standard benchmark algorithm. [ABSTRACT FROM AUTHOR]

The design and analysis of various types of antennas is necessary to consider the impact of electromagnetic radiation transmitter and receiver module before the antenna is constructed. Electromagnetic radiation of antennas and its impact on the environment is the subject of many studies. The programming environment FEKO (FEldberechnung bei Körpern mit beliebiger Oberflache) is translates as "Calculation of electromagnetic field objects of any shape" already offered by its name the space for the design and analysis of the antennas of any shape. First parts of this article discusses environment FEKO. Another section is devoted to design and analyze a dipole antenna as the primary representative of the antennas in terms of electromagnetic radiation, which was the basis for the simulation. [ABSTRACT FROM AUTHOR]

At present, as users' requirements for bandwidth and transmission media capacity increase, development of new technologies needs to meet the requirements. Optical fibers have offered solutions in this area, but such implementation of connections in some areas is costly. An effective solution of this problem is application of FSO (Free Space Optics) technology. FSO technology makes it possible to achieve transmission rates comparable with optical fibers at a distance of up to 10km. However, this technology has other drawbacks. One of them is the sensitivity to weather changes, in particular sensitivity to presence of fog. In this case, the transmitted optical beam interacts with water particles in atmosphere, which significantly affects quality of received optical signal. In an extreme case, there may be a connection failure that is undesirable. One solution is to deploy a backup line. In our case, we have designed a radio link in the unlicensed 2.46GHz band using microstrip antenna. [ABSTRACT FROM AUTHOR]