FAST DOA ESTIMATION OF THE SIGNAL RECEIVED BY TEXTILE WEARABLE ANTENNA ARRAY BASED ON ANN MODEL

MLP_DoA module, being an integral part of the smart TWAA DoA subsystem, intended for fast DoA estimation is proposed. Multilayer perceptron network is used to create the MLP_DoA module that provides a radio gateway location in azimuthal plane at its output when a spatial correlation matrix, found by receiving the radio gateway signal using two-element textile wearable antenna array, is on its input. MLP_DoA network training with monitoring the generalization capabilities on the validation set of samples is applied. The accuracy of the proposed modeling approach is compared to the classical approach in MLP_DoA module training previously developed by the authors. Comparison of the presented ANN model with the root MUSIC algorithm in terms of accuracy and program execution time is also done

PREDICTION OF THE EM SIGNAL DELAY IN THE IONOSPHERE USING NEURAL MODEL

Neural model capable to accurately and efficiently predict a propagation delay of electromagnetic signal in the ionosphere is proposed in this paper. The model performs this prediction for a given geographic location in Europe between 40° (N) and 70° (N) latitude and 10° (W) and 30° (E) longitude, according to the following parameters: particular day in a year, time during the day and frequency of a signal carrier. Architecture of the model consists of four multilayer perceptron (MLP) networks with the task to estimate, for the known values of the previously mentioned input parameters of the model, the approximate value of free ions concentration in the atmosphere along the signal propagation path above the geographic location of the receiver. Based on the estimated ions concentration and taking into account the considered frequency of the signal carrier, the model calculates the time delay of signal propagation in the ionosphere. The developed neural model is applicable on the whole territory of Republic of Serbia, for all four weather seasons in the period of low solar activity. The results of using the proposed model for the prediction of time delay of the GPS (Global Positioning System) signal in the area of city of Niš are provided in the paper

NUMERICAL COMPACT MODELING APPROACH OF DISPERSIVE MAGNETOELECTRIC MEDIA BASED ON SCATTERING PARAMETERS

Z-TLM based compact modeling approach for dispersive media exhibiting magnetoelectric coupling is presented in this paper. Scattering parameters based representation of considered medium is created in a form of compact model by extracting effective electromagnetic parameters using a retrieval method, and implementing them into a non-uniform TLM grid. Proposed approach is illustrated here on the example of dispersive isotropic chiral medium modeling

EXPERIMENTAL SHIELDING EFFECTIVENESS STUDY OF METAL ENCLOSURE WITH ELECTROMAGNETIC ABSORBER INSIDE

In this paper, the impact of an electromagnetic absorber inside a protective metal enclosure is analyzed. The absorber is put inside the enclosure in order to improve its shielding effectiveness, especially at the first resonant frequency. Different absorber's sheet positions inside the enclosure are analyzed. The absorber sheet dimensions are fitted to correspond the enclosure's walls. The experimental procedure is conducted in a semi-anechoic room. The numerical TLM simulations of the EM filed distribution inside enclosure are conducted in order to consider position of the absorber sheet on different walls

Determination of electromagnetic field exposure in public spaces

The monitoring of electromagnetic (EM) field, caused by the presence of radio frequency (RF) and microwave radiation from ICT devices as various sources of EM field, has emerged as an important technical and social challenge in terms of planning, management and usage of open public spaces. Considering the necessity of EM field level determination in the context of using ICT devices in service areas, as well as monitoring of EM field exposure in public spaces, the several technical issues have been foreseen in the analyses based on corresponding examples: from the method for modelling of EM field propagation in the vicinity of RF and microwave sources - base stations for mobile networks, broadcasting transmitters, local wireless networks, together with the distribution of EM field from ICT devices, through the appropriate measurement and exposure assessment methods, to the adequate software support for geo-visualisation, the data acquisition and processing.Funded by the Horizon 2020 Framework Programme of the European Union.peer-reviewe

NUMERICAL CALCULATION OF SHIELDING EFFECTIVENESS OF ENCLOSURE WITH APERTURES BASED ON EM FIELD COUPLING WITH WIRE STRUCTURES

In this paper a shielding effectiveness of protective metal enclosure with apertures and receiving antenna placed inside is numerically considered. The purpose of antenna, here considered as a dipole, is to detect the electromagnetic (EM) field level within the enclosure and to transfer this information via a coaxial cable to network analyzer. This follows the experimental procedure used to measure the shielding effectiveness of enclosure. Numerical model, based on the Transmission-Line Matrix (TLM) method and enhanced with so-called wire node, is used to simulate this experimental setup in order to investigate how much the antenna/cable presence underestimates the level of shielding effectiveness due to their two-way coupling with EM field inside enclosure. The numerical model is first verified with experimental results available in literature and then used to estimate the influence of radius and length of dipole-receiving antenna and the impact of cable presence on the distribution of EM field inside the enclosure and resonant frequencies shift

Application of metamaterials for the microwave antenna realizations

In this paper, the application of left-handed metamaterials for the realization of microwave antennas has been considered. Special emphasis is placed on lens antennas based on gradient-index metamaterials, and their advantages and enhanced features in comparison with conventional microwave antennas are highlighted

Efficient DoA Tracking of Variable Number of Moving Stochastic EM Sources in Far-Field Using PNN-MLP Model

An efficient neural network-based approach for tracking of variable number of moving electromagnetic (EM) sources in far-field is proposed in the paper. Electromagnetic sources considered here are of stochastic radiation nature, mutually uncorrelated, and at arbitrary angular distance. The neural network model is based on combination of probabilistic neural network (PNN) and the Multilayer Perceptron (MLP) networks and it performs real-time calculations in two stages, determining at first the number of moving sources present in an observed space sector in specific moments in time and then calculating their angular positions in azimuth plane. Once successfully trained, the neural network model is capable of performing an accurate and efficient direction of arrival (DoA) estimation within the training boundaries which is illustrated on the appropriate example

Digital filter-based 1D TLM model of dispersive anisotropic conductivity panel

One-dimensional (1D) Transmission Line Matrix (TLM) method with Z-transforms, is applied in the paper to allow for an efficient time-domain simulation of thin anisotropic conductive panel of dispersive behavior. It uses a digital filter model to incorporate the scattering coefficients of the panel at two TLM cells interface in order to avoid a fine meshing of panel thickness. Model validation is done for a panel made of carbon-fibre material whose electric conductivity is anisotropic and assumed to be frequency dependent according to the Drude model. Fine TLM mesh results are used to verify the model accuracy. [Projekat Ministarstva nauke Republike Srbije, br. TR32024

Lossy gradient index transmission optics with arbitrary periodic permittivity and permeability and constant impedance throughout the structure

A remarkably simple exact analytical solution is obtained for the electromagnetic field distribution across infinite metamaterial-containing composites with any arbitrary periodic variation of complex effective permittivity and permeability for the case of constant impedance across the structure. Arbitrary temporal dispersion and losses are allowed and the model is generally applicable to different inhomogeneous and anisotropic media simultaneously containing positive and negative refractive index constituents, as long as the effective medium approximation remains valid. The analytical solution is validated by a dispersive numerical model of lossy metamaterials that uses a transmission line matrix method based on Z-transforms, where a close agreement between the analytic and numerical results is obtained