Ana Jovanovic

A General Solution of the Thin Circular Loop Radiation

A general solution of the thin wire circular loop radiation is offered, without assuming a certain current distribution in advance. The solution is valid for any radius-wavelength ratio and for both near and far field. The field potentials are expressed through the general wave equation basis functions in spherical coordinate system. A zero electric field along the loop is achieved as a sum of the radiation field and time-independent excitation field. The unknown-expansion coefficients are found by the Galerkin method. For highly accurate fulfillment of the boundary condition only twelve modes were required. The current distribution was found uniform for a very small loop, but also close to uniform for certain much larger electric lengths. It was also found that in a far zone both E ϕ and E θ exist, with E ϕ being some ten times greater than E θ, if the source occupies a very small portion of the loop.

Comparative performance study of DOA algorithm applied on linear antenna array in smart antenna systems

A smart antenna system with innovative signal processing can enhance the resolution of a signal direction of arrival estimation. Super resolution algorithms take advantage of array antenna structures to better process the incoming signals and they also have the ability to identify multiple targets. This paper presents a comparative performance study and geometrical optimization between MUSIC (Multiple Signal Classification), MVDR (Minimum Variance Distortionless Response) and Min Norm direction of arrival algorithms used in linear antenna array. We studied the effect of antenna array parameters in terms of its size and element spacing. In simulations we study the influence of angle of arrival on algorithm behaviour.

The analysis of the biconical antenna by the least-squares boundary residual method

Abstract The paper offers another approach to the radiation of the biconical antenna. This is one of the possible applications of the more general theory of the radiation problem that is based on the use of the Least-squares boundary residual method. The theory appeared to be equally efficient both for symmetric and asymmetric bicone antenna, and also for small and large cone angles.

Radiation pattern synthesis using a chaotic beamforming algorithm

Purpose The purpose of this paper is to use the proposed algorithm for the fast adaptation of the antenna array radiation pattern on the particular scenario of the incoming signals. The fitness function to be minimized includes the precise estimation of signals’ arrival angles, setting the deep nulls in the directions of the interfering signal, the reduction of the main lobe’s width and the reduction of side lobes. Design/methodology/approach Unlike conventional adaptive algorithms, the proposed algorithm allows synthesis of radiation patterns in the case of a larger number of incident desired and interfering signals. The proposed method also reduces the width of the dead zone. Findings In this paper a comparison of the results obtained from the chaotic beamforming algorithm with the results obtained by using the Sequential Quadratic Programming method is presented. Originality/value The chaotic beamforming algorithm is proposed here. It is based on the optimization of the least mean square and on the variable step-size least mean square algorithms, using chaos theory for synthesis of the radiation pattern of the linear antenna array.

The application of graph theory for the design of reconfigurable fractal antenna

This paper presents the possibility of using methods of graph theory for analysis and design of reconfigurable antennas. The Sirepinski fractal dipole antenna with MEMS switches was analyzed. By changing of the flow of surface currents, the frequency characteristics of the antenna is changed. As the reconfigurable antenna is set of independent parts, graph theory can be used to connect all possible topologies with appropriate electromagnetic performance in order to achieve the desired frequency characteristics, impedance, or polarization. Graph theory facilitates the design of the antenna and its frequency adjustment of a mathematical model describing the problem. Simulations were p in the software package AWR.

Adaptive Array Beamforming Using a Chaotic Beamforming Algorithm

The Chaotic beamforming adaptive algorithm is new adaptive method for antenna array’s radiation pattern synthesis. This adaptive method based on the optimization of the Least Mean Square algorithm using Chaos theory enables fast adaptation of antenna array radiation pattern, reduction of the noisy reference signal’s impact, and the improvement of the tracking capabilities. We performed simulations for linear and circular antenna arrays. We also compared the performances of the used and existing algorithms in terms of the radiation pattern comparison.

Prilagođenje dijagrama zračenja kratkih antenskih nizova upotrebom Haotičnog beamforming algoritma

U ovom radu je korišćen Haotićni beamforming adaptivni algoritam, zasnovan na optimizaciji Least Mean Square (LMS) algoritma upotrebom Teorije haosa sa ciljem postizanja adaptacije i prilagođenja dijagrama zraćenja kratkih antenskih nizova konkretnom scenariju dolaznih signala. Ova adaptivna šema, omogucava postizanje željenog dijagrama zraćenja u uslovima bez šuma i sa zašumljenim referentnim signalom u prisustvu interferirajućih signala. Simulacije su radene za linearne antenske nizove sa razlićitim brojem elemenata.

Time-frequency representation-based identification of chaos in erbium-doped fiber ring laser

In this paper chaos identification and determination of values of parameters that correspond to chaotic behaviour in erbium-doped fiber ring laser is considered. Method based on the time-frequency representation of signals is used for determination of chaotic boundaries in one and two-parameter space. Obtained results agree well with those that can be found in literature.

Field Analysis of the Archimedean Spiral Antenna

Abstract This article offers an alternative to investigating the radiation of the Archimedean spiral antenna. This is one of the possible applications of the more general theory of the radiation problem that is based on the use of the least-squares boundary residual method. The field potentials are expressed through the general wave equation basis functions in a spherical coordinate system. For highly accurate fulfillment of the boundary condition, only 20 modes were required. All field components in both the near and far zones are derived from the radial component of magnetic and electric vector potentials.

The least-squares boundary residual method in the antenna analysis

It has been shown that the Least squares boundary residual method can be very efficiently used in radiation problems. Magnetic vector potential is expressed as a linear combination of the wave equation eigenfunctions appropriate for arbitrary shaped antenna. The unknown expansion coefficients follow from minimization of the square error in the boundary condition fulfillment.The boundary condition had to be formulated in a form more suitable for numerical calculation. The method is applied to the axially symmetrical structures, such as symmetrical and asymmetrical thin wire dipoles and conical end of coaxial cable.