Stylianos C. Panagiotou

THEORETICAL APPROACH OF THE INTERACTION BETWEEN A HUMAN HEAD MODEL AND A MOBILE HANDSET HELICAL ANTENNA USING NUMERICAL METHODS

The interaction of a helical antenna,mounted on a mobile handset,with a human head phantom is investigated in this paper. Using the Genetic Algorithms (GA) technique combined with the Method of Moments (MoM),an optimization of the antenna structure is achieved regarding the input impedance at the operating frequency. The Finite Difference Time Domain (FDTD) method is then applied to simulate the handsets function in the close region of a spherical homogeneous and heterogeneous head phantom. A formula,based on an application of an existing model proposed by Kuster and Balzano for dipole antennas,provides a rather accurate prediction of the induced Specific Absorption Rate (SAR) values in the human head due to the radiating helical antenna. The concept of relating the SAR to the current on the antenna is used in this study to formulate the final expression. Moreover,using the theory of regression,the results of the calculated peak or average SAR are correlated with the distance between the antenna and phantom and with the standing wave ratio (SWR) at the antenna feed point. Thus,the conception that the SAR is indeed related to the antenna operational parameters is reinforced by the outcome of the current study.

Optimizing a PIFA Using a Genetic Algorithms Approach

An optimized planar inverted F antenna (PIFA), used in mobile communications, is proposed in this paper. With the aid of the Genetic Algorithms (GA) optimization technique, a PIFA with a wide impedance bandwidth and a sufficient gain for use in mobile communications is presented. A comparison with results emerging from an application of the Finite Difference Time Domain (FDTD) method is demonstrated.

Indoor environments propagation simulation using a hybrid MoM and UTD electromagnetic method

Radio channel observation and characterization is indispensable in mobile communications systems development. Efficient propagation prediction is crucial for rapid and cost-effective systems deployment. On-site measurements, statistical models, propagation prediction and deterministic modeling are widely used for the qualification of radio channels. In this paper, a simulation tool for deterministic channel modeling in indoor environments is evolved. A hybrid combination of the Method-Of-Moments (MoM) and the Uniform Theory of Diffraction (Utd) is used. Statistical characteristics of a simple office room are calculated and the results are in excellent agreement with corresponding results of relative research on the field.RésuméL’observation et la caractérisation du canal de propagation sont indispensables au développement des systèmes de radiocommunication avec les mobiles. Une bonne estimation de la propagation est critique pour le déploiement rapide et à faible coût des systèmes. Des mesures in situ, des modèles statistiques et déterministes de propagation radioélectrique sont largement utilisés pour la qualification du canal de propagation. Dans l’article présenté, un outil d’ingénierie radioélectrique de modélisation déterministe du canal de propagation a été développé. Il est basé sur une méthode hydride combinant la Méthode des Moments et la Théorie Uniforme de la Diffraction. Les caractéristiques statistiques en environnement bureau sont évaluées et les résultats sont conformes aux résultats des recherches correspondantes.

A new, compact, low-cost switched-beam array for fixed and portable applications in the V UHF band

A low-cost and profile switched-beam array, suitable for fixed and portable DVB-T applications in the V UHF band, is proposed in this paper. The array comprises eight wire elements lying on the horizontal plane and a set of four switching beam patterns is provided. Sufficient front gain and impedance matching is achieved with the aid of a genetic algorithm.

OCULUS Sea Track Fusion Service

Oculus Sea is a complete solution regarding maritime surveillance and communications at Local as well as Central Command and Control level. It includes a robust and independent track fusion service whose main functions include: 1) Interaction with the User to suggest the fusion of two or more tracks, confirm Track ID and Vessel Metadata creation for the fused track, and suggest de-association of two tracks 2) Fusion of same vessel tracks arriving simultaneously from multiple radar sensors featuring track Association, track Fusion of associated tracks to produce a more accurate track, and Multiple tracking filters and fusion algorithms 3) Unique Track ID Generator for each fused track 4) Track Dissemination Service. Oculus Sea Track Fusion Service adopts a system architecture where each sensor is associated with a Kalman estimator/tracker that obtains an estimate of the state vector and its respective error covariance matrix. Finally, at the fusion center, association and track state estimation fusion are carried out. The expected benefits of this system include multi-sensor information fusion, enhanced spatial resolution, and improved target detection.

Design of a Dual-Band, Switched-Beam Dipole Array, with Elements Failure Correction

Switched-beam arrays (SBAs) are considered to be attractive alternatives to fully adaptive arrays (mainly due to deployment and maintenance cost) and can be used in order to increase system capacity and spectral efficiency. In this paper, dual-band operation and array failure correction of switched beam dipole arrays are considered. Dual-band operation is needed in a growing number of telecommunications systems (e.g. GSM900/1800, or WiFi/WiMAX), while array failure needs to be corrected remotely in cases of base station or satellite antennas. A genetic-algorithm based technique is proposed, and the design of a dual-band antenna array, with the ability to remain fully functional after one element failure, is presented. To the best of our knowledge, a joint design technique for dual-band operation and element failure correction is not present in open literature. The suitability of the proposed array is demonstrated via numerical results.