Papers by Soras Constantine
The radiation efficiency of a mobile handset as a function of its relative position to the user's... more The radiation efficiency of a mobile handset as a function of its relative position to the user's head, has been investigated. The study was based on theoretical results taken through electromagnetic modelling using MoM and on experimental results obtained by a measuring procedure using a mock-up handset and a phantom head in an anechoic chamber. The distance between antenna and the head as the handset is moving away from the head in the horizontal direction is found to be the main factor affecting the radiation efficiency in comparison with the movement of the handset vertically or horizontally on the "ear to nose" direction.
ΔΙΔΑΚΤΟΡΙΚΗ ΔΙΑΤΡΙΒΗ, 1989
ΣΤΗΝ ΔΙΑΤΡΙΒΗ ΑΝΑΠΤΥΣΣΕΤΑΙ ΜΙΑ ΟΛΟΚΛΗΡΩΜΕΝΗ ΜΕΘΟΔΟΣ ΥΠΟΛΟΓΙΣΜΟΥ ΤΟΥ ΒΕΛΤΙΣΤΟΥ ΜΕΓΕΘΟΥΣ ΤΗΣ ΦΩΤΟΒΟ... more ΣΤΗΝ ΔΙΑΤΡΙΒΗ ΑΝΑΠΤΥΣΣΕΤΑΙ ΜΙΑ ΟΛΟΚΛΗΡΩΜΕΝΗ ΜΕΘΟΔΟΣ ΥΠΟΛΟΓΙΣΜΟΥ ΤΟΥ ΒΕΛΤΙΣΤΟΥ ΜΕΓΕΘΟΥΣ ΤΗΣ ΦΩΤΟΒΟΛΤΑΙΚΗΣ ΣΥΣΤΟΙΧΙΑΣ ΤΗΣ ΓΩΝΙΑΣ ΚΛΙΣΕΩΣ ΤΗΣ ΚΑΙ ΤΗΣ ΧΩΡΗΤΙΚΟΤΗΤΟΣ ΤΩΝ ΣΥΣΣΩΡΕΥΤΩΝ ΟΠΟΙΟΥΔΗΠΟΤΕ ΑΥΤΟΝΟΜΟΥ ΦΩΤΟΒΟΛΤΑΙΚΟΥ ΣΥΣΤΗΜΑΤΟΣ. ΜΕ ΑΦΕΤΗΡΙΑΤΑ ΜΕΣΑ ΜΗΝΙΑΙΑ ΜΕΤΕΩΡΟΛΟΓΙΚΑ ΔΕΔΟΜΕΝΑ ΚΑΙ ΧΡΗΣΙΜΟΠΟΙΩΝΤΑΣ ΕΥΚΟΛΑ ΠΡΟΣΔΙΟΡΙΣΙΜΕΣ ΠΑΡΑΜΕΤΡΟΥΣ, ΔΗΜΙΟΥΡΓΕΙΤΑΙ ΑΡΧΙΚΑ ΕΝΑ ΠΛΗΘΟΣ ΥΠΟΨΗΦΙΩΝ ΣΥΣΤΗΜΑΤΩΝ ΙΚΑΝΩΝ ΝΑ ΤΡΟΦΟΔΟΤΗΣΟΥΝ ΟΠΟΙΟΔΗΠΟΤΕ ΜΕΣΟ ΩΡΙΑΙΟ ΠΡΟΦΙΛ ΤΟΥ ΦΟΡΤΙΟΥ. ΚΑΤΟΠΙΝ ΕΠΙΛΕΓΟΝΤΑΙ ΤΑ ΣΥΣΤΗΜΑΤΑ ΠΟΥ ΕΞΑΣΦΑΛΙΖΟΥΝ ΜΙΑ ΠΡΟΚΑΘΟΡΙΣΜΕΝΗ ΑΞΙΟΠΙΣΤΙΑ ΚΑΛΥΨΕΩΣ ΤΟΥ ΦΟΡΤΙΟΥΚΑΙ ΜΕΤΑΞΥ ΤΩΝ ΤΕΛΕΥΤΑΙΩΝ ΕΠΙΛΕΓΕΤΑΙ ΩΣ ΒΕΛΤΙΣΤΟ ΤΟ ΟΙΚΟΝΟΜΙΚΩΤΕΡΟ. ΤΟ ΚΡΙΤΗΡΙΟ ΤΗΣ ΑΞΙΟΠΙΣΤΙΑΣ ΠΟΥ ΧΡΗΣΙΜΟΠΟΙΕΙΤΑΙ ΕΙΝΑΙ Η ΠΙΘΑΝΟΤΗΣ ΑΠΟΤΥΧΙΑΣ, ΤΟΥ ΣΥΣΤΗΜΑΤΟΣ LOEP (LOSS OF ENERGY PROBABILITY). Η ΟΙΚΟΝΟΜΙΚΗ ΑΞΙΟΛΟΓΗΣΗ ΓΙΝΕΤΑΙ ΜΕ ΤΗΝ ΚΥΚΛΟΒΙΟΤΙΚΗ ΚΟΣΤΟΛΟΓΗΣΗ, ΣΤΗΝ ΟΠΟΙΑ ΧΡΗΣΙΜΟΠΟΙΕΙΤΑΙ ΚΑΙ ΕΝΑ ΜΟΝΤΕΛΟ ΤΗΣ ΔΙΑΡΚΕΙΑΣ ΖΩΗΣ ΤΩΝ ΣΥΣΣΩΡΕΥΤΩΝ. Η ΠΡΟΤΕΙΝΟΜΕΝΗ ΜΕΘΟΔΟΣ, ΠΟΥ ΕΙΝΑΙ ΥΛΟΠΟΙΗΣΙΜΗ ΣΕ ΠΡΟΣΩΠΙΚΟ ΥΠΟΛΟΓΙΣΤΗ, ΧΡΗΣΙΜΟΠΟΙΕΙΤΑΙ ΓΙΑ ΤΗΝ ΕΠΙΛΟΓΗ ΤΟΥ ΒΕΛΤΙΣΤΟΥ ΜΕΓΕΘΟΥΣ ΤΟΥ ΑΥΤΟΝΟΜΟΥ ΦΩΤΟΒΟΛΤΑΙΚΟΥ ΣΥΣΤΗΜΑΤΟΣ ΠΟΥ ΚΑΛΕΙΤΑΙ ΝΑ ΚΑΛΥΨΕΙ ΤΙΣ ΕΝΕΡΓΕΙΑΚΕΣ ΑΝΑΓΚΕΣ ΜΙΑΣ ΑΠΟΜΕΜΑΚΡΥΣΜΕΝΗΣ ΚΑΤΟΙΚΙΑΣ. ΤΟ ΠΡΟΤΕΙΝΟΜΕΝΟ ΒΕΛΤΙΣΤΟ ΣΥΣΤΗΜΑ ΣΥΓΚΡΙΝΕΤΑΙ ΤΕΛΙΚΑ ΜΕ ΕΚΕΙΝΟ ΠΟΥ ΕΧΕΙ ΗΔΗ ΕΓΚΑΤΑΣΤΑΘΕΙ ΣΕ ΕΝΑ ΕΛΛΗΝΙΚΟ ΝΗΣΙ.
Progress In Electromagnetics Research C, 2009
A hybrid electromagnetic-network analysis of the antennaschannel multiple input multiple output (... more A hybrid electromagnetic-network analysis of the antennaschannel multiple input multiple output (MIMO) communication subsystem is presented. The analysis is based on the antenna effective and realized effective length matrices, which relate in a compact mathematical way the radiated and received electric field intensities to the network characteristics of actual and coupled transmitting (Tx) and receiving (Rx) multi-element antenna (MEA) systems. The effective length matrices are calculated via the active power gain and phase antenna patterns obtained by means of any full wave computational electromagnetics (CEM) field solver. It is shown that the realized effective length matrix is suitable for the S-parameter analysis of a MIMO communication link, while the effective length matrix is convenient for its Z-parameter analysis. The effective length matrix framework is applied to a free space 2× 2 coupled dipoles MIMO system and its results are in excellent agreement to those obtained by a Method of Moments (MoM) based field solver.
The diversity and Multiple Input Multiple Output (MIMO) performance provided by common phase cent... more The diversity and Multiple Input Multiple Output (MIMO) performance provided by common phase center multi element antenna (CPCMEA) systems is evaluated using two practical methods which make use of the realized active element antenna patterns. These patterns include both the impact of the mutual coupling and the mismatch power loss at antenna ports. As a case study, two and four printed Inverted F Antenna (IFA) systems are evaluated by means of Effective Diversity Gain (EDG) and Capacity (C). EDG is measured in terms of the signal-to-noise ratio (SNR) enhancement at a specific outage probability and in terms of the SNR reduction for achieving a desired average bit error rate (BER). The concept of receive antenna selection in MIMO systems is also investigated and the simulation results show a 43% improvement in the 1% outage C of a reconfigurable 2x2 MIMO system over a fixed 2x2 one.
In this paper a printed fractal Minkowski monopole is presented for use in wireless terminal devi... more In this paper a printed fractal Minkowski monopole is presented for use in wireless terminal devices utilizing single and multi element antenna systems. In the case of a single element system the effect of the antenna's placement with respect to the ground plane is examined and a method to fine tune the system in its worst case situation is proposed. The influence of the ground plane dimensions on the system's impedance and radiation characteristics is also investigated and general conclusions are drawn. Subsequently, a four element antenna system for diversity applications is investigated. The diversity performance is evaluated by means of the envelope correlation coefficient, the mean effective gain and the effective diversity gain. The impact of the mutual coupling on the system's performance is also addressed.
Measurements and numerical simulation of 3D radiation patterns of a mobile phone model in the pre... more Measurements and numerical simulation of 3D radiation patterns of a mobile phone model in the presence of a human head phantom have been performed. The relative amount of the EM power absorbed in the head was obtained for several distances of the phone. It was found that significant reduction of the absorbed power (about 50%) could be achieved by moving the phone for only 1 cm away from the head. Agreement between theoretical and experimental results was found to be very good.
Measurements and numerical simulation of 3D radiation patterns of a mobile phone model in the pre... more Measurements and numerical simulation of 3D radiation patterns of a mobile phone model in the presence of a human head phantom have been performed. The relative amount of the EM power absorbed in the head was obtained for several distances of the phone. It was found that significant reduction of the absorbed power (about 50%) could be achieved by moving the phone for only 1 cm away from the head. Agreement between theoretical and experimental results was found to be very good.
IET Microwaves, Antennas & Propagation, 2010
A stochastic electromagnetic-circuit methodology for evaluating the generalised selection combini... more A stochastic electromagnetic-circuit methodology for evaluating the generalised selection combining (GSC) diversity performance of coupled and arbitrarily terminated multi-element antenna (MEA) systems when operating in Rayleigh fading environments is proposed. The methodology is based on the effective length matrix, which connects the incident electric fields to the received voltage and current vectors, and on the newly introduced stochastic generation of realistic propagation environments by means of the angular power density functions and the cross polarisation power ratio of the incoming plane waves. The generated statistical ensemble of voltage and current vectors is then used to determine the receive GSC diversity performance metrics, that is mean effective gain (MEG), envelope correlation coefficient (r e) and effective diversity gain (EDG). Two compact MEA configurations comprising two and four printed inverted F antennas (IFA) operating in a uniform propagation scenario at the 5.2 GHz band are investigated under various GSC schemes, which include the selection (SC) and the maximal ratio (MRC) as special cases. The simulated values of MEG, r e and EDG under the MRC scheme are in excellent agreement to those obtained from wellestablished closed-form methodologies.
17th International Conference on Applied Electromagnetics and Communications, 2003. ICECom 2003., 2003
In this paper the fundamental aspects of indoor radio propagation are presented and the possibili... more In this paper the fundamental aspects of indoor radio propagation are presented and the possibility to characterize a dynamic channel by means of a static model based on the Finite Difference Time Domain method (FDTD) is examined. A 3D office environment is simulated in the 434 MHz ISM band for the characterization of channel operation according to the dominating distortions. The obtained results, which are in agreement with the theoretical values, verify that the channel operation is slow flat fading with No ISI making the application of the spatial diversity the most appropriate scheme.
A novel fractal rectangular curve microstrip antenna is investigated as an efficient scheme of mi... more A novel fractal rectangular curve microstrip antenna is investigated as an efficient scheme of miniaturization. Based on simulation results the element possesses good size reduction ability without compromising significantly on the antenna's bandwidth and efficiency. The radiation patterns between the conventional quarter wavelength patch and the shorted fractal element are similar, concluding that the latter can be used to replace the former. Moreover, the novel geometry has several degrees of freedom that can be used to either reduce further the size of the antenna or keep the bandwidth to a satisfactory level. The novel geometry was also considered for production of circular polarization and exhibited very good results.
The diversity and Multiple Input Multiple Output (MIMO) performance provided by compact multi ele... more The diversity and Multiple Input Multiple Output (MIMO) performance provided by compact multi element antennas (MEA) with common phase center is evaluated using two practical methods which make use of the realized active element antenna patterns, including thus both mutual coupling and mismatch at antenna ports. As a case study, two and four printed Inverted F Antenna (IFA) systems are evaluated in terms of Effective Diversity Gain (EDG) and Capacity (C). The concept of receive antenna selection is also investigated and the simulation results show a 43% improvement in the 1% outage C of a reconfigurable 2x2 MIMO system over a fixed 2x2 one.
IEEE Transactions on Antennas and Propagation, 2008
The integration of compact printed multielement antenna (MEA) systems on small diversity and mult... more The integration of compact printed multielement antenna (MEA) systems on small diversity and multiple input multiple output (MIMO) terminal devices operating in the 5.2 GHz Industrial, Scientific and Medical (ISM) band is presented. The investigated MEA systems comprise up to six printed elements (inverted F and Minkowski monopole antennas) and their performance is evaluated by means of the effective diversity gain (EDG) and the 1% outage MIMO capacity. The role of the propagation environment (both outdoor and indoor) on EDG is examined, proving that the uniform scenario is a good approximation to many real environments. The tradeoff study between system's performance and number of integrated antenna elements indicates that both diversity and MIMO performance saturate when placing more than five closely spaced elements. Even the least efficient 6-element system however, can be advantageously used as a reconfigurable 2-element array under the concept of receive antenna selection, since it provides significantly improved MIMO performance over a conventional 2-element fixed one. The paper concludes with a summary of useful guidelines for the MEA design optimization procedure that emanated from this study.
IEEE Antennas and Propagation Magazine, 2002
Microwave and Optical Technology Letters, 2004
A novel folded Koch monopole antenna printed over a wireless device's ground plane is presented. ... more A novel folded Koch monopole antenna printed over a wireless device's ground plane is presented. Due to its favorable characteristics, the element was further considered for the implementation of a two-branch diversity system and proved to achieve a good diversity performance under both switched and combining schemes. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 374–378, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11386
Three-branch antenna diversity systems using various monopoles printed on wireless devices are de... more Three-branch antenna diversity systems using various monopoles printed on wireless devices are demonstrated. The antenna elements used are the Inverted F, the Koch and the Minkowski monopole. Computed results for the return losses and the radiation patterns are presented. The calculated envelope cross correlation and mean effective gain of the antennas satisfy the criteria for achieving good diversity performance. The impact of the mutual coupling between the antenna elements on their radiation efficiency and mean effective gain is also addressed.
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Papers by Soras Constantine