C. Soras

Integrating Compact Printed Antennas Onto Small Diversity/MIMO Terminals

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 systems 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.

Analysis of a modified Sierpinski gasket monopole antenna printed on dual band wireless devices

The traditional Sierpinski gasket monopole antenna is well known for its multiband behavior, but it cannot be printed on the circuit board of a portable wireless device due to the limited space availability. In this paper a modified Sierpinski gasket monopole antenna is presented that possesses a small physical size, high efficiency and the ability to allocate both the 2.4 and 5.2 GHz Industrial Scientific and Medical bands without the need of a matching network. The modified element respects the multiband behavior of the gasket since the input impedance characteristics of the upper bands maintain their symmetry. Several modification techniques are proposed making the monopole very flexible in terms of band allocation and fine-tuning. The dimensions of the ground plane are also proven to play a significant role on the operational bandwidth of the antenna system.

A NOVEL METHOD FOR DETERMINING THE OPTIMUM SIZE OF STAND-ALONE PHOTOVOLTAIC SYSTEMS

Abstract A method is presented to select the optimum tilt angle, photovoltaic array area and battery storage capacity of stand-alone photovoltaic systems. This method uses monthly average meteorological data and easily acquirable system parameters in order to determine possible photovoltaic system sizes, capable of supplying any given monthly average hourly load profile. The optimum system selected is that with the minimum life-cycle cost while ensuring a desired reliability level. In the life-cycle cost computations a battery-life model has been used to determine the number of battery bank replacements. The reliability criterion used is the loss-of-energy probability. The method can be implemented on a personal computer and is applied to an illustrative example, where the optimum system size proposed by this methodology is compared with that of a newly installed system on a Greek island.

A reduced size fractal rectangular curve patch antenna

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 antennas 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.

Ground plane effect on the performance of a printed Minkowski monopole antenna

This paper concentrates on a printed Minkowski monopole antenna that uses the ground plane as an active part of the radiating system. The effect of the antennas placement on the input impedance characteristics of the antenna-ground system is initially investigated and a method to fine tune the system in its worst case is proposed. The influence of the ground plane dimensions on the resonant frequency, bandwidth and input resistance are also examined.

Finite Element Modeling of Minkowski Monopole Antennas Printed on Wireless Devices

A novel monopole antenna element printed on the circuit board of a wireless device is presented. Following the Minkowski fractal curve along with folding techniques, the proposed element is an electrically small self-resonant antenna with high efficiency and wide bandwidth. Due to its miniature size, it can be used in dual antenna portable devices operating in the 2.4 GHz band, in order to achieve antenna diversity under all combining schemes. The performance of the investigated configurations was predicted through finite element simulations, which proved to be computationally more demanding than their moment method counterparts.

Four-element printed monopole antenna systems for diversity and MIMO terminal devices

Four-element antenna diversity systems suitable for operation in diversity and MIMO wireless devices for single (2.4 or 5.2 GHz) and dual band operation are addressed. The antenna elements used are the Minkowski, the Inverted F and the Koch monopole. 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 indicating that the type of the antennas, their placement and their electrical distance are key parameters in the design of an efficient multi element antenna system.

Three-branch antenna diversity systems on wireless devices using various printed monopoles

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

Mobile Phone Antenna Performance and Power Absorption in Terms of Handset Size and Distance from User's Head

In this work numerical simulation and measurements of three-dimensional radiation patterns of a mobile handset model in the presence of a human head phantom were performed at 1800 MHz. Based on theoretical and experimental results, the influence of the human head on the radiation efficiency of the handset has been investigated as a function of the handset size and the distance between the head and the handset during its operation. Furthermore, the relative amount of the electromagnetic power absorbed in the head has been obtained. It was found that significant reduction of the absorbed power (about 50%) with proportional increment of the handset radiation efficiency could be achieved by moving the phone for 1 cm only away from the head. Agreement between theoretical and experimental results was found to be very good.

Diversity and MIMO performance evaluation of compact multi element antennas with common phase center

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 2times2 MIMO system over a fixed 2times2 one.