Christos Oikonomopoulos-Zachos

A 3-Port Antenna for MIMO applications

As well known, the capacity of a radio frequency channel can be enlarged by multiple input multiple output (MIMO) antenna system. By using identical antennas with the same orientation, a certain antenna distance must be respected for achieving the full MIMO gain. On mobile terminals, usually only a limited surface area for antennas is available. Therefore multiport antennas with small dimensions are requested, which offer sufficient decoupling between the ports. The present paper describes a 3-port antenna, operating at 5.6 GHz, which can be used e.g. for MIMO-WLAN applications. The design is outlined and simulated and measured results are given.

A MIMO antenna array with shaped beam in waveguide technology for WiFi base stations

in this paper a dual polarized antenna array with shaped beam for outdoor WiFi access points, e.g. hotspots operating at the upper WiFi frequency band of 5.8 GHz is described. The aperture is composed of 64 waveguide antenna elements. By controlling the amplitude and the phase of only 24 elements, a shaping of the pattern in the main beam is achieved. Both polarisations are also excited by each antenna element. The presented base station array has therefore a broad half power beamwidth allowing for an easy alignment/installation of the base stations in the field. Last but not least, it shows low correlation factors which mean that it can be also used for MIMO antenna systems.

A printed monopole ESPAR antenna for Truck-to-Truck communications

Driver safety, traffic efficiency and green transportation can be significantly improved by Truck-to-Truck (T2T) communications. This paper proposes a 5.9 GHz Electronically Switched Parasitic Array Radiator (ESPAR) antenna that employs three printed monopoles as array elements. The antenna demonstrates a reconfigurable radiation pattern and compact dimensions that make it ideal for installing it in the side mirrors of a heavy duty vehicle (truck). By adjusting the voltage supply at two PIN diode switches, the antenna can operate in three different states and provide three different radiation patterns (one quasi-omni, two directive beams) to the T2T link user. An ESPAR antenna prototype is manufactured and experimentally characterized, demonstrating a good agreement between simulation and experimental results. The proposed antenna exhibits a satisfying impedance matching and a considerable gain enhancement in the two opposite directions when the antenna operates in the directive mode. An interesting investigation is also performed on the exact location of the antenna inside the truck side mirror.

Efficient EM-simulation of large vehicles for Car2Car communication

This paper presents simulation results regarding different antenna mounting positions for Car2Car applications at a frequency of 5.9 GHz. In particular, results are shown for truck model and personal use vehicles. A very important aspect for the Car2Car communication is the omnidirectional characteristic of the resulting radiation pattern, which is difficult to achieve especially in case of a truck drugging a container. The performance of the different mounting antenna positions on such large structures is examined and evaluated based on full wave EM simulations with an FDTD tool.

Applying simplification algorithms for efficient EM-simulations of a complex Galileo satellite model

Efficient antenna development involves precise electromagnetic (EM) simulation of the antenna and all surroundings. Most accurate results can be obtained by using CAD data of all parts belonging to the antenna and objects in its vicinity. However, depending on size and number of parts involved this can lead to a huge amount of data which can not be handled by current EM simulation tools anymore. Thus, usually a trade-off between simulation accuracy and object size needs to be found. In this paper, simplification algorithms for automatically reducing CAD data of a Galileo II satellite are introduced and tested.