Task description and Expected results
Finally the analog front-end design will devote some effort to the study of antennas specially designed for cognitive radio
approaches. This imposes at least a high bandwidth performance, but also some reconfigurable beam steering approaches for
maximizing antenna gain in certain directions. The steering is fundamental not only for data communication purposes, but also
for power transmission as it will maximize the energy absorption for powering up the RF transceivers.
In what respect to the compact multiband antenna design, one possibility is the use of fractal antennas namely due to the
compact size, multi-frequency operation and wide operation bandwidth. Basically, fractal geometries are self-filling structures
that can be scaled without increasing the overall size. This characteristic provides a chance for antenna designers to explore
more new geometries suitable for small antenna design. Another approach that has been employed in the design of compact
antenna is to introduce lumped elements such as chip inductors directly on the radiation element, which can effectively reduce
the size of the antenna. This is a research topic that appeared recently and currently there is limited research work in this
related field, and will be followed in this project.
Moreover, significant improvements on the transmission rate can be achieved by the integration of MIMO antenna arrays on the
wireless devices, something that has been included in the recent released standards such as IEEE 802.11n and Long Term
Evolution (LTE). This implies that at least two antennas are required to be equipped on one wireless device. In this TSK one
promising technique to be followed is to apply both the neutralizing and reconfigurable techniques on the antenna array. The
principle of the neutralizing technique is to introduce a shorting line to neutralize the current of the two antennas, which in turn
increases their isolation. This technique can also be explained as adding a suspending line to reduce the coupling between two
antennas. Reconfigurable antennas are predicted to be one of the best candidates for future high data rate wireless
communication systems.
Finally the advances in Materials that exhibit novel electromagnetic property that cannot be found in nature are attracting much
attention of the research community. Such structures, known as meta-materials, are designed to have properties and operate in
ways that bulk materials cannot. One example of such microwave metamaterials are electromagnetic band-gap (EBG)
structures. Many researchers are using Metallic Electromagnetic Band Gap (MEBG) on antenna design that exhibits two unique
characteristics: surface wave suppressing when used as EBG surface and in-phase reflection (90 degree to -90 degree) which
can be used as an Artificial Magnetic C onductor (AMC ). Since EBG is a recent technology, improvements on present techniques
for the design of microwave circuits and antennas are continuously being made. Some effort will also be put in this study and its
application to C R transceivers.
In this task it is expected that a strong collaboration exists between the other TSK, and some strategies will change depending
on the findings on other TSK’s.
At the end of this TSK it is expected that the state of the art will be improved in the following topics:
• Wide bandwidth antennas
• Beam steering for wireless power scavenging
• MIMO strategies for increasing data rate transmission
• Meta-material antennas for C R approaches
The task will be based mainly on the expertise of IT-Aveiro team, since the background in the area will allow a faster evolution
time. In this task 3 PhD researchers, 2 PhD students and one of the Bolseiros will devote its time to developed this work.
Mem bers of the research team in this task:(BI) Bolseiro de Investigação (Mestre) 1; João Nuno Pimentel da Silva Matos; Luis Pedro Marques Brás; Nuno Miguel Gonçalves
Borges de C arvalho; Pedro Renato Tavares Pinho; Tiago Miguel Valente Varum;
