Task description and Expected results:
By definition, cognitive radios are supposed to be capable of understanding a wide variety of signals. The problem is that the
communication standards, in use today, were not designed so that a single radio would be able to easily decode them all, and,
hence, the high bandwidth, linearity and large dynamic range are requirements usually associated with cognitive radios.
Improving any one of these key aspects, however, usually adds a significant cost in terms of energy consumption. This may be
acceptable if a steady energy source is always available, but, for battery-powered devices, that is definitely not the case. One
possibility to minimize this problem is to use electromagnetic radiation for actively charge and contribute to the radio front-end
power up. This task will be devoted exactly to study and to propose techniques for electromagnetic energy harvesting and
scavenging, by focusing its study in RF-DC converters, and, also, on power storage that could efficiently link with the RF
transceiver design. In this task the study of the nonlinear process inherent to this RF-DC conversion will be studied, and
combined with the RF front-end design of the previous tasks. So some of the objectives to follow in this task would be:
- Integrating aggressive partial shutdown capabilities into the devices from previous tasks (right at the design stage), so that at
any hardware module is only active when it absolutely needs to;
- The development of software routines for low-level energy management;
- Increasing RF efficiency by identifying and reducing the most significant power losses;
- Taking advantage of multiple non-conventional energy sources, like RF (because it can be fully controlled) and solar (generally
beyond control, yet abundant in many environments and thus worth looking at);
- Optimizing the efficiency of RF-DC c converters to maximize energy collection;
- Addressing issues related with energy storage (in addition to energy harvesting), because the capability to store excess of
energy for later use can be extremely useful;
While the aforementioned energy sources may not be able to produce enough energy to avoid the need for a battery (that would
be the best case scenario), they should be able to, at least, help to reduce its discharge rate substantially. It should be noted
that building high efficiency RF energy harvesters requires equally efficient antennas, and, hence, the design of energy efficient
antennas suitable for RF energy harvesting (coordinated with TSK 3) should also be considered;
In this task it is expected that a strong collaboration exists between among the other TSK,tasks and some strategies will change
depending on the findings on of other TSK’s tasks.
At the end of this TSK task it is expected that the state of the art will be improved in the following topics:
• Energy Efficiency;
• Use of better strategies for reducing energy spending in the radio transceiver;
• Study of collaborative ways between the physical and the higher layers in a transceiver to minimize consumption;
• System design architectures having in mind energy patterns;
• Electromagnetic Energy Harvesting and Scavenging;
• Optimized receivers for Wireless Power Transmission, with special focus on RF-DC converters;
• Extract energy from electromagnetic signals to power up mobile units;
• Integration of Energy Harvesting and All digital radios;
• C ollaborate with the antenna TSK to maximize energy collection;
• Energy Storage;
• Study alternative energy storage mechanism to cope with the energy scavenging circuits;
The task will be based mainly on the expertise of IT-Aveiro and IT-C ovilha 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 participate in the developing of
this work.
Mem bers of the research team in this task: (BI) Bolseiro de Investigação (Mestre) 1; Alírio de Jesus Soares Boaventura; João Nuno Pimentel da Silva Matos; Nuno Miguel
Gonçalves Borges de C arvalho; Pedro Renato Tavares Pinho; Ricardo Dias Fernandes;
