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Títol: Design and simulation of a radiofrequency energy harvester optimized at low input powers

Estudiants que han llegit aquest projecte:


Departament: EEL

Títol: Design and simulation of a radiofrequency energy harvester optimized at low input powers

Data inici oferta: 23-05-2022     Data finalització oferta: 23-01-2023

Estudis d'assignació del projecte:
Tipus: Individual
Lloc de realització: EETAC
Paraules clau:
RF Harvesting, rectenna, L-matching network, sensor nodes, IoT
Descripció del contingut i pla d'activitats:
Radiofrequency (RF) energy can be harvested in order to power
autonomous sensors either from the surrounding environment or
from dedicated sources. A particular example are RFID tags
powered from nearby RF transmitters. Thus, its application is
transversal to many applications where autonomous sensors can or
could be used, e.g. in industrial processes, agriculture,
logistics, transport vehicles (including planes), etc. A
conventional RF harvester is mainly composed a rectenna and a
maximum power point tracker (MPPT). The rectena is composed by an
antenna, a matching network and a rectifier. At low power levels,
e.g. -20 dBm and below, the power efficiency of the RF harvester
severely decreases. This work aims to increase the efficiency at
these low powers. Working frequencies will be atthe 868 MHz and
2.4 GHz unlicensed bands.

The work includes a literature review about the topic including
that generated by the host group, the design of the RF harvester
(analytical analysis and simulations with the ADS software) as
well as its implementation and experimental test. Whenever the
results are good enough, a research article can be generated for
an international conference or journal.
Overview (resum en anglès):
This project presents the design and implementation from simulations of a system that allows it to capture radiofrequency energy used to supply small IoT devices with very low power consumption. Specifically, a frequency of 868 MHz is used and low input power values are considered (-20 dBm).

The objective of the first chapter is to frame the concept of energy harvesting, what it is and its different sources, solar, wind and thermal among others. Furthermore, the energy source on which the project is focused, radiofrequency energy, is explained thoroughly.

The second chapter explains the different parts that compose the receiving antenna, which is based on a rectenna (rectifying antenna). The elements of the matching network are described, which are a capacitor in series and a coil in parallel, as well as the rectifier, which consists of a Schottky diode, a capacitor, and the load, which is mocked by a resistor.

In the third chapter, an explanation is given of the results of the simulations carried out with different methodologies using the Harmonic Balance simulation. It starts with the verification of how each individual element affects the system. It continues by finding the optimal values of the elements of the matching network that maximise the total efficiency. Once this has been done, the real values of these same elements are obtained. Finally, the transmission lines are simulated, first ideally and then using microstrips with different substrates, FR4, RO4003 and RO4350.

Finally, the results of the optimal values and the total efficiencies resulting from the different methodologies used in the project are compared. It can be concluded that the optimum efficiency results are obtained with the microstrip lines and not with real matching network elements.

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