SMALL ANTENNAS FOR 5G AND IOT

Oliveira, Tiago Emanuel da Silva

http://hdl.handle.net/10400.8/7248

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Authors

Oliveira, Tiago Emanuel da Silva

Advisor(s)

Caldeirinha, Rafael Ferreira da Silva

Reis, João Ricardo Vitorino

Abstract(s)

In this dissertation, the author’s work on small form factor antennas for 5th Generation of mobile network (5G), Internet of Things (IoT) and Wireless Sensor Network (WSN), is presented. After a dedicated literature review on the topic, several antennas were designed and further optimised utilising a full-wave electromagnetic solver (Computer Simulation Technology (CST)-Microwave Studio (MWS)). Three of the developed antenna designs were prototyped, tested and characterised in laboratory environment and, finally applied to a real-world scenario of a wireless sensor network. In a first iteration, a high-gain wideband parasitic microstrip antenna, for 5G and IoT applications at 26 GHz, is presented. An antenna, composed of miniaturised parasitic patches, has been studied and optimised to operate at 26 GHz, aiming at the 5G New Radio (NR) Frequency Range 2 (FR2) band n258. The proposed antenna uses eight microstrip patches as parasitic elements, in a squared layout, surrounding a central probe-fed patch. The patches operating as parasitic elements are coupled by the magnetic and electric field created by the central active patch. Subsequently, the development of directional antennas, for WSN Base Station (BS), is performed. In particular, two antenna designs have need studied: a microstrip Quasi-Yagi antenna followed by a enhanced lunar waning crescent Quasi-Yagi antenna. The latter, considered as a novel antenna design, follows the planar Quasi- Yagi concept and employs a microstrip dipole as the driven element and, waning crescent shaped reflector and directors, to manipulate the shape of the radiation pattern. The antenna is designed and optimised to operate in the 2.4 GHz ISM band, attending the ease of integration in a multi-sector BS antenna configuration. A small differential slotted microstrip patch antenna to be implemented in a sensor node operating at 2.4 GHz, is also proposed. This particular antenna design takes advantage of slotted resonant elements to reduce its overall size. In particular, specific project requirements, such as: resonating frequency, gain, Half-Power Beam-Width (HPBW) are taken into consideration when dimensioning the antenna. Further studies on the impact of vegetation and fire on the antenna performance are carried out. The simulations were performed using CST-MWS mimicking several application scenarios: involved by soil, vegetation and fire, approximating the model to a real case scenario of a wildfire. Finally, the implementation of a WSN based on WiFi protocol and using LoPy4 transceivers, is proposed. The WSN is composed of a multi-sector base station and several sensor nodes used for environmental monitoring. The antenna previously developed have been used in the BS and sensor nodes implementation. The implementation and performance assessment of such network in real scenarios is presented, and metrics such as area coverage and max range are determined in the field.