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- Metamaterial-Inspired Flat Beamsteering Antenna for 5G Base Stations at 3.6 GHzPublication . Reis, João Ricardo; Vala, Mário; Oliveira, Tiago Emanuel; Fernandes, Telmo Rui; Caldeirinha, Rafael Ferreira SilvaIn this paper, a metamaterial-inspired flat beamsteering antenna for 5G applications is presented. The antenna, designed to operate in the 3.6 GHz at 5G frequency bands, presents an unique flat form factor which allows easy deployment and low visual impact in 5G dense scenarios. The antenna presents a multi-layer structure where a metamaterial inspired transmitarray enables the two-dimensional (2D) beamsteering, and an array of microstrip patch antennas is used as RF source. The use of metamaterials in antenna beamsteering allows the reduction of costly and complex phaseshifter networks by using discrete capacitor diodes to control the transmission phase-shifting and subsequently, the direction of the steering. According to simulations, the proposed antenna presents steering range up to ±20◦, achievable in both elevation and azimuth planes, independently. To prove the concept, a prototype of the antenna has been built and experimentally characterised inside an anechoic chamber. Although constructed in a different substrate (FR4 substrate) as initially designed, beamsteering ranges up to 8◦ in azimuth and 13◦ in elevation, limited to the proposed case-studies, are reported with the prototype, validating the antenna and the usefulness of the proposed design.
- High Performance Antennas for Early Fire Detection Wireless Sensor Networks at 2.4 GHzPublication . Oliveira, Tiago E. S.; Reis, João R.; Vala, Mário; Caldeirinha, Rafael F. S.In this paper, high performance antennas are pro-posed for massive deployment of wireless sensor networks (WSN) for early fire dectection in forested areas. A differential slotted microstrip patch antenna and a Quasi-Yagi microstrip antenna are proposed to be implemented in a WSN at 2.4 GHz (ISM band). Firstly, a microstrip Quasi-Yagi antenna has been studied and optimised to operate at 2.4 GHz, which is sough to be deployed as part of a sectorized base-station. The antenna is comprised of one reflector and six directors around a microstrip patch to create an end-fire radiation pattern. According to simulations, the optimised antenna reaches a gain of 9.41 dBi and a half-power beamwidth of 70° at 2.44 GHz, with a operating frequency band from 2.27 to 2.83 GHz. For the sensor node, a very small differential slotted microstrip patch antenna is proposed, which has been redesigned and optimised to operate at 2.4 GHz. The proposed design takes advantage of slotted resonant elements in order to reduce the overall size of the antenna. Simulation results ensure a realised gain of 4.15 dBi at 2.44 GHz and an operating frequency band from 2.37 to 2.5 GHz. The results present in this paper were performed by using the simulation software CST-MWS.