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- Metamaterial-inspired Flat-Antenna Design for 5G Small-cell Base-Stations Operating at 3.6 GHzPublication . Reis, João R.; Fernandes, Telmo R.; Patrício Carreira Vala, Mário António; Caldeirinha, Rafael F. S.In this paper, a flat-beamsteering antenna for 5G applications is being presented. The antenna, designed to operate at 3.6 GHz (5G new radio (NR) frequency range 1 (FR1) band n78), presents a 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 utilised as RF source. The use of metamaterials for beamsteering control allows for the reduction of costly and complex phase-shifter 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 13.9 dBi of gain, 100 MHz of bandwidth with a maximum steering range of ±20 degrees, achievable in both elevation and azimuth planes, independently.
- Radiowave Propagation Modelling of Dual Wildfire Front Spreading over Hilly Terrain at 700 MHzPublication . Faria, Stefânia; Vala, Mário; Coimbra, Pedro; Leonor, Nuno; Felício, João; Fernandes, Carlos A.; Salema, Carlos; Caldeirinha, Rafael F. S.In this paper, a study of a fire front spreading over flat and sloped terrains and how these fire fronts may have impact on radiowave communications are presented. The phenomenon is modelled using Fire Dynamics Simulator (FDS) and the Cold Plasma Model (CPM), using pine needles as fuel heap. Fire parameters such as Heat Release Rate (HRR), Mass Loss Rate (MLR) and fuel consumption are presented and analysed. Attenuation effects at 700 MHz are calculated considering the Full-Stack Model (FSM) and Transmission Line Model (TLM). Simulation results clearly demonstrate that the slope of the terrain profile in the presence of a dual fire front spreading up the hill has significant impact on the additional excess loss of around 2.5 dB, yielding an overall excess loss of 3.5 dB for such a small-scale fire simulation.