Browsing by Author "Caldeirinha, R. F. S."
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- Extension of the dRET Model to Include Scattering from Tree Trunks in Microcell Urban Mobile ScenariosPublication . Caldeirinha, R. F. S.; Fernandes, T. R.; Leonor, N.; Ferreira, D.This paper proposes a framework for extending the applicability of the discrete RET (dRET) model to accommodate radiowave scattering from tree trunks, particularly in microcell urban mobile scenarios, at micro- and millimetre wave frequencies. This framework aims to provide accurate modelling of the signal emanated inside and around isolated blocks of tree trunks, for instances, in raised canopy forests or in urban street canyons like scenarios. Model validation against measurement results inside an anechoic chamber for a double line of regularly spaced metallic and dielectric trunks at 18.8 GHz, as well as recommendations for a more encompassing model, are presented.
- Two-dimensional antenna beamsteering using metamaterial transmitarrayPublication . Reis, J. R.; Al-Daher, Zaid Al-Daher; Copner, Nigel Copner; Caldeirinha, R. F. S.; Fernandes, T.A new two-dimensional (2D) beamsteering antenna technique using a metamaterial transmitarray structure is proposed in this paper. The proposed technique allows the steering of the main lobe of the original antenna pattern in both elevation and azimuth planes when coupled to a conventional horn antenna. This has been demonstrated on a 5 × 5 unit-cell stacked structure, in which electromagnetic simulations, performed at 5.35 GHz, allowed the evaluation of the unit-cell parameters and the behaviour of the array. A fixed steering output with range of θ = 25° and φ= 25° in spherical coordinates is achieved by means of electromagnetic simulations and validated against experimental results, clearly demonstrating the potential of using metamaterials structures for beamsteering purposes.