Percorrer por autor "Reis, Joao R."
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- Disruptive Future of Radar Based on All-Digital PN Signal ProcessingPublication . Ribeiro, Carlos; Ferreira Gil, João; Caldeirinha, Rafael; Reis, Joao R.; Sardo, Andre; Duarte, Luis; Leonor, NunoThis paper presents the first results on the design and implementation of a real-time and high resolution monostatic radar at 24 GHz, based on the sliding correlation of pseudonoise (PN) sequences. The real-time radar, with a high time resolution better than 4ns, is used for moving target identification (MTI) in the presence of highly dense clutter, under harsh environments and severe weather conditions (fog, snow and fire smoke or plume). A radar signal processing based on alldigital PN sequences is proposed, which represents a quantum leap in radar future front-end architecture. Results obtained in a controlled environment, inside an anechoic chamber, are presented and a benchmark with a commercially-of-the-shelf solution is presented. © 2019 IEEE.
- Measurements and Modelling of Spatial Diversity using 2D TransmitarrayPublication . Reis, Joao R.; Hammoudeh, Akram; Copner, Nigel; Caldeirinha, RafaelThis paper disseminates the results of the first experimental trials on Spatial Diversity (SD) with beamsteering capabilities by the means of 2D transmitarray and thus reduced RF chains. The SD arrangement is composed of a dual antenna configuration in which beamsteering is activated by using electronically reconfigurable transmitarray (eRT) in front of the two single directive antennas. The experimental radiation patterns obtained at 5.2 GHz proves the usefulness of the concept.
- On the Practical Limitations of Scalable Electronic 2D Beamsteering Using Metamaterials at Micro and Millimetre-wave FrequenciesPublication . Vala, Mário; Reis, Joao R.; Caldeirinha, Rafael F. S.In this paper, the practical limitations of scalable electronic two-dimensional (2D) beamsteering using metamaterials at Micro- and Millimetre-wave frequencies, are addressed. In particular, the practical effects of using varactor diodes on a metamaterial-based beamsteering transmitarray, are studied and characterised, at four different frequencies of interest: 5, 14, 28 and 60 GHz. The parasitic effects intrinsic to such components, namely the internal resistance and internal inductance, are being studied. A thorough parametric analysis in CST Microwave Studio is conducted, in order to ascertain how the varactor's parasitics affect the frequency response, insertion loss, bandwidth and maximum achieved phase shift and consequent beamsteering resolution, at the proposed frequencies. The parametric study targets the parasitic resistance and inductance values of varactor diodes commercially available, making this study useful for any RF transmitarray implementation.