Browsing by Author "Maslovski, Stanislav I."
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- Conjugate impedance matched metamaterials: physical modeling and wave interaction effectsPublication . Maslovski, Stanislav I.; Ferreira, Hugo R. L.; Medvedev, Iurii O.; Brás, Nuno G. B.; Abraray, Abdelghafour; Fernandes, Telmo; Silva, Henrique J. A.; Topa, António L.Conjugate impedance matched metamaterials are shown to be effective traps for electromagnetic waves. Objects made of such materials are able to receive radiation even when it is not directly incident on their surface. Here, we develop methods of physical modeling of such objects and investigate interactions of conjugate impedance matched superabsorbers with passing electromagnetic radiation. We study realizations of such metamaterials with meshes of loaded transmission lines and develop a theory of electromagnetic wave propagation and absorption in such media. Peculiar wave propagation, wave trapping and absorption effects in metamaterial black holes and wormholes are demonstrated. Possible modifications under the goal of optimizing absorption while minimizing complexity of the involved metamaterials are discussed. Conjugate-impedance matched superabsorbers may find applications as efficient harvesters of electromagnetic radiation, and as novel antennas and sensors.
- Design and optimization of compact array rectennas for harvesting wireless powerPublication . Abraray, Abdel Ghafour; Fernandes, Telmo, Telmo Rui Carvalhinho Cunha, Telmo R.; Maslovski, Stanislav I.The problem of maximization of the power received by an array of compact antennas connected to a number of loads (such as rectifiers) through an optimal matching network is investigated, analytically, numerically and by means of a prototype. The matching network is optimized to match the antennas and load impedances. A decrease in conversion efficiency may be caused by the parasitic capacitance of the rectifier diode. To overcome this issue, we propose an improved detector topology. In this topology, a series inductor L is included in the conventional half bridge detector in order to compensate the effect of the rectifier parasitic capacitance. This LC resonance technique, significantly increases the available DC output power. Measured maximum values of the rectifier's RF-to-DC conversion efficiency of 30% and 50% have been obtained for input power levels ranging from −10 dBm and −2 dBm, at frequencies of approximately 1.84 GHz. The output DC voltage of the rectifier with two input signals of 0 dBm was measured to be 3.10 V at 1.84 GHz.