9 documents found, page 1 of 1
Modeling temperature dynamic effects for high‐power light‐emitting diodes
Kyatam, Shusmitha; Rodrigues, Luís; Alves, Luis N.; Maslovski, Stanislav I.; Mendes, Joana C.Temperature is a dynamic variable in most electronic devices. As the device operates, it generates heat, which translates in a temperature increase. Available models commonly disregard these variations due to the fact that they manifest at very large time scales. However, temperature dynamic effects have profound implications on the device model and on our common understanding. This paper discusses implications...
Estimation of maximum temperature and thermal crosstalk between two active elem...
Kyatam, Shusmitha; Maslovski, Stanislav I.; Neto, Hugo; Alves, Luis N.; Mendes, Joana C.The operating temperature plays a key role in the performance and lifetime of photonic integrated circuits (PICs). Miniaturization and increasing heat dissipation promote thermal crosstalk effects and pose additional challenges to the PIC designer. The European Photonics Industry Consortium recommends thermal modeling during design phase. However, a fully numerical optimization of a particular layout requires a...
Design and optimization of compact array rectennas for harvesting wireless power
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...
Conjugate impedance matched metamaterials: physical modeling and wave interacti...
Maslovski, Stanislav I.; Ferreira, Hugo R. L.; Medvedev, Iurii O.; Brás, Nuno G. B.; Abraray, Abdelghafour; Fernandes, Telmo; Silva, Henrique J. A.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 realizatio...
Overcoming black body radiation limit in free space: metamaterial superemitter
Maslovski, Stanislav I.; Simovski, Constantin R; Tretyakov, Sergei AHere, we demonstrate that the power spectral density of thermal radiation at a specific wavelength produced by a body of finite dimensions set up in free space under a fixed temperature could be made theoretically arbitrary high, if one could realize double negative metamaterials with arbitrary small loss and arbitrary high absolute values of permittivity and permeability (at a given frequency). This result ref...
Spatially confined UHF RFID detection with a metamaterial grid
Morgado, Tiago A.; Alves, Jorge M.; Marcos, João S.; Maslovski, Stanislav I.; Costa, Jorge R.; Fernandes, Carlos A.; Silveirinha, Mário G.The confinement of the detection region is one of the most challenging issues in Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) systems. Here, we propose a new paradigm to confine the interrogation zone of standard UHF RFID systems. Our approach relies on the use of an all-planar metamaterial wire grid to block the radiation field (i.e., the far-field) of the reader antenna, and thereby obtain...
Uniaxial indefinite material formed by helical-shaped wires
Morgado, Tiago A.; Maslovski, Stanislav I.; Silveirinha, Mário G.We demonstrate that a racemic array of helical-shaped metallic wires may be regarded as a local uniaxial epsilon-negative (ENG) material even when the metal conductivity is very large (e.g. in the microwave regime) and, as a result, enables strong negative refraction over a wide frequency range. Based on the negative refraction effect, we demonstrate partial focusing of p-polarized electromagnetic radiation usi...
Perfect lensing with phase-conjugating surfaces: toward practical realization
Maslovski, Stanislav I.; Tretyakov, SergeiIt is theoretically known that a pair of phase-conjugating surfaces can function as a perfect lens, focusing propagating waves and enhancing evanescent waves. However, the known experimental approaches based on thin sheets of nonlinear materials cannot fully realize the required phase conjugation boundary condition. In this paper, we show that the ideal phase-conjugating surface is, in principle, physically rea...
Generalized additional boundary conditions for wire media
Maslovski, Stanislav I.; Morgado, Tiago A.; Silveirinha, Mário G.; Kaipa, Chandra S. R.; Yakovlev, Alexander B.We generalize additional boundary conditions (ABCs) for wire media by including arbitrary wire junctions with impedance loading. Special attention is given to the conditions at the interface of two uniaxial wire media with metallic patches at the junction. The derived ABCs are validated against full-wave numerical simulations.