Person: Torres García, Alicia E.
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Torres García
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Alicia E.
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Ingeniería Eléctrica, Electrónica y de Comunicación
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0000-0001-7952-7910
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811111
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Publication Open Access Ku band low profile asymmetric Bull’s-Eye antenna with reduced side lobes and monopole feeding(IEEE, 2018) Beaskoetxea Gartzia, Unai; Torres García, Alicia E.; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa eta Elektronikoa; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaIn this paper, a linearly polarized low profile and asymmetric Bull’s-Eye leaky wave antenna fed by a monopole operating at 13 GHz is presented. Broadside radiation from the monopole is achieved by surrounding it with an asymmetric array of semicircular metallic strips on a grounded dielectric slab. With this implementation we demonstrate high gain with a weight of less than 80 g and lower side lobe levels compared to previous designs fed by a resonant slot. The measured antenna shows an experimental gain of 19.4 dBi with only 5 periods and a side lobe level of −16 dB (−20.3 dB for the numerical ideal case at f = 12.6 GHz), along with a narrow 6º beamwidthPublication Open Access Enhancing the infrared and visible emission properties of calcium silicate hydrate for radiative cooling using metamaterials(IEEE, 2022) Lezaun Capdevila, Carlos; Dolado, J. S.; Torres García, Alicia E.; Pérez Escudero, José Manuel; Liberal Olleta, Íñigo; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenTwo periodic structures composed of metal cylinders with different orientations are used to improve the solar reflection of calcium silicate hydrate (CSH) while maintaining its atmospheric emission. Interesting effects have been found when the distance between bars is small, suggesting that lattice effects, arising from the interaction between the rods could be leveraged in the design of these metamaterials. The size of the metal bars is selected based on state of the art micro-manufacturing techniques. This study limits its scope to a CSH gel model; i.e. the most important component of cement-based materials. Further research will be undertaken to consider a best description of the dielectric function of concrete.Publication Open Access Evolutionary algorithms applied to multi-layered radiative cooling metamaterials(IEEE, 2022) Lezaun Capdevila, Carlos; Jorajuria Gómez, Tania; Torres García, Alicia E.; Herrera, Pilar; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenA newly design method for designing multi-layered radiative cooling metamaterials based on genetic algorithms (GAs) is exposed. The developed GA has been tested in three cases, resulting in three different structures that achieve, theoretically under direct sunlight, a net cooling power of 39.96 W/m 2 , 57.78 W/m 2 and 61.77 W/m 2 . Such devices are composed of 9, 15 and 24 layers respectively with a total thickness of less than 4.8 µm in the worst case. By the nature of the method, fewer design experience in metamaterials is needed, as well as it is free-cost, due to the use of analytical calculations for the emissivity of the meta materials instead of a commercial generic electromagnetic solver. Automated design of radiative cooling multi-layered structures and other applications in the infrared range can be further developed with this work.Publication Open Access A gap waveguide fed circular polarization antennas in the millimeter wave range(IEEE, 2020) Pérez Quintana, Dayan; Torres García, Alicia E.; Ederra Urzainqui, Íñigo; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónIn this work, a novel circular polarization (CP) antennas in ridge gap waveguide (RGW) working in the V-band of the millimeter-wave spectrum is presented. CP is generated in a simple and effective way by means of two orthogonal feeder arms that excite a CP in a rotated square-shaped slot placed on top metallic lid. Parametric simulation studies demonstrate that a difference between both arms length of approximately λ/4 leads to high-purity CP within a relatively broad bandwidth. A square-shaped slot antenna is manufactured and experimentally analyzed. A broadband matching with a reflection coefficient magnitude below -10 dB (S11 <; -10 dB) is achieved from 60.5 to 69.3 GHz. Applying the axial ratio criterion (AR <; 3 dB) the bandwidth in CP is 10.74%, with respect to the central frequency. The maximum gain at broadside is 5.49 dB at 66.8 GHz.Publication Open Access Design of multi-layered radiative cooling structures using evolutionary algorithms(IEEE, 2022) Lezaun Capdevila, Carlos; Jorajuria Gómez, Tania; Torres García, Alicia E.; Herrera, Pilar; Beruete Díaz, Miguel; Institute of Smart Cities - ISC; Ingeniería Eléctrica y Electrónica; Ingeniaritza Elektrikoa eta Elektronikoa; Gobierno de Navarra / Nafarroako GobernuaIn this work we present a novel way to design thinfilm radiative cooling metamaterials based on genetic algorithms. Three simulations with different design constraints have been done, resulting in three structures that achieve 39.96 W/m2 , 57.78 W/m2 and 61.77 W/m2 under direct sunlight, respectively. These structures are shorter than 5 µm of height and are composed of 9, 15 and 24 layers. This design method has the advantages of being automatable, needs fewer design experience in metamaterials and does not rely on commercial simulators. This work opens the path to an easy way of automated design of thin-film multi-layered devices for radiative cooling and other applications in the infrared range.Publication Open Access Suppressed-scattering spectral windows for radiative cooling applications(Optica, 2023) Pérez Escudero, José Manuel; Torres García, Alicia E.; Lezaun Capdevila, Carlos; Caggiano, Antonio; Peralta, Ignacio; Dolado, Jorge S.; Beruete Díaz, Miguel; Liberal Olleta, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenThe scattering of light by resonant nanoparticles is a key process for enhancing the solar reflectance in daylight radiative cooling. Here, we investigate the impact of material dispersion on the scattering performance of popular nanoparticles for radiative cooling applications. We show that, due to material dispersion, nanoparticles with a qualitatively similar response at visible frequencies exhibit fundamentally different scattering properties at infrared frequencies. It is found that dispersive nanoparticles exhibit suppressed-scattering windows, allowing for selective thermal emission within a highly reflective sample. The existence of suppressed-scattering windows solely depends on material dispersion, and they appear pinned to the same wavelength even in random composite materials and periodic metasurfaces. Finally, we investigate calcium-silicate-hydrate (CSH), the main phase of concrete, as an example of a dispersive host, illustrating that the co-design of nanoparticles and host allows for tuning of the suppressed-scattering windows. Our results indicate that controlled nanoporosities would enable concrete with daylight passive radiative cooling capabilities.Publication Open Access Compact groove diamond antenna in gap waveguide technology with broadband circular polarization at millimeter waves(IEEE, 2020) Pérez Quintana, Dayan; Torres García, Alicia E.; Ederra Urzainqui, Íñigo; Beruete Díaz, Miguel; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de ComunicaciónIn this paper, three compact antennas using the Ridge Gap Waveguide (RGW) technology working in the millimeter-wave band (60 GHz), with a high-purity and broadband circular polarization (CP) are numerically and experimentally analyzed. The structure is fed from the bottom by means of a standard WR-15 waveguide (V-band) to make it compatible with standard measurement systems. It is coupled with a miniaturized step transition to a ridgeline that ends in two arms of different lengths. CP is generated in a simple and effective way, by means of two orthogonal feeder arms that excite a CP in a diamond-shaped slot on top. Simulations and measurements have an excellent agreement reaching a matching bandwidth (S11 <-10 dB) from 60.3 to 69.6 GHz (> 9 GHz). Applying the axial ratio criterion (AR < 3 dB) the bandwidth in CP is 14.48%, with respect to the central frequency (59 to 70 GHz). The maximum gain is obtained with the most evolved design incorporating a diamond aperture with a horn taper and a circular groove, reaching a value of 11.12 dB at 67.3 GHz.Publication Open Access Metal-free design of a multilayered metamaterial with chirped Bragg grating for enhanced radiative cooling(Optica, 2023) Osuna Ruiz, David; Lezaun Capdevila, Carlos; Torres García, Alicia E.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Institute of Smart Cities - ISC; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio IngeniaritzarenA wideband, all-dielectric metamaterial structure for enhancing radiative cooling is investigated. The structure is optimized to reflect most of the solar irradiance window (between 0.3 µm–3 µm), which is one of the biggest challenges in highly efficient radiative cooling coatings. The design is based on the principles of Bragg gratings, which constitutes a simple synthesis procedure to make a broadband reflector of reduced dimensions, without metallic layers, while keeping a flat enough response in the entire bandwidth. Numerical results show that reflection of solar irradiation can be easily tailored and maximized using this method, as well as the net cooling power of the device, about ∼79 W/m2 at daytime (about double at night-time) and a temperature reduction of 23 K (assuming no heat exchange) and 7 K assuming a heat exchange coefficient of 10 W/m2/K, for a device and ambient temperatures of 300 K and 303 K, respectively. This occurs even in detriment of absorption in the atmospheric window (8 µm–13 µm). Results also show the importance of efficiently reflecting solar irradiance for such technologies and its relevance in synthesis and design without using metallic components.