Open Access
Dual-band and integrated detectors for submillimetre applications
(2020) Torres García, Alicia E.; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren
La primera parte de este trabajo está enfocada en el diseño de detectores multibanda asequibles e integrados en el rango de los terahercios. De esta manera se puede obtener información de diferentes rangos espectrales en una sola medida reduciendo así el costo, las dimensiones, el peso y el consumo energético del receptor. Con este objetivo se diseñaron concretamente dos detectores doble banda. El primero de ellos opera simultáneamente en la banda submilimétrica y en el infrarrojo. El segundo detector se diseñó para trabajar en las bandas milimétrica y submilimétrica. La segunda parte de esta tesis combina conceptos y tecnologías de ambos dominios (electrónico y fotónico) y puede constituir un punto de partida para la creación de una nueva forma de detectores heterodinos integrados en silicio.
Open Access
Towards cooling concrete: evaluation of cement and cement composites under realistic climatic conditions
(Elsevier, 2025-04-15) Torres García, Alicia E.; Agbaoye, Ridwan O.; Carlosena Remírez, Laura; Goracci, Guido; Lezaun Capdevila, Carlos; Dolado, Jorge S.; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Ingeniaritza
Finding scalable, cost-effective and environmentally safe solutions for Passive Daytime Radiative Cooling (PDRC) is essential for addressing energy and climate challenges. This study demonstrates the feasibility of achieving PDRC using only cement-based compounds, without the need for additional whitening agents or other additives. Unlike previous approaches that rely on external additives, the proposed solution leverages two fundamental cement phases—portlandite and tobermorite—offering a scalable and low-impact alternative. The research evaluates the radiative cooling potential of these phases, along with two widely used cements—white cement (WC) and ordinary Portland cement (OPC), by analyzing and comparing their homogenized complex permittivities, derived using the Kramers-Kronig (KK) method. Simulations were conducted to assess the cooling power over one year across three different climates using actual meteorological data. The portlandite exhibits positive Pcool, maintaining a temperature equal to or below the ambient temperature more than 90 % of the time in dry desert and warm temperate locations. Indoor controlled measurements results reveal that portlandite (CH) may exhibit temperatures 15 °C lower than OPC and 5 °C lower than WC.
Open Access
A Chebyshev transformer-based microstri-to-groove-gap-waveguide inline transition for MMIC packaging
(IEEE, 2019) Pérez Escudero, José Manuel; Torres García, Alicia E.; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
The gap waveguide technology has become an alternative to millimeter- and submillimeter-wave electronic circuit packaging thanks to the loss reduction associated with its use. In this paper, a simplified design of an inline transition between a microstrip and a groove gap waveguide (GGW) operating at the W-band is presented. The transition consists of a tapered microstrip line and a Chebyshev adapter that couple the quasi-TEM mode of the microstrip line to the so-called vertical mode of the GGW. The simplicity of this design makes this transition appropriate for monolithic microwave integrated circuit (MMIC) packaging at millimeter frequencies and above. The simulation results have been experimentally validated in the W-band. A good performance has been achieved, resulting in a return loss better than 10 dB and a mean insertion loss lower than 2 dB.
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 Gobernua
In 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.
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 Ingeniaritzaren
The 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.
Open Access
Modified Soret lenses for dual band integrated detectors at submillimetre and millimetre wavelengths
(IEEE, 2020) Torres García, Alicia E.; Pérez Escudero, José Manuel; Gonzalo García, Ramón; Ederra Urzainqui, Íñigo; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
This paper presents a planar silicon integrated subharmonic mixer on top of a photonic-crystal platform. The local oscillator (LO) power is injected through a 2D photonic crystal (PC) slab to a resonant cavity that effectively couples the signal to a planar bow-tie antenna. The same antenna, which is printed on the top of the PC cavity, contains an antiparallel Schottky diode pair which performs the down-conversion. The proposed design is a simple, easy to integrate, low cost, low profile device. Moreover, the described fabrication process is compatible with active components integration. The performance of the design has been experimentally demonstrated showing good agreement with the simulation and is comparable with the state of-the-art of planar mixers. The work presented here is based on concepts and technologies from electronics and photonics domains and may be a good starting point for the creation of new devices, allowing the integration and upgrading of existing techniques from both worlds.
Open Access
A simplified design inline microstrip-to-waveguide transition
(MDPI, 2018) Ederra Urzainqui, Íñigo; Gonzalo García, Ramón; Pérez Escudero, José Manuel; Torres García, Alicia E.; Ingeniaritza Elektrikoa, Elektronikoaren eta Telekomunikazio Ingeniaritzaren; Institute of Smart Cities - ISC; Ingeniería Eléctrica, Electrónica y de Comunicación
A simplified design of an inline transition between microstrip and rectangular waveguide is presented in this paper. The transition makes use of a dielectric filled rectangular waveguide (DFRW) as an intermediate step, which simplifies manufacturing and allows for an analytical design. The behavior of the transition has been experimentally validated in the W-band by means of a back-to-back configuration. Good performance has been achieved: a return loss greaterthan 10 dB and mean insertion loss lower than 1 dB.
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 Comunicación
In 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.
Open Access
Nanoparticle derived suppressed-scattering bands for radiative cooling
(IEEE, 2023) Lezaun Capdevila, Carlos; Pérez Escudero, José Manuel; Torres García, Alicia E.; Caggiano, Antonio; Peralta, Ignacio; Dolado, Jorge S.; Liberal Olleta, Íñigo; Beruete Díaz, Miguel; Ingeniería Eléctrica, Electrónica y de Comunicación; Ingeniaritza Elektrikoa, Elektronikoa eta Telekomunikazio Ingeniaritza; Institute of Smart Cities - ISC
Light scattering using resonant nanoparticles is crucial for improving sun irradiance reflection in a daytime radiative cooler. Popular nanoparticles in radiative cooling literature are analyzed in terms of scattering performance due to material dispersion. Different scattering properties in the infrared range have been detected while a similar behavior can be achieved in the solar range due to changes in material dispersion. Also, suppressed scattering windows are produced by dispersive nanoparticles, allowing high reflectance while enabling thermal emission selectively. Material dispersion alone produces such scattering windows, thus, given a material, they will always remain in the same region regardless geometry and location of particles. Lastly, calcium silicate hydrate (CSH), the main phase of concrete, is studied as a dispersive host example. These results demonstrate the importance of a co-design between host and nanoparticles dispersion for daytime radiative cooling and that nanoporosities design are a key ingredient that could allow concrete-based daytime radiative coolers.
Open Access
Enhancing the infrared and visible emission properties of calcium silicate hydrate for radiative cooling using metamaterials
(IEEE, 2022) Lezaun Capdevila, Carlos; Dolado, Jorge 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 Ingeniaritzaren
Two 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.