BUSCADOR RECOLECTA

This work reviews the design and applicability of beam-forming networks based on Coherently Radiating Periodic Structures (CORPS-BFN) at Terahertz (THz) frequency bands. These versatile networks offer two operation modes: a continuous beam steering – feeding an antenna array with a linearly progressive phase distribution – using a reduced number of phase controls; or a multi-beam operation, generating independent, overlapped beams. These networks are built upon the concatenation of power combiners/dividers (PCDs) with isolated outputs. The isolation is provided by monolithically integrated resistors, implemented with Ti/TiO
thin films for the first time. In this work, a planar prototype of a
(inputs/outputs) microstrip CORPS-BFN for operation in the WR3.4/WM-864 band (220–330 GHz) on a thin 50
m Indium Phosphide (InP) substrate is designed, fabricated, and characterized. The measured S-parameters show a reflection coefficient better than -15 dB and an insertion loss between 1.6 and 3.2 dB in the whole band. In addition, an isolation better than 20 dB between the input ports has been measured. An overall remarkable agreement is observed between the measurements and the simulations. Last, the applications, scalability and efficiency of this type of networks at the targeted band are discussed in detail., This research was funded partially by the FPU Program from the Spanish Ministry of Science and Innovation, grant No. FPU18/00013, and project PID2019-109984RB-C43 (FRONT-MiliRAD); by the Deutsche Forschungs-Gemeinschaft (DFG, German Research Foundation) under Project 287022738-CRC/TRR 196 MARIE (Projects C02, C05, C06, C07 and S03); by BMBF (smartBeam, 6GEM grant No. EFRE-0400215, grant No.16KISK017 and grant No.16KISK039) and by the NRW/EFRE Terahertz-Integrationszentrum (Open6GHub and THz.NRW). Open Access funding provided by Universidad Pública de Navarra.

This article presents the design of a flat Luneburg
metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW)
loaded with metallic pins whose height is modulated to get an
effective refractive index that follows the Luneburg equation.
A Groove GW (GGW) H-plane horn is used to illuminate
the metalens, such that the rays are collimated and a planar
wavefront is generated in the direction of propagation. Since the
structure at hand is planar, it can be efficiently integrated on flat
surfaces. Moreover, the fully metallic structure is mechanically
robust and presents lower losses than lenses including dielectric
substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The
metalens yields an input reflection coefficient (S11) below −10 dB
from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth
is 26.2% with respect to a center frequency of 60 GHz, with a
peak of 22.5 dB at 61 GHz. These features make this design an
interesting solution for millimeter-wave (MMW) applications., This work was supported in part by MCIN/AEI/
10.13039/501100011033/FEDER “Una manera de hacer Europa” under
Project RTI2018-094475-B-I00 and in part by the Spanish State
Research Agency under Project PID2019-109984RBC43/AEI/10.13039/
501100011033.

In this article we compare two solutions to improve the radiation pattern of a slotted Substrate Integrated Waveguide (SIW) antenna: use of an E-plane array and covering it with a metasurface (MTS). To this aim, we compare the changes in performance, radiation pattern and aperture efficiency. We will see the advantages that the metasurface has over the typical array., The authors would like to thank financial support by UPNA’s PhD scholarship program and the Spanish State Research Agency, Project No. PID2019-109984RBC43/AEI/10.13039/501100011033.

This paper considers the problem of supporting immediate response operations after a disaster with information about the available road network to reach certain locations. We propose an online algorithm that aims to minimize the route length required by an unmanned aerial vehicle (UAV) to explore the road accessibility of potential victim locations. It is assumed that no information about disruptions in the road network is available at the start of the exploration. The online algorithm applies two movement and three orientation strategies. Additionally, a cutting strategy is used to restrict the search space after new information about the state of single roads is obtained. We consider a road and an aerial network for the movements of the UAV, since it is not necessary to follow the route of a road any longer, if it can be marked as disrupted. In extensive numerical studies with artificial and real-world test instances, it is evaluated for different disruption levels, which combinations of movement and orientation strategies perform best. Additionally, we propose different refuelling strategies for the UAV and present how they differ in the number of refuelling operations and the required additional route length. The results show that an efficient online algorithm can save valuable exploration time., This work has been partially supported by the Österreichische Nationalbank (OeNB) (17703) and the Erasmus+ Program (2018-1-ES01-KA103-049767). We also acknowledge the support of the UPNA doctoral program and the PID2019-111100RB-C22/AEI/10.13039/501100011033 project.

A novel photonic-assisted 2-D Terahertz beam steering chip using only two tuning
elements is presented. The chip is based on an array of three leaky wave antennas (LWAs) with
a monolithically integrated beamforming network (BFN) on a 50 µm-thick indium phosphide
substrate. The THz beam angle in elevation (E-plane) is controlled via optical frequency tuning
using a tunable dual-wavelength laser. An optical delay line is used for azimuth (H-plane) beam
control. The simulated beam scanning range is 92° in elevation for a frequency sweep from
0.23 THz to 0.33 THz and 69.18° in azimuth for a time delay of 3.6 ps. For the frequency range
from 0.26 THz to 0.32 THz, it is confirmed experimentally that the THz beam scans from −12°
to +33°, which is in good agreement with the numerical simulations. The beam direction in
azimuth scans with a total angle of 39° when applying a delay difference of 1.68 ps. A good
agreement is found between theoretically predicted and experimentally determined THz beam
angles with a maximum angle deviation below 5°. The experimental scanning angles are limited
due to the mechanical constraints of the on-wafer probes, the on-chip integrated transition and
the bandwidth of the THz receiver LNA. The mechanical limitation will be overcome when using
a packaged chip., Deutsche Forschungsgemeinschaft (Project-ID 287022738– CRC/TRR 196(Project C07)); Bundesministerium für Bildung und Forschung (6GEM, grant No. EFRE-0400215, grant No.16KISK017, grant No.16KISK039,
NRW/EFRE Terahertz-Integrationszentrum (THzIZ), Open6GHub); Agencia Estatal de Investigación (/MCIN/AEI/
10.13039/501100011033, PID2019-109984RB-C43/AEI/10.13039/501100011033, PID2020-112545RB-C53); Ministerio de Ciencia e Innovación (FPU Program 00013/2018).

In this paper the design and experimental validation of a fourth-harmonic mixer based on Schottky diodes working around 300 GHz is presented. The main novelty of this work consists in the integration of an MMIC-based local oscillator, working around 75 GHz, and a mixer in the same metallic block housing. A prototype has been characterized using the Y-Factor method and yields a best measured conversion loss and an equivalent noise temperature of 14 dB and 9600 K, respectively. This performance is comparable to the state-of-the-art for this type of mixer., This research was funded by the Spanish MINECO, Project No. TEC2016-76997-C3-1-R, and by the Spanish State Research Agency, Project No. PID2019-109984RB-C43/AEI/10.13039/501100011033.

We propose a novel experiment, the Canfranc Axion Detection Experiment (CADEx), to probe dark matter axions with masses in the range 330–460 μeV, within the W-band (80–110 GHz), an unexplored parameter space in the well-motivated dark matter window of Quantum ChromoDynamics (QCD) axions. The experimental design consists of a microwave resonant cavity haloscope in a high static magnetic field coupled to a highly sensitive detecting system based on Kinetic Inductance Detectors via optimized quasi-optics (horns and mirrors). The experiment is in preparation and will be installed in the dilution refrigerator of the Canfranc Underground Laboratory. Sensitivity forecasts for axion detection with CADEx, together with the potential of the experiment to search for dark photons, are presented., SA and JM are supported by
grants PID2019-108122GB-C32 and the Maria de Maeztu grant CEX-2019-000918-M of
ICCUB. The work of UPCT and IFIC is supported by grant PID2019-108122GB-C33, funded
by MCIN/AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”. JMGB
thanks the grant FPI BES-2017-079787, funded by MCIN/AEI/10.13039/501100011033
and by “ESF Investing in your future”. The work of Universidad de Cantabria is supported by the Ministry of Science and Innovation under Grant PID2019-110610RB-C22.
CAB and IMDEA-Nanoscience work is supported by grants PID2019-105552RB-C41 and
PID2019-105552RB-C44 and by Comunidad de Madrid under Grant P2018/NMT-4291.
IMDEA-Nanoscience acknowledges financial support from “Severo Ochoa” Programme for
Centers of Excellence in R&D (MINECO, Grant SEV-2016-0686). D.G. and A.G also
acknowledge Grant DEFROST N62909-19-1-2053 from ONR Global. RBB, FJC, BJK,
EMG, JMS and PV thank the Spanish Agencia Estatal de Investigación (AEI, MICIU)
for the support to the Unidad de Excelencia María de Maeztu Instituto de Física de
Cantabria, ref. MDM-2017-0765. RBB, FJC, EMG and PV thank the Spanish Agencia
Estatal de Investigación (AEI, MCI) for the funds received through the research project,
ref. PID2019-110610RB-C21. RBB, FJC, BJK, EMG, JMS and PV also thank the ‘Dark
Collaboration at IFCA’ working group for useful discussions. The work done by ANTERAL
S.L. is supported by project QON-Space financed by the Navarra Government Project No.
0011-1365-2021-000220. UPNA acknowledges financial support from the Spanish State
Research Agency, Project No. PID2019-109984RB-C43/AEI/10.13039/501100011033 and
Project No. PID2020-112545RB-C53/MCIN/AEI/ 10.13039/501100011033.

In this paper, the use of a metasurface to improve the radiation properties of a Substrate Integrated Waveguide based slotted antenna is proposed. The design process of a metasurface covered 8 element slot antenna array following a Chebyshev distribution is presented and its performance is compared with that of a conventional one. The results demonstrate the improvement in the radiation performance that can be achieved, without affecting the bandwidth., The authors would like to thank financial support by UPNA’s PhD scholarship program and the Spanish Agencia Española de Investigación under project PID2019-109984-RB-43/AEI/10.13039/501100011033

Additive manufacturing technology is rapidly overcoming some of its initial limitations and, thus, creating a very useful engineering option for prototyping complex geometries for a wide range of electronic devices. Based on important advantages such as turn-around, reliability, material waste reduction, and low implementation costs, the technology is being continuously developed and improved. This paper presents a completely 3D-printed microstrip patch antenna to demonstrate the feasibility of a new conductive Acrylonitrile Butadiene Styrene (ABS) material in the fabrication of three-dimensional (3D) antennas using additive manufacturing method. The prototype of the antenna has been fabricated using Raise3D E2 printer, commercial ABS and a new ABS filament developed by Naitec for dielectric and conductive parts of the antenna, respectively. The fabricated antenna is compact and light. Preliminary prototypes and fabrication techniques are presented., The authors would like to thank Navarre Government for
the funding provided by “Ayudas para la contratación de
doctorandos y doctorandas, Doctorados industriales 2021”,
Resolución 87E/2021 and Project AMELEC, PC017-018
AMELEC - Advanced Manufacturing of Materials, as well
as the Spanish Research Agency, for funding the Project
PID2019-109984-RB-43/AEI/10.130 39/501100011033.

Las redes sociales se han convertido en una de las principales fuentes de información, especialmente entre los más jóvenes. Al mismo tiempo, se ha incrementado la producción y circulación de información falsa o fake news a través de las redes. En este contexto, resulta crucial que los jóvenes adquieran estrategias y competencias para realizar una lectura crítica de la información que consumen. Este estudio busca analizar el comportamiento del alumnado de secundaria ante la información falsa y el efecto de una intervención didáctica, realizada online durante la pandemia de la covid-19, cuyo objetivo era que el alumnado desarrollara competencias para detectar noticias falsas. Se trata de una investigación participativa con un diseño de pre-test y post-test. Los resultados muestran que el alumnado incrementó su competencia para identificar algunos tipos de falsedad como la información no probada y la información tergiversada, si bien tuvo problemas para reconocer información descontextualizada o el uso de lenguaje discriminatorio. Las estrategias que más utilizó son la comprobación de datos en internet y el uso de verificadores. Se observaron comportamientos diferenciados entre el alumnado que identificó la información falsa y el que no lo hizo. Las conclusiones apuntan a la necesidad de trabajar en el aula de forma integral, extensiva y transversal la evaluación de la información partiendo de las habilidades que el alumnado ya posee., This paper reviews the different remote sensing techniques found in the literature to monitor plant water status, allowing farmers to control the irrigation management and to avoid unnecessary periods of water shortage and a needless waste of valuable water. The scope of this paper covers a broad range of 77 references published between the years 1981 and 2021 and collected from different search web sites, especially Scopus. Among them, 74 references are research papers and the remaining three are review papers. The different collected approaches have been categorized according to the part of the plant subjected to measurement, that is, soil (12.2%), canopy (33.8%), leaves (35.1%) or trunk (18.9%). In addition to a brief summary of each study, the main monitoring technologies have been analyzed in this review. Concerning the presentation of the data, different results have been obtained. According to the year of publication, the number of published papers has increased exponentially over time, mainly due to the technological development over the last decades. The most common sensor is the radiometer, which is employed in 15 papers (20.3%), followed by continuous-wave (CW) spectroscopy (12.2%), camera (10.8%) and THz time-domain spectroscopy (TDS) (10.8%). Excluding two studies, the minimum coefficient of determination (R2) obtained in the references of this review is 0.64. This indicates the high degree of correlation between the estimated and measured data for the different technologies and monitoring methods. The five most frequent water indicators of this study are: normalized difference vegetation index (NDVI) (12.2%), backscattering coefficients (10.8%), spectral reflectance (8.1%), reflection coefficient (8.1%) and dielectric constant (8.1%)., This research was funded by the Spanish MINECO, Project No. TEC2016-76997-C3-1-R, and by the Spanish State Research Agency, Project No. PID2019-109984RBC43/AEI/10.13039/501100011033.

In this paper the design and experimental characterization of a combined doublersubharmonic mixer based on Schottky diodes which uses a 75 GHz MMIC based local oscillator is presented. This solution integrates in the same substrate the doubler and the mixer, which share the same metallic packaging with the local oscillator. The prototype has been fabricated and measured. For characterization, the Y-Factor technique has been used and the prototype yields a best conversion loss and equivalent noise temperature of 11 dB and 1976 K, respectively, at 305 GHz. This performance is close to the state of the art, and shows the potential of this approach, which allows a significant reduction in terms of size and volume., This research was funded by the Spanish MINECO, Project No. TEC2016-76997-C3-1-R, and by the Spanish State Research Agency, Project No. PID2019-109984RB-C43/AEI/10.13039/501100011033.

This work addresses the lack of moisture content estimation models for food products in the millimeter-wave frequency range and showcases the potential of this range for designing compact, cost-effective, and in-line food moisture sensors. The moisture content estimation models developed in this study are intended for flour-based mixtures in the 67-110 GHz frequency range and are derived by means of a nondestructive and contactless monitoring system. To this aim, data obtained by continuous-wave (CW) vector network analyzer (VNA) spectroscopy is used to create two different models, both with a coefficient of determination ( R2 ) of 0.97. One model is based on the theoretical response obtained by means of the Looyenga effective medium theory (EMT) model, while the other is based on measured data. Both models have been experimentally validated with root mean square error (RMSE) values of 0.4% and 0.35%, respectively. These small estimation errors show the potential of this frequency range to design compact, cost-effective, and in-line food moisture sensors. This research contributes to improving quality control and monitoring of moisture levels in flour-based mixtures., This work was supported in part by the Spanish State Research Agency
under Project PID2019-109984RBC43/AEI/10.13039/501100011033 and in
part by the Government of Navarra through the Project IAFOOD under Grant
0011-1411-2020-000024.

This paper discusses different design alternatives for a high gain planar antenna at 240 GHz. The antenna is based on a Fabry-Perot configuration, where two different partial reflection surfaces (PRS) are considered: a free standing metallic plate and a metallized quartz substrate. Similar performance has been found between both alternatives., The authors would like to thank financial support by the Agencia Española de Investigación under project PID2019-109984-RB-43/AEI/10.13039/501100011033.

The Gap Waveguide technology utilizes an Artificial Magnetic Conductor (AMC) to prevent the propagation of electromagnetic (EM) waves under certain conditions, resulting in various gap waveguide configurations. In this study, a novel combination of Gap Waveguide technology and the traditional coplanar waveguide (CPW) transmission line is introduced, analyzed, and demonstrated experimentally for the first time. This new line is referred to as GapCPW. Closed-form expressions for its characteristic impedance and effective permittivity are derived using traditional conformal mapping techniques. Eigenmode simulations using finite-element analysis are then performed to assess its low dispersion and loss characteristics. The proposed line demonstrates an effective suppression of the substrate modes in fractional bandwidths up to 90%. In addition, simulations show that a reduction of up to 20% of the dielectric loss can be achieved with respect to the traditional CPW. These features depend on the dimensions of the line. The paper concludes with the fabrication of a prototype and validation of the simulation results in the W band (75–110 GHz)., This research was funded by the Spanish Ministry of Science and Innovation within the FPU Program grant no. FPU18/00013 and project PID2019-109984RB-C43—FRONT-MiliRAD.

We propose a novel experiment, the Canfranc Axion Detection Experiment (CADEx), to probe dark matter axions with masses in the range 330–460 μeV, within the W-band (80–110 GHz), an unexplored parameter space in the well-motivated dark matter window of Quantum ChromoDynamics (QCD) axions. The experimental design consists of a microwave resonant cavity haloscope in a high static magnetic field coupled to a highly sensitive detecting system based on Kinetic Inductance Detectors via optimized quasi-optics (horns and mirrors). The experiment is in preparation and will be installed in the dilution refrigerator of the Canfranc Underground Laboratory. Sensitivity forecasts for axion detection with CADEx, together with the potential of the experiment to search for dark photons, are presented., SA and JM are supported by grants PID2019-108122GB-C32 and the Maria de Maeztu grant CEX-2019-000918-M of ICCUB. The work of UPCTand IFIC is supported by grant PID2019-108122GB-C33, funded by MCIN/AEI/10.13039/501100011033/ and by “ERDF A way of making Europe”. JMGB thanks the grant FPI BES-2017-079787, funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”. The work of Universidad de Cantabria is supported by the Ministry of Science and Innovation under Grant PID2019-110610RB-C22. CAB and IMDEA-Nanoscience work is supported by grants PID2019-105552RB-C41 and PID2019-105552RB-C44 and by Comunidad de Madrid under Grant P2018/NMT-4291. IMDEA-Nanoscience acknowledges financial support from “Severo Ochoa” Programme for Centers of Excellence in R&D (MINECO, Grant SEV-2016-0686). D.G. and A.G also acknowledge Grant DEFROST N62909-19-1-2053 from ONR Global. RBB, FJC, BJK, EMG, JMS and PV thank the Spanish Agencia Estatal de Investigación (AEI, MICIU) for the support to the Unidad de Excelencia María de Maeztu Instituto de Física de Cantabria, ref. MDM-2017-0765. RBB, FJC, EMG and PV thank the Spanish Agencia Estatal de Investigación (AEI, MCI) for the funds received through the research project, ref. PID2019-110610RB-C21. RBB, FJC, BJK, EMG, JMS and PV also thank the ‘Dark Collaboration at IFCA’ working group for useful discussions. The work done by ANTERAL S.L. is supported by project QON-Space financed by the Navarra Government Project No. 0011-1365-2021-000220. UPNA acknowledges financial support from the Spanish State Research Agency, Project No. PID2019-109984RB-C43/AEI/10.13039/501100011033 and Project No. PID2020-112545RB-C53/MCIN/AEI/ 10.13039/501100011033., Peer reviewed