Programa del congreso

The normal component of the field induced on the cerebral cortex by non-invasive neuromodulation techniques is considered the main responsible for the neuronal depolarization responsible for the neurophysiological and therapeutic effects obtained through its application. By means of two electrode settings oriented to the stimulation of the motor area, we evaluated the said component within the framework of the optimization strategies of the spatial focus on this area in the tDCS techniques, observing significant differences in the orientation of the incident field in different landmarks of the motor area. In order to establish a relationship between these results and the neurophysiological response obtained experimentally, further studies that assess the induced neuronal response in greater detail will be required.

This paper presents the time domain study of an Ultra-wideband (UWB) printed monopole antenna. The antenna, with a size of 36 x 40 mm², works within the operating range of medical imaging and UWB applications. In this work, two identical antennas are used in far field conditions placed in face to face and side by side configurations. The transmission parameters, the group delay and the transmission of pulses, as well as the calculation of the System Fidelity Factor, are analysed in measurement and simulation. As it has been possible to verify, the results obtained have been satisfactory given the great similarity between the transmitted and received pulses.

This paper presents the process carried out to design a hybrid microstrip and stripline resonator at 2.3 GHz. The final purpose of this resonator is the electrical characterization of biological material inside a non-invasive microwave system for breast tumour detection. The design was made with two different high frequency simulators, Advanced Design System for circuital design and High Frequency Electromagnetic Simulation Software for electromagnetic design. A prototype of the designed resonator was fabricated onto a low-cost FR4 substrate and was measured with a Vector Network Analyzer. To obtain the dielectric constant of the biological materials, different concentrations of water and Triton X-100 were used as reference. A six-order equation was calculated to fit the frequency response of the resonator and the dielectric constant of the material under test. Finally, several measured were carried out to obtain the dielectric constant of different materials with a relative error lower than 4%.

In this paper, an omni-directional antenna solution is presented to improve the accuracy of indoor location systems, particularly MYSPHERA Bluetooth Real-Time Locating System (RTLS).

Emitting antennas with an irregular radiation pattern are not suitable for existing localization techniques due to received signal strength variation in the locators. The approach to an isotropic radiation pattern in the emitting device is what is achieved with presented design using two timeswitched antennas with opposing radiation patterns.

This solution allows to receive a uniform signal in the locators and increases precision for any technique, frequency or technology used.

For MYSPHERA this means more reliability, allowing better processes optimization and increasing efficiency in hospitals.

Despite the continuous improvement of cochlear implant (CI) devices and their widespread application, the large inter-subject variability observed in clinical practice continues to make the prognosis of individual CI outcomes challenging. User-specific anatomical characteristics, as well as stimulation parameters, may influence the individual patterns of electric current induced. This paper aims to develop a finite-element (FE) computational virtual head model that integrates the cochlea and the electrode array with the patient’s full head anatomy. Interestingly, a full head modelling approach can realistically emulate both intra and extra-cochlear current pathways, thus providing an estimate of the current shunted towards surrounding tissues. This would allow us to predict relevant clinical conditions, such as the undesired facial nerve stimulation. The results include simulations of intra-cochlear voltages and current densities over the facial nerve when stimulating different apical, medial and basal cochlea sites.

En este trabajo se desarrolla un método para optimizar la arquitectura de una red neuronal profunda. Se enmarca en un proyecto en el que se analizan imágenes dermatoscópicas para detectar la presencia o no de patrones representativos del carcinoma basocelular (BCC). Previa a la optimización de la arquitectura, se parte de una red neuronal que obtiene una sensibilidad de 0,7854 y un especificidad igual a 0,8187. Con la arquitectura encontrada se mejoran los resultados, obteniéndose una sensibilidad igual a 0,902 y una especificidad 0,8219

The present work describes the adaptations performed to a prototype of a smart bioimpedance spectroscopy device for use in the operating room and its application to the study of graft viability in the kidney transplantation process. The main novelties of the work compared to a previous prototype are related to the incorporation of improvements so that the device can be used autonomously by the clinical team in the operating room, without the need for intervention by technical staff. Other work improvements have been related to the research and development of a sterilizable electrode system, an optimization of the input impedance of the sensorization stage and a new measurement approach that improves the repeatability of bioimpedance estimations.

Chronic Obstructive Pulmonary Disease (COPD) patients often suffer from muscular atrophy of the peripheral muscles, which negatively influences physical activity capacity, quality of life, and even survival. However, muscle evaluation has not been commonly incorporated into clinical practice due to the complexity and cost of the reference techniques. In this work, a prototype of a smart, easy-to-use and low-cost bioimpedance device for body composition analysis has been adapted to perform measurements in the quadriceps region and its application to the evaluation of muscle atrophy in patients with COPD. The device has been validated technically in laboratory and clinically in a controlled hospital setting. In a first evaluation in with COPD patients, the correlation of the quadriceps muscle thickness obtained by a reference method (echography) was analyzed with respect to the bioimpedance parameters estimated by the prototype. The results of the correlation analysis confirm the feasibility of the approach and encourage further investigation with the prototype.

Los avances de la última década en cuanto a algoritmos y computación se refiere han proporcionado la posibilidad de desarrollar modelos de aprendizaje profundo cada vez más complejos y versátiles. En este artículo se discute la viabilidad de una red neuronal profunda, Deeplabv3+, para la segmentación semántica de retinografías con el propósito de ayudar al diagnóstico del glaucoma. Con este objetivo se pretende segmentar las regiones conocidas como disco óptico y excavación, cuya relación permite conocer el estado de la enfermedad. Los resultados demuestran la viabilidad de utilizar este tipo de modelos para segmentar imágenes médicas con precisión, pudiendo aportar cierta ayuda al personal sanitario.

Este artículo describe un método robusto y eficiente para la segmentación y medida del grosor de la capa de fibras nerviosas de la retina en tomografías de coherencia óptica, también llamadas OCTs. El método se basa en la segmentación eficaz de la capa de fibras mediante morfología matemática y su

posterior ajuste de forma precisa al contorno real de la misma mediante una implementación de contornos activos. Para poder comprobar la validez del método propuesto, se ha evaluado con una base de datos que contiene 290 OCTs pertenecientes a 145 pacientes y dichos resultados se han comparado con los obtenidos mediante ”el escáner” empleado en oftalmología para realizar dicho cálculo.

En este artículo se presenta el diseño y realización

de un diplexor en guía de onda y una antena de bocina con lente

de alta ganancia. Ambos componentes han sido especialmente

diseñados para comunicaciones de haz fijo punto a punto 5G en

los rangos de frecuencia de 71/76 GHz y 81/86 GHz (Banda E). El

diplexor está formado por dos filtros paso banda basados en la

combinación de una función de filtrado paso bajo y paso alto.

Además, el diplexor proporciona tolerancias de fabricación muy

relajadas, lo que hace que no necesite ningún tipo de sintonización

reduciendo sus costes de fabricación. En el caso de la antena, para

gozar de alta directividad en dichas frecuencias, se utiliza una

antena de bocina con lente que proporciona más de 38 dBi de

ganancia que cumple las máscaras ETSI. El subsistema propuesto

combina las ventajas de sus altas prestaciones frecuenciales así

como un ensamblaje mecánico sencillo, por lo que resulta

especialmente atractivo para aplicaciones 5G, debido al bajo coste.

Rain attenuation is the major signal impairment for radio links operating at frequencies above 10 GHz and in the EHF (30-300 GHz). The use of such high frequency in terrestrial radio links is one key element in future high data rate front/backhauling services needed in 5G deployments and future wireless generations. Due to the lack of experimental measurements for that frequency band, one approach to determine the link viability is to estimate rain attenuation by using information about the rain drop size distribution (DSD). In this work, specific attenuation for rain is calculated for five frequencies ranging from 40 to 200 GHz, using twelve years of DSD data gathered with a laser disdrometer. Specifically, the extinction cross section, needed for the calculation, is computed for spherical drops by using the Mie theory and using the CST MWS software for non-spherical drops. Once non-spherical drop results are available, polarization analyses are also generated. Results show that at the higher analyzed frequencies, the extinction cross section is moderately higher when the spherical drop model is used. Also, a higher variability of the attenuation for a given rain rate is observed, whereas the differences between the horizontal and vertical polarizations are smaller.

Los modelos de propagación basados en la teoría de trazado de rayos pueden estimar, con cierto detalle, las contribuciones multicamino que alcanzan la antena del receptor, pero tienen dificultades para estimar las contribuciones difusas. En este trabajo se presenta un modelo empírico de scattering difuso que puede incorporarse a los modelos de canal basado en la teoría de trazado de rayos, o simuladores de canal. El modelo de scattering difuso ha sido desarrollado a partir de medidas experimentales del canal radio en el dominio de la frecuencia. Las medidas se realizaron entre 25 y 40 GHz, lo que ha permitido particularizar los resultados en las bandas de 26, 28, 33 y 38 GHz, por ser éstas donde se realizarán los despliegues de 5G en milimétricas. Las medidas se llevaron a cabo en condiciones de propagación con visión directa (LOS, line-of-sight) y obstrucción de la línea de vista (OLOS, obstructed LOS). Los resultados muestran que cuando se introduce el scattering difuso en los modelos de canal es posible predecir con mayor exactitud las métricas que describen el comportamiento dispersivo del canal radio.

In this paper, the design of two telemetry and one GNSS antennas embedded in a single conformal prototype is presented. This multiband low-profile antenna will be integrated in Europa’s first suborbital launcher, MIURA-1. This solution is not only interesting for the launcher’s market, but also, due to the ease of integration in curved surfaces, has potential applications in the space, aviation, or automotive industries.

An improved equiangular spiral antenna with circular polarization is proposed as the radiating element for a phased array antenna intended for new generation space launchers. The spiral antenna has been designed in printed technology in order to achieve a low profile configuration capable to be embedded in the fuselage of the launcher. The bidirectional radiation of the spiral is converted into a unidirectional radiation by introducing the antenna in a metallic cavity. Furthermore, an absorber corona is added inside the cavity. The inclusion of absorbent material inside the cavity is necessary to maintain the radiation characteristics of the antenna without increasing its size as well as to adjust the axial and impedance ratio produced by the cavity. The spiral antenna has been simulated and fabricated in order to experimentally validate its radiating performance. Besides the phased array will operate from 2.0 to 2.3 GHz, wideband results of the spiral antenna has been obtained. The antenna, with a diameter of 0.6λ at 2.0 GHz, provides a 52% relative bandwidth (2.0-3.4 GHz) with a very pure circular polarization.

This contribution contains the general lines of the project Erasmus+ UNIFORS 2020, focused on soft skills at university curricula. A wide survey on demanded and needed soft skills in companies is the support to define a program for a course for training soft skills among university students. The selection of soft skills for such a course, as well as the definition and the experience in delivering it, are the contents of the work.

El proyecto de Talentos inclusivos es una innovadora experiencia llevada acabo desde la Universidade da Coruña en colaboración con ASPACE Coruña (Asociación de padres de personas con parálisis cerebral) y la Consellería de Educación de la Xunta de Galicia.

En este proyecto desde ASPACE, las personas con parálisis cerebral presentan una serie de dificultades con las que se encuentran en el día a día. Los profesores universitarios del CITIC definen unos retos tecnológicos para resolver esas dificultades y se organizan grupos de trabajos colaborativos formados por alumnos de instituto (cuarto de la ESO y primero de bachillerato) y personas con parálisis cerebral para desarrollar una solución tecnológica que solucione el reto definido. Los profesores de instituto y de universidad tutorizan el trabajo del grupo. En este curso 2020/2021, se han definido 45 retos, han participado 8 institutos y están desarrollando soluciones para resolver 10 de esos retos.

Con este proyecto se busca por un lado visibilizar los problemas con los que se enfrenta en su vida diaria la persona con discapacidad y por otro lado que los chicos de instituto experimenten como la tecnología aplicada puede ayudar a mejorar la calidad de vida de las personas.

The results obtained in University degrees are evaluated annually by means of different statistical indicators. There are several factors that can disrupt these indicators, so it is important to conduct detailed studies that go beyond the calculation of a result based on academic grades. In this paper, we will conduct a multilevel study to determine the impact of the online model used during the 2019-2020 academic year under the effects of COVID-19. We will start by comparing the trend of some of those indicators for the Degree in Computer Engineering of the three universities of the Galician university system. Subsequently, we will further study these indicators by course level and quarter in the case of one of the degrees, and we will finish by focusing on the analysis of several subjects of this degree.

The educational software tool Dosher is presented for the analysis of super heterodyne demodulation of signals, being applicable for enhancing the understanding and learning of the principles of communication theory mainly in Telecommunication engineering. This tool is intended to assist students (high school, undergraduate as well as Ph.D.) about the knowledge of the so-called super heterodyne receivers. Thanks to Dosher (DOwn Super HEterodyne Receiver), students will be able to check how the demodulation process from radiofrequency band down to base band takes place in the frequency domain. Furthermore, they will be able to fully design the receiver, analyze the unwanted effect called Image Frequency, or create reports compiling the expected results and design obtained. To the best of the authors’ knowledge, neither professional nor educational software alternatives for the learning of this field of communication theory have been proposed so far. Dosher is a user-friendly teaching-oriented software developed with MATLAB that successfully combines the use of signal graphical representation with accurate results at any stage of the receiver.

La propagación electromagnética dentro de cavidades puede mostrar comportamiento caótico. Esto sucede para la mayoría de geometrías siempre que las pérdidas no sean muy elevadas. La caracterización del comportamiento electromagnético es, por tanto, poco práctico desde el punto de vista tradicional, ya que muy pequeños cambios en el problema (frecuencia, geometría, permitividad y permeabilidad del interior, cambios de temperatura, cambios de presión, etc.) producen grandes cambios en el campo electromagnético interior. Es por ello que una caracterización estocástica es más conveniente que una caracterización determinista. Bajo este enfoque, recientemente se ha introducido el concepto de función de Green estocástica. En esta comunicación, se demostrará que la función de Green estocástica es una variable aleatoria de tipo Cauchy para entornos no disipativos y una variable aleatoria de tipo $\alpha-$estable más general para entornos disipativos de muy bajas pérdidas.

Scattering of arbitrary cross-section parallel cylinders is calculated by means of the transition matrix of each single scatterer and the general translational matrix for cylindrical waves. Although there are several methods to obtain the transition matrix of a cylindrical scatterer, the general translational matrix, by contrast, has always been calculated using Graf’s addition theorem due to its efficiency. However, restriction of validity of this theorem prevents its application in those cases where, for a pair of cylinders, the center of one of them falls within the minimum circular cylinder that circumscribes the other. In order to overcome this limitation, a transformation between cylindrical waves and plane waves, and propagation of the latter, is proposed. To this aim, it is shown that an adequate truncation of the evanescent plane wave spectrum should be carried out. As an example, the scattering of a group of infinite elliptic metallic cylinders is computed.

A new model order reduction strategy based on the reduced-basis method is carried out in this work. Starting off from time-harmonic Maxwell's equations, a new representation of the original Maxwell system is developed. First, a reduced basis approximation allows for a reduced-order representation of electrodynamics in the frequency band of interest. As a result, the Kurokawa series representation for electromagnetics turns pretty much into a finite sum of dominant eigenresonances, which stand upon global eigenmodes of the Maxwell system. This gives rise to a linear dynamical system in electromagnetics and, after a proper arrangement, provides extremely useful physical information from which an electrical engineer can get actionable design insights.

In this work, we use computational electromagnetics as an actual design tool and several realistic design applications will be considered during the presentation.

In this paper, we extend the Multimode Equivalent

Network (MEN) formulation for the analysis of encapsulated

microwave components that are composed by metallizations with

a non-negligible thickness. To accomplish this goal, the analysis is

divided in two steps: first we formulate two different equivalent

networks corresponding to the two thick steps present in the

structure, and then we cascade them to obtain the final network

that characterizes the complete circuit. This theoretical approach

is validated through two practical microwave bandpass filters.

We experimentally demonstrate in these examples that zerothickness

approximations are not accurate to solve this kind

of problems, thereby demonstrating the importance of the MEN

extension proposed in this contribution.

This work investigates the application of the JMCFIE

formulation to the discontinuous Galerkin surface integral

equation method for the electromagnetic analysis of arbitrarily

shaped piecewise homogeneous objects. In the proposed scheme,

nonoverlapping boundary surfaces and interfaces between materials

can be handled independently, without any continuity

requirement through multi-material junctions and tear lines

between surfaces in contact. The proposed formulation can

readily address nonconformal multi-material junctions, where

three or more material regions meet. This completely avoids

the cumbersome junction problem, which no longer requires

any special treatment. Numerical experiments will be shown to

validate the accuracy and demonstrate the great versatility of

the proposed JMCFIE-DG formulation for the management and

solution of complex composite objects with junctions.

This contribution presents the nonlinear characterization up to 50 GHz of a PIN diode commonly used as switch for reconfigurable devices at microwave applications. Nonlinear models are extracted by means of X-parameter measurements supported on accurate calibration and de-embedding procedures.

Results are validated by S-parameter measurements in the low power signal regime and by harmonic measurements in the large signal regime. The use of these models for reconfigurable antennas assessment is discussed.

The implementation of a non-quasi-static model for Schottky diodes into a commercial Computer-Aided Design tool is described. This formulation relies on a non-quasi-static charge definition that depends on two quasi-static functions: charge and delay. The model considers the use of the Nonlinear Function Sampling operator in order to extract each of this quasi-static components. This model implementation has been tested under Harmonic Balance analysis with some numerical examples. The performance of the proposed element observed in these preliminary tests allows being optimistic in the upcoming validation under realistic experimental conditions.

In this paper, a direct learning architecture is employed for the digital predistortion of a power amplifier with a concurrent dual-band input signal. Conventional dual-band behavioral models need to cope with a large number of regressors, being prone to algebraic issues that arise in the computation of the inverse of the covariance matrix. Ridge regularization is applied to the modelling equation in order to improve the stability of the learning process and the precision of the estimated coefficients in validation. Experimental results for the linearization performance achieved with the proposed approach are provided for a class AB power amplifier driven by two concurrent 10-MHz 5G New Radio signals.

The implementation of Wireless Communication Systems through Software Defined Radio (SDR) platforms are haven special attention from the researcher community. Our research team has developed a Co-operative System SDR platform to demonstrate the viability and advantages to use A\&F and D\&F protocols in LTE network. However, currently, the 5G Mobile Communications are receiving enormous attention and our platform should be upgraded to increase the required capacities to implement New Radio (NR) relaying technologies. In this paper, the nonlinearity study of Power Amplifier (PA) to increasing the benefits of our Relay Node Co-operative System SDR platform has been performed. The study consists in several experiments in a realistic laboratory environment. Besides, other tests conducted, Non-Line-of-Sight (NLOS) scenario, 64-QAM modulation scheme, as well as LTE signal are considered. From the results, the Error Vector Magnitude (EVM) of the enhanced SDR platform shows better performance and allows to increase the reach of the Backhaul Link (Base Station-to-Relay Node Link). Furthermore, this work constitutes the next stage for the implementation of a 5G NR Co-operative System SDR platform.

An omnidirectional conformal array antenna has been implemented in air-filled waveguide technology for the 37-40 GHz band. The input port of the antenna is implemented by a standard WR28 rectangular waveguide. The TE10 mode excited in the rectangular waveguide is used to generate the TE01 mode inside a circular waveguide by a TE10-TE01 mode converter. The circular waveguide path is progressively expanded forming a radial waveguide structure, where the TE01 mode is also expanded and radially propagated by several radiating apertures. Due to the radial symmetry of the structure, an omnidirectional radiating performance with low ripple can be achieved. This structure has been 3D manufactured using the direct metal laser sintering technology. It has been measured in order to experimentally validate its performance. A very good agreement between simulations and measurements, a reflection coefficient below -10 dB, a low ripple omnidirectional performance in a conical cutting plane, a very low cross-polar radiation as well as a total efficiency higher than 73% are obtained. This conformal antenna design is proposed for 5G New Radio indoor applications.

In this communication, a half-mode waveguide based on Gap Waveguide technology for rapid prototyping is presented. A power divider is designed for demostration purposes. The power divider is constructed from two non-contacting metal pieces. The horizontally-polarized power divider is housed in the bottom piece. The height of the groove is about half that which would be required to propagate the fundamental mode. The top cover is a uniform pinned surface that acts as a High Impedance Surface (HIS) over the groove of the bottom plate. The simulated reflection coefficient shows values of less than -15 dB in the bandwidth of interest (28 to 31 GHz). This design stands out for its ease of fabrication and opens a horizon for cheaper and more robust GW designs for mass production.

This contribution presents the characterization of a stripline embedded in a coaxial system. The stripline has been manufactured using HIPS as the main substrate. The metallic strip has been manufactured on 50mm thick kapton film which is binded to the main substrate. The transmission line plays a very important role in the overall performance of the ultrawideband radiating element currently under development. A multiline method has been used for the characterization of

the stripline. The influence of the conductivity obtain in the fabrication of the conductive ink on the propagation characteristics of the transmission line is analyzed. Simulations and measurements assess the goodness and possible negative effects of the fabrication process to rely on it for future designs.

The design, manufacturing and characterization of

a Ku-band orthomode transducer (OMT) is presented in this

paper. The OMT topology uses a T-junction with a circular waveguide

body, two rectangular waveguides attached to the main

cylinder and having fundamental modes with different boundary

conditions at the symmetry plane. The short-circuited bottom of

the cylinder includes simple matching elements optimized along

the rest of the OMT for easing the manufacturing by Selective

Laser Melting (SLM) in a single block. The restrictions imposed

by this type of additive manufacturing are included in the design

process, to provide a structure with performance suitable for

satellite applications. A Ku-band prototype in the frequency

band 13.4 - 15.6 GHz is tested, obtaining return loss better

than 20 dB in this 15.2% band, with isolation of at least 45

dB between orthogonal polarizations. In addition, the results for

the insertion loss are better than 0.18 dB, showing the potential

of SLM in structures traditionally requiring spark erosion or

high-accuracy milling. The OMT has ben also characterized in

radiation, confirming the good experimental results.

This contribution describes the design process of a flat polarizer reflectarray antenna in Ka-band for high data throughput from nanosatellites. The reflectarray has been designed to focus a high-gain beam while converting the incident polarization from dual-linear polarization into dual-circular. The flat surface of the reflectarray simplifies the mounting of the antenna on the small spacecraft and the linear-to-circular polarization conversion allows to reduce the number of components in the feed chain, also reducing the cost and complexity of the antenna subsystem. A 165 mm reflectarray antenna operating in Ka-band (31.8-34.7 GHz) has been designed with and without the polarization conversion. The results prove that the polarization conversion can be achieved while maintaining the performance of the antenna.

In this paper, a flat lens antenna using Gap Waveguide (GW) technology working in the millimeter waves band is designed. The metamaterial lens is fed using a Groove Gap Waveguide (GGW) horn antenna in order to achieve a plane wavefront at broadside. Both devices, metalens and GGW antenna achieve excellent radiation results when combined together. Due to the fully metallic composition, the structure presents more robustness, low loss, and adaptability to a flat surface, apt for millimeter wave application.

In this work, the design of a band-pass filter, based on a periodic structure that uses modified sections of a single-ridge waveguide (SRW) as the unit cell to produce the electromagnetic band-gap (EBG) at the desired frequency, is successfully addressed. The effect of the dimensions of the SRW height profiles in the different characteristics of the filter (lower cut-off frequency, and center frequency and bandwidth of the rejection-band) is analysed through the dispersion diagram of the infinitely periodic structure with different unit cells. The proposed topology and design process is used to implement a 54% fractional bandwidth band-pass filter centered at 5.4 GHz using low-cost 3D additive manufacturing techniques, which allow fast prototyping and the fabrication of complex geometries. Experimental measurements are in good agreement with the expected simulated response of the designed band-pass filter, showing good matching in the pass-band, and a deep rejection band.

In this article, three dual circularly-polarized K-band horn antennas are designed and experimentally validated. All designs are based on a common topology: a square waveguide input, a bowtie-shaped polarizer, and a flare section. Either left or right-handed radiation can be achieved by exciting one of the degenerate modes in the square waveguide. The bowtie polarizer outstands as a simple, easy-to-manufacture way of obtaining circular polarization. The three designs differ just in the flare section: a circular aperture, a square aperture and a bowtie-shaped aperture have been considered. The advantages of each aperture type will be discussed. The prototypes have been manufactured by Direct Metal Laser Sintering, allowing a single-block assembly. Over 20% bandwidth with axial ratio under 3 dB and gain around 19 dBi has been experimentally obtained in the three designs.

This paper presents the design, optimization and simulation of a novel 12x12 W-Band waveguide slotted array antenna based on stacked glide-symmetric metal sheets fed by a groove gap waveguide (GGW). This paper also proposes a new unit cell. The suggested unit cell has serpentine-shaped holes in a glide-symmetric configuration with the goal of minimizing the separation between parallel waveguides. To demonstrate the viability of the proposed unit cell, a 12x12 W-Band waveguide slotted array antenna at 92 GHz was designed and simulated. The results show that the proposed slot array antenna has a reflection coefficient below −10 dB within 91.3 GHz to 93 GHz, and the peak directivity and gain are about 29.7 dBi and 28.8 dB, respectively, at 92 GHz.

This paper shows in detail the 3D printing and electroplating process for a WR-28 rectangular waveguide. The characteristics of the printing process that must be taken into account to obtain the best possible print and to avoid problems that may arise are analyzed. Several studies are also carried out on the copper plating process using the electroplating method, changing the current applied to the piece, the amount of plating time and adding a copper deposition retardant additive that helps to reduce the roughness of the surfaces. In addition, possible errors that can lead to faulty electroplating are discussed.

This work describes a new design strategy for improving the power handling capability (PHC) of groove gap waveguides (GGW). First, a theoretical analysis is carried out to study the distribution of the quasi-TE10 mode and the variation of the PHC for different configurations and frequencies. Then, in order to minimize the strength of the maximum electric field above the pins, three of the main geometrical dimensions of the nails are optimized. Finally, the numerical results show that by using this strategy, the corona discharge power thresholds can be enhanced without degrading the electrical response.

In this work a microstrip line to empty substrate integrated waveguide (ESIW) transition based on Bézier curves has been designed for different substrate heights and for different working band frequencies (WR-75 and WR-42). The transition is fully integrated into the ESIW guide and does not require an additional taper in the microstrip line. Therefore, radiation loss is reduced. The microstrip to ESIW transition is realized by applying Bézier curves to a dielectric slab embedded into the ESIW and at its corners (ESIW). Bézier curves allow to shape the transition with a greater control as compared to exponential or gradient curves used in previous works. Besides, a prototype has been manufactured obtaining good agreement between the simulated and the measured results.

A new compact balanced-to-balanced dual-band diplexer composed of two balanced dual-band bandpass filters in a multilayer configuration is proposed in this contribution. The two balanced bandpass filters are based on the use of magnetically coupled open-loop resonators. The magnetic coupling results in a strong inherent common-mode rejection, greater than 40 dB within all of the passbands. The four passbands are close to each other in under 700 MHz in the L band, used for many applications such as mobile services or satellite navigation. Measurements of a prototype example are provided to validate the obtained simulation results and verify the value of the proposed structure.

Additive tridimensional printers have opened new applications of dielectric and conductive materials for microwaves systems. Manufacturing dielectric pieces by 3D printers is relatively easy. The knowledge of dielectric properties, relative dielectric constant and loss tangent, allows the design of microwave components such as lenses or molding surfaces for microwave and millimeter wave absorbers. The experimental measurements of dielectric properties of Polylactic Acid (PLA) and resin materials commonly used in 3D printers, in frequency bands from 8 to 110 GHz, by using different methods, have permitted the design of special shaped molding surfaces for the manufacturing of microwave and millimeter wave absorbing devices. This paper presents characterization methods and experimental results.

We present a detailed design of a radio-frequency graphene-based phase shifter. The operating principle of the system consists in loading a transmission line (TL) with a bias-tunable capacitor implemented as a state-of-the-art metalinsulator- graphene (MIG) diode. In the analysis carried out in this work, the focus is set on obtaining a full comprehension of the main figures of merit of a unit-cell stage, which is formed by a TL loaded with the MIG diode, so that it can be arbitrarily replicated and thus periodically concatenated, guarantying low insertion losses (IL) and high return losses (RL). Such a distributed system allows achieving a desired phase shift range for a targeted application. In this regard, we predict the operation of a 10-stage phase shifter at 3 GHz providing an almost linear phase shift range of around 24.09 degrees in the bias window [-1.5, 0.5]V, with insertion losses (IL) of 1.29 dB and return losses (RL) of 20.14 dB.