Programa del congreso

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.

The video game sector is one of the fastest-growing industries in recent times and one with the most solid expectations to continue expanding in the following years. One key element in the future of these applications is the adoption of the cloud gaming paradigm, which allowing vent user equipment. Nonetheless, this approach establishes hugely challenging requirements on the network side in order to support high amount of data exchanged with the lowest latency possible. Here, the present work describes the main metrics associated with the performance and requirements of this novel service. Finally, a comparison between different technologies such as Ethernet, WiFi, LTE and 5G is given, showing the performance of each technology in the provision of these kind of services in terms of lag and smoothness.

Traffic forecasting with high time resolution (i.e., hour) is key to manage network slicing in 5G networks. However, the high dynamism of actual cellular networks makes predicting future traffic fluctuations an incredibly arduous task. In this context, amazing results obtained from other fields of research have put deep-learning models into the spotlight. This work presents a comparative study of the performance of different deep-learning models to forecast hourly cell traffic in both Downlink (DL) and Uplink (UL). For this purpose, a dataset from a live LTE network is collected for 2 months. Both classical and multi-tasking deep learning approaches have been considered. Results show that multi-tasking models combining recurrent and convolutional layers show the highest accuracy, revealing that the information of neighbor cells is useful when forecasting traffic in cells serving social events.

This work describes an 8-pixel imaging optical receiver for multiple-input multiple-output (MIMO) indoor visible light communications (VLC) based on space-division multiple access (SDMA). The communication system also uses an adaptive orthogonal frequency-division multiplexing (OFDM) modulation scheme, enabling multi-user transmission with constrained inter-user interference. The simulation results show that the proposed optical receiver offers a smoother system behavior irrespective of its orientation when receptor moves throughout a 4-lamp room as compared with using a 4-pixel imaging optical receiver, which suits better with realistic indoor scenarios where receiver orientation with respect to light lamps cannot be easily controlled.

Free space optical (FSO) communications have been considered a competitive alternative to the radio frequency systems (RF) due to its large bandwidth. Analytical close-form expressions for the probability error are derived for a variety of atmospheric conditions assuming intensity modulation/direct detection (IM/DD) link using on-off keying (OOK). The gamma-gamma distribution will be used to model the random variation of irradiance due to its validity for any turbulence condition. In addition, a spatial diversity technique in the receiver side is proposed to improve the link performance and the impact of the correlation among channels will be studied. The analytical results, numerically verified by Monte-Carlo simulations, will give us an idea of the feasibility of using this technology in a near future.

In this paper, we study the performance of a drone-to-ground free-space optical (FSO) link with energy harvesting in the presence of both atmospheric gamma-gamma turbulence and pointing errors. Furthermore, we assume that the direct current component of the FSO signal, which is normally filtered out, can be employed for energy harvesting at the drone, increasing its autonomy. To this end, a variant of the classic OOK modulation is considered. Analytical closed-form expressions are derived for a variety of scenarios. Monte Carlo simulations are also carried out to verify our analytical results.

A software has been implemented that applies the spectral-domain Method of Moments (spectral MoM) to the analysis of periodic multilayered structures with a number of metallized interfaces alternating patches and apertures. The Non-Uniform Fast Fourier Transform (NUFFT) is used to obtain the Fourier transform of the basis functions in the case where the periodic grids are skewed, which makes it possible the analysis of non-rectangular periodic lattices with tightly packaged elements. The in-house software is used to design a fifth-order frequency selective surface (FSSs) made of hexagonal patches and apertures with 35% of bandwidth. Our design results are compared with CST results, and excellent agreement is found. The in-house software turns out to be around 13 times faster than CST, which makes it very convenient for full-wave electromagnetic optimization.

Here we analyze a periodic circular waveguide loaded with transversal holey metallic plates. Specifically, we study the effects of higher symmetries when the holes have an elliptical shape. It is shown that the position of the center as well as the orientation of the elliptical holes strongly determine the bandwidth and characteristics of the passbands. In general, it is observed that holes in a higher-symmetric configuration produce a wider bandwidth with less dispersion. We also studied the case of two different interleaved periodicities with different symmetries: conventional, single-glide, and double-glide. Single and double glide symmetries present a similar behavior as their conventional counterpart, namely, there appear two near passbands. Additionally, two 4-fold twist-symmetric structures are studied. When the minor semi-axis of the elliptical holes is directed along the waveguide radial direction, the mode propagates in a narrow band and shows both forward and backward characteristics. On the other hand, when the major ellipse's semi-axis is located along the radial direction, a low-dispersive mode propagates in a wide frequency band.

To design and characterize radio environments with metasurfaces, it is necessary to know the scattering properties of finite-size anomalously reflecting (phase-gradient) metasurfaces. Recently, different approaches have been proposed to tackle the problem.

In this presentation, we will present a comparison between alternative analytical models.

We will first derive a general formulation for the far-field scattering of reflective metasurfaces based on the Huygens principle. Then we will specify the assumptions of known models. The first model that we will study is based on the assumption that at each point of the metasurface the reflected field equals the incident field multiplied by a controllable reflection coefficient. Then we will analyze the same structure with an analytical model based on the use of macroscopic reflection coefficients following the theory of diffraction gratings. Finally, we will numerically analyze the structure and compare the results.

A novel technique to design Fabry-Pérot antennas with non-homogeneous PRS is described. It takes advantage of a transmission line circuit model to efficiently obtain all necessary unit cell designs that satisfy the cavity resonance condition. This approach allows an increase in directivity for a given footprint without decreasing the bandwidth. Some design examples are presented, showing the evolution from a simple single-layer PRS to a non-homogeneous two-layers one. Through electromagnetic simulations, the latter one achieves an increase of about 3 dB in directivity while maintaining the bandwidth. This way, the gain-bandwidth product is improved from a value of 5 to almost 9, effectively raising the antenna efficiency.

The concept of Gap Waveguides and suppression of modes propagating between a Perfect Electric and Perfect Magnetic Conducting is applied to Coplanar Waveguides to propose a new low-loss, low-dispersion transmission line. Three different versions of the line are proposed and compared among themselves and other typical CPW implementations. The main theory behind this concept and Finite Element simulations are provided to support and validate the idea. A prototype is currently being fabricated and experimental validation is expected in the forthcoming months

In this work, the corona discharge thresholds in microstrip bandpass filters (BPFs) are studied, and a new design strategy is proposed for enhancing the peak power handling capability (PPHC). For this purpose, we suggest a new topology based on circled-end resonators to achieve a reduction of the maximum peak voltage (Vpeak) and avoid sharp corners. First, a theoretical analysis is carried out to obtain an expression for modeling the reduction of Vpeak. Next, a second study shows the variation of the PPHC for different sizes of the rounded-ends. Finally, the effectiveness of the proposed solution is validated by means of experimental measurements, showing a PPHC enhancement of 2.10 dB compared to a conventional microstrip BPF with rectangular-end resonators.

The use of 3D printed technology for designing wideband flat lenses is

explored in this work. Different types of lenses are analyzed, all of

them with wideband characteristic in the Ka band. The design of these

graded index lenses is made using different commercial filaments and

playing with different infill percentages always taking into account as

well mechanical limitations. A study of their performance when scanning

the beam is also presented. Some prototypes have been manufactured and

measured showing an excellent performance including low loss

characteristic in this high frequency band.

Multi-feed shaped-beam perforated dielectric transmitarray in millimeter-band

Design of a Fresnel lens at 60GHz

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.

The enhancement of virtualization in new generation cellular networks involves the arising of new paradigms in network management. Network Slicing is known as one of the key enablers for the wide range of different high QoS demanding services that are expected to be supported by 5G. The correct sharing of the underlying resources implies a complex architecture that makes virtualization difficult to be full controllable. The Noisy Neighbour is identified as an entity that uses most of the underlying resources, while other virtual units are suffering a lack of them. This work presents an emulated 5G Noisy Neighbour scenario, in which the impact of this entity is evaluated through the Virtual Network Functions of the 5G Core, in order to assess the degradation that KPIs suffer when a Noisy Neighbour appears. The present work also evaluates the effectiveness of a Machine Learning Noisy Neighbour identification model, based on the metrics gathered from the proposed framework, and proposes the application of Artificial Intelligence for predicting network performance, based on network inputs and CPU resources used by the Virtual Network Functions, and a prediction model to forecast the amount of CPU resources that may be demanded by the network in each moment. This approach intends to enhance the resources awareness in a virtualized cellular network, what is posed as crucial for efficiently managing the Noisy Neighbour problem.

Unlike previous generations of mobile communications, 5G is intended to cover a wide variety of scenarios and services with different characteristics and requirements. In this context, the network management team tasks are becoming unattainable. This work develops a system that automatically analyses network data and based on it, recommends cell parameter changes to enhance the performance of the network. A Decision Support System(DSS) that draws the relationship between cell types, cell states and configuration parameters is proposed.

We investigate the impact of a product-channel attack against wireless physical layer security with different diversity techniques. The attack proposed is based on introducing synthetic fading that aims to make the base station transmit at a rate higher than the secrecy capacity. We demonstrate that a low complex transmit antenna selection (TAS) criterion based on the eavesdropper channel improves the robustness against the attack better than the traditional maximal ratio transmission (MRT) scheme or the TAS based on the legitimate channel. Analytical results and simulations are provided to corroborate this fact.

Mobile network users are demanding with regard to the quality of the services, forcing the operators to solve the network degradations in the shortest time possible. For this purpose, a method for root cause diagnosis of degradations is proposed. It is based on different correlations (among CMs and a KPI) and the weighted average of sigma points to provice a ranking of possible causal candidates. Finally, this method is tested on metrics obtained from a commercial equipment.

The use of Time Division Duplex (TDD) has not been fully adopted by operators in LTE networks and its previous generations. In contrast, the fifth generation (5G) is introducing new technical motivations for its use. In order to achieve network flexibility as well as to provide service to every use case, it is necesary to adapt the resources allocated to DL and UL. On the other hand, beamforming techniques require sharing channel state information regularly in both directions. Hence, TDD is a promising option, although it may cause various interference types. The aim of this work is to analyze the Cross-Link Interference (CLI). To do this, a complete scenario simulation has been configured with different conditions, while the signal- to-interference-plus-noise ratio (SINR) has been monitored.

In this work we present the experimental characterization of a terahertz (THz) superoscilatory lens implemented on an ultra-thin metasurface (thickness <0.04λ0). This metalens improves the transmission efficiency and the focal properties of other super-oscillatory lenses found in the literature based on different design modalities (such as lenses based on opaque and transparent areas). At the frequency fexp = 295 GHz, the manufactured metalens improves by 25% the classical resolution limit imposed by the diffraction of electromagnetic waves, showing at the same time a gain of 18.2 dB and a very low side lobe level (13 dB). In addition, the metalens achieves a resolution better than the diffraction limit in a fractional bandwidth greater than 18% and high levels of transmission and focusing efficiency. The novel design procedure on which the proposed device is based opens new doors for obtaining devices with potential applications in THz imaging techniques, microscopy and communications, among others

In this communication, the reconfigurability mechanisms for beam steering at a fixed frequency in a leaky-wave antenna based on Huygens metasurfaces are reviewed. A preliminary design for a forward-to-backward scanning antenna at 24 GHz is proposed based on the use of a commercial liquid crystal (er ranging from 2.46 to 3.54). The simulation results show that the beam steers when the permittivity of the liquid crystal (partially filling the waveguide, with a 560 um high layer) is reconfigured. It is shown that the antenna can meet the challenges of this technology (a very thin layer of liquid crystal and a not very wide range of permittivity) while obtaining scanning from -15 to 15º maintaining the directivity around 17 dBi, including broadside.

In this communication, the behavior of a chiral metasurface that takes advantage of oblique incidence to transform the polarization state of the incident wave is analyzed. In contrast with other publications, the novelty of this work lies on the distribution of the chiral particles. The proposed metasurface has been characterized using the finite difference time domain engine of the full wave 3D EM simulator, Keysight EMPro. With the aid of this numerical tool, different configurations have been studied: sawtooth profile and zigzag profile structures, with different mutual twist angle and angle of incidence. The combination of intrinsic and extrinsic chirality shows a great influence on the circular dichroism.

Abstract- In this paper, we have designed a Substrate Integrated Waveguide Slotted Antenna (SIW-SA) covered by a metasurface. Thanks to this planar technology, we reduce the manufacturing complexity and its volume. The design process of a SIW and an 8 slot antenna following a Chebyshev distribution to control the SLL is presented. We will compare the performance of this antenna with a conventional one and demonstrate the improvement in the radiation aperture. This comparison shows that gain enhancement is achieved when the metasurface is used, thanks to the increase of effective area. Besides, the bandwidth of this new configuration is not affected, being similar in both cases.

This work contains the numerical study of a highly efficient and ultrathin bi-layer PB HWP metasurface consisting of H-shaped, elements with a transmission efficiency of 90.15% and a thickness < λ/13. A numerical analysis along with the measurements confirmed the device’s ability to convert a CP wave’s handedness at 87 GHz. Furthermore, a metalens composed by identical H-shaped bi-layered PB HWP meta-atoms is numerically demonstrated showing an excellent behavior at 87 GHz.

Gallium arsenide (GaAs) metamorphic high electron mobility transistors (mHEMT) and a grounded coplanar waveguide environment offer remarkable electronic properties, placing them into a key position for millimeter wave (mmW) and sub-mmW power amplifiers (PAs). At these high frequencies it is a great challenge to obtain accurate models that predict the real performance of the active components (i.e. transistors). This paper presents an experimental validation of a cascode configuration based on a multiport transistor model. The inhouse model shows very high accuracy for measurements in a broad range of frequencies (0.1 - 330 GHz). The good correlation of the simulation of the model and the posterior measurements was verified by the fabrication of a G-band (140 - 220 GHz) PA module. The packaged PA showed a small-signal gain of more than 13.4 dB for a broad bandwidth of 56 % and a maximum output power of 4.61 dBm at 210 GHz.

In this work, we develop a novel Monte Carlo method for solving the electromagnetic scattering problem. The method is based on a formal solution of the scattering problem as a modified Born series whose coefficients are found by a conformal transformation. The terms of the Born series are approximated by sampling random elements of its matrix representation, computed by the Method of Moments. Unlike other computational techniques, this Monte Carlo method does not require communications between processors, which makes it suitable for large parallel executions.

A gradient index flat lens with a directive beam-steering radiation pattern and configurable dual circular polarization is discussed in this contribution. The dielectric lens, designed to operate at W band (70-100 GHz), is perforated to achieve a radial decreasing dielectric permittivity characteristic, so high-directivity beam with planar wave front can be obtained. A precisely designed stereolithography 3D structure is adhered to the surface of the lens to turn the vertical or horizontal electric field polarization into RHCP or LHCP, respectively. An open-ended square waveguide is used as feeding structure in order to generate the vertical and horizontal polarization by the excitation of the degenerate modes TE10 and TE01. The system can achieve a wide beam-steering range of ±30° in both azimuth and elevation planes, attained by applying precise displacements to the feeding square waveguide position. In order to experimentally validate the antenna performance, the design is fabricated and measured.

New telecommunication and radar systems at high frequencies require high directive antennas with low scan losses to compensate the path loss and propagation attenuation. Geodesic lens antennas are a good candidate to these new applications since they can provide high directivity, high efficiency and low scan losses. Here, we explain how to produce rotationally symmetric geodesic lenses based on transformation optics. In particular, we calculate the equivalent geodesic shape of a Luneburg lens, which is able to transform cylindrical waves into planar waves. In order to demonstrate the potential of this technique, we designed a 11-port geodesic lens antenna, which is able to scan 120º. The beams have a maximum gain of 20 dB at 30 GHz with 0.5 dB scan losses. We describe possible manufacturing techniques, including their advantages and drawbacks in terms of assembly misaligments, surface roughness and tolerances.