35 research outputs found
Design of new radiating systems and phase shifters for 5G communications at millimeter-wave frequencies
With the arrival of the new generation of communications, known as
5G, the systems that constitute it must offer better performance in terms
of data speed, latency and connection density than the previous generation
of communications. For 5G, an allocation of the frequency ranges that
will support future wireless communications has been established. This
allocation is formed by a range of frequencies corresponding to bands below 6
GHz and the other range of frequencies includes bands above 24 GHz. In the
latter frequency range, which includes part of the millimeter-wave frequency
band (from 30 GHz to 300 GHz), the development of new radio frequency
(RF) components is necessary because their design and manufacture is a
technological challenge.
As the frequency that supports wireless communications increases, propagation
losses also increase. Therefore, these losses must be compensated
by the radiating systems in 5G to make these communications possible. The
RF devices that make up these new systems must provide high antenna gain,
be power efficient and offer spatial reconfigurability of the radiated signal.
In this thesis, the main objective is the design of both guided and radiating
RF devices to provide design solutions for future 5G systems at
millimeter-wave frequencies. In particular, the contributions made have
been to the design of phase shifters and antenna arrays. To improve efficiency
at millimeter-wave frequencies, these devices have been designed in
waveguide technology.
Phase shifters are essential RF devices to control the phase shift of the
electromagnetic wave that will be radiated to a certain spatial direction by
an antenna array. The design of beamforming networks requires the implementation
of phase shifters that produce a fixed or variable phase shift value.
However, the design and fabrication of these devices at millimeter-wave frequencies
is a complex task. In this thesis, four designs of waveguide phase
shifters that produce both fixed and variable phase shift are presented. For
phase shifters that provide a fixed phase shift, the value of this phase shift
along the frequency is tuned in a desired manner by using periodic structures
with higher symmetries. These types of configurations provide both
flexibility in the design process and improved electromagnetic performance
such as greater operating bandwidth. All the phase shifters have been implemented
in gap-waveguide technology to demonstrate its effectiveness in
these devices for millimeter-wave frequencies.
Regarding the radiating systems, two feeding strategies have been considered
in the design process. First, the design of a 70 GHz centered antenna
array implemented in gap-waveguide technology combined with the use of
separate waveguides in E-plane is proposed. In this design, the feed is guided
through a waveguide corporate-feed network. Second, the design of a reflectarray
whose unit cells are formed using three-dimensional geometries is
presented. In this case, the feeding is done in free space by radiation from
a source antenna. In the previous designs, the fabrication of the prototypes
was done by 3D printing based on stereolithography. Finally, using unit
cells with three-dimensional geometries, the design of radiating devices with
more complex functionalities such as reflection/transmission with high directivity
and reconfiguration of the reflected radiation by means of graphene
structures are proposed.Con la llegada de la nueva generación de comunicaciones, denominada
5G, los sistemas que la conforman deben ofrecer unas mejores prestaciones en
términos de velocidad de datos, latencia y densidad de conexiones respecto
a la generación de comunicaciones anterior. Para 5G se ha establecido una
asignación de los rangos de frecuencia que van a soportar las futuras comunicaciones
inalámbricas. Esta asignación se compone por un rango de
frecuencias correspondiente a las bandas por debajo de los 6 GHz y el otro
rango de frecuencias engloba a las bandas por encima de los 24 GHz. En
este ´ultimo rango de frecuencias, en el cual están incluidas parte de la banda
de las frecuencias milimétricas (desde 30 GHz a 300 GHz), es necesario el
desarrollo de nuevos componentes de radiofrecuencia (RF) ya que su diseño
y fabricación supone un reto tecnológico.
Al aumentar la frecuencia que soporta las comunicaciones inalámbricas,
las pérdidas por propagación también aumentan. Es por ello por lo que
estas pérdidas deben ser compensadas por los sistemas radiantes en 5G para
que las comunicaciones sean posibles. Los dispositivos de RF que componen
estos nuevos sistemas deben proporcionar una alta ganancia de antena, ser
eficientes en términos de potencia y ofrecer reconfigurabilidad espacial de la
señal radiada.
En esta tesis, el objetivo principal es el diseño de dispositivos de RF
tanto guiados como radiantes para ofrecer soluciones de diseño a los futuros
sistemas 5G en frecuencias milimétricas. De manera particular, las
contribuciones realizadas han sido al diseño de desfasadores y agrupaciones
de antenas. Para mejorar la eficiencia en frecuencias milimétricas, estos
dispositivos han sido diseñados en tecnología en guía de ondas.
Los desfasadores son dispositivos RF esenciales para controlar el desfase
de la onda electromagnética que será radiada hacia una cierta dirección espacial
por una agrupación de antenas. Las redes de beamforming tienen la
necesidad de implementar en su diseño desfasadores que producen un valor
de desfase fijo o variable. Sin embargo, el diseño y fabricación de estos
dispositivos en frecuencias milimétricas resulta una tarea de alta dificultad.
En esta tesis se presenta cuatro diseños de desfasadores en guía de onda
que producen un desfase tanto fijo como variable. Para los desfasadores
que proporcionan un desfase fijo, el valor de este desfase a lo largo de la
frecuencia es ajustado de manera deseada mediante el uso de estructuras periódicas con simetrías superiores. Este tipo de configuraciones proporcionan
tanto flexibilidad en el proceso de diseño como una mejora de las
características electromagnéticas como puede ser un mayor ancho de banda
de operación. Todos los desfasadores realizados han sido implementados en
tecnología gap waveguide para demostrar su efectividad en estos dispositivos
para frecuencias milimétricas.
Respecto a los sistemas radiantes, se han considerado dos estrategias de
alimentación en el proceso diseño. En primer lugar, se propone el diseño
de un array centrado a 70 GHz implementado en tecnología gap waveguide
combinado con el uso de guías de onda separadas en plano E. En este diseño,
la alimentación es guiada a través de una red de alimentación corporativa
en guía de onda. En segundo lugar, se presenta el diseño de un reflectarray
cuyas celdas unitarias son formadas mediante geometrías tridimensionales.
En este caso, la alimentación se hace en el espacio libre mediante la radiación de una antena fuente. En los anteriores diseños, la fabricación de
los prototipos se realizó mediante impresión 3D basado en estereolitografía.
Finalmente, a través del uso de celdas unitarias con geometrías tridimensionales,
se proponen el diseño de dispositivos radiantes con funcionalidades
más complejas como la reflexión/transmisión con alta directividad y la reconfiguración de la radiación reflejada mediante estructuras con grafeno.Tesis Univ. Granada
Ray-Tracing Model for Generalized Geodesic-Lens Multiple-Beam Antennas
Geodesic lenses are a compelling alternative to traditional
planar dielectric lens antennas, as they are low loss and
can be manufactured with a simple mechanical design. However,
a general approach for the design and analysis of more advanced
geodesic-lens antennas has been elusive, limiting the available
tools to rotationally symmetric surfaces. In this article, we present
a fast and efficient implementation built on geometrical optics
and scalar diffraction theory. A numerical calculation of the
shortest ray path (geodesic) using an open-source library helps
quantify the phase of the electric field in the lens aperture,
while the amplitude is evaluated by applying ray-tube power
conservation theory. The Kirchhoff-Fresnel diffraction formula
is then employed to compute the far field of the lens antenna. This
approach is validated by comparing the radiation patterns of a
transversely compressed geodesic Luneburg lens (elliptical base
instead of circular) with the ones computed using commercial
full-wave simulators, demonstrating a substantial reduction in
computational resources. The proposed method is then used in
combination with an optimization procedure to study possible
compact alternatives of the geodesic Luneburg lens with size
reduction in both the transverse and vertical directions
V-Band Fully Metallic Geodesic Luneburg Lens Antenna
Antennas in emerging millimeter-wave (mm-wave) appli-
cations are often required to have low losses and produce a steerable
directive beam. These properties are achievable with fully metallic
geodesic Luneburg lens antennas. In this communication, we report the
first experimental verification of a geodesic Luneburg lens antenna in the
V-band. The designed lens antenna is fed with 13 waveguides providing
beam switching capability in a 110◦ range. The lens is implemented
in the parallel plate waveguide (PPW) technology. The antenna is
manufactured in two pieces, and a tolerance analysis indicates that
gaps between the pieces can cause a severe performance degradation.
Based on this tolerance analysis, two measures are taken to alleviate
the manufacturing tolerances for the prototype. First, electromagnetic
band gap (EGB) structures are placed around the feeding waveguides.
Second, the electrical contact between the two pieces is improved in
critical regions. Two prototypes are manufactured, one without and one
with the extra measures implemented. The measured radiation patterns
of the prototype without these measures have high side lobes and low
realized gain compared with the simulation. The measurements of the
robust version of the prototype agree well with the simulations and
demonstrate the applicability of geodesic Luneburg lens antennas for
applications in the V-band.Strategic Innovation Program Smarter Electronics System under Project High-Int
2019-02103European Space Agency
European Commission
4000125905/18/NLVR Project
2019-0393
Phase Shifter for Millimeter-Wave Frequency Range Based on Glide Symmetric Structures
The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we propose a mm-wave phase shifter whose elements have a glide-symmetric configuration to achieve a greater phase shift in the same waveguide space than the non-glide-symmetric case. The glide-symmetric phase shifter is implemented in waveguide technology and is formed by rows of metallic pins that produce the desired phase shift. To assess the better performance of the glide-symmetric phase shifter, it is compared to its non-glide-symmetric version whose metallic pins are located only in one of the broad sides of the waveguide. The operating frequency range of the phase shifter is 67 to 75 GHz. Results show a 180 degree phase shift in regard to the reference waveguide without pins, and 50 degrees more than the non-glide-symmetric version.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
3-D Metamaterials: Trends on Applied Designs, Computational Methods and Fabrication Techniques
This work was funded in part by the Predoctoral Grant FPU18/01965 and in part by the
financial support of BBVA Foundation through a project belonging to the 2021 Leonardo Grants for
Researchers and Cultural Creators, BBVA Foundation. The BBVA Foundation accepts no responsibility
for the opinions, statements, and contents included in the project and/or the results thereof, which
are entirely the responsibility of the authors.Metamaterials are artificially engineered devices that go beyond the properties of conventional
materials in nature. Metamaterials allow for the creation of negative refractive indexes;
light trapping with epsilon-near-zero compounds; bandgap selection; superconductivity phenomena;
non-Hermitian responses; and more generally, manipulation of the propagation of electromagnetic
and acoustic waves. In the past, low computational resources and the lack of proper manufacturing
techniques have limited attention towards 1-D and 2-D metamaterials. However, the true potential of
metamaterials is ultimately reached in 3-D configurations, when the degrees of freedom associated
with the propagating direction are fully exploited in design. This is expected to lead to a new era in
the field of metamaterials, from which future high-speed and low-latency communication networks
can benefit. Here, a comprehensive overview of the past, present, and future trends related to 3-D
metamaterial devices is presented, focusing on efficient computational methods, innovative designs,
and functional manufacturing techniques.Predoctoral Grant FPU18/01965BBVA Foundatio
A 1-to-8 Fully Modular Stacked SIW Antenna Array for Millimeter-Wave Applications
This paper presents a vertically stacked SIW antenna array
that enables different array configurations with the minimum number
of SIW layers. This achievement lies in the modular feature offered by
the proposed design. Specifically, 4 distinct array configurations can be
produced with only 3 different design of SIW layers. Depending on the
number of SIW layers employed in the stacked antenna, the directivity
in the E-plane is modified. To obtain an equal and in-phase power
distribution among the array elements, H- and E-plane corporate feeding
networks are efficiently implemented in each array configuration. Array
configurations of 1, 2, 4 and 8 radiating layers are offered by the proposed
modular array, where each radiating layer is formed by 8 H-plane horn
antennas. The simulated directivity for the array configurations ranges
from 15.8 dBi to 23.8 dBi and the main beam direction remains fixed along
the operating frequency range. The array design has been manufactured
and agreement between simulated and measured results are observed.
The measured impedance bandwidth in all the array configurations is
from 35 GHz to 41 GHz (15.79% bandwidth) with a reduction in the
E-plane beamwidth as the number of radiating layers increases.Spanish GovernmentEuropean Commission PID2020-112545RB-C54
Junta de Andalucia B-TIC-402-UGR18
A-TIC-608-UGR20
P18.RT.4830
PYC20-RE-012-UGR
FPU20/00256
FPU18/0196
Optimized Varactor Parasitic Modelling in the Millimeter-Wave Band.
This work explores the utilization of varactors in the millimeter-wave (mm-wave) band, specifically focusing on their application in voltage-controlled reconfigurable devices. Varactors, or variable capacitors, can adjust capacitance through voltage control, making them ideal for creating rapidly variable systems for radiofrequency (RF) applications. However, parasitic elements in varactors can significantly affect their performance when moving up to the millimeter-wave band and limit their efficiency. Therefore, this work aims to present an optimization approach that accurately calculates the parasitic model for these varactors.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Holey SIW Horn Antenna Based on an H-plane Lens-wise Wavefront Collimation
This paper presents an H-plane SIW horn antenna whose
directivity is enhanced using holey unit cells along the horn flaring. By
wisely drilling the horn antenna, it is possible to reduce the phase error in
the aperture which is a common problem in horn antennas if the optimum
dimensions are not employed. An analysis of the distribution of the unit
cells along the horn antenna has been carried out to achieve the desired
equivalent refractive indices. By changing the hole radius, different
equivalent refractive indices can be tuned with a wideband performance.
This fact enables the implementation of a collimation zone inside the horn
antenna which transforms the pseudo-circular wavefront into a quasiplanar
one in the radiating aperture. The produced directivity is similar
to the horn antenna with the optimum dimensions but a longitudinal
reduction of 53.7% and a higher realized gain are achieved. A holey
SIW horn antenna is designed and manufactured. The measured results
show an impedance bandwidth performance below -10 dB from 34.3
GHz to 44.5 GHz (25.9%) with a realized gain above 10 dBi. The gain
difference regarding a SIW horn antenna without the collimation zone
is about 2-3 dBi in the operating frequency range
Gain-Reconfigurable Hybrid Metal-Graphene Printed Yagi Antenna for Energy Harvesting Applications
This paper presents a hybrid metal-graphene printed Yagi antenna with reconfigurable gain that operates in the 5.5-GHz band. The balun and the driven elements are made of copper, while the directors are made of graphene. The graphene acts as a tunable material in the design. By switching the conductivity of the graphene, it is achieved a similar effect to adding or subtracting directors in the antenna. Hence the gain of the printed Yagi can be easily controlled. This could be of special interest in RF energy harvesting in the design of reconfigurable harvesting elements.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Cross-Polarization Control in FSSs by Means of an Equivalent Circuit Approach
This work was supported in part by Spanish Research and Development National Program under Project TIN2016-75097-P, Project RTI2018-102002-A-I00, Project TEC2017-84724-P, Project PID2020-112545RB-C54, and Project EQC2018-004988-P; in part by the Predoctoral under Grant FPU18/01965; and in part by Junta de Andalucia under Project P18-RT-4830 and Project B-TIC-402-UGR18.This paper presents an ef cient equivalent circuit approach (ECA), based on a Floquet modal
expansion, for the study of the co- and cross-polarization in frequency selective surfaces (FSS) formed by
periodic arrays of patches/apertures in either single or stacked con gurations. The ECA makes it possible the
derivation of analytical expressions for the generalized scattering parameters associated with the proposed
circuit networks. Furthermore, the proposed circuit approach is an ef cient surrogate model that can be
combined with optimization techniques and arti cial intelligence algorithms for the ef cient design of FSS
structures, saving efforts in the computation compared to time-consuming full-wave simulators and tedious
synthesis (simulation-assisted) techniques. Due to the simplicity of the topology of the involved networks,
the ECA can also be advantageously used to gain physical insight. The proposed approach is applied and
validated in different FSS con gurations where the cross-pol component plays a fundamental role in the
design, as in circular polarizers, polarization rotators, and reflectarray cells.Spanish Research and Development National Program TIN2016-75097-P
RTI2018-102002-A-I00
TEC2017-84724-P
PID2020-112545RB-C54
EQC2018-004988-P
FPU18/01965Junta de Andalucia P18-RT-4830
B-TIC-402-UGR1