Time-Modulated Phased Array Controlled With Nonideal Bipolar Squared Periodic Sequences

© 2019 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/LAWP.2019.2892657.[Abstract]: Bipolar (±1) sequences with no zero state suit particularly well for safeguarding the switched feeding network efficiency when applied to time-modulated arrays. During the zero state of a conventional time-modulating sequence, if a given array element is switched off, a certain amount of energy of the transmitted/received signal is wasted. We propose a novel single sideband time-modulated phased array (TMPA) architecture governed by realistic bipolar squared sequences in which the rise/fall time of the switches is considered. By using single-pole dual-throw switches and nonreconfigurable passive devices, the TMPA exploits, exclusively, the first positive harmonic pattern while exhibiting an excellent performance in terms of efficiency and control level of the undesired harmonics without using synthesis optimization algorithms (software simplicity).This work has been funded by the Xunta de Galicia (ED431C 2016-045, ED341D R2016/012, ED431G/01), the Agencia Estatal de Investigaci´on of Spain (TEC2015-69648-REDC, TEC2016-75067-C4-1-R) and ERDF funds of the EU (AEI/FEDER, UE).Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

Analog Beamforming Using Time-Modulated Arrays With Digitally Preprocessed Rectangular Sequences

© 2018 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/LAWP.2018.2797971.[Abstract]: Conventional time-modulated arrays are based on the application of variable-width periodical rectangular pulses (easily implemented with radio frequency switches) to the individual antenna excitations. However, a serious bottleneck arises when the number of exploited harmonic beams increases. In this context, the modest windowing features of the rectangular pulses produce an inflexible and ineffective harmonic beamforming. The use of other pulses, such as sum of weighted cosines, partially solves these issues at the expense of introducing additional non-timing variables. We propose the discrete-time preprocessing of rectangular pulses before being applied to the antenna to accomplish an agile, efficient, and accurate harmonic beamforming, while keeping the simplicity of the hardware structure.This work has been funded by the Xunta de Galicia (ED431C 2016-045, ED341D R2016/012, ED431G/01), the Agencia Estatal de Investigación of Spain (TEC2013-47141-C4-1-R, TEC2015-69648-REDC, TEC2016-75067- C4-1-R) and ERDF funds of the EU (AEI/FEDER, UE).Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

Dual-Signal Transmission Using RF Precoding and Analog Beamforming With TMAs

© 2018 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/LCOMM.2018.2848274[Absctract]: Time-modulated arrays (TMAs) receiving beamforming provide a noteworthy hardware simplicity given the ability of this multi-antenna technique to transform spatial diversity into frequency diversity. However, the dual behavior at transmission seems to be as simple as limited: a given signal is simultaneously transmitted over all the different TMA harmonic patterns. We investigate the efficient and simultaneous transmission of two different signals over the same physical antenna using two independent harmonic beam-patterns of the TMA. For that purpose, we propose an innovative dual-signal TMA transmitter based on two complementary operations: the complex mixing of the baseband signals and the TMA processing with quadrature and time-delayed periodic pulses.This work has been funded by the Xunta de Galicia (ED431C 2016-045, ED341D R2016/012, ED431G/01), the Agencia Estatal de Investigación of Spain (TEC2015-69648-REDC, TEC2016-75067-C4-1-R) and ERDF funds of the EU (AEI/FEDER, UE).Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

Time-Modulated Multibeam Phased Arrays With Periodic Nyquist Pulses

© 2018 IEEE. This version of the article has been accepted for publication, after peer review. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. The Version of Record is available online at: https://doi.org/10.1109/LAWP.2018.2880087.[Abstract]: We present a single sideband time-modulated multibeam phased array governed by periodic Nyquist pulsed signals. A Nyquist pulse is a physically realizable approach to the ideal sinc function. Hence, its low-pass spectrum suits particularly well for time-modulated arrays (TMAs) to perform harmonic beam steering. Contrarily to switched TMAs and standard solutions based on variable phase shifters, the performance and complexity of the proposed time modulation scheme is rather robust when increasing the number of multibeams.This work has been funded by the Xunta de Galicia (ED431C 2016-045, ED341D R2016/012, ED431G/01), the Agencia Estatal de Investigaci´on of Spain (TEC2015-69648-REDC, TEC2016-75067-C4-1-R) and ERDF funds of the EU (AEI/FEDER, UE).Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

Time-modulated multibeam phased arrays with periodic Nyquist pulses

We present a single sideband time-modulated multibeam phased array governed by periodic Nyquist pulsed signals. A Nyquist pulse is a physically realizable approach to the ideal sinc function. Hence, its low-pass spectrum suits particularly well for time-modulated arrays (TMAs) to perform harmonic beam steering. Contrarily to switched TMAs and standard solutions based on variable phase shifters, the performance and complexity of the proposed time modulation scheme is rather robust when increasing the number of multibeams.Comment: 4 pages, 4 figures, Published in IEEE Antennas and Wireless Propagation Letter

Hybrid Precoding With Time-Modulated Arrays for Mmwave MIMO Systems

[Abstract]: We consider the utilization of time-modulated arrays (TMAs) as a simple and cost-effective approach to hybrid digital–analog precoding in millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems. Instead of conventional variable phase shifters (VPSs), our proposed TMA hybrid precoders use radio frequency (RF) switches followed by 1-bit VPSs in the analog part. We study the insertion losses at mmWave of a TMA analog precoding network in terms of sideband radiation and hardware efficiency. In addition, we present different algorithms for the design of both the baseband and RF parts of a TMA hybrid precoder. The proposed methods exhibit different tradeoffs between performance, complexity, and power efficiency. Finally, TMA precoders are compared to those implemented with conventional VPSs in terms of insertion losses, chip area, and cost, concluding that precoding with TMAs is a competitive solution for mmWave MIMO systems.This work was supported in part by the Xunta de Galicia under Grant ED431C 2016-045, Grant ED341D R2016/012, and Grant ED431G/01, in part by the AEI of Spain under Grant TEC2015-69648-REDC and Grant TEC2016-75067-C4-1-R, and in part by ERDF funds under Grant AEI/FEDER, EU.Xunta de Galicia; ED431C 2016-045Xunta de Galicia; ED341D R2016/012Xunta de Galicia; ED431G/0

Estudio de los efectos producidos por la modulación temporal aplicada a una agrupación de antenas en sistemas de transmisión digital

Programa Oficial de Doutoramento en Tecnoloxías da Información e as Comunicacións en Redes Móbiles. 5032V0[Resumo] Os selos de identidade das comunicacións móbiles e sen fíos de hoxe en día son a demanda continua e crecente de mobilidade, capacidade e fiabilidade, xunto cun firme e definitivo compromiso coa sustentabilidade. Baixo estas premisas, as antenas intelixentes –capaces de sensar a contorna electromagnética e adaptar de xeito eficaz as súas características de radiación– están chamadas a xogar un papel crucial nas ditas comunicacións. Neste senso, os estándares sen fíos actuais consideran técnicas multi-antena encamiñadas a explotar a diversidade espacial, o multiplexado espacial e o conformado de feixe, acadando así mellores niveis de fiabilidade e capacidade. Con todo, ditas vantaxes obtéñense a expensas dun incremento da complexidade do sistema, factor non sempre asumible en termos de tamaño e eficiencia enerxética. Consecuentemente, suscítanse unha serie de retos de cara a desenvolver tecnoloxías de antena axeitadas e capaces de dar resposta ás anteriores prestacións no espazo limitado que dita a mobilidade. O concepto de agrupación de antenas modulada temporalmente (TMAs, do inglés time-modulated arrays) é unha técnica multi-antena que achega unha simplificación hardware significativa: o seu diagrama de radiación contrólase mediante a sinxela aplicación de pulsos periódicos de duración variable ás excitacións individuais da agrupación. A natureza non lineal desta operación causa a aparición de diagramas de radiación nas frecuencias harmónicas dos pulsos periódicos aplicados. A técnica pode empregarse para mellorar a topoloxía do nivel dos lóbulos secundarios do diagrama de radiación na frecuencia central e/ou para explotar de xeito proveitoso os diagramas dos harmónicos, dotando á antena de capacidades de antena intelixente. Esta tese é o resultado dunha investigación das TMAs dende unha perspectiva interdisciplinaria, é dicir, non soamente dende a óptica do diagrama de radiación ou das agrupacións de antenas, senón tamén dende un punto de vista de procesado do sinal. Máis concretamente, a tese é unha análise en profundidade da aplicación das TMAs ás comunicacións dixitais, desenvolvida en catro etapas: 1) análise matemática da posibilidade de transmitir sinais dixitais mediante TMAs, identificando as restricións para salvagardar a integridade do sinal e cuantificando a potencia radiada, 2) caracterización da taxa de erro de bit dun sistema de comunicación dixital que incorpora un TMA en recepción explotando o seu modo fundamental e considerando canles con ruído branco Gaussiano, 3) estudo das prestacións das TMAs –explotando os harmónicos– na recepción de sinais de comunicación dixitais con diversidade angular en canles multitraxecto con esvaecemento, 4) caracterización de TMAs para conformado de feixe mediante o uso de pulsos de suma de cosenos ponderados no lugar de pulsos rectangulares, chegando ás denominadas TMAs melloradas, dotadas dunha resposta superior en termos de flexibilidade e eficiencia.[Resumen] Hoy en día, los sellos de identidad de las comunicaciones inalámbricas son la demanda continua y creciente de movilidad, capacidad y fiabilidad, junto con un firme y definitivo compromiso con la sostenibilidad. Bajo estas premisas, las antenas inteligentes –capaces de sensar el entorno electromagnético y adaptar de forma eficaz sus características de radiación– están llamadas a jugar un papel crucial en dichas comunicaciones. En este sentido, los estándares inalámbricos actuales consideran técnicas multiantena encaminadas a explotar la diversidad espacial, el multiplexado espacial o el conformado de haz, alcanzando así mejores niveles de fiabilidad y capacidad. Sin embargo, dichas ventajas se obtienen a expensas de un incremento de la complejidad del sistema, factor no siempre asumible en términos de tamaño y eficiencia energética. En consecuencia, se plantean una serie de retos en el desarrollo de tecnologías de antena adecuadas, capaces de dar respuesta a las anteriores prestaciones en el espacio limitado que dicta la movilidad. El concepto de agrupación de antenas modulada temporalmente (TMAs, del inglés time-modulated arrays) es una técnica multiantena que aporta una simplificación hardware significativa: su diagrama de radiación se controla mediante la sencilla aplicación de pulsos periódicos de duración variable a las excitaciones individuales de la agrupación. La naturaleza no lineal de esta operación causa la aparición de diagramas de radiación en las frecuencias armónicas de los pulsos periódicos aplicados. La técnica se puede utilizar para mejorar la topología del nivel de los lóbulos secundarios del diagrama de radiación en la frecuencia central y/o para explotar de forma beneficiosa los diagramas de armónicos, dotando a la antena de capacidades de antena inteligente. Esta tesis es el resultado de una investigación de las TMAs desde una perspectiva interdisciplinar, es decir, no solamente desde la óptica del diagrama de radiación o de las agrupaciones de antenas, sino también desde un punto de vista de procesado de señal. Más concretamente, la tesis es un análisis en profundidad de la aplicación de las TMAs a las comunicaciones digitales, desarrollada en cuatro etapas: 1) análisis matemático de la factibilidad de transmitir señales digitales mediante TMAs, identificando las restricciones para salvaguardar la integridad de la señal y cuantificando la potencia radiada, 2) caracterización de la tasa de error de bit de un sistema de comunicación digital que incorpora una TMA en recepción explotando su modo fundamental y considerando canales con ruido blanco Gaussiano, 3) estudio de las prestaciones de las TMAs –explotando los armónicos– en la recepción de señales digitales con diversidad angular en canales multitrayecto con desvanecimiento, 4) caracterización de TMAs para conformado de haz mediante el uso de pulsos de suma de cosenos ponderados en lugar de pulsos rectangulares, llegando a las denominadas TMAs mejoradas, dotadas de una respuesta superior en términos de flexibilidad y eficiencia.[Abstract] An ever-increasing demand for higher mobility, capacity and reliability, together with a definitive compromise with sustainability, are the hallmarks of mobile and wireless communications systems nowadays. Under these premises, smart antenna devices –capable of sensing the electromagnetic environment and suitably adapting its radiation features– are correspondingly called to play a crucial role. In this sense, today’s wireless standards consider multiple-antenna techniques in order to exploit space diversity, spatial multiplexing and beamforming to achieve better levels of reliability and capacity. Such advantages, however, are obtained at the expense of increased system complexity which may be unaffordable in terms of size and energy efficiency. Consequently, some technical challenges remain to develop the adequate antenna technologies capable of supporting the aforementioned features in a limited physical space that the mobility demand dictates. The concept of time-modulated array (TMA) is a feasible multi-antenna technique that provides a significant hardware simplification: its radiated power pattern is controlled by the simple application of variable-width periodical pulses to the individual array excitations. The nonlinear nature of such an array operation causes the appearance of radiation patterns at the harmonic frequencies of the applied periodic pulses. The technique can be used for improving the side-lobe level topology of the radiation pattern at the central frequency and/or to profitably exploit the harmonic patterns in order to supply smart antenna capabilities. This thesis is the result of an investigation of TMAs from an interdisciplinary perspective, i.e., not only under a radiation pattern or an antenna array outlook but also from a signal processing point of view. More specifically, the thesis deals with an in-depth analysis of the application of TMAs in digital communications developed in four stages: 1) mathematical analysis of the feasibility of transmission of digital signals over TMAs, identifying the restrictions to safeguard the integrity of the signal and quantifying the radiated power, 2) characterization of the bit error rate of a digital communication system that incorporates a receive-TMA exploiting its fundamental mode and considering additive white Gaussian noise channels, 3) study of the performance of TMAs –exploiting their harmonics– for the angle diversity reception of digital communication signals over multipath fading channels, 4) an approach to the characterization of beamforming TMAs which use sum of weighted cosines pulses instead of rectangular ones, leading to the so-called enhanced time-modulated arrays, which endows them with a better response in terms of flexibility and efficiency

Efficient wireless coverage of in-building environments with low electromagnetic impact

The city of tomorrow is a major integrating stake, which crosses a set of major broad spectrum domains. One of these areas is the instrumentation of this city and the ubiquity of the exchange of data, which will give the pulse of this city (sensors) and its breathing in a hyper-connected world within indoor and outdoor dense areas (data exchange, 5G and 6G). Within this context, the proposed doctorate project has the objective to realize cost- and energy- effective, short-range communication systems for the capillary wireless coverage of in-door environments with low electromagnetic impact and for highly dense outdoor networks. The result will be reached through the combined use of: 1) Radio over Fiber (RoF) Technology, to bring the Radio Frequency (RF) signal to the different areas to be covered. 2) Beamforming antennas to send in real time the RF power just in the direction(s) where it is really necessary