Papers by Eduardo Martinez-de-Rioja
2022 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (AP-S/URSI)
International Journal of RF and Microwave Computer-Aided Engineering
2019 13th European Conference on Antennas and Propagation (EuCAP), 2019
This contribution proposes the use of single and dual reflectarray configurations to provide mult... more This contribution proposes the use of single and dual reflectarray configurations to provide multi-spot coverage in Ka-band from a geostationary satellite, using a smaller number of apertures and feeds than conventional reflector systems. First, a 1.8-m parabolic reflectarray antenna has been designed to produce multiple spot beams through the generation of two beams per feed in orthogonal circular polarization (CP) at Tx and Rx frequencies. Moreover, a dual RA configuration has been designed to produce two spot beams in orthogonal CP from a single feed in dual linear polarization (LP). The simulated results are compared for the two designed antennas, showing the feasibility of both configurations and their potential to be used for multiple beam applications in Ka-band.
Electronics
This paper presents a novel approach to synthesizing curved reflectarrays using Geometrical Optic... more This paper presents a novel approach to synthesizing curved reflectarrays using Geometrical Optics (GO). It introduces the concepts of virtual normal and path length shift, which enable a vector-based formulation of the problem that can be solved using ray tracing techniques. The formulation is applied for the design of two different versions of a Dual Bifocal Reflectarray with a parabolic main surface and a flat subreflectarray. The first version aims to enhance the performance of the multibeam antenna by providing a focal ring located at the feed cluster plane. The second version focuses on improving the scanning characteristics of the antenna in the horizontal plane by incorporating two foci. The synthesis procedure yields samples of the path length shift or its derivatives. To reconstruct the phase distribution, an interpolation scheme is employed and described in this paper. Numerical results are presented for both the focal-ring and two-foci configurations, demonstrating the f...
2023 17th European Conference on Antennas and Propagation (EuCAP)
2023 17th European Conference on Antennas and Propagation (EuCAP)
2021 15th European Conference on Antennas and Propagation (EuCAP), 2021
This contribution presents the design and simulations of a 1.8-m parabolic reflectarray to genera... more This contribution presents the design and simulations of a 1.8-m parabolic reflectarray to generate a multi-spot coverage from a geostationary satellite. The antenna has been designed to generate two spaced beams per feed in orthogonal circular polarizations (CP) simultaneously at transmission and reception frequencies in Ka-band. The parabolic reflectarray operates by the variable rotation technique independently applied at 19.7 GHz and 29.5 GHz to split the orthogonal CP beams focused by the parabolic surface. The proposed design technique and the simulated results have been experimentally validated by the manufacturing and testing of a 0.9-m parabolic reflectarray with the same operating principle. The proposed antenna technology can be used to provide multispot coverages in Kaband from geostationary satellites, with the advantage of reducing to one-half the number of antennas and feed-chains commonly required using conventional reflectors.
2021 15th European Conference on Antennas and Propagation (EuCAP), 2021
This contribution presents the design of a passive shaped-beam reflectarray to improve coverage i... more This contribution presents the design of a passive shaped-beam reflectarray to improve coverage in 5G cellular networks. The reflectarray has been designed to produce a broadened and deflected beam in dual-linear polarization at 27.7 GHz. The unit cell provides more than 360º range of phase variation and a robust performance under large angles of incidence (around 50º). Phase-only synthesis has been applied to obtain the required phase distribution on the reflectarray to fulfill the scenario requirements in terms of beam pointing and HPBW. The designed reflectarray exhibits a stable behavior within the 27.2-28.2 GHz band, showing the potential of this technology for millimeter-wave 5G communications.
2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2018
This communication presents the design of a dual bifocal reflectarray (RA)system consisting of a ... more This communication presents the design of a dual bifocal reflectarray (RA)system consisting of a parabolic main RA and a flat RA sub reflector. The concepts of path length shift and virtual normal are introduced to describe the synthesis procedure. An application example is presented for being used as multifed onboard antenna in satellite communications.
IEEE Transactions on Antennas and Propagation, 2020
The development of base stations (BSs) with large aperture antenna arrays, enabled partially by t... more The development of base stations (BSs) with large aperture antenna arrays, enabled partially by the utilization of cmWave and mmWave frequency bands, will require radiated testing in fading conditions. In this paper, the objective is to investigate the suitable measurement distances and physical dimensions of the over-the-air setups for the performance evaluation of massive multiple-input multiple-output (MIMO) BSs in anechoic chambers with multiple probes. Setup dimension is the major cost factor in the test systems and is thus the key issue to be investigated. The purpose is to determine whether the conventional far field criteria must be followed when determining the range of the setup or if they can be relieved. The impact of limited test setup dimension on various metrics, e.g., far field criteria, field performance within the test area, system link budget analysis, direction of arrival estimation algorithm as well as multiuser MIMO sum-rate capacity are investigated to determine the range of the test setup. It was found that the link budget does not support for the measurement distances claimed by the Fraunhofer distance. Most of the utilized metrics, especially the sum rate capacity, indicate that smaller setup sizes can still yield reasonable measurement accuracy. Simulations were performed at 2.6, 3.5, and 28 GHz frequencies. INDEX TERMS Massive MIMO base station, performance evaluation, over the air testing, multi-probe anechoic chamber setup.
IEEE Transactions on Antennas and Propagation, 2020
Learning models of artificial intelligence can nowadays perform very well on a large variety of t... more Learning models of artificial intelligence can nowadays perform very well on a large variety of tasks. However, in practice, different task environments are best handled by different learning models, rather than a single universal approach. Most non-trivial models thus require the adjustment of several to many learning parameters, which is often done on a case-by-case basis by an external party. Meta-learning refers to the ability of an agent to autonomously and dynamically adjust its own learning parameters or meta-parameters. In this paper, we show how projective simulation, a recently developed model of artificial intelligence, can naturally be extended to account for meta-learning in reinforcement learning settings. The projective simulation approach is based on a random walk process over a network of clips. The suggested meta-learning scheme builds upon the same design and employs clip networks to monitor the agent's performance and to adjust its meta-parameters on the fly. We distinguish between reflex-type adaptation and adaptation through learning, and show the utility of both approaches. In addition, a trade-off between flexibility and learning-time is addressed. The extended model is examined on three different kinds of reinforcement learning tasks, in which the agent has different optimal values of the meta-parameters, and is shown to perform well, reaching near-optimal to optimal success rates in all of them, without ever needing to manually adjust any meta-parameter.
IEEE Antennas and Wireless Propagation Letters, 2020
This letter presents a dual-polarized and dual-frequency reflectarray backed by a frequency selec... more This letter presents a dual-polarized and dual-frequency reflectarray backed by a frequency selective surface (FSS) with application to shared aperture Ku/Ka-band satellite communication antennas. The reflectarray has been designed to operate simultaneously at 20 and 30 GHz (downlink and uplink frequencies in Ka-band) using a single-layer configuration, where the printed elements are etched on the upper substrate of a two-layer triband FSS. The FSS has been designed to be transmissive at 12 GHz (downlink frequency in Ku-band) and reflective at 20 and 30 GHz. An 18 × 18-cm2 prototype has been fabricated and tested, showing a good matching with the simulations. The measured gains are 28.5 dBi at 20 GHz and 32.25 dBi at 30 GHz.
International Journal of Microwave and Wireless Technologies, 2019
A novel dual-polarization, single-layer reflectarray has been designed and manufactured to operat... more A novel dual-polarization, single-layer reflectarray has been designed and manufactured to operate at receive (20 GHz) and transmit (30 GHz) frequencies for Ka-band terminal antennas. The reflectarray unit cell is composed of several types of resonant elements printed on the upper side of a conductor-backed substrate, which are designed to produce a collimated beam at 20 and 30 GHz in dual polarization. Cross-shaped loops are used to provide the required phases at 20 GHz, while crossed dipoles and modified truncated rings are used to control the phasing at 30 GHz. The resonant lengths of the proposed elements have been adjusted cell by cell by means of a two-dimensional interpolation method to achieve the required phase shift at each frequency. Two different feeds have been used to illuminate the reflectarray at 20 and 30 GHz. The measured gain is 28.02 dBi at 20 GHz and 32.14 dBi at 30 GHz. The measurement results show that the radiation patterns of the designed single-layer reflec...
IEEE Antennas and Propagation Magazine, 2019
This paper presents some recent developments in multiple beam antennas (MBAs) based on reflectarr... more This paper presents some recent developments in multiple beam antennas (MBAs) based on reflectarrays for communication satellites in K-and Ka-bands. The existing high throughput satellites commonly employ four reflector antennas to provide cellular coverage formed by multiple spot beams in a four color scheme. Reflectarray antennas are proposed as an attractive solution for the design of novel MBA configurations to produce multi-spot coverage with a smaller number of apertures than conventional MBA systems based on reflector technology. Single and dual reflectarray configurations have been considered for this purpose, exploiting the reflectarrays' ability to produce independent beams in different polarizations and frequencies.
IEEE Antennas and Wireless Propagation Letters, 2018
This paper presents a new bifocal design procedure for dual reflectarray antennas in offset confi... more This paper presents a new bifocal design procedure for dual reflectarray antennas in offset configurations. The technique starts by considering an axially symmetric geometry with the reflectarrays placed in parallel planes, which allows the rotation of a 2D bifocal design around the symmetry axis. To reach a more compact configuration and obtain smoother phase distributions, the reflectarrays are tilted and their phases adjusted by means of a ray-tracing routine. The technique has been validated by numerical simulations through the comparison with a previous center-fed dual reflectarray prototype. Finally, the simulations of an offset dual reflectarray antenna with tilted reflectarrays are presented, providing 0.56º beam spacing at 20 GHz for multi-spot satellite applications in Ka-band.
IEEE Transactions on Antennas and Propagation, 2018
This contribution describes a design concept of a reflectarray antenna to produce four adjacent b... more This contribution describes a design concept of a reflectarray antenna to produce four adjacent beams per feed through the simultaneous use of polarization and frequency discrimination The feed position is computed to produce two adjacent beams in different frequencies accounting for the beam squint effect, which ensures a minimum phase variation between the phase distributions at the two frequencies. The other two beams in orthogonal polarization are generated by implementing in the reflectarray a different phase-shift for each polarization. This contribution presents the design, manufacturing and measurement of a 43-cm demonstrator that operates at transmit frequencies in Ka-band. The proposed concept can be suitable for multiple spot beam satellites in Ka-band, enabling a reduction in the number of antennas and feeds needed to provide the multi-spot coverage.
IEEE Transactions on Antennas and Propagation, 2017
A reflectarray antenna capable of operating independently in the transmit frequencies (from a sat... more A reflectarray antenna capable of operating independently in the transmit frequencies (from a satellite) in Ku-band (11-13 GHz) and Ka-band (19-20 GHz) has been proposed and demonstrated. To prove that independent beams can be optimized in each frequency band using separate feeds, a 25-cm demonstrator that generates a focused beam in dual polarization (linear or circular) has been designed, manufactured, and tested. The reflectarray cells comprise two stacked sets of coupled parallel dipoles for each polarization, which permits an independent optimization of the phase for each frequency and polarization. The simulated and measured radiation patterns for both copolar and crosspolar components are in good agreement in Ku-and Ka-bands.
2016 IEEE International Symposium on Antennas and Propagation (APSURSI), 2016
This contribution describes a design concept based on beam squint effect in printed reflectarrays... more This contribution describes a design concept based on beam squint effect in printed reflectarrays that allows to produce multiple contiguous beams at 19.5 and 20 GHz, by discriminating in frequency. A 1.6-m reflectarray has been proposed to produce 10 beams separated 0.5 degree using five feeds with frequency reuse. The simulated radiation patterns show a peak gain better than 47.6 dBi, with side-lobe levels close to-22 dB. The proposed concept can be suitable for multiple spot beam satellites in Ka-band.
2016 IEEE International Symposium on Antennas and Propagation (APSURSI), 2016
This contribution describes the design of a printed reflectarray antenna to operate at 19.7 and 2... more This contribution describes the design of a printed reflectarray antenna to operate at 19.7 and 29.5 GHz with independent beams in H and V polarizations. A dual-frequency dual-polarization reflectarray cell, made of two stacked sets of parallel dipoles for each polarization, is proposed. The dipole lengths are adjusted to produce the required phase-shift at each frequency and each polarization. A 1.6-m reflectarray has been designed to produce two closely spaced beams in H and V polarizations. The simulated radiation patterns show a gain of 48.3 dBi at 19.7 GHz and 50.7 dBi at 29.5 GHz, with side-lobe levels close to-25 dB and low cross-polar radiation.
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Papers by Eduardo Martinez-de-Rioja