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19 pages, 2747 KiB

Open AccessFeature PaperArticle

Efficient General Reflectarray Design and Direct Layout Optimization with a Simple and Accurate Database Using Multilinear Interpolation

by Daniel R. Prado, Jesús A. López-Fernández and Manuel Arrebola

Electronics 2022, 11(2), 191; https://doi.org/10.3390/electronics11020191 - 08 Jan 2022

Cited by 2 | Viewed by 1603

Abstract

In this work, a simple, efficient and accurate database in the form of a lookup table to use in reflectarray design and direct layout optimization is presented. The database uses N-linear interpolation internally to estimate the reflection coefficients at coordinates that are not [...] Read more.

In this work, a simple, efficient and accurate database in the form of a lookup table to use in reflectarray design and direct layout optimization is presented. The database uses N-linear interpolation internally to estimate the reflection coefficients at coordinates that are not stored within it. The speed and accuracy of this approach were measured against the use of the full-wave technique based on local periodicity to populate the database. In addition, it was also compared with a machine learning technique, namely, support vector machines applied to regression in the same conditions, to elucidate the advantages and disadvantages of each one of these techniques. The results obtained from the application to the layout design, analysis and crosspolar optimization of a very large reflectarray for space applications show that, despite using a simple N-linear interpolation, the database offers sufficient accuracy, while considerably accelerating the overall design process as long as it is conveniently populated. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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13 pages, 12589 KiB

Open AccessArticle

Fully Metallic Reflectarray for the Ku-Band Based on a 3D Architecture

by Jaime Velasco, Ignacio Parellada-Serrano and Carlos Molero

Electronics 2021, 10(21), 2648; https://doi.org/10.3390/electronics10212648 - 29 Oct 2021

Cited by 3 | Viewed by 2064

Abstract

This document presents the design and manufacture of a reflectarray (RA) antenna for the Ku-band that is based on a fully-metallic 3D architecture. The reflectarray unit cell is formed by a square-shaped waveguide section ending in a short circuit, which is the reflectarray [...] Read more.

This document presents the design and manufacture of a reflectarray (RA) antenna for the Ku-band that is based on a fully-metallic 3D architecture. The reflectarray unit cell is formed by a square-shaped waveguide section ending in a short circuit, which is the reflectarray back ground plane. Each cell has the ability of configuring the phase of its own reflected field by means of resonators perforated on the walls of the cell waveguide section. The resonator-based waveguide cell introduces the 3D character to the design. The geometry of the resonators and the size variation introduces the phase behavior of each cell, thus, conforming the radiation pattern of the reflectarray. This design explores the potential of phase value truncation (six states and two states) and demonstrates that proper pattern results can be obtained with this phase truncation. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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13 pages, 5752 KiB

Open AccessArticle

Shaped-Beam Reflectarray Design by Means of Social Network Optimization (SNO)

by Michele Beccaria, Alessandro Niccolai, Riccardo E. Zich and Paola Pirinoli

Electronics 2021, 10(6), 744; https://doi.org/10.3390/electronics10060744 - 21 Mar 2021

Cited by 4 | Viewed by 1906

Abstract

In this work, an innovative approach for the design of a shaped-beam reflectarray (RA) is presented. It is based on the use of a novel evolutionary algorithm (EA), named Social Network Optimization (SNO), that presents good capabilities in terms of convergence and reliability, [...] Read more.

In this work, an innovative approach for the design of a shaped-beam reflectarray (RA) is presented. It is based on the use of a novel evolutionary algorithm (EA), named Social Network Optimization (SNO), that presents good capabilities in terms of convergence and reliability, and therefore it is suitable for optimizing a complex problem such as the one of interest. The full-wave analysis of a small–medium configuration designed with the proposed approach and the experimental characterization of a prototype proved the effectiveness of the adopted method. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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12 pages, 8670 KiB

Open AccessArticle

Real-Time Mode Switching and Beam Scanning of High-Gain OAM Waves Using a 1-Bit Reconfigurable Reflectarray Antenna

by Ziyang Wang, Xiaotian Pan, Fan Yang, Shenheng Xu and Maokun Li

Electronics 2020, 9(12), 2181; https://doi.org/10.3390/electronics9122181 - 18 Dec 2020

Cited by 15 | Viewed by 3297

Abstract

A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. [...] Read more.

A reconfigurable electromagnetic surface has been studied to realize the adjustable orbital angular momentum (OAM) beams for real-time wireless communication and dynamic target detection in the future. OAM mode switching realized by many previous designs suffers from low gains without OAM beam scanning. In this article, a 1-bit reconfigurable reflectarray antenna is designed, fabricated, and tested for the real-time control of OAM mode switching and large-angle vortex beam scanning in three-dimensional space. The proposed reflectarray surface is composed of 1-bit electronically reconfigurable cells, and the size is 24 λ × 24 λ with 2304 units. The reconfigurable element is designed by using a radiation patch loading a PIN diode with effective control of two states, “ON” and “OFF”, for the demand of 180° phase difference. The reflectarray surface can be assigned to a code sequence of 0 or 1 by the Field-Programmable Gate Array (FPGA) in real time. Henceforth, the coding surface can dynamically control the generation of high-gain OAM beams, where only the optimized phase distributions on the surface need to be changed according to demand. To verify the concept, a large-scale reflectarray surface is fabricated and measured with an oblique feed at 15°. Different OAM-carrying phase distributions for different OAM beam states are calculated and tested. The test results show that the OAM mode switching between l = 1 and l = 2 is realized, and other variable modes such as l = 3 or l = 5 can also be achieved by modifying the phase encoding sequence. Furthermore, the direction of the vortex beams can be accurately controlled with gains over 20 dBi, and the large-angle vortex beam scanning is verified. Therefore, all results demonstrate that the proposed 1-bit reconfigurable reflectarray is efficient for the regulation and control of OAM-carrying beams for the demand of real-time dynamic wireless communications in the future. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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18 pages, 1467 KiB

Open AccessFeature PaperArticle

Systematic Study of the Influence of the Angle of Incidence Discretization in Reflectarray Analysis to Improve Support Vector Regression Surrogate Models

by Daniel R. Prado, Jesús A. López-Fernández and Manuel Arrebola

Electronics 2020, 9(12), 2105; https://doi.org/10.3390/electronics9122105 - 10 Dec 2020

Cited by 7 | Viewed by 1795

Abstract

A systematic study concerning the discretization of the angle of incidence in surrogate models obtained with support vector regression (SVR) is presented. The problem addressed in this work arises from the dependence of the reflection coefficients on the angle of incidence. While the [...] Read more.

A systematic study concerning the discretization of the angle of incidence in surrogate models obtained with support vector regression (SVR) is presented. The problem addressed in this work arises from the dependence of the reflection coefficients on the angle of incidence. While the direct coefficients are usually stable with the angle of incidence, this is not the case with the cross-coefficients, which translates this behavior to the crosspolar component of the radiation pattern. Then, correctly assessing this influence and minimizing radiation pattern distortion allow training SVR surrogate models per angle of incidence without penalizing accuracy in the prediction of the far field. The results shown in this work are directly relevant to improving the computational performance of SVRs applied to reflectarray design since they allow reducing the dimensionality of the models by generating surrogate models per angle of incidence instead of including the angles of incidence as input variables. In addition, it highlights the importance of a proper discretization of the angles of incidence for a correct prediction of the crosspolar pattern for its subsequent optimization, especially for advanced space applications with tight crosspolar requirements. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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17 pages, 4098 KiB

Open AccessCommunication

Fast Preconditioner Computation for BICGSTAB-FFT Method of Moments with NURBS in Large Multilayer Structures

by Rafael Florencio, Álvaro Somolinos, Iván González and Felipe Cátedra

Electronics 2020, 9(11), 1938; https://doi.org/10.3390/electronics9111938 - 17 Nov 2020

Cited by 1 | Viewed by 1390

Abstract

Fast computation of the coefficients of the reduced impedance matrix of the method of moment (MM) is proposed by expanding the basis functions (BFs) in pulses and solving an equivalent periodic problem (EPP) for analyzing large multilayer structures with non-uniform rational basis spline [...] Read more.

Fast computation of the coefficients of the reduced impedance matrix of the method of moment (MM) is proposed by expanding the basis functions (BFs) in pulses and solving an equivalent periodic problem (EPP) for analyzing large multilayer structures with non-uniform rational basis spline (NURBS) modeling of the embedded layout. These coefficients are required by the computation of sparse approximate inverse (SAI) preconditioner, which leads an efficient iterative version of the MM. This reduced coefficient matrix only considers the near field part of the MM matrix. Discrete functions of small sizes are required to implement the pulse expansion and EPP. These discrete functions of small size lead to discrete cyclic convolutions that are computed in a very fast way by fast Fourier transform (FFT)-accelerated matrix–vector multiplication. Results obtained using a conventional laptop show an analysis of very large multilayer structures with resonant layouts, as whole reflectarrays of electrical size 40 times the vacuum wavelengths, where the iterative MM with a SAI preconditioner can be 22.7 times faster than the pure iterative MM without any preconditioner. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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17 pages, 4335 KiB

Open AccessArticle

BICGSTAB-FFT Method of Moments with NURBS for Analysis of Planar Generic Layouts Embedded in Large Multilayer Structures

by Rafael Florencio, Álvaro Somolinos, Iván González and Felipe Cátedra

Electronics 2020, 9(9), 1476; https://doi.org/10.3390/electronics9091476 - 09 Sep 2020

Cited by 3 | Viewed by 1827

Abstract

BICGSTAB-FFT method of moment (MM) scheme is proposed to analyze several levels of planar generic layouts embedded in large multilayer structures when the layout geometries are modeled by NURBS surfaces. In this scheme, efficient computation of normalized error defined in iterative bi-conjugate gradient [...] Read more.

BICGSTAB-FFT method of moment (MM) scheme is proposed to analyze several levels of planar generic layouts embedded in large multilayer structures when the layout geometries are modeled by NURBS surfaces. In this scheme, efficient computation of normalized error defined in iterative bi-conjugate gradient stabilized (BICGSTAB) method for large multilayer structure analysis problems is implemented. The efficient computation is based on pulse expansion with dense equi-spaced mesh of generalized rooftop basis functions (BFs) defined on NURBS surfaces and equivalent periodic problem (EPP) in order to apply fast Fourier transforms (FFT). Moreover, efficient computation of Green’s functions for multilayer structure is implemented for near and far field regions. Experimental and numerical validations of whole printed reflect array antennas of electrical size between 8 and 16 times the vacuum wavelengths are shown. In these validations, CPU time consumptions of the proposed method are obtained with results between few minutes and half an hour using a conventional laptop. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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15 pages, 3014 KiB

Open AccessArticle

Design of Ku- and Ka-Band Flat Dual Circular Polarized Reflectarrays by Combining Variable Rotation Technique and Element Size Variation

by Rafael Florencio, Daniel Martinez-de-Rioja, Eduardo Martinez-de-Rioja, Jose A. Encinar, Rafael R. Boix and Vicente Losada

Electronics 2020, 9(6), 985; https://doi.org/10.3390/electronics9060985 - 12 Jun 2020

Cited by 4 | Viewed by 3079

Abstract

In this work circularly polarized flat reflectarray antennas are designed to work at downlink frequencies in Ku- and Ka-band. The design approach for circular polarization radiation combines both the variable rotation technique (VRT) and the element size variation technique (ESVT). The reflectarray element [...] Read more.

In this work circularly polarized flat reflectarray antennas are designed to work at downlink frequencies in Ku- and Ka-band. The design approach for circular polarization radiation combines both the variable rotation technique (VRT) and the element size variation technique (ESVT). The reflectarray element employed consists of a rotable split ring operating at 12 GHz (Ku-band) that surrounds two orthogonal sets of parallel dipoles of variable size operating at 20 GHz (Ka-band). Rotations of split rings and different sizes of dipoles are exploited as degrees of freedom by VRT and ESVT for designing focused beams dual band dual circular polarized reflectarrays. The split ring can be used to achieve single focused beams for circular polarization by VRT at 12 GHz, and the set of orthogonal dipoles can be used to achieve two focused beams for dual circular polarization by ESVT at 20 GHz. In this way, the reflectarray element has been used to design two flat dual band circularly polarized reflectarrays that generate three pencil beams either in the same direction or in different directions: one pencil beam with right-hand circular polarization (RHCP) at 12 GHz and two pencil beams with both RHCP and left-hand circular polarization (LHCP) at 20 GHz. The designed reflectarrays are carried out under local periodicity assumption by means of in-house electromagnetic software that applies the Method of Moments in the Spectral Domain. Validations of the in-house electromagnetic software show significant CPU time savings with respect to CPU time consumption provided by commercial software of general purpose as CST electromagnetics software. Numerical results of radiation patterns produced by the designed reflectarrays show efficiencies around 65% and a bandwidth of 6% for a main beam cross-polarization discrimination of 25 dB. The numerical results are satisfactorily validated by CST software and a tolerance errors study has been numerically carried out with acceptable results. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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16 pages, 3942 KiB

Open AccessArticle

Bifocal Dual-Reflectarray Antenna to Generate a Complete Multiple Spot Beam Coverage for Satellite Communications in Ka-Band

by Eduardo Martinez-de-Rioja, Jose A. Encinar and Giovanni Toso

Electronics 2020, 9(6), 961; https://doi.org/10.3390/electronics9060961 - 09 Jun 2020

Cited by 2 | Viewed by 3913

Abstract

This paper presents a novel multibeam transmitting dual-reflectarray antenna able to generate a complete multiple spot coverage from a geostationary satellite in Ka-band (20 GHz). The bifocal design technique has been exploited for the first time to reduce by 50% the beam deviation [...] Read more.

This paper presents a novel multibeam transmitting dual-reflectarray antenna able to generate a complete multiple spot coverage from a geostationary satellite in Ka-band (20 GHz). The bifocal design technique has been exploited for the first time to reduce by 50% the beam deviation factor with respect to the equivalent monofocal antenna, allowing to produce adjacent beams separated by only 0.56° in the antenna offset plane. In order to guarantee an acceptable spillover, the main reflectarray has been oversized in the same plane where the beams are compressed, resulting in an elliptical reflectarray of 3.5 m × 1.8 m. The interleaved beams required to provide the complete multi-spot coverage are produced in the orthogonal polarization, using the same aperture and feeds. The proposed antenna requires a smaller main aperture (about half of the area) and a lower number of feeds than other configurations that use a single oversized reflector to generate a complete multi-spot coverage, showing promising results for communication satellite applications in the Ka-band. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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Review

Jump to: Research

26 pages, 6711 KiB

Open AccessReview

Aspects of Efficiency Enhancement in Reflectarrays with Analytical Investigation and Accurate Measurement

by M. Hashim Dahri, M. Haizal Jamaluddin, Fauziahanim C. Seman, M. Inam Abbasi, N. Fazreen Sallehuddin, Adel Y. I. Ashyap and M. Ramlee Kamarudin

Electronics 2020, 9(11), 1887; https://doi.org/10.3390/electronics9111887 - 10 Nov 2020

Cited by 11 | Viewed by 3582

Abstract

This paper presents a thorough review of the techniques involved in the enhancement of the efficiency performance of the reflectarray antenna. The effect of the selection of a suitable patch element or a proper feeding mechanism on efficiency improvement is studied in detail. [...] Read more.

This paper presents a thorough review of the techniques involved in the enhancement of the efficiency performance of the reflectarray antenna. The effect of the selection of a suitable patch element or a proper feeding mechanism on efficiency improvement is studied in detail. Reflectarray loss quantification is examined in relation to the design techniques involved in the efficiency improvement. A low loss patch element with a wide reflection phase range and a properly illuminated reflectarray aperture are supposed to offer high efficiency performance. Additionally, the placement, the orientation and the position of a patch element on the reflectarray surface can also affect its efficiency performance. Mathematical equations were developed to estimate the efficiencies of circular and square aperture reflectarray antennas by considering their feed footprints. Moreover, a step by step practical method of predicting and measuring the total efficiency of a reflectarray antenna is presented. The two selected apertures of the reflectarray consisting of the square patch element configuration are fabricated and measured at a frequency of 26 GHz. Their measured efficiencies have been estimated using the derived equations, and the results were compared and validated using the efficiencies obtained by the conventional gain-directivity relation. Full article

(This article belongs to the Special Issue New Trends in Reflectarray and Transmitarray Antennas)

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