Reflectarray Element Research Articles

Single-Layer Metasurface-Based Reflectarray Antenna with H-Shaped Slotted Patch for X-Band Communication.

In this study, a metasurface-based reflectarray is designed for X-band applications. The unit cells are equipped with an H-shaped slotted patch for additional resonance and phase range. Linear phase variation by altering the length of the patch is realized with a range exceeding 480∘. The reflectarray is designed and fabricated on a thin and high-quality Rogers 5880 substrate. The Finite Element Boundary Integral (FEBI) method is used to simulate a 23×23 element reflectarray and then fabricated to achieve the measured results using an anechoic chamber. The peak gain of the proposed reflectarray is 25.5 dBi recorded with an aperture efficiency of 63.7% at a center frequency of 10 GHz. The cross-polarization and side-lobe levels in the entire band are less than -33 dB and -21 dB, respectively. Moreover, the proposed reflectarray antenna achieves a 20% 1-dB gain bandwidth.

A Novel Electromagnet-Controlled Reflectarray Element Employing 1-Bit Height Locking System with Low Power Consumption

A Novel Electromagnet-Controlled Reflectarray Element Employing 1-Bit Height Locking System with Low Power Consumption

W‐band large‐scale high‐gain filtering reflectarray antenna

AbstractThis article presents a W‐band three‐layer reflectarray antenna that can be easily fabricated using printed circuit board (PCB) process. The proposed reflectarray element is composed of substrate integrated waveguide (SIW) structure and slot‐coupled patch. By controlling the length of SIW in each element, the compensation phases required for the reflectarray to generate focused beam at in‐band frequencies are realized. However, at the out‐of‐band frequencies, the elements fail to provide the required compensation phases as the incident electromagnetic wave cannot couple to the SIW. Thus, filtering performance is realized. A circular aperture prototype reflectarray comprising of 5024 elements are employed to yield a high‐gain narrow beam. The measured results show that the proposed reflectarray antenna attains a peak gain of 40.5 dB at 94 GHz with aperture efficiency of 41.3%, and out‐of‐band suppression higher than 22 dB.

A liquid metal based 1-bit reconfigurable reflectarray antenna for beam-scanning applications

In this letter, a 1-bit reconfigurable reflectarray antenna (RRA) using liquid metal with high gain, high aperture efficiency is proposed to realize beam steering. The reflectarray element consists of three layers: the top and bottom layers both have a translucent resin casing with one thin dielectric layer in between. The top layer is a square ring structure while the bottom layer is a complementary structure to the top layer with four channels. The middle layer is a thin dielectric layer for supporting top and bottom layers. The 1 bit state of RRA means the top casing is filled with liquid metal while the bottom casing is the air, otherwise means 0 bit states. The phase difference between two states is nearly 180°which is suitable for designing 1 bit RRA. Finally, a 20×20 reflectarray is designed, simulated and measured to validate the performance. Both simulated and measured results show that the proposed liquid metal based RRA can effectively generate scanning beams within ±40°and the maximum measured gain is 24.08dBi with aperture efficiency of 20.36%. The proposed RRA is compact and has structural flexibility using liquid metal, which can be applied in modern wireless communication systems.

Low-Profile Wideband 1-bit Reconfigurable Transmitarray With 2-D Beam-Scanning Capacity

In this article, a folded low-profile wideband 1-bit reconfigurable transmitarray (RTA) with 2-D beam-scanning capacity is proposed. To reduce the profile of the whole RTA, the ray tracking mechanism and the feed optimization are introduced. A 1-bit wideband RTA element with polarization selection function and polarization rotation function is designed based on a regular hexagonal resonant patch and p-i-n diodes. Furthermore, a specially designed waveguide structure is fabricated to verify the performance of the RTA element. To achieve the low-profile design, a wideband polarization rotation reflectarray (PRRA) element acting as the reflecting surface is proposed, and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times $ </tex-math></inline-formula> 2 U-slotted planar patch antenna is designed to replace the horn. With these designs, the profile can be compressed by two-thirds compared with the conventional space-fed architecture. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times16$ </tex-math></inline-formula> -elements low-profile RTA is designed and fabricated. The measured and simulated radiation patterns are in good agreement. The measured peak gain is 19.6 dB, corresponding to an aperture efficiency of 13.8%, and the measured 3 dB gain bandwidth is 17.5% (from 15.1 to 18 GHz). Good scanning performance with ±60° scanning coverage in both principal planes has been obtained, and the scan losses are 3.97 and 4.15 dB, respectively. Besides, the measured sidelobe levels (SLLs) and cross-polarization levels remain better than −15 and −20 dB, respectively, at all beam directions.

Broadband Reflectarray Using Circular Cosine Curve Elements

An automated design methodology of large-aperture broadband reflectarray is proposed by exploiting the unique properties of circular cosine curve elements with the slope of frequency-phase (F-P) response that can be changed by adjusting two degrees of freedom. The single-layer miniaturized element (0.3λ) with quadrantal symmetry provides the phase range coverage of 360° and negligible reflection loss for either dual-linear or dual-circular polarization. The variable slope of the F-P response facilitates the optimal arrangement of reflectarray elements minimizing spatial dispersion over the wideband. A 60 × 60 offset-fed reflectarray prototype with dimensions of 960 × 960 mm is designed and fabricated. The measured 33.6 dB of peak gain, 20% of the 1-dB bandwidth, and a 52.9% aperture efficiency are achieved, exhibiting excellent radiation performance. In addition, a 26 × 26 center-fed reflectarray was designed for comparison with a simulated 1-dB bandwidth of more than 35%, which is regarded as a highly acceptable result.

An All-Metal, Simple-Structured Reflectarray Antenna With 2-D Beam-Steerable Capability

An all-metal reflectarray (RA) element based on the variable-rotation technique is presented in this letter. The RA element, based on an elliptical inner conductor and a circular outer conductor, exhibits continuous 360° phase coverage with negligible element loss over a wide range of incident angles and frequencies. A 10 GHz prototype with 121 manually rotated elements was simulated, fabricated, and tested. The proposed RA antenna has two-dimensional beam-steerable capability up to 45° elevation angle. The measured results agree well with the simulated counterparts. For demonstration, four different steering cases are presented as examples by manually adjusting the rotation angle of the RA elements. The maximum measured antenna gain is 26.2 dBi, corresponding to an aperture efficiency of 66%. A 1.3 dB gain drop was measured during beam scanning from 0° to 40°.

A Dual Ka/Q-Band Reflectarray

Introduction. Duplex satellite communication is commonly arranged using two spaced frequency bands, with one band receiving and the other band transmitting signals to a satellite. The main task of a communications satellite antenna system consists in providing an identical coverage area across all involved frequency bands, which is often a challenging task for conventional parabolic reflector antennas. Reflectarrays allow an independent control of the reradiated wave phase in spaced frequency bands, which can be used to create efficient multi-band antenna systems for modern communication satellites.Aim. To develop a Ka/Q-frequency range phase-correcting element and to create on its basis a dual-band reflectarray for operation with orthogonal circular polarizations and identical gains in a given sector of angles in significantly spaced frequency ranges.Materials and methods. Numerical studies were carried out using the finite element analysis method. Radiation patterns were measured using the near field scanning method.Results. A single-layer dual-band phase-correcting reflectarray element was developed for operation with orthogonal circular polarizations with low losses and a weak dependence of the relative position of the elements on the phase characteristic. On the basis of the proposed element, a reflectarray consisting of 24 465 two-frequency elements was synthesized and manufactured. The developed prototype of a single-layer dual-band reflectarray demonstrated good characteristics, with the efficiency reaching 56 and 36 % in the Ka- and Q-frequency ranges, respectively, and an almost identical minimum gain in the ±0.75° angle sector.Conclusion. The research results confirm the potential of the developed reflectarray to successfully replace conventional parabolic reflectors installed both on modern communication satellites and as part of ground-based satellite terminals in the millimeter wavelength range.

A Study on Scattering Performance of Reflectarray Element Covered by Dielectric Superstrate

In this article, effect of a dielectric superstrate on scattering performance of reflectarray elements is clarified. At first, analytical electric field expressions of an infinite line current backed by a ground plane with the dielectric superstrate and so-called resonance conditions derived by Sugio et al., are reviewed. According to the electric field expressions and reciprocity, enhancement of the scattering field strength by the dielectric superstrate under the resonance conditions is expressed analytically. Since the scatterers are illuminated by the incident wave arriving from outside of the scatterers, the effect of its incident angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> on the scattering field strength is also studied. Based on inequalities that are derived from the electric field expressions, range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> for enhancing the scattering field strength by the dielectric superstrate under the resonance conditions is found. As a result, it is found that the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{i}$ </tex-math></inline-formula> is independent of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r} \gg 1$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> is relative permittivity of the dielectric superstrate. Numerical simulation is performed, and it is demonstrated that the analytical formulae derived here are useful for predicting the effect of the dielectric superstrate on practical reflect array elements such as dipole, patch, and loop elements. Results and theories demonstrated in this article give quantitative guidelines on designing the reflectarray elements covered by the superstrate from the viewpoints of angle dependence, geometry, and permittivity of the superstrate.

A Reconfigurable Reflectarray Antenna With an 8 μm-Thick Layer of Liquid Crystal

This article demonstrates an electronically scanned reflectarray antenna based on liquid crystal (LC). The LC-based reflectarray element was designed as a periodically loading of parallel H-shaped polygons on two metal layers. To realize a tunable reflection phase and reduce the inhomogeneity effect of LC, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mu \text{m}$ </tex-math></inline-formula> -thick LC layer was designed as a varactor rather than a substrate. In simulations, the adjustable reflection-phase range of the proposed element was 180° in the frequency band 21–21.5 GHz. The design concept was verified on a reflectarray prototype containing 26 rows of the basic elements. In addition, a 32-channel control circuit was designed and fabricated for biasing. The measured results confirmed a tunable phase range of 150° at 23.8 GHz. The disagreements between the simulated and measured results are discussed, and a test process is proposed. As a proof of concept, the main beam was steered to 0°, −40°, and −60° in one plane. The result confirmed the high beam-steering capability of the proposed reflectarray with measured gains above 18 dB at 23.8 GHz. This work provides useful references for the design and measurement of LC-based reflectarray antennas.

Design of a frequency selective surface‐backed microstrip reflectarray antenna using Minkowski ring elements

A novel frequency selective surface (FSS)-backed subwavelength reflectarray element is proposed in this article. The element consists of an inner square ring and an outer Minkowski ring. The proposed fractal element could achieve smaller interelement spacing and better reflection phase performance due to its space-filling property and self-similar geometry. An 11 × 11-element reflectarray with reduced element spacing of 0.38 λ 0 ( λ 0 -the free space wavelength at 5.8 GHz) is designed. A FSS is used to replace the perfect electric conductor (PEC) ground. In the working frequency, the electromagnetic waves are reflected and result in a smoother and more linear reflection phase curve. Moreover, the radar cross section (RCS) of the reflectarray antenna is also reduced by using the FSS ground. A prototype antenna is then fabricated and measured. The measured results show that the antenna has a peak gain of 18.6 dBi, and an aperture efficiency of about 31.9%. A measured 1-dB gain bandwidth of 14.3% is obtained. Meanwhile, the measured cross-polarization and side-lobe levels are −20 dB and −13 dB, respectively. The simulated results demonstrate that the monostatic RCS can be significantly reduced with a fractional bandwidth of 32.76% and 44.83% for the lower and upper bands with reduced levels of 5 dB, respectively.

Metal‐only ultra‐wideband reflectarray

A metal-only ultra-wideband polarisation-selective reflectarray element using the true time delay is proposed herein. The element affords a large bandwidth with a tuneable reflection phase. An offset-fed reflectarray prototype using the proposed element was designed, and it exhibited stable radiation patterns from 4 to 35 GHz (over 8:1 bandwidth), a low loss, and a measured maximum efficiency of 54.6%. The special metal-only feature circumvents the need for dielectric substrates and ground planes; such features result in a simple structure that allows it to be used in harsh environments such as space.

A Single-Layer 10–30 GHz Reflectarray Antenna for the Internet of Vehicles

A novel ultra-wideband (UWB) reflectarray antenna for the Internet of Vehicles (IoV) is introduced in this paper. By simply connecting the neighboring reflectarray elements, the proposed reflectarray antenna achieves a remarkable radiation pattern bandwidth of 20 GHz, ranging from 10 GHz to 30 GHz. To explain the operating principles of the proposed reflectarray antenna, the equivalent circuit (EQC) model of the unit cell is built, which also provides an efficient and rapid way to analyze the performance of the proposed reflectarray element. It is found from the EQC analysis that the connected elements can achieve better reflection phase responses than conventional separated elements, thereby improving the array bandwidth. As a proof of concept, a 503-element reflectarray antenna simultaneously covering the vehicle-to-satellite bands (12.25–12.75 GHz/14.0–14.5 GHz/19.6–21.2 GHz/29.4–31.0 GHz), the 24-GHz short-range vehicle radar band (24.25–26.65 GHz) and the 5G millimeter-wave band (27.5–28.35 GHz) is designed, fabricated, and characterized. The experimental results demonstrate that the presented reflectarray antenna can maintain undistorted beams, high antenna gain, low cross-pol level, and moderate aperture efficiency over a bandwidth of 100%, i.e., from 10 to 30 GHz. With its simple and planar aperture as well as excellent performance, the proposed reflectarray antenna can be a promising candidate for vehicles that require reliable high data-rate satellite links and 5G millimeter-wave connections simultaneously.

Design of Microfluidic Reflectarray Elements for Multi-Reconfiguration Using Liquid Metal

Using an alloy of non-toxic liquid metal (Galinstan) is proposed to implement multi-reconfiguration in reflectarray elements. Reflectarray antennas are an interesting technology for dynamically controlling, simultaneously or individually, different properties of the antenna (beam shape and pointing direction, field polarization, and frequency of operation) according to the system’s demand. The use of liquid metal, which can potentially be used to re-shape the topology of the unit cell, along with advances in the micro-and nanofluidics field, provides more flexibility for efficiently implementing such multi-reconfiguration. A frequency-reconfigurable reflectarray element is based on the well-known aperture-coupled cell, and a phase-reconfigurable cell based on single-and multi-resonance dipoles is proposed at 28 GHz. One advantage of microfluidics is that the concept can easily be extended to much higher frequencies, where other devices start to be expensive, inefficient, or limited in terms of multi-reconfiguration. The microfluidic technology required to implement the dipole-based element is demonstrated using a microfluidic burst-valve chip. Additionally, a simplified RF proof-of-concept is presented using the well-known waveguide simulator technique from 15 GHz to 22 GHz (WR51). The results obtained constitute an important first step toward the implementation of multi-reconfigurable reflectarray antennas.

An Ultrawideband Polarization-Selective Reflectarray

This letter presents a novel ultrawideband polarization-selective reflectarray with true-time delay. The reflectarray element can be perceived as a combination of a polarization grid and Vivaldi antenna, so is characterized by large bandwidth, low cross polarization, and polarization selectivity. A reflectarray using these elements arranged in a 41 × 41 square grid operating from 6 to 32 GHz is designed, fabricated, and tested. The feed is provided by four pyramidal horn antennas operating at the working frequency (C, X, Ku/K, and Ka bands). In measurements, the reflectarray shows stable radiation patterns from 6 to 32 GHz (more than 5:1 frequency range) and has a maximum aperture efficiency of 40%. It also has the low cross polarization below −28 dB across the entire band and has the characteristic of polarization selectivity.

Design of a wideband bowtie‐shaped reflectarray antenna loaded with parasitic split rings

AbstractA novel bowtie‐shaped structure loaded with three concentric split rings is proposed for designing wideband reflectarray antenna with low optimizing complexity. The broadband characteristic of the proposed reflectarray element is realized by exciting multi‐resonances through the surrounded concentric split rings. Furthermore, a linear phase curve covering about 700° can be achieved by simply adjusting the flare angle of the concentric split rings. Based on the element, a prototype of the proposed reflectarray antenna with a diameter of 180 mm is simulated and measured. According to the measured results, the peak gain is 22.8 dBi at 10 GHz corresponding to an aperture efficiency of 42%. Besides, 3‐dB gain bandwidth of 28% (8.5–11.3 GHz) is obtained, and the cross‐polarization levels are below −25 dB for both principal planes.

A Ku-Band Foldable Reflectarray Based on a Maltese-Cross Microstrip Element

Introduction. Reflectarrays have a number of design and functional advantages over their closest analogue - reflector antennas (RA). Although microstrip elements are the most preferred reflectarray elements, single-layer microstrip elements do not allow accurate phase control due to the limited phase adjustment range and a high phase slope. The use of multilayer elements significantly complicates the antenna design and increases its cost. The development of a single-layer element that allows more than 360° phase adjustment and a low phase curve slope is urgent.Aim. To develop a single-layer microstrip phase-correcting element with a phase adjustment range of more than 360° and to design a reflectarray on its basis for operation in satellite communication networks.Materials and methods. Numerical studies were carried out using finite element analysis and the finite-difference time-domain method. Radiation patterns were measured using the near-field scanning method in an anechoic chamber.Results. A phase-correcting element based on a single-layer Maltese cross-shaped microstrip element with close to linear dependence of element size on the phase of the reradiated wave and more than 360° phase adjustment range was developed. On the basis of the investigated element, a foldable reflectarray was designed. The reflector consists of four subarrays, which provide its compact folding for transportation. The results of experimental studies confirmed a high efficiency of the reflectarray, the gain of which is 1.5 dB lower than that of an identical overall dimensions RA in a 7 % operating frequency band. The operating frequency band of the reflectarray in 1 dB gain zone was 11 %.Conclusion. On the basis of a Maltese cross microstrip element, it is possible to implement a single-layer reflectarray with a more than 10 % frequency band. The developed prototype showed the possibility of creating highly efficient foldable reflectarrays for operation in satellite communication and television terminals.

Design and Validation of a Reflectarray Antenna with Optimized Beam for Ground Target Monitoring with a DVB-S-Based Passive Radar.

A reflectarray antenna with an optimized sectorial beam is designed for the surveillance channel of a DVB-S-based passive radar (PR). The employment of satellite illuminators requires a high gain antenna to counteract the losses due to the great distance from the transmitter, but without forgetting a beamwidth wide enough to provide angular coverage. A method based on optimizing the position of several contiguous beams is proposed to achieve the required sectorial pattern. Different reflectarray elements are designed to achieve S-curves with smooth slopes and covering all the required phases (the S-curve represents the reflection phase of a single element, as a function of size, rotation and incidence angle). The real phase and modulus of the reflection coefficient of each element are considered in the optimization process to achieve the best real prototype. Geometry has been studied and adapted to employ commercial elements for the feed, feed-arm and the structure that holds the aperture. The designed prototype has been characterized in an anechoic chamber achieving a stable gain greater than 19 dBi in almost the complete DVB-S band, from GHz to 12 GHz with a sectorial beam of . The prototype has also been validated in PR trials in terrestrial scenarios allowing the detection of cars at distances up to 600 m away from the PR, improving the performance achieved with commercial parabolic dish antennas.

A Broadband Circularly Polarized Reflectarray With Magneto-Electric Dipole Elements

This communication reports a broadband circularly polarized (CP) reflectarray operating at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> -band. An asymmetric dual-polarized magneto-electric (ME) dipole is proposed as the reflectarray element to realize broadband cophasal far-field radiation based on the element rotation technique. Broad bandwidth and high-purity circular polarization are achieved. The fabricated prototype shows a 1.5 dB axial ratio (AR) and 3 dB AR bandwidth of 37% and 42%, respectively. Peak gain of 25.4 dBic and peak aperture efficiency of 60% are experimentally obtained. The aperture efficiency remains higher than 45% over a wide bandwidth spanning from 8.3 to 12.4 GHz. Specifically, the proposed element can be realized on an air gap-free low-profile single-board substrate configuration, owing to the wideband characteristic of the ME dipole. This comparatively robust and easy-to-fabricate structure would be desirable for many applications including broadband satellite communications.

A Circularly Polarized 1 Bit Electronically Reconfigurable Reflectarray Based on Electromagnetic Element Rotation

A circularly polarized (CP) reflectarray with 2-D electronically steerable beam is reported. The reconfigurable CP reflectarray element is realized using a circular-patch-based structure with p-i-n diodes incorporated. A new electronical phase manipulation method is proposed based on the element rotation technique and by additionally exploiting symmetries in the field distribution of the element's fundamental resonant mode. Element rotation can be equivalently achieved by altering the biasing voltage and changing the electromagnetic behavior of the reflective phasing cell. The proposed design approach brings about simplification in element configuration, leading to a reduction in the number of required diodes by a factor of one half. Practical concerns of the element and biasing complexity as well as the insertion loss are, therefore, well-handled. A fully functional 16×16 reconfigurable CP reflectarray is designed, fabricated, and tested to validate the concept. Good beam focusing and 2-D dynamic beam steering capabilities are confirmed through experiments, along with decent polarization purity and comparatively high aperture efficiency. The proposed simple and robust design could be attractive for implementing lightweight, low-cost, and large-scale 2-D reconfigurable CP reflectarrays.