Beam-steering Antenna Research Articles

A three-sector array with switchable beams

A design for beam steering antenna arrays is described. The radiating element of the array is mainly composed of dual coplanar slotted-patch antennas, a metallic reflector, and several PIN diodes embedded in the slots. By controlling the states of the diodes, the operation of the slotted-patch antennas can be switched among three modes. These operation modes can generate three radiation beams respectively directed to ϕ = 0°, 40°, and −40° in the H-plane. On the basis of the pattern reconfigurable antenna element, a three-sector triangular array operated at 2.2 GHz is developed. The measured results demonstrate that the sector array can provide nine radiation beams which are steerable over a full 360° in the azimuthal plane; in addition, each switched beam has a half-power beamwidth of about 60° and a cross-polarization level of lower than −20 dB. Detailed designs of the sector array and its feeding network are presented. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1357–1361, 2017

An X-band bifunctional antenna using anisotropic transparent meta-surface

An integration of a transmitarray antenna and a beam-steering antenna has been achieved and experimentally demonstrated. The antenna system operating at X-band (8–12 GHz) is implemented by a well-optimized transparent meta-surface and launched by polarization-controlled feed antennas. The transparent meta-surface, with polarization-independent property, consists of 12 × 12 elements with a parabolic phase distribution at y-direction and a linear phase gradient at x = direction, respectively. Illuminating the meta-surface with differently-polarized electromagnetic waves, anomalous phenomena of beam bending and focusing are clearly observed. The performances of the antenna system are investigated in depth through near-field analysis and far-field measurements. Numerical and experimental results coincide well, indicating that the proposed antenna system advances in many aspects such as bifuncional radiation patterns, a broad bandwidth and also a simple fabrication process based on the convenient print circuit board (PCB) technology.

Sentinel-1 TOPS interferometry for along-track displacement measurement

The European Space Agency’s Sentinel-1 mission, a constellation of two C-band synthetic aperture radar (SAR) satellites, utilizes terrain observation by progressive scan (TOPS) antenna beam steering as its default operation mode to achieve wide-swath coverage and short revisit time. The beam steering during the TOPS acquisition provides a means to measure azimuth motion by using the phase difference between forward and backward looking interferograms within regions of burst overlap. Hence, there are two spectral diversity techniques for along-track displacement measurement, including multi-aperture interferometry (MAI) and “burst overlap interferometry”. This paper analyses the measurement accuracies of MAI and burst overlap interferometry. Due to large spectral separation in the overlap region, burst overlap interferometry is a more sensitive measurement. We present a TOPS interferometry approach for along-track displacement measurement. The phase bias caused by azimuth miscoregistration is first estimated by burst overlap interferometry over stationary regions. After correcting the coregistration error, the MAI phase and the interferometric phase difference between burst overlaps are recalculated to obtain along-track displacements. We test the approach with Sentinel-1 TOPS interferometric data over the 2015 Mw 7.8 Nepal earthquake fault. The results prove the feasibility of our approach and show the potential of joint estimation of along-track displacement with burst overlap interferometry and MAI.

Array pattern optimization for steerable linear isotropic antenna array using novel particle swarm optimization

In this paper, the beam steerable isotropic Linear Antenna Array is designed for reducing the side lobe level using evolutionary optimization technique. The optimization techniques particle swarm optimization (PSO) and Novel PSO are used to reduce the side lobe level (SLL) as well as to steer the main beam in specific direction. In this design of steerable Linear arrays, the amplitude excitations are optimized. Obtained results show that the maximum peak of SLL of the resultant patterns is as per requirement. This paper presents a good performance in the array factor response and suppressed SLL for different numbers of elements and different values of the steering angle of direction of the main beam with evolutionary optimization.

A phase shifter using waffle-iron ridge guides and its application to a beam steering antenna

A phase shifter using waffle-iron ridge guides and its application to a beam steering antenna

Two-Dimensional Beam-Steering Phased-Array Antenna With Compact Tunable Phase Shifter Based on BST Thick Films

This letter presents a novel approach for 2-D electrical beam-steering antennas based on barium–strontium–titanate (BST) thick film at 12 GHz. The phased array consists of 16 microstrip patch antenna elements with individual phase shifters as well as a 1:16 feeding network. As key components in the circuit, the array is equipped with phase shifters based on concept of the composite right/left-handed transmission line. The phase shifters have compact structure for beam steering of planar arrays, where the antenna elements are arranged over a planar substrate. The phase shifters utilize interdigital capacitor varactors with inkjet-printed BST composite thick films. Furthermore, a simple biasing concept is implemented for controlling the phase shifter. The beam scanning range of the ${4\times 4}$ elements array is $\pm$ 25 $^{\circ}$ in both E- and H-plane as demonstrated by the measurements.

Performance Investigation of a Mobile Terminal Phased Array With User Effects at 3.5 GHz for LTE Advanced

This letter discusses the performance investigation of a beam-steerable antenna system at 3.5 GHz with user effects. To show how to investigate the performance of such a system, an antenna array system in a metal frame structure is used as one example. The antenna system includes four phased subarrays. Each subarray consists of two slot antenna elements. In the application, it is possible to control the beam by phase in each subarray and switch the main beam direction among the four phased subarrays, depending on the incoming power and interference directions. The main idea in this letter is to evaluate the performance of the phased array system by using the metrics of total scan pattern and coverage efficiency with CTIA standards. The proposed antenna system is simulated and measured in free space and with user effects. Losses in both scan angles and coverage efficiency due to the user effects are also given and discussed in this letter.

Broadband 3-D Luneburg Lenses Based on Metamaterials of Radially Diverging Dielectric Rods

In this letter, we describe and study microwave Luneburg lenses using a broadband metamaterial composed of radially diverging dielectric rods. The gradual Luneburg's permittivity profile is achieved in this lens through arranging identical thin rods with a spatially variable cross section in various radial directions with a subwavelength separation. The performance of the considered metamaterial lenses was studied by full-wave numerical simulation and measurements in an anechoic chamber. The results reveal that, although anisotropy of the structure causes aperture phase errors, the structure composed of diverging dielectric rods may still operate as a cylindrical or spherical Luneburg lens. Advantageously, the considered design is attractive for mass production of large-scaled beam-steering antennas because the lens is composed of identical shaped dielectric parts.

Modeling and design of metasurfaces for beam scanning

The aim of the present contribution is to show that a judicious phase engineering in metasurfaces can be efficiently used in the design of low-profile beam-steerable antennas. We present the design, simulation and experimental validation of the proposed low-profile antennas. The phase modulation on the metasurface is derived from the ray optics analysis. Such a non-uniform metasurface is utilized as a partially reflective surface in Fabry–Perot cavity antenna. Beam scanning is obtained, and depending on the phase modulation applied, the scan angle can be controlled. Furthermore, an active metasurface incorporating electronic components is fabricated and tested in an electronically steerable antenna.

Wideband, co-polarization anomalous reflection metasurface based on low-Q resonators

Wideband anomalous reflection using metasurface is usually accompanied by polarization conversion, which changes the polarization state of reflected waves. In this paper, we propose to realize wideband, co-polarization anomalous reflection using reflective phase gradient metasurface (PGM). To this end, a resonator with low quality factor Q is firstly designed as the elementary sub-unit of the PGM. Due to the wideband magnetic resonance of the resonator, nearly constant phase gradient can be achieved in a quite wideband from 14.0 to 21.0 GHz. Both the simulation and experiment verify the wideband, co-polarization anomalous reflection using the PGM. Since the polarization of reflected wave is unchanged after reflection, such PGMs can be used in many applications such as reflect array antennas, beam-steering antennas and radar cross-section reduction.

Full-Space Electronic Beam-Steering Transmitarray With Integrated Leaky-Wave Feed

A new low-profile, full-space, electronic beam-steering antenna architecture which combines the full-space beam-steering properties of reconfigurable transmitarrays with the low-profile feeding characteristics of leaky-wave antennas is proposed. The design uses an integrated leaky-wave feed to spatially distribute power across a reconfigurable transmitarray aperture in a low-profile manner while individual element phase control using varactor diodes enables full-space pencil-beam-steering. A $6\times 6$ element array was fabricated and experimentally verified, and full-space (both azimuth and elevation) beam-steering was demonstrated at angles up to 45° off broadside with a total efficiency for all scan angles on the order of 25%–35%. The design demonstrates a tenfold reduction in the overall thickness over the original transmitarray, improved aperture amplitude distribution control, as well as improved spillover control. The design also acts as a lower cost, scalable alternative to phased arrays as it does not require a complicated beamforming network and the feed and aperture are easily scaled.

2-D Beam-Steerable Integrated Lens Antenna System for 5G <inline-formula> <tex-math notation="LaTeX">$E$ </tex-math> </inline-formula>-Band Access and Backhaul

The new services available through smart devices require very high cellular network capacity. The capacity requirement is expected to increase exponentially with the forthcoming 5G networks. The only available spectrum for truly wideband communication (>1 GHz) is at millimeter wavelengths. The high free space loss can be overcome by using the directive and beam-steerable antennas. This paper describes a design and the measurement results for a lens antenna system for $E$ -band having 2-D beam-steering capability. Continuous beam-switching range of about $\pm 4 {^{\circ }} \times \pm 17^{\circ }$ is demonstrated with the lens having the maximum measured directivity of 36.7 dB. Link budget calculation for backhaul application using the presented lens antenna system is presented and compared with the measurement results of the implemented demo system.

Fixed frequency broadside–endfire beam steerable antennas

A novel reconfigurable broadside–endfire microstrip antenna is proposed. The beam steering is achieved by reconfiguring the ground plane. The ground plane can be reconfigured either into a high-impedance surface for broadside radiation or into a surface waveguide for endfire radiation. A DC bias line, not connected to the folded dipole feed in any way, is used to switch the PIN diodes. PIN diodes are soldered on the back of the antenna and have no possibility of interfering with the feed. The proposed antenna is designed to work at the ISM 2.45 GHz band with a combined 2:1 VSWR bandwidth of 110 MHz and a combined radiation coverage of 133° on the H-plane. A 5 V power supply or a 9 V battery can be used to operate the active antenna.

FSS-Inspired Transmitarray for Two-Dimensional Antenna Beamsteering

A novel two-dimensional (2-D) beamsteering transmitarray inspired on frequency selective surfaces is proposed in this paper. Individual phase range is applied to each transmitarray element and thus enabling the steering of the main lobe of an original antenna pattern in both elevation and azimuth planes (2-D-beamsteering). This has been demonstrated on a ${5{\times}\,5}$ unit-cell stacked structure, loaded with surface mount capacitors, coupled to the aperture of a standard gain horn antenna. Additionally, a complete parametric study based on electromagnetic (EM) simulations using CST Microwave Studio is presented to evaluate and characterize unit-cell parameters and the behavior of the array with various numbers of stacked layers and separation distances. Antenna beamsteering with ranges up to ${Az=25^{o}}$ and ${El=25^{o}}$ are achieved by means of EM simulations and validated against experimental results performed on a physical prototype at 5.3 GHz. The comparisons yield positive results and clearly demonstrate the potential and limitations of using such structures for beamsteering purposes.

Interferometric Processing of Sentinel-1 TOPS Data

Sentinel-1 (S-1) has an unparalleled mapping capacity. In interferometric wide swath (IW) mode, three subswaths imaged in the novel Terrain Observation by Progressive Scans (TOPS) SAR mode result in a total swath width of 250 km. S-1 has become the European workhorse for large area mapping and interferometric monitoring at medium resolution. The interferometric processing of TOPS data however requires special consideration of the signal properties, resulting from the ScanSAR-type burst imaging and the antenna beam steering in azimuth. The high Doppler rate in azimuth sets very stringent coregistration requirements, making the use of enhanced spectral diversity (ESD) necessary to obtain the required fine azimuth coregistration accuracy. Other unique aspects of processing IW data, such as azimuth spectral filtering, image resampling, and data deramping and reramping, are reviewed, giving a recipe-like description that enables the user community to use S-1 IW mode repeat-pass SAR data. Interferometric results from S-1A are provided, demonstrating the mapping capacity of the S-1 system and its interferometric suitability for geophysical applications. An interferometric evaluation of a coherent interferometric pair over Salar de Uyuni, Bolivia, is provided, where several aspects related to coregistration, deramping, and synchronization are analyzed. Additionally, a spatiotemporal evaluation of the along-track shifts, which are directly related to the orbital/instrument timing error, measured from the SAR data is shown, which justifies the necessity to refine the azimuth shifts with ESD. The spatial evaluation indicates high stability of the azimuth shifts for several slices of a datatake.

Compact Beam Steering Antenna With Low-Loss Co$_2$ Y-Type Hexagonal Ferrite Elements for Wireless Multiple-Input Multiple-Output (MIMO) Antenna Applications

A low-loss Co $_2$ Y hexagonal ferrite (Ba $_2$ Co $_{1.9}$ Zn $_{0.1}$ Fe $_{12}$ O $_{22}$ ) has been developed for miniaturization and performance improvement of wireless multiple-input multiple-output (MIMO) antennas. The ferrite material has permittivity and permeability of 6.7 and 2.1, respectively, with dielectric loss tangent less than 0.007 and magnetic loss tangent less than 0.034 below 2.5 GHz. A beam steering antenna operating at 2.4 GHz band was designed and fabricated using the ferrite elements having a total volume of 18 mm × 18 mm × 100 mm, which has compact size, low loss, and good radiation characteristics. The antenna offers three modes with nine radiation beam patterns at the frequencies of 2.4 GHz band. The measured peak gain of all beam patterns ranges from 4.0 to 6.8 dBi.

Beam-Steerable Planar Antenna Using Circular Disc and Four PIN-Controlled Tapered Stubs for WiMAX and WLAN Applications

A planar beam-steerable antenna aimed at WiMAX and WLAN applications is presented. The design uses a single-layer structure, which includes a central circular disc surrounded by four PIN-controlled tapered microstrip stubs. Using the PIN diodes, the stubs change their status from grounded to open-ended mode to provide pattern reconfigurability in four directions. To support WiMAX and WLAN applications, the antenna is designed to operate at IEEE 802.11b/g standard 2.4 GHz with a bandwidth of 150 MHz in all the four states. A prototype on FR4 substrate with thickness of 6.4 mm and radius of 50 mm is designed and tested. The measured and simulated results of the antenna indicate that the direction of the main beam can be successfully controlled at four specific directions ( $ \varphi = 0^{\circ}$ , 90 $^{\circ}$ , 180 $^{\circ}$ , 270 $^{\circ}$ ), at a deflection angle of 35 $^{\circ}$ from the boresight with a stable gain of more than 5 dBi and front-to-back ratio of more than 20 dB across the band 2.38–2.53 GHz.

Comparison of horizontal winds and turbulent eddy dissipation rates obtained by two different multi-receiver techniques – Spaced Antenna and Postset Beam Steering

The horizontal winds and eddy dissipation rates (ε) obtained by two multi-receiver techniques, Spaced Antenna (SA) and Postset Beam Steering (PBS), are compared and contrasted, using Middle and Upper atmospheric radar measurements. Comparison of mean horizontal winds obtained by both methods indicates a good agreement in zonal and meridional winds. On the other hand, the agreement in ε derived by SA and PBS is good in the lower troposphere (below ~9km), but the profiles of ε show some discrepancy in the upper troposphere. While the discrepancy is relatively more in layers of depleted turbulence, it is small in layers of enhanced turbulence. Comparison of signal-to-noise ratio and turbulence variations reveal that these variations are not due to specular echoes, rather due to anisotropic turbulence. The study suggests that these techniques and correction formulae for spectral width work well in the regions of enhanced turbulence but yield relatively less accurate values in regions of depleted turbulence.

STEERABLE ARRAY ANTENNA USING A 2 × 2 BUTLER MATRIX FOR 5G APPLICATIONS

This paper presents the design of a beam steerable array antenna based on branch line coupler (BLC) at 28 GHz frequency band for fifth generation (5G) wireless applications. The array is designed using Rogers RT/duroid 5880 substrate material of 0.254 mm thickness and dielectric constant of 2.2. The designed antenna has six elements array and is fed by a BLC which serves as a beamformer to obtain the beam scanning ranging from -16 to +16 degrees. The maximum gain of 14.5 dBi and a wideband that cover from 25.2 GHz to 32 GHz was obtained by measurement. The proposed antenna is applicable to 28 GHz frequency band proposed for 5G wireless communications. All simulated and measured results are clearly presented.

Foreword to the Special Issue on Multichannel Space-Based SAR

The papers in this special section focus on space-based synthetic aperture radar (SAR)technology. With the advent of active electronically steerable phased-array SAR antennas equipped with more than one receive channel (i.e., analog-/digital converter) on the most recent generation of commercial/civilian spacecraft, such as RADARSAT-2, TerraSAR-X & TanDEM-X, PAZ, and ALOS-2, relatively mature singlechannel SAR imaging is now rapidly evolving into advanced, multiaperture SAR concepts. The spatial diversity of multiple parallel receive channels can, for instance, be used to discriminate moving objects from the stationary background, to determine the underlying topography of the backscattering terrain, or to measure the large-scale surface motion using single-pass interferometry. The flexible programmability of this newest generation of SAR satellites offers quasi-seamless antenna beamsteering at a rate equivalent to the pulse repetition frequency and, in conjunction with sophisticated array signal processing algorithms, opens up novel radar concepts and capabilities that were not previously possible.