Two-dimensional Beam Steering Research Articles

Electronically Steerable Parasitic Patches for Dual-Polarization Reconfigurable Antenna Using Varactors

This paper presents a dual-polarized reconfigurable antenna loading electronically steerable parasitic patches. The proposed dual-polarized antenna is surrounded by four parasitic patches each of which is mounted by two varactor diodes on the ground. By tuning the varactors, continuous two-dimensional beam-steering can be achieved for each of the polarization. A prototype of the proposed antenna is fabricated and measured. Excellent agreement between the simulated and measured results is observed. It is observed that the maximum beam-scanning angles in E-plane and H-plane are greater than ±25∘, which is suitable for 5G base station applications.

A Novel Wideband and High-Efficiency Electronically Scanning Transmitarray Using Transmission Metasurface Polarizer

Inspired by the recent progress of metasurfaces, a novel wideband and high-efficiency electronically reconfigurable transmitarray (TA) is presented that can enable two-dimensional (2-D) beam steering and multiple beam mode switching in a digital manner. The proposed unit cell consists of a reconfigurable anisotropic metallic resonator, which locates between a pair of orthogonally oriented subwavelength metal gratings. One-bit phase quantization is obtained by controlling the ON or OFF state of two positive-intrinsic-negative (p-i-n) diodes integrated on the anisotropic metallic resonator layer. To choke the radio frequency (RF) signal effectively, a bias layer is connected by the metallic via hole to the center of the resonator, where the electric field is minimal. The simulated results show that the proposed unit cell can achieve a low insertion loss of 1 dB from 9.3 to 10.9 GHz for two phase states. Then, the radiation performance of a 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,10$ </tex-math></inline-formula> element array fed by a pyramidal horn antenna is theoretically calculated, simulated, and measured. The measured maximum gain is 19.1 dBi at 10.0 GHz with an aperture efficiency of 25.8% and a 3 dB gain bandwidth of 15.9%. The measured results demonstrate the 2-D beam scanning capability within the 50° range.

Non-Mechanical Beam Steering and Adaptive Beam Control Using Variable Focus Lenses for Free-Space Optical Communications

Free-space optical communications (FSOCs) are gaining popularity as a promising solution to the capacity crunch of aerial and satellite backhaul networks for next-generation mobile communication systems. A major technical challenge associated with such FSOC systems in motion is the pointing, acquisition, and tracking (PAT). To facilitate PAT, it is absolutely necessary to steer the optical beam over a wide angle and also adjust the beam divergence angle adaptively to the link condition and the amount of pointing error. The conventional methods to steer the optical beam and/or to adjust the beam divergence angle rely on mechanical mechanisms. Recently, the optical beam steering technique using variable focus lenses has been proposed and demonstrated. By using an on-axis variable focus lens followed by two decentered variable focus lenses, we can steer the optical beam over a wide range in a non-mechanical fashion. In this paper, we explore the possibility of using variable focus lenses for the realization of beam steering and adaptive beam control for FSOCs. For this purpose, we employ three variable focus lenses, one on-axis lens for adaptive beam divergence control and two decentered lenses for two-dimensional beam steering. We demonstrate the simultaneous beam steering and adaptive beam control capability of this variable focus lens-based system over a 104-m long free-space optical link. We evaluate the maximum beam steering angle and beam quality as we vary the offset distance of decentered variable focus lenses. Also evaluated experimentally is the impact of gravity on the beam quality. Finally, we show that the beam steering and adaptive beam control techniques implemented by variable focus lenses improve the performance of 10-Gb/s FSOC system considerably in the presence of pointing errors.

Metamaterial-Inspired Flat Beamsteering Antenna for 5G Base Stations at 3.6 GHz.

In this paper, a metamaterial-inspired flat beamsteering antenna for 5G applications is presented. The antenna, designed to operate in the 3.6 GHz at 5G frequency bands, presents an unique flat form factor which allows easy deployment and low visual impact in 5G dense scenarios. The antenna presents a multi-layer structure where a metamaterial inspired transmitarray enables the two-dimensional (2D) beamsteering, and an array of microstrip patch antennas is used as RF source. The use of metamaterials in antenna beamsteering allows the reduction of costly and complex phase-shifter networks by using discrete capacitor diodes to control the transmission phase-shifting and subsequently, the direction of the steering. According to simulations, the proposed antenna presents steering range up to , achievable in both elevation and azimuth planes, independently. To prove the concept, a prototype of the antenna has been built and experimentally characterised inside an anechoic chamber. Although constructed in a different substrate (FR4 substrate) as initially designed, beamsteering ranges up to in azimuth and in elevation, limited to the proposed case-studies, are reported with the prototype, validating the antenna and the usefulness of the proposed design.

Parallel emitted silicon nitride nanophotonic phased arrays for two-dimensional beam steering.

In this Letter, a two-dimensional (2D) beam steering on silicon nitride (SiNx) nanophotonic phased arrays from visible to near-infrared wavelengths is reported for the first time, to the best of our knowledge. In order to implement beam steering along the transverse direction for one-dimensional waveguide surface grating arrays, wavelengths from 650 to 980 nm provided by the supercontinuum laser are used to excite the phased array. Then the beams are parallel radiated with steering angles in a sequence of 26.84° to -16.54∘ along the transverse direction, and a continuous line in the far field consisting of parallel emitted spots is produced with a total view angle of 43.38°. Moreover, this continuous far-field line is steered along the longitudinal direction with massive wavelengths simultaneously tuned by phase shifts from -π/2 to over +π/2. This method with massive parallel wavelengths emitted paves a new way for 2D steering on SiNx nanophotonic phased arrays.

Two-Dimensional Terahertz Beam Steering Based on Trajectory Deflection of Leaky-Mode

Free-space transmission of terahertz waves open great opportunities for wireless communication and sensing in the Beyond 5G/6G paradigm. Nevertheless, terahertz transmission suffers from severe diffraction losses due to the shorter wavelengths than the microwaves. To compensate for the diffraction losses, point-to-point transmission by directional beams is indispensable. However, implementing terahertz beam steering is still challenging due mainly to the lack of practical phase shifters. To circumvent this challenge, we demonstrate a novel strategy of two-dimensional (2-D) terahertz beam steering based on trajectory deflection of leaky-mode at around 300 GHz. We use a pair of metal plates with a mesh surface, in which the phase velocity exceeds the light speed in free-space. The leaky-mode can be steered vertically by a phase matching condition controllable with frequency sweep and horizontally by graded refractive index controllable with small tilt of the plate. The result confirms 2-D beam steering without relying on phase shifters.

Design and realization of two-dimensional beam steering actuated by dielectric elastomer

A two-dimensional beam steering device is an essential optical element for many applications, such as free-space optical communications, light detection and ranging, and microscopy. The purpose of the paper is to develop a two-dimensional beam steering device with a simple structure and a large beam steering angle. The principle of beam steering is based on the decentred lens. The decentred lens is placed on the center of the dielectric elastomer and the movement of the decentred lens is actuated by the dielectric elastomer The dielectric elastomer is divided into four quadrants and the top and bottom surfaces of the four quadrants of dielectric elastomer are coated by compliant electrodes. Through applying different voltages on the four quadrants, the decentred lens can move and the beam is steered in a two-dimensional direction. We develop a prototype and carried out imaging experiments to verify the proposed beam steering method. The experimental results show that the maximum translation distance of the decentred lens is 1.496 mm at an actuation voltage of 5 kV. The function of two-dimensional beam steering is realized and the maximum beam steering angle of the device is 11.98°. Such a two-dimensional beam steering device promises a potential solution in various beam steering systems.

Design and Measurement of a Reconfigurable Transmitarray Antenna With Compact Varactor-Based Phase Shifters

A reconfigurable transmitarray antenna (RTA) with 360° continuous transmission phase controlling capability is designed and experimentally validated in this letter. The proposed RTA element is based on the receiver-transmitter structure. A compact varactor-based analog phase shifter using a coupled-line structure is utilized to provide a 0° to 180° continuous transmission phase. Two PIN diodes integrated on the active transmitter patch are alternatively turned <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> to generate an additional 180° phase shift using the current reversal mechanism. The element simulations show a magnitude insertion loss varying from 0.95 to 1.35 dB at 5.6 GHz, and a wide 3-dB transmission bandwidth of 16.7%. A prototype composed of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{16 \times 16}}$</tex-math></inline-formula> elements is fabricated and measured. The measured broadside gain is 23.7 dBi at the design frequency with a 3-dB gain bandwidth of 15.7%. Good two-dimensional (2-D) beam steering capability within ±60° is also experimentally verified.

Two-Dimensional Beam Steering Active Lens With Simple Grid Bias Lines at 19 GHz

This paper presents two-dimensional (2D) beam-steering of an active lens with simple grid bias lines at 19 GHz. In general, 2D beamforming in azimuth and elevation planes requires one-to-one unit cell control for a 2D phase distribution on a planar lens. In this work, the 2D phase distribution is achieved with only <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> vertical and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> horizontal bias lines for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> × <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> unit cells. The active unit cell is based on an I-shaped resonator and includes a varactor diode associated with two bias lines shared by neighboring unit cells. The five-layer unit cell achieves a phase range of more than 360°. The 32×32 unit-cell-stacked prototype demonstrates pencil beam scanning up to ±40° in the E- and H-planes with a 15.8% 3-dB bandwidth, a 17.5-dBi broadside gain, and low power consumption of 5.2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> W per beam switching. The 2D beam-steering for (θ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , Φ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) = (30°, 45°) is verified through simulation and experimental results at 19 GHz.

Light Detection Functionality of Photonic-Crystal Lasers

The photonic-crystal surface-emitting laser is a new-generation semiconductor laser capable of emitting a high-power, high-quality (i.e., high-brightness) beam, as well as on-chip two-dimensional beam steering, lasing in various wavelength regimes, and on-chip ultra-short self-pulsation, owing to their freedom of light-matter control. Here we introduce light detection as a new functionality, wherein the photonic-crystal laser is operated under reverse-bias conditions. We find that the photonic-crystal laser operated under reverse-bias conditions has a very high shunt resistance and a low dark current, which are essential qualities to achieve high detectivity. In addition, high responsivity is achieved by utilizing proper band-edge-modes and Q-matching conditions for resonant light absorption. Furthermore, by employing photonic-crystal lasers as the detector as well as the laser source, a direct time-of-flight distance measurement is successfully demonstrated.

Solid-state FMCW LiDAR with two-dimensional spectral scanning using a virtually imaged phased array.

The beam-steering device is a critical component in LiDAR systems for 3D imaging. Solid-state beam-steering devices attract the most attention for their advantages of robustness, fast beam-steering speed, and stability. However, solid-state beam-steering devices, such as optical phased arrays (OPAs), are challenging to realize 2D scanning ability. Here we employed a virtually imaged phased array (VIPA) in the LiDAR system to realize all solid-state two-dimensional (2D) beam-steering based on dispersion only. A frequency swept laser source is used for performing optical frequency-modulated continuous-wave (FMCW) ranging and 2D beam steering simultaneously. The 2D disperser is compact and can be easily implemented owing to its simple structure. The mechanism of continuous scanning and ranging is beneficial for obtaining high lateral resolution, and a lateral resolution of 0.06° is achieved. 3D maps of the object at a distance of 2 m are obtained with cm-level ranging precision. The frame rate of the proposed LiDAR system only depends on the wavelength-tuning speed of the swept laser source, with the potential to realize ultrafast solid-state LiDAR systems.

Light-driven rotation of gratings formed by electroconvection patterns in cholesteric liquid crystals

While morphological gratings made of solid structural materials have permanent periodicity, gratings induced by a periodic flow provide wide tunability utilizing the pattern formation mechanism and its dependence on the material properties. As a paradigm of such flow, here electric-field induced patterns, manifestations of electroconvection, are reported in a hybrid aligned cholesteric liquid crystal containing a chiral photosensitive dopant. The irradiation by UV light rotates the pattern via alteration of the helical pitch, where the magnitude and direction of the rotation angle depends on the UV light intensity, the concentration and type of the chiral dopant. A prototype grating capable of two-dimensional beam steering is demonstrated. Such tunability will guide chemists to search for smart molecular structures so as to control complex fluids in developing photonic devices with desired parameters.

Hybrid Integrated Silicon Nitride–Polymer Optical Phased Array For Efficient Light Detection and Ranging

Silicon nitride (SiN) optical phased arrays (OPAs) have emerged as a potential alternative to their silicon counterparts, owing to their low nonlinearity, easy scalability, and low propagation loss. However, the development of SiN OPAs for light detection and ranging (LiDAR) applications has attracted less attention due to the low thermo-optic (TO) effect of SiN. Moreover, SiN OPAs are considered to be undesirable for transmitters in LiDAR systems because of the limited longitudinal tuning efficiency of SiN grating antenna. We present a hybrid integrated SiN-polymer OPA for realizing an efficient LiDAR. Owing to the large TO effect of polymer, the proposed OPA with polymeric phase modulators resolves the power dissipation drawback of the SiN devices. The polymeric modulators are integrated with a SiN power splitter and grating antenna, and the coupling loss is alleviated via a spot-size converter. Additionally, a steering angle magnifying lens is used to enhance the tuning efficiency of the antenna, expanding the longitudinal beam steering range. The prepared OPA transmitter equipped with the lens exhibits decent two-dimensional beam steering, featuring stable emission characteristics over a 12° × 30° field of view. With the transmitter, efficient time-of-flight based LiDAR is demonstrated to provide a detection range of 10 m under a peak optical power of 55 dBm. The proposed SiN-polymer OPA is highly anticipated to circumvent the challenges of conventional SiN counterparts and potentially spearhead the development of a prominent OPA platform for advanced LiDAR schemes.

Practical two-dimensional beam steering system using an integrated tunable laser and an optical phased array.

A practical two-dimensional beam steering solid-state system based on the synthesis of one-dimensional wavelength tuning and a one-dimensional optical phased array is demonstrated and investigated. The system incorporates an integrated multiple-channel-interference widely tunable laser, an integrated 32-channel optical phased array, an offline phase error correction unit, and home-made control electronics. The introduction of the integrated tunable laser avoids the traditional bulky light source fed into the optical phased array, making the architecture promising to be miniaturized. In addition, a calibration method based on particle swarm optimization is proposed and proved to be effective to correct the phase errors existing in the arrayed channels and improve the emitted far-field quality. Other practical aspects, such as high-speed control and cost, are taken into the consideration of the system design as well. Under the control of home-made electronics, the laser exhibits a tuning range of 50 nm with a 44 dB side-mode suppression ratio, and the system presents the characteristics of low divergence (0.63∘×0.58∘), high side-lobe suppression ratio (>10dB), and high-speed response (<10µs time constant) in an aliasing-free sweeping range of 18∘×7∘.

High-Intensity Airborne CMUT Transmitter Array With Beam Steering

A $2\times 2$ high-intensity CMUT transmit array that is capable of two-dimensional beam steering is presented. The device uses an ac drive voltage at half the ultrasound frequency without any dc bias, enabling the usage of the entire gap height. The device is designed using a large signal equivalent model approach. A fabrication method that requires a single lithographic mask has been used. The fabricated devices are operated at 76 kHz to beam steer at various angles. An equivalent element pressure of 144 dB// $20~\mu $ Pa at the transducer surface was measured. The entire half-space can be steered without any sidelobes and the beam obtained from the array is in excellent agreement with the theoretical predictions. [2020-0253]

PCB-Based Design of a Beamsteerable Array With High-Gain Antennas and a Rotman Lens at 28 GHz

This letter presents a low-cost single-layer printed circuit board (PCB) design of a Rotman lens and an eight-element Yagi–Uda antenna array suitable for radio frequency (RF) beamsteering at 28 GHz. The antenna array realizes 19 dBi gain due to the guiding parasitic elements of each antenna element and a shaped ground plane surrounding the array. The array radiates in a direction parallel to the PCB enabling the possibility for two-dimensional beamsteering by stacking the PCBs. Integrated with an RF switch network, the design has seven switchable beams to the directions $-\text{30}^\circ$ , $-\text{20}^\circ$ , $-\text{10}^\circ$ , 0 $^\circ$ , 10 $^\circ$ , 20 $^\circ$ , and 30 $^\circ$ . The measured realized gain is still as high as 4–10 dBi including losses of the Rotman lens and the RF switches, thanks to the high-gain antenna array design. The array works wideband across 25.5–28.5 GHz where broadside beam gains are better than 8 dBi. This is the first letter in the literature introducing an experimentally verified design of a PCB endfire antenna array at 28 GHz including all necessary components for RF beamsteering, i.e., a Rotman lens and a switch network.

32 Gbps Data Transmission With 2D Beam-Steering Using a Silicon Optical Phased Array

We demonstrate optical wireless transmission with two-dimensional (2D) beam-steering using an optical phased array (OPA). The OPA consists of 64-elements of electro-optic p-i-n phase shifters and thermo-optic tunable n-i-n grating radiators, employed for 2D beam-steering in the transversal and longitudinal directions. The design of the transmitter and receiver device parameters allowed the error-free transmission of 32 Gbps data over a distance of 3 m. The beam-steering range covered 46.0°/10.2° in the transversal/longitudinal direction with a beam divergence of 0.7°/0.9°. When compared with a transmission over fiber, it was confirmed that free-space transmission through the OPA did not degrade the quality of the tens of Gbps signals.

In brief

PAGE 476 Chinese researchers present an irregular pentagonal patch array antenna, featuring a multilayer structure to enable dual-band and multi-mode orbital angular momentum (OAM) generation. The proposed array has the potential generate 6 different OAMs in 3 frequency bands and may provide new ideas for generating multi-mode vortex electromagnetic waves. PAGE 482 A multiplier design technique for stochastic computing is presented. The proposed design offers exact output and latency in the order of 2N, where N = the input precision. Compared to state of the art deterministic methods, the proposed design is faster by a factor of 2N. The technique is verified by mathematical analysis and simulation. Schematic diagram of proposed antenna array's element PAGE 501 Researchers from the Republic of Korea demonstrate integrated one-dimensional optical phase arrays (OPAs) for wide-angle, two-dimensional beam-steering in a 26.5 mm2 area. The 2-D OPA consists of 16 1-D transversal steering OPAs, whose radiators have different grating periods – allowing assignment of different longitudinal angles. Carry save adder in proposed design for N = 3. Full adder and half adder are denoted by fa and ha respectively. PAGE 510 Chinese researchers present an edge-attention-based geodesic distance which can be applied to the simple linear iterative clustering (SLIC) framework for PolSAR image superpixel segmentation, improving performance without an increase in computational expense. Experiments show the superiority of the proposed distance both qualitatively and quantitatively. Structure and design parameters of the grating radiator. PAGE 490 A collaboration of Chinese researchers propose two schemes to help prevent unwanted sideslip by wheeled mobile robots when turning. A controller is proposed combining robust control and model predictive control. Together the longitudinal velocity can be adjusted according to the state of the robot, whilst the model predictive control is used to achieve path tracking. Superpixel segmentation on PolSAR images over Changle using SLIC with the proposed distance. Fuzzy-NMPC system structure.

Wide beam steering by slow-light waveguide gratings and a prism lens

A lattice-shifted photonic crystal waveguide (LSPCW) maintains slow light as a guided mode and works as an optical antenna when a kind of double periodicity is introduced. Selecting one LSPCW from its array and converting the fan beam to a spot beam using a collimator lens allows non-mechanical, two-dimensional beam steering. We employed a shallow-etched grating into the LSPCW as the double periodicity to increase the upward emission efficiency and designed a bespoke prism lens to convert the steering angle in a desired direction while maintaining the collimation condition for the steered beam. As a result, a sharp spot beam with an average beam divergence of 0.15° was steered in the range of40∘×4.4∘without precise adjustment of the lens position. The number of resolution points obtained was 4256. This method did not require complicated and power-consuming optical phase control like that in optical phased arrays, so it is expected to be applied in complete solid-state light detection and ranging.

Lens-based integrated 2D beam-steering device with defocusing approach and broadband pulse operation for Lidar application.

We propose an integrated two-dimensional beam-steering device based on an on-chip silicon-nitride switch/emitter structure and off-chip lens for light detection and ranging (Lidar) application at 1550 nm. In this device, light is guided by a 1 × 16 switch to one grating emitter in a 4 × 4 grating-emitter array. The beam from the grating emitter is collimated and steered by a fixed lens. By changing the grating emitter that emits light, different beam-steering angle can be achieved. A divergence angle of 0.06° and a field of view of 2.07° × 4.12° in the far field are achieved. The device has O(log2N) power consumption for N emitters, allows digital control and achieves 18 dB background suppression. Blind-zone elimination and broadband operation are also achieved in our lens-based beam-steering device. Therefore, it is suitable for broadband solid-state Lidar application.