Two-dimensional Beam Scanning Research Articles

Risley-Prism-Based Dual-Circularly Polarized 2-D Beam Scanning Antenna With Flat Scanning Gain

Although the two-dimensional (2-D) beam scanning antenna based on the Risley-prism (R-P) principle has been proposed, the previous research mainly used linear phase progression phase-shifting surfaces, which has the problem that the gain decreases rapidly when the beam scans to a large angle in the elevation plane. Here, exponential phase gradient phase-shifting surfaces based on the Risley-prism principle are innovatively proposed, which can realize the flat scanning gain of 2-D beam scanning antenna. In addition, a rotatable polarization control surface is introduced to make the proposed 2-D beam scanning antenna work in dual-circular polarization. The experimental results show that the maximum scanning angle of the antenna is 52° in the elevation plane and 360° in the azimuth plane. In particular, the gain variation of the beam is only 0.6 dB within elevation angle 45°, showing a flat scanning gain characteristic.

Cavity-Backed Circularly Polarized Cross-Dipole Phased Arrays

In this letter, a 16 × 16 Ku-band circularly polarized phased array is proposed. The antenna element comprises a cross dipole, a metal cavity, and a threaded SMP connector. The metal cavity makes the gain of the antenna increased and the mutual coupling between the array elements is reduced, thus ensuring good impedance matching and axis ratio (AR) during the two-dimensional beam scanning. The mutual coupling of the center element at center frequency is -26.6 dB when the cavity is added. The proposed phased array achieves the impedance bandwidth (| <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</b> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | ≤ - 10 dB) of 10.1% (13.1-14.5 GHz) when scanning ±40° in the xz plane and yz plane. AR of the main lobe is less than 2 dB in the total scanning range. The gain fluctuation is less than 3 dB during scanning. This letter presents the measurement and simulation results, verifying that the phased array has good performance.

Compact solid-state optical phased array beam scanners based on polymeric photonic integrated circuits

Optical phased array (OPA) devices are being actively investigated to develop compact solid-state beam scanners, which are essential in fields such as LiDAR, free-space optical links, biophotonics, etc. Based on the unique nature of perfluorinated polymers, we propose a polymer waveguide OPA with the advantages of low driving power and high optical throughput. Unlike silicon photonic OPAs, the polymer OPAs enable sustainable phase distribution control during beam scanning, which reduces the burden of beamforming. Moreover, by incorporating a tunable wavelength laser comprising a polymer waveguide Bragg reflector, two-dimensional beam scanning is demonstrated, which facilitates the development of laser-integrated polymeric OPA beam scanners.

Two-Dimensional Fast Beam Scanning Lidar System Based on FPGA Control

Two-Dimensional Fast Beam Scanning Lidar System Based on FPGA Control

Dually modulated photonic crystals enabling high-power high-beam-quality two-dimensional beam scanning lasers

Mechanical-free, high-power, high-beam-quality two-dimensional (2D) beam scanning lasers are in high demand for various applications including sensing systems for smart mobility, object recognition systems, and adaptive illuminations. Here, we propose and demonstrate the concept of dually modulated photonic crystals to realize such lasers, wherein the positions and sizes of the photonic-crystal lattice points are modulated simultaneously. We show using nano-antenna theory that this photonic nanostructure is essential to realize 2D beam scanning lasers with high output power and high beam quality. We also fabricate an on-chip, circuit-driven array of dually modulated photonic-crystal lasers with a 10 × 10 matrix configuration having 100 resolvable points. Our device enables the scanning of laser beams over a wide range of 2D directions in sequence and in parallel, and can be flexibly designed to meet application-specific demands.

Frequency-Domain and Spatial-Domain Reconfigurable Metasurface.

The recently proposed digital reconfigurable metasurfaces make it possible to manipulate electromagnetic (EM) waves flexibly. However, most existing reconfigurable metasurfaces can only exhibit a relatively single performance in the spatial domain. Here, we propose a general frequency- and spatial-domain reconfigurable metasurface (FSRM) that can manipulate the EM waves and realize reconfigurable functions in multifrequency bands. In the frequency domain, FSRM can convert different linearly polarized (LP) incident waves into left- and right-hand circularly polarized reflected waves, in which PIN diodes are used to switch the polarization conversions in different frequency bands. When the polarization direction of the incident LP wave is 45° from the +x-axis, the FSRM modulates the incident waves as a 1-bit programmable metasurface in the spatial domain. Two-dimensional beam scanning, vortex beams with orbital angular momentums, and specific beams with desired transmission directions are demonstrated via real-time adjustment of the digital coding state. To validate the modulation methodology, an FSRM prototype is fabricated and measured, which could respond to different functions for different polarization incidences. The measured results agree well with the theoretical analyses. The proposed FSRM will provide new opportunities for smart material designs.

A K / Ka ‐band dielectric and metallic 3D printed aperture shared multibeam parabolic reflector antenna for satellite communication

A K/Ka-band (22-33 GHz) high-gain aperture shared multibeam parabolic reflector antenna is proposed. It performs a two-dimensional beam scanning from a shared single parabolic reflector by introducing off-focal feeds. The feed array is placed on and off the focal of the parabolic reflector. Traditionally, the feed blockage has a great impact on the performance of the antenna, which reduces the gain and increases the sidelobe level. The purpose of this paper is to suppress the negative effects of feed blockage by using hybrid material processing method. Both dielectric and metallic 3D printing technologies are used for antenna fabrication. The parabolic reflector antenna is printed by selective laser melting using aluminum alloy. The feed array and the supporting structures are printed by stereolithography apparatus in resin to control the blockage. The method helps to suppress the sidelobe level from −10 to −15 dB and to enhance gain by up to 2.3 dBi. The reflection coefficient is less than −10 dB, while the coupling coefficient between the ports is less than −20 dB over the entire designed band. At 31.5 GHz, the simulated maximum gain of the antenna are 30.7, 29.1, and 29.7 dBi, when different port separately excites. Multiple beams at ±15° and 0° are observed on both E- and H-planes. Besides, it also verifies the possibility to use dielectric and metallic 3D printing technologies in hybrid for microwave device fabrication.

A Novel 1-Bit Reconfigurable Transmitarray Antenna Using a C-Shaped Probe-Fed Patch Element With Broadened Bandwidth and Enhanced Efficiency

A 16 ×16 -element reconfigurable transmitarray antenna (RTA) is designed and experimented in this paper. The proposed element consists of a receiving (Rx) structure and a transmitting (Tx) structure. The rectangular patch with C-shaped probe-fed is designed as the Tx structure to obtain the characteristics of broad bandwidth and low loss, where the U-shaped slot patch is designed as the Rx structure to obtain simple structure. Two PIN diodes are symmetrically integrated on the C-shaped feeding line. By turning them ON or OFF simultaneously, the induced current directions are reversed, thus achieving two phase states with 180° phase difference. The low insertion loss of 0.47 dB and the 3-dB transmission bandwidth of 16.0% are achieved by employing the stepped impedance matching technique. A Ku-band 256-element reconfigurable prototype with 512 PIN diodes is designed, fabricated, and measured. The measured peak gain at 12.2 GHz are 22.1 dBi with aperture efficiency of 21.2% and a 3-dB gain bandwidth of 12.3%. The measured results demonstrate the two-dimensional electronic beam scanning capability within ±60° as well. The proposed 1-bit RTA design exhibits good radiation performance, making it a promising candidate for advanced wireless communication applications.

Effects of laser-induced periodic surface structures on the superconducting properties of Niobium

It is well known that the use of ultrashort (fs) pulsed lasers can induce the generation of (quasi-) periodic nanostructures (LIPSS, ripples) on the surface of many materials. Such nanostructures have also been observed in sample’s surfaces irradiated with UV lasers with a pulse duration of 300 ps. In this work, we compare the characteristics of these nanostructures on 1-mm and on 25-μm thick niobium sheets induced by 30 fs n-IR and 300 ps UV pulsed lasers. In addition to conventional continuous or burst mode processing configurations, two-dimensional laser beam and line scanning modes have been investigated in this work. The latter allows the processing of large areas with a more uniform distribution of nanostructures at the surface. The influence of the generated nanostructures on the superconducting properties of niobium has also been explored. For this aim, magnetic hysteresis loops have been measured at different cryogenic temperatures to analyse how these laser treatments affect the flux pinning behaviour and, in consequence, the superconductor’s critical current values. It was observed that laser treatments are able to modify the superconducting properties of niobium samples.

A K-Band 3-D Printed Focal-Shifted Two-Dimensional Beam-Scanning Lens Antenna With Nonuniform Feed

A K-band (18-26.5 GHz) two-dimensional (2-D) beam scanning antenna is proposed. The hyperbolic lens is fed by an array of focal-shifted horns with nonuniform aperture. The feed at the focal point of the lens generates the boresight vertical beam, while the off-focal feeds are responsible for tilted beams. The nonuniform horn aperture helps to mitigate the gain decrement from the lens aperture tapering. It is fabricated taking full advantage of dielectric and metallic 3-D printing technologies. The lens is printed by stereolithography apparatus (SLA) in resin. The feed horn array is printed by selective laser melting (SLM). Process-wise, it features low cost, short turnaround time, and the capability to implement complex geometries versus traditional computer numerical control machining and mold casting. Simulation and measurement indicate that the antenna features desirable matching below -15 dB and mutual coupling between adjacent port below -25 dB. The gain is above 23 dBi across the K-band. Multiple beams at ±32°, ±12°, and 0° are observed on E- and H-planes. The proposed design can either function as multibeam antenna or a beam-scanning antenna together with switches. It is a capable candidate for applications such as multiple target tracking and wide region monitoring.

Cascaded Butler Matrix with Two-Dimensional Beam Scanning Capability at 28 GHz for 5G Wireless System

Cascaded Butler Matrix with Two-Dimensional Beam Scanning Capability at 28 GHz for 5G Wireless System

New functionalities of potassium tantalate niobate deflectors enabled by the coexistence of pre-injected space charge and composition gradient

In most beam steering applications such as 3D printing and in vivo imaging, one of the essential challenges has been high-resolution high-speed multi-dimensional optical beam scanning. Although the pre-injected space charge controlled potassium tantalate niobate (KTN) deflectors can achieve speeds in the nanosecond regime, they deflect in only one dimension. In order to develop a high-resolution high-speed multi-dimensional KTN deflector, we studied the deflection behavior of KTN deflectors in the case of coexisting pre-injected space charge and composition gradient. We find that such coexistence can enable new functionalities of KTN crystal based electro-optic deflectors. When the direction of the composition gradient is parallel to the direction of the external electric field, the zero-deflection position can be shifted, which can reduce the internal electric field induced beam distortion, and thus enhance the resolution. When the direction of the composition gradient is perpendicular to the direction of the external electric field, two-dimensional beam scanning can be achieved by harnessing only one single piece of KTN crystal, which can result in a compact, high-speed two-dimensional deflector. Both theoretical analyses and experiments are conducted, which are consistent with each other. These new functionalities can expedite the usage of KTN deflection in many applications such as high-speed 3D printing, high-speed, high-resolution imaging, and free space broadband optical communication.

Real-time two-dimensional beam steering with gate-tunable materials: a theoretical investigation

A leaky-wave antenna is proposed that furnishes two-dimensional (2-D) beam scanning in both elevation and azimuth planes via electrical control in real time, and at a single frequency. The structure consists of a graphene sheet on a metal-backed substrate. The 2-D beam-scanning performance is achieved through the proper biasing configuration of graphene. Traditional pixel-by-pixel electrical control makes the biasing network a huge challenge for chip-scale designs in the terahertz regime and beyond. The method presented here enables dynamic control by applying two groups of one-dimensional biasing on the sides of the sheet. They are orthogonal and decoupled, with one group offering monotonic impedance variation along one direction, and the other sinusoidal impedance modulation along the other direction. The conductivity profile of the graphene sheet for a certain radiation angle, realized by applying proper voltage to each pad underneath the sheet, is determined by a holographic technique and can be reconfigured electronically and desirably. Such innovative biasing design makes real-time control of the beam direction and beamwidth simple and highly integrated. The concept is not limited to graphene-based structures, and can be generalized to any available gate-tunable material system.

A Fabry–Pérot Antenna With Two-Dimensional Electronic Beam Scanning

A novel fixed-frequency electronically steerable Fabry–Perot Antenna (FPA) with electronic two-dimensional (2-D) (azimuth and elevation) steering capability is presented. The configuration is based on a centrally fed Fabry–Perot cavity (FPC) loaded with a tunable high impedance surface (HIS). Varactor diodes are used to electronically tune the HIS reflection coefficient, forming four azimuthal sectors that are independently controlled by four control signals, respectively. It is demonstrated that this simple configuration generates a pencil beam that can be pointed to eight discrete azimuthal directions, whereas continuous elevation scanning is also attained simultaneously for each azimuthal direction by controlling the leaky-wave propagation constant. The theory, simulation analysis, and experimental results obtained from a prototype operating at 5.5 GHz are presented to validate the antenna design.

Experimental characterization of two-dimensional pencil beam scanning proton spot profiles

Dose calculations of pencil beam scanning treatment plans rely on the accuracy of proton spot profiles; not only the primary component but also the broad tail components. Four films are placed at several locations in air and multiple depths in Solidwater® for six selected energies. The films used for the primary components are exposed to 50–200 MU to avoid saturation; the films used for the tail components are exposed to 800, 8000 and 80 000 MU. By applying a pair/magnification method and merging these data, dose kernels down to 10−4 of the central spot dose can be generated. From these kernels one can calculate the dose-per-MU for different field sizes and shapes. Measurements agree within 1% of dose-kernel-based calculations for output versus field size comparisons. Asymmetric, comet-shaped profile tails have a bigger impact at superficial depths and low energies: the output difference between two orientations at the surface of a rectangular field of 40 mm×200 mm is about 2% at the isocentre at 100 MeV. Integration of these dose kernels from 0 to 40 mm radius shows that the charge deficit in the Bragg peak chamber varies <2% from entrance to the end of range for energies <180 MeV, but exceeds 5% at 225 MeV.

Spectrometer and scanner with optofluidic configuration

We present a spectrometer and scanner based on optofluidic configurations. The main optical component of the spectrometer is a compound optical element consisting of an optofluidic lens and standard blazed diffraction grating. The spectrum size can be changed by filling the lens cavity with different liquids. The scanner comprises two hollow 45° angle prisms oriented at 90° to each other. By changing the liquid inside the prisms, two-dimensional light beam scanning can be performed.

Actuator Mechanism Using Suspension-wire for 2D Scanning

Laser beam scanning technology has been used in various machinery such as laser beam printers, laser processing machines. Recently, the usage such as distance sensors for automobiles, area sensors for robots has expanded further. According to it, the miniaturization of beam scanning equipment, advanced features, and low-pricing have also come to be called for strongly. We suggest a method of two-dimensional beam scanning by driving a lens with an electromagnetic actuator. We use suspension wires to hold the scan lens. As a result, two-dimensional beam scanning is possible by simple structure. This paper describes the structure of the scanner module system and characteristics of the prototype model.

Two-dimensional beam-scanning microstrip leaky-wave antenna

A novel two-dimensional beam-scanning microstrip leaky-wave antenna (MLWA) is presented. The proposed antenna consists of two half-width MLWA with a phase-shifter. This new type of MLWA has the advantages of two-dimensional beam-scanning and suppressing back lobes. This reduced size MLWA is useful in automotive radar systems and air traffic control.

2D Beam Scanning Planar Antenna Array Using Composite Right/Left-Handed Leaky Wave Antennas

A novel two-dimensional (2D) beam scanning antenna array using composite right/left-handed (CRLH) leaky-wave antennas (LWAs) is proposed. The antenna array consists of a set of CRLH LWAs and a Butler matrix (BM) feeding network. The direction of the beam can be scanned two-dimensionally in one plane by changing frequency and in the other plane by switching the input ports of the BM. A four-element antenna array in the microstrip line configuration operating at 10.5 GHz is designed with the assistance of full-wave simulations based on the method of moment (MoM) and the finite-element method (FEM). The antenna array is fabricated and radiation characteristics are measured. The wide range 2D beam scanning operation with the angle from -30deg to +25 deg in one plane by sweeping frequency from 10.25 GHz to 10.7 GHz and with four discrete angles of -46 deg, -15 deg, +10 deg, and +35 deg in the other plane by switching the input port is achieved.

Fiber-optic scanning two-photon fluorescence endoscope

We report on the development of a miniature, flexible, fiber-optic scanning endoscope for two-photon fluorescence imaging. The endoscope uses a tubular piezoelectric actuator for achieving two-dimensional beam scanning and a double-clad fiber for delivery of the excitation light and collection of two-photon fluorescence. Real-time imaging of fluorescent beads and cancer cells has been performed.