Accurate Beam Steering Research Articles

Terahertz wave beam control using optical phased array and array photomixer

Terahertz waves technology has attracted attention as a means of achieving ultrahigh-speed, high-capacity wireless communications. However, terahertz waves have high propagation loss due to their HF and high directivity. Therefore, terahertz wave intensity enhancement and beam steering are required. In this study, we discussed beam control of the terahertz wave generated by arrayed photomixers using an optical phased array (OPA). It was revealed that the terahertz beam steering by the OPA can be controlled with an error of less than 10°. Furthermore, we developed an automatic terahertz beam deflection system based on a hill-climbing algorithm and feedback control to improve the beam steering accuracy.

A 4 × 4 Active Antenna Array with Adjustable Beam Steering.

An adjustable 4×4 antenna array with electrical beam steering and polarization control is presented. Here, adjustability means the ability to correct the beam steering angle post-calibration. The objective is to improve the steering accuracy which is critical in point-to-point communication as inaccuracy will cause transmission failure due to a missed target. The accuracy is enhanced by adjusting the beam steering angle in beamforming calculations. To execute this, the system is calibrated by measuring several unit cells of a partial 4×4 array structure at different voltage bias points and calculating an average model of the phase shift profile. This reduces the phase error from variations between components and robust beam steering is achieved. This technique is utilized in far-field measurements, and fairly accurate initial beam steering angles are achieved at 3 GHz. The accuracy is further improved by over or under steering the desired angle in the beamforming calculations to finally achieve the steering angle of interest with an accuracy of 2∘. Overall, the main beam is incrementally steered from 0∘ to 45∘ with the gain ranging from 4.7 dB to 2.8 dB. The polarization control is also demonstrated in horizontal and vertical directions for a linearly polarized wave.

해상 환경에 따른 전자빔 보상방법 연구

In this study, motion compensation for electronic beams in sea environments is proposed. Because the radar on a ship fluctuates according to the sea environment, it is necessary to compensate for the fluctuation to achieve accurate beam steering. Unlike the fluctuations in the pitch and yaw directions, where only compensation for the beam steering value is required, the fluctuation in the roll direction causes the beam to rotate. Therefore, compensation for the rotation of the beam in the roll direction is necessary. For this purpose, beam rotation and 2-D beam steering were performed. Finally, the proposed method is applied to a 20×20 array and verified.

Design of a microwave power transmission demonstration system for space solar power station

A microwave power transmission (MPT) demonstration system was assembled to comprehensively emulate the operating mode of MPT in space solar power station (SSPS). Based on solid power amplifier and phased antenna array, this system comprised three main parts, that is, microwave power transmitting subsystem, microwave power rectenna subsystem, and power beam steering subsystem. It was employed to validate the constraint relationship between beam collection efficiency and the sizes of transmitting antenna and rectenna, transmission distance, operation frequency. High efficiency rectifying and accurate beam steering were also demonstrated. The power transmitting antenna was composed of 64 sub-arrays of patch antennas, with the dimension of 1.2 × 1.2 m2. In addition, the rectenna array was constructed as a corner truncated square with the side length of 2 m. Its design was based on the concept of perfectly matched layer and integrated rectifying surface. The power beam steering subsystem, implemented with software retrodirective idea, pointed the microwave beam to the rectenna according to the direction of arrival of the pilot signal. The experimental MPT system, operating at 5.8 GHz, transmitted 910 W microwave power across 30 m distance. At the power receiving end, the optimum rectenna conversion efficiency of 49.3% was obtained. With aid of the beam steering subsystem, beam granularity, and beam steering accuracy of 0.23 and 0.18° were achieved, respectively. The compositive experiment verified all function as power transmitting, receiving, rectifying, and steering of MPT system. MPT technology is thus driven toward engineering application, and will ultimately space solar power exploration.

An Accurately Steerable, Compact Phased Array System for Narrowbeam Ultrasound Transmission

For over more than a decade, ultrasound phased arrays have been playing a leading role in domains such as noninvasive diagnostic examination, nondestructive testing and sonar, and will continue to be indispensable in a wide range of new applications. Unlike the aforementioned traditional scanning systems, many new applications require a transmit-only configuration and work in the low ultrasound frequency range, consequently posing new challenges in low-cost phased array design. However, two sought-after features are still missing in current low-cost ultrasound phased array systems, namely broadband transmission and wide angular beam steering. In this work, a low-cost ultrasound phased array system is presented that enables the transmission of both narrowband and broadband signals. Accurate beam steering is achieved through the concept of Direct Digital Synthesis (DDS). The design features small, wide bandwidth MEMS transducers enabling grating lobe free beam patterns at high frequency and a broad angular beam steering range. The presented prototype supports 64 speaker elements and allows very fine amplitude and phase control over each transducer stage with respectively 10-bit and 12-bit resolution. The beam steering performance is validated for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}\times {10}$ </tex-math></inline-formula> calibrated uniform linear array design. In these measurements, an accuracy in the order of just a few degrees was observed, even at a steering angle of 70° off-axis.

A Multibeam Steerable Parametric Array Loudspeaker for Distinct Audio Content Directing

The parametric acoustic effect has gained much interest in airborne applications as parametric acoustic loudspeakers (PALs) for the unique characteristics of generating self-demodulated low-frequency acoustic waves with high directivity. The development of PAL applications currently requires advanced spatial control of demodulated audio signals for more sophisticated sound field reproduction. Targeting to enhance the control flexibility, this paper proposes an efficient, fully FPGA-based PAL system to provide multiple low-distortion audio signals of different contents to separate directions from a single PAL device. The proposed system can achieve accurate beamsteering by providing channel time delays in nanosecond resolution and can generate independent parametric beams from a time-division-multiplexing (TDM) scheme. The paper presents a compact and scalable FPGA solution for PAL in signal preprocessing, beamsteering, and multi-beam control. The proposed system is verified in simulation and demonstrative experiments for the realization of flexible steering of multiple distinct audio signals into desired directions simultaneously under the TDM control.

Task Autonomy of a Flexible Endoscopic System for Laser-Assisted Surgery.

Laser beam steering has been widely studied for the automation of surgery. Currently, flexible instruments for laser surgery are operated entirely by surgeons, which keeps the automation of endoluminal surgery at the initial level. This paper introduces the design of a new workflow that enables the task autonomy of laser-assisted surgery in constrained environments such as the gastrointestinal (GI) tract with a flexible continuum robotic system. Unlike current, laser steering systems driven by piezoelectric require the use of high voltage and are risky. This paper describes a tendon-driven 2 mm diameter flexible manipulator integrated with an endoscope to steer the laser beam. By separating its motion from the total endoscopic system, the designed flexible manipulator can automatically manipulate the laser beam. After the surgical site is searched by the surgeon with a master/slave control, a population-based model-free control method is applied for the flexible manipulator to achieve accurate laser beam steering while overcoming the noise from the visual feedback and disturbances from environment during operation. Simulations and experiments are performed with the system and control methods to demonstrate the proposed framework in a simulated constrained environment.

Evaluation of a Planar Reconfigurable Phased Array Antenna Driven by a Multi-Channel Beamforming Module at Ka Band

In this paper, a planar active phased array antenna demonstration with linear polarization (LP) at Ka Band (28-30 GHz) is presented. The proof of concept is carried out to evaluate the possible problems that may arise, to analyze possible calibration stages and to assess the viability of the integration of an active system with a Multi-Channel Beamforming Module (MCBM). To fulfill this task an $8\times 8$ -element planar array arranged in column subarrays of $1\times 8$ elements for 1D beam steering is proposed. The single element consists of a printed circular patch connected to a microstrip feeding line through metallic vias in a multilayered structure. Both the amplitude and phase distributions are performed by a commercial integrated circuit (IC) designed for transmission purposes, from the common port to each of the 8 output ports. Thus, an evaluation of the IC performance is also included within this work. Despite the inherent amplitude and phase feeding errors of the IC, the beam-steering accuracy of the system is reasonable. A nice correspondence between the simulated and measured $8\times 8$ -element array beam steering directions is obtained, with errors below 1° in the steering of the beam.

Grating lobe suppression in optical phased arrays by loading near-wavelength grating.

Optical phased arrays based on optical waveguides are compelling components enabling efficient and accurate beam steering. However, to avoid crosstalk between the waveguides, the element pitch is typically larger than one wavelength, which gives rise to grating lobes in real space. In this Letter, we report that near-wavelength gratings can be employed to suppress the grating lobes by utilizing the angular low-pass-filter characteristics. The properly designed near-wavelength grating acts as an angle-sensitive transmission structure. Nearly 100% transmissivity can be realized at small incident angles. However, it quickly declines to a low level when the incident angle is over the critical one. Then, a simple line current array is utilized to demonstrate the grating lobe suppression effect with the grating designed for TE-polarized incidence. Finally, we demonstrate that by loading the proposed grating designed for TM-polarized incidence upon a waveguide grating array with a 2.4 µm pitch, a grating lobe suppression of 10 dB can be achieved when scanning up to ±14∘.

Wide Field-of-View Locating and Multimodal Vital Sign Monitoring Based on ${X}$ -Band CMOS-Integrated Phased-Array Radar Sensor

In this article, an X -band complementary metal-oxide-semiconductor (CMOS)-integrated phased-array radar sensor is proposed to enable the subject localization and multimodal vital sign monitoring. With the accurate beam-steering (ABS) technique realized by both true-time delay and phase shifting at the transmitter, the phased-array radar sensor achieves 60° steering coverage for the locating and monitoring on the targeted subjects with fine beam-steering precision. With the interferometric time-phase analysis (ITPA) algorithm adopted to the dechirped signal at the receiver, the vital signs and falling are detected by the radar sensor. Fabricated in 65-nm CMOS technology, the radar sensor occupies 5.8 mm 2 of silicon area and consumes 740.7-mW power. A series of experiments was carried out to demonstrate the capabilities of the prototype radar sensor on localizing the targeted subjects, discerning vital signs, and detecting falling in a wide field of view (FoV).

이동형 지구국을 위한 저부엽 빔 형성 안테나에 관한 연구

Phased array antennas are commonly used in earth stations because of their fast and accurate beam steering characteristics. The sidelobe of earth station antennas is strictly regulated internationally to avoid affecting the adjacent satellites. To suppress the side lobe of the phased array antenna, the accurate amplitude and phase of the signal must be fed to each radiating element. This paper proposed a method for calculating the amplitude and phase of a signal. The proposed method can rapidly and accurately calculate the amplitude and phase of each radiating element signal by setting an arbitrary phase in the radiation pattern reference. In addition, the proposed method was verified through a beamforming problem that satisfies the domestic radiation pattern reference.

A 2–5.5 GHz Beamsteering Receiver IC With 4-Element Vivaldi Antenna Array

In this article, we present a four-element Vivaldi antenna array and beamsteering receiver IC for the fifth-generation mobile network (5G) new radio (NR). The implemented receiver utilizes a delay-based local-oscillator phase shift technique for accurate beamsteering, and it exhibits 1° to 2.4° phase tuning capability for 2-5 GHz bandwidth accordingly. On-chip delay measurement is performed with pilot signal generation and delay estimation capable of 2-ps accuracy. The IC is fabricated on 28-nm CMOS technology, it occupies an area of 1.4 × 1.4 mm 2 , including bonding pads, and consumes 22.8 mW at 2 GHz for single-receiver path operation. The receiver demonstrates wideband over-the-air reception with the prototype antennas.

High precision beam steering using a liquid crystal spatial light modulator

Liquid crystal spatial light modulators (LCSLMs) are novel phase modulation devices. Due to the dielectric properties of the orientation layer, the orientation layer has a voltage division effect on the driving voltage. A more effective analysis of the relationship between the driving voltage and phase modulation properties of LCSLMs is needed, as well as improved beam steering accuracy. In this paper, we establish an electrical model of an LCSLM, and propose a method for quantitatively calculating the liquid crystal (LC) layer voltage. This differential iterative method based on nonlinear least squares is used to analyze the LC molecular directors. Considering the thickness of the orientation layer, we calculate the LC director distribution and the voltage division effect of the LC layer, obtaining a more accurate electro-optic characteristic curve of the LCSLM, and verify the calculations by experiment. Experimentally, the average beam pointing error of the LCSLM was 0.0098° at 532 nm, representing a significant improvement of the beam steering accuracy.

A proposed method for linear accelerator photon beam steering using EPID.

Beam steering is the process of calibrating the angle and translational position with which a linear accelerator's (linac's) electron beam strikes the x‐ray target with respect to the collimator rotation axis. The shape of the dose profile is highly dependent on accurate beam steering and is essential for ensuring correct delivery of the radiotherapy treatment plan. Traditional methods of beam steering utilize a scanning water tank phantom that makes the process user‐dependent. This study is the first to provide a methodology for both beam angle steering and beam translational position steering based on EPID imaging of the beam and does not require a phantom. Both the EPID‐based beam angle steering and beam translational steering methods described have been validated against IC Profiler measurement. Wide field symmetry agreement was found between the EPID and IC Profiler to within 0.06 ± 0.14% (1 SD) and 0.32 ± 0.11% (1 SD) for flattened and flattening‐filter‐free (FFF) beams, respectively. For a 1.1% change in symmetry measured by IC Profiler the EPID method agreed to within 0.23%. For beam translational position steering, the EPID method agreed with IC Profiler method to within 0.03 ± 0.05 mm (1 SD) at isocenter. The EPID‐based methods presented are quick to perform, simple, accurate and could easily be integrated with the linac, potentially via the MPC application. The methods have the potential to remove user variability and to standardize the process of beam steering throughout the radiotherapy community.

Performance analysis for W‐band antenna alignment using accurate mechanical beam steering

ABSTRACTThis article presents a study of antenna alignment impact on bit error rate for a wireless link between two directive W‐band horn antennas where one of them is mechanically steered by a Stewart platform. Such a technique is applied to find the optimal alignment between transmitter and receiver with an accuracy of 1° both in azimuth and elevation angles. The maximum degree of misalignment which can be tolerated is also reported for different values of optical power in the generation of W‐band signals by photonic up‐conversion. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1125–1128, 2017

SWIPT in 3-D Bipolar Ad Hoc Networks With Sectorized Antennas

In this letter, we study the simultaneous wireless information and power transfer (SWIPT) concept in 3-D bipolar ad hoc networks with spatial randomness. Due to the three spatial dimensions of the network, we introduce a 3-D antenna sectorization that exploits the horizontal and vertical spatial separations. The impact of 3-D antenna sectorization on SWIPT performance is evaluated for the power-splitting technique by using stochastic geometry tools. The theoretical and numerical results show that the 3-D sectorization achieves a more accurate beam steering in the 3-D space, which can be beneficial for both the information and the power transfer.

Two-Dimensional Quantization Method for Phased-Array Scanning

This paper describes a method for controlling the phase shifters in an electronically scanned two-dimensional phased-array antenna with digital phase shifters. The control algorithm, referred to as two-dimensional quantization (TDQ), significantly reduces the beam-steering errors and the quantization sidelobes caused by the digital phase quantization for a two-dimensional array by increasing the effective phase resolution in the scan-plane direction, and improving the stair-step approximation to an ideal linear phase gradient. This is accomplished by independently adjusting the phases of elements in the plane perpendicular to the scan plane to obtain the desired effective phase gradient. Examples are given showing that a 32 by 32 element planar array with three-bit phase shifters using this method can achieve a beam-steering accuracy equivalent to an array with eight-bit phase shifters. This permits the use of phase shifters with fewer bits to achieve the same beam-steering accuracy, reducing the cost of the array.

Multi-Beam Spatio-Spectral Beamforming Receiver for Wideband Phased Arrays

This paper reports the first analog integrated spatio-spectral beamforming front-end. The proposed front-end allows for accurate beam steering of signals with large fractional bandwidths, thus minimizing beam squinting, and simultaneous and independent steering of multi-carrier signals. Different spatio-spectral beamforming strategies are discussed and compared. As a proof of concept, an 8 GHz 2-channel, 4-frequency phased-array beamformer is designed and implemented in 65 nm CMOS. The IF signal on each channel is frequency split using an all passive 4-point analog FFT. The orthogonal frequency outputs are then beam-steered using an all passive I-Q vector-combiner. The RF circuit draws 22.8 mA from a 1.2 V supply while the analog baseband consumes 135 μW at 120 MS/s (9 pJ/conv.).

Time Reversal Based Broadband Synthesis Method for Arbitrarily Structured Beam-Steering Arrays

We propose a novel broadband beam pattern synthesis method to synthesize arbitrarily structured beam-steering arrays by utilizing time reversal technique. Unlike conventional frequency-domain array synthesis methods, this method achieves array excitation by taking the Fourier Transform of the time reversed version of the transient signals received by antenna elements. Using this method, designers can determine the array excitation over a wide frequency range at once by a single run of time reversal experiment, instead of performing time-consuming multi-objective optimizations of beam pattern cost-functions at each frequency. Furthermore, it does not require explicit measurements of element mutual coupling and platform scattering effects since the time reversal signals have implicitly taken into account those effects. The proposed method is theoretically analyzed with the antenna reciprocity and numerically validated with three dipole arrays of different configurations. The results show that this new method is capable of realizing accurate beam steering over a wide frequency band if the desired steering angle is located in the feasible angular scope of beam scan. The beam patterns with accurate beam steering are successfully achieved over a bandwidth of more than 1.5 GHz for three different dipole arrays, i.e., a typical linear dipole array, a grounded circular dipole array, and a dome-shaped dipole array.

Integrated holographic system for all-optical manipulation of developing embryos

We demonstrate a system for the combined optical injection and trapping of developing embryos. A Ti:sapphire femtosecond laser in tandem with a spatial light modulator, is used to perform fast and accurate beam-steering and multiplexing. We show successful intracellular delivery of a range of impermeable molecules into individual blastomeres of the annelid Pomatoceros lamarckii embryo by optoinjection, even when the embryo is still enclosed in a chorion. We also demonstrate the ability of the femtosecond laser optoinjection to deliver materials into inner layers of cells in a well-developed embryo. By switching to the continuous wave mode of the Ti:sapphire laser, the same system can be employed to optically trap and orient the 60 μm sized P. lamarckii embryo whilst maintaining its viability. Hence, a complete all-optical manipulation platform is demonstrated paving the way towards single-cell genetic modification and cell lineage mapping in emerging developmental biology model species.