Large Scan Angles Research Articles

Complementary split resonant ring inspired wide-angle frequency-scanning patch array leaky-wave antenna with open-stopband suppression

In this paper, a wide-angle scanning and dual-linearly polarized leaky-wave antenna (LWA) is proposed based on symmetrical complementary split resonant ring (CSRR) feeding lines. The CSRR excites high-dispersed spoof surface plasmon polaritons (SSPPs) and is inspired to enlarge the scanning angle of the circular patch array antenna. The coupling between CSRR and circular patch determines the unit cell dispersion characteristics of LWA, and the coupling between CSRR and circular patch is controlled by designing their respective periods, p/b, to suppress the open-stopband and reduce the grating lobe, The value of p/b controls the frequency range of the open-stopband. Two parallel CSRR feeding lines are located on the bottom layer of the antenna and feed the array antenna of 11 circular patches above the feeding layer with both differential and common modes excitations. The two modes switch with 1-bit phase shifters on the two parallel feeding lines fed with a Wilkinson power splitter and electronically switch dual-linearly polarized radiations. The proposed scenario of the LWA prototype is validated through simulations and experiments. According to the measurements, horizontally polarized radiation achieves large beam scanning angle from −59.5° to +40° in the frequency range from 8 to 11 GHz with common mode excitation. And vertically polarized radiation scanning the main beam from −47° to +41° in the frequency range from 7.8 to 10.8 GHz with differential-mode excitation. The measured peak gains of the two polarizations are 14.4 dBi and 14.2 dBi, respectively, and the cross-polarization ratios are above 21 dB.

Structural Analysis of Glazed Tubular Tiles of Oriental Architectures Based on 3D Point Clouds for Cultural Heritage

Abstract. Laser scanning, along with its resultant 3D point clouds, constitutes a prevalent method for the documentation of cultural heritage. This paper introduces a novel workflow for the structural analysis of glazed tubular tiles that adorn the roofs of historical buildings in the Orient, utilizing 3D point clouds. The workflow integrates a robust segmentation algorithm utilizing the maximum principal curvature and normal vectors. Moreover, clustering algorithms, including DBSCAN, are incorporated to refine the clusters and thus increase segmentation accuracy. Structural analysis is enabled by cylindrical model fitting, which allows for the estimation of parameters and residuals. While the results exhibit commendable performance in individual tile segmentation, it is imperative to address the impact of substantial variations in scanning range and incident angles before engaging in the structural analysis fitting process. The results of experiment demonstrate that under conditions of significantly large scanning angles, the root mean square error (RMSE) for inadequately fitted tiles can extend to 0.066 m, surpassing twice the RMSE observed for well-fitted tiles. The proposed workflow proves to be applicable and exhibits significant potential to advance practices in cultural heritage documentation.

Synthesis of Antenna Array Radiation Pattern at Large Scanning Angles Using Genetic Algorithm

At present, in most modern communication systems, for example, in modern satellite terminals, the use of scanning beam antennas, i. e. antenna arrays is assumed. At the same time, at large scanning angles, the side lobe level (SLL) increases strongly and decrease in the gain is observed. In this regard, the problem of finding a procedure for synthesizing an amplitude-phase distribution (APD) with low SLL and high gain (G) at large scanning angles comes up. One of the ways to reduce SLL and compensate for the decrease in G is to synthesize the optimal APD (in terms of the maximum G and minimum SLL) using optimization algorithms. At the same time, taking into account the characteristics of the radiation pattern of the array emitters requires numerical electrodynamic calculation. The goal of this paper is to develop a procedure for the synthesis of APD with low SLL for linear and rectangular antenna arrays at various, including large, scanning angles and compensation for G reduction using a genetic algorithm and numerical electrodynamic calculation. The methods for studying the characteristics of antenna radiators are numerical electrodynamic modeling by the finite element method (FEM) in Ansys HFSS computer-aided design system and optimization of the APD for a given radiation pattern(RP) by a random search method using partial diagrams of antenna elements. The novelty is the combination of accurate numerical electrodynamic calculation of the RP of antenna elements and optimization search for APD for the synthesis of the required RP using partial diagrams. As a result, a procedure for APD synthesis of linear and uniform rectangular equidistant (for example, 8- and 64-element) antenna arrays has been developed, taking into account the exact electrodynamic characteristics of antenna elements and their mutual resistance. Radiation patterns were obtained taking into account the effect of neighboring elements, with the help of which, using a genetic algorithm, APDs on emitters were found at different scanning angles. The change in SLL and G of the antenna array is analyzed at different scanning angles using different APDs. The proposed algorithm allows to synthesize APD for a RP with low SLL and high G at scanning angles up to 40° for linear antenna array and up to 80° in the case of a uniform rectangular antenna array. The results of this work are relevant in the problems of radiation pattern synthesis, since the proposed solution provides a significant gain in the radiation pattern synthesis rate of APD of linear and rectangular antenna arrays, especially for systems with a large number of antenna elements. At the same time, it is possible to maintain a high G at large scanning angles, and achieve a significant reduction of SLL.

Beam Steering Technology of Optical Phased Array Based on Silicon Photonic Integrated Chip.

Light detection and ranging (LiDAR) is widely used in scenarios such as autonomous driving, imaging, remote sensing surveying, and space communication due to its advantages of high ranging accuracy and large scanning angle. Optical phased array (OPA) has been studied as an important solution for achieving all-solid-state scanning. In this work, the recent research progress in improving the beam steering performance of the OPA based on silicon photonic integrated chips was reviewed. An optimization scheme for aperiodic OPA is proposed.

Wide-angle high-precision electronically controlled continuous beam scanning implementation based on MLAS cascaded AFOC

Microlens array scanner (MLAS), as a rapidly growing branch of the semisolid micro-mechanical beam scanning system, can achieve large-scale beam scanning through small-scale (μm) physical motion, which is an effective beam scanning scheme that balances aperture, field of view (FOV), inertia, and other vital indicators. However, the discrete addressing caused by the periodic structure of microlens array (MLA) will affect the scanning accuracy in applications. We design and develop a continuous laser beam scanning device with an effective aperture of 20 mm based on MLAS and adaptive fiber collimator (AFOC), and the scanning beam quality is close to the diffraction limit. In addition, the electrical control mechanism of the device is explained, which achieves a scan FOV of 20°, a scan angular velocity of 10,000°/s, and two-dimensional (2D) scan. This approach effectively realizes a beam scanning system with excellent comprehensive performance, including large aperture, large scan angle, high precision, high speed, tunable wavelength, and high power.

Experimental realization of an ultra-thin and continuous scanning metasurface mimicking a Luneburg lens

Luneburg lens is traditionally a spherical dielectric with centro-symmetric and graded refractive index, which has been widely applied in civilian and military fields due to its outstanding abilities of focusing or collimating electromagnetic waves. However, the existing designs of Luneburg lens generally suffer from the disadvantages of bulkiness, complex fabrication process, and limited scanning angles, etc. Herein, a planar metasurface that could mimic the planar Luneburg lens is designed by utilizing the addition theorem. It has been experimentally verified that the Luneburg-like lens has large and continuous scanning angles from −52° to 52° at a frequency of 10 GHz if an excitation antenna is moved along a straight line. Besides, the total thickness of the proposed lens is only 3 mm and it has the advantages of low cost, ease of fabrication, as well as being isolated from the feeder. As a result, the proposed Luneburg-like lens has great potential values of being flexibly applied in numerous fields.

A circularly polarized phased array antenna with 60° scanning in the D-plane using a top-loaded patch

The requirements for circularly polarized (CP) phased array antennas are growing with the rapid development of electronic systems. To achieve a low-profile, wideband, and large scanning-angle CP, we constructed a novel CP unit cell with a two-layer folded coupling patch and a top-loaded patch. The design of the folded coupling patch was based on the principle of reverse current cancellation. Compared with the single-layer coupling patch, the folded coupling patch suppressed the occurrence of strong in-band resonance and obtained a wider axial ratio (AR) bandwidth. To solve the problem of AR performance deterioration in the D-plane scanning, we introduced the top-loaded patch to replace the thick wide-angle impedance matching layer, which improved the difference in co-polarization components and reduced cross-polarization level. Thus, a large scanning angle of more than 60° in the D-plane was obtained. An 8 × 8 planar array based on the proposed CP unit cell was designed. The array achieved a 3.9:1 (3.2–12.5 GHz) AR bandwidth and up to 60° scanning angle in the D-plane and 70° in the E-/H-plane; an AR smaller than 3 dB was demonstrated over the entire scanning range.

Design of Leaky-Wave Antenna With Wide-Angle Backfire-to-Forward Beam Scanning Based on Generalized Pattern Synthesis

Frequency-scanning antenna has been extensively explored in radar and vehicle communication systems, but it is a challenge to provide methodological guidance to achieve a wide scanning angle. Here, a generalized pattern synthesis method is proposed and a leaky-wave antenna with wide scanning range is designed to verify the technique. First, a generalized antenna element (GAE) is presented, whose main beam can steer continuously with frequency. Meanwhile, the phase constant of the leaky wave determines the beam direction of the array factor. Then, a leaky-wave antenna can steer with a large beam scanning angle and stable gain as patterns of the array factor and the GAE are manipulated simultaneously. To verify, a prototype SIW LWA with double-layer transverse slots is fabricated and measured. Experimental results show this antenna achieves continuous dual-beam scanning from backfire (-90∘) to forward (±20∘) from 12.4 GHz to 19.9 GHz with a total coverage range of 220∘ and the realized gain varying from 8.3 dBi to 12.8 dBi.

Millimeter-Wave Wide-Angle Scanning Phased Array Antenna Based on Heterogeneous Beam Elements

By imitating the element inclined beam distribution of a curved surface conformal (CSC) phased array antenna (PAA), a pseudo-curved surface conformal (PCSC) PAA realizes wide-angle scanning while maintaining a planar low profile. Inspired by the PCSC PAA, this communication proposes a PAA based on heterogeneous beam elements (HBEs) to realize wide-angle scanning. Using HBEs introduces a new design degree of freedom (DoFs), namely the element beam shape, to PAA. By optimizing HBEs and their arrangement, the effective aperture of a PAA can be increased at large scanning angles, and thus the scanning range can be improved. To verify the idea, first, a wide-beam 1×4-element subarray is developed. Then, a standard 4×4-element PAA is implemented using four uniform 1×4-element subarrays, achieving a >±60° 3-dB gain variation scanning range. At last, based on the standard PAA, by adjusting its structure to tailor four subarrays’ beam inclinations, a 4×4-element HBE PAA is designed. It further improves the scanning range to >±70° at an average cost of ~1.5dBi broadside scanning gain within the 5G mmWave band (24.25-29.5GHz, 19.5%). To the authors’ best knowledge, compared with the former planar mmWave PAAs, the proposed design shows the widest scanning range in a wide bandwidth.

Nonlinear Dynamics of Large-Angle Circular Scanning With an Aluminum Nitride Micro-Mirror

This paper introduces a model for nonlinear dynamics of a resonant micro-mirror designed for large-angle circular scanning. The mirror is driven by aluminum nitride thin-films within a chip-scale vacuum package, which permits large scan angles to be achieved at low voltages, but with substantial nonlinearity in the mirror’s dynamic response. A nonlinear mirror model is proposed and analyzed to identify major trends in mirror performance and implications for mirror design. Analysis focuses on coupling between two axes, which has not been closely examined for multi-axis micro-mirrors. Coupling between axes is found to be capable of augmenting scan amplitude or causing mirror response to collapse from a circular scan patter to an ellipse or line scan, depending on relative strength of model parameters. Good agreement is achieved between modeled and experimental micro-mirror response, with scan amplitudes near <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm$</tex-math> </inline-formula> 13 degrees under 1.5 V excitation.2022-0181

Research of Non-mechanical Beam Scanning Technology

Laser beam scanning technology has been widely used in various fields such as LIDAR, photoelectric detection and space optical communication, etc. Mechanical scanning has problems such as inflexibility and low scanning rate. This paper introduces the basic principles of acoustic-optical scanning, electro-optical scanning, optical phased array and MEMS scanning, and analyses the advantages and disadvantages of several scanning methods and the main application scenarios, and finds that the current optical scanning technology is developing towards large scanning angle, high accuracy, fast response and miniaturization, among which the liquid crystal optical phased array and MEMS scanning technology are relatively mature. The scanning angle of the LCD optical phased array can reach ±10°, and the scanning angle of the MEMS can reach 6.6°*4.4°, which has a broad development prospect.

A Novel Reflection-Mode Fabry–Perot Cavity Antenna With Broadband High Gain and Large Beam-Scanning Angle by Janus Partially Reflective Surface

Operational mechanism and design methodology of a novel reflection-mode (R-mode) Fabry–Perot cavity antenna (FPCA) are proposed in this article. Unlike common transmissive-mode (T-mode) FPCAs, the R-mode one places the feed antenna outside the cavity and introduces a Janus partially reflective surface (PRS), reducing the coupling between the feed and the FP cavity, while obtaining flexible displacement freedom of the feed to achieve a large beam scanning angle. The proposed R-mode FPCA employs a compact triple-layered Janus PRS, a simple ground plane, and a linearly polarized microstrip feed. The Janus PRS is applied to achieve bidirectional asymmetric transmission from the outside to the inside of the cavity to ensure the excitation efficiency and gain enhancement. In addition, a beam scanning model is proposed to obtain the spatial position of the feed and the maximum beam scanning angle under the specific antenna size. Finally, a proof-of-concept prototype is designed, fabricated, and measured at X-band. The measurement results agree well with the simulation, the 3 dB gain bandwidth of 19.7% is achieved. The peak gain in this range is 17.35 dBi and a large 3-D beam scanning range of [−35°, 35°] is also obtained.

On the design of piezoelectric MEMS scanning mirror for large reflection area and wide scan angle

This study designs and implements the piezoelectric MEMS scanning mirror with large scan angle and reflection area for light beam manipulating applications. In this design, the scanning mirror has a large mirror plate (3 mm in diameter) supported by two T-shape torsional springs. The U-shape piezoelectric cantilever acts as the actuator to drive the scanning mirror through the transmission spring. The analytical model is established to provide the design guideline of transmission spring to increase the scan angle. In application, the proposed designs are fabricated on the SOI (silicon on insulator) wafer deposited with the PZT film. Measurements indicate the fabricated mirror could reach an optical scan angle of 140-degree (mechanical scan angle of ±35-degree) when driving at its resonant frequency of 1.5 kHz with a unipolar driving voltage of 42 V. Moreover, no vacuum environment is required for the presented scanning mirror to achieve the above scan angle. This is an extremely large optical scan angle for the MEMS scanner with a mirror plate of 3 mm in diameter. In addition, another U-shape piezoelectric cantilever serves as the position sensor to detect the scan angle of mirror plate. The sensing signals show good linearity with the scan angles and can be exploited as the feedback control. Measurements also demonstrate that the micro scanner could withstand 1500 g shock loading, and the deviation of scan angle is less than 10% after the cycling test under 10 V pp resonant driving in 95%RH and room temperature for 0.2 billion cycles.

Dual broad Band-Stop Polarization-Insensitive and scanning angle stability Frequency Selective Surface

In this communication, broad dual band-stop characteristics, polarization–insensitive FSS with large scanning angle stability is developed. A simple square ring with T – shaped resonator is implemented to develop dual-band characteristics. L – Shaped and circular ring metallic layers are incorporated on the proposed unit cell FSS to get optimum polarization insensitive dual-stop frequency bands. The proposed FSS is fabricated on one side of a single layer FR4 substrate. The smallest dimension of the unit cell is 0.1λ0×0.1λ0×0.01λ0 (10.2mm×10.2mm×1.6mm), where λ0 is the free space wavelength at the lower cutoff frequency of 1.97 GHz. The proposed −10 dB dual-band FSS has rejection characteristics over the frequency ranges of (1.97 GHz – 4.06 GHz) and (8 GHz – 12.3 GHz). The achieved −20 dB bandwidth are (2.74 GHz – 3.43 GHz) and (9.5 GHz – 11 GHz) under the TE mode. Equivalent circuit model is implemented to ensure the validity of the work. The fabricated FSS can be used to shield EM wave for S–band and X–band applications.

Two-Dimensional High-Efficiency Transceiver Integrated Optical Phased Array With Dual-Port Antenna

We propose a 1 × 32 silicon photonics transceiver integrated optical phased array (OPA) with a large scanning angle. It can process receive and transmit signals simultaneously, which effectively increases the on-chip signal transmission efficiency. The simulation shows that the phase-tuned 62.2° lateral beam steering without grating lobe and the wavelength-tuned 31.2° longitudinal beam steering can be achieved in the transmitting mode, and the overall optical loss is less than 9.1 dB. In the receiving mode, the combination of the two detection methods reduces the complexity of the system while ensuring the sensitivity of the system. According to statistics, an effective collection area of 43.3% per unit area can be achieved in the receiving mode, which provides a reliable guarantee for subsequent high-quality signal processing.

Scanning Angle Extension of a Millimeter-Wave Antenna Array Using Electromagnetic Band Gap Ground

A compact phased array with extended beam steering characteristics for the millimeter-waveband of the fifth-generation (5G) applications is presented in this communication. An E-shaped patch antenna placed on an electromagnetic bandgap ground (EBGG) with operating bandwidth of 24.2–27.5 GHz is used as the basic building block of the eight-element linear array. The array utilizes both the in-phase reflection characteristic for broad element radiation pattern and the bandgap characteristic for mutual coupling reduction for limited inter-element spacing of the proposed array. The existence of the EBGG enables a compact array with the inter-element spacing of around 0.4 wavelengths at the center frequency, yet the isolation between each element is still above 17 dB within the whole band of interest, which also helps to increase the array directivity at large scanning angles. The scanning angle of the array with the electromagnetic bandgap (EBG) structure ranges from −75° to 75° at 26 GHz within 3 dB scanning loss. The proposed EBGG extends the antenna array’s spatial coverage and enables a compact size of the array, which is very attractive for 5G millimeter-wave (mm-wave) application.

Single-beam leaky-wave antenna with wide scanning angle and high scanning rate based on spoof surface plasmon polariton

We propose a single-beam leaky-wave antenna (LWA) with a wide-scanning angle and a high-scanning rate based on spoof surface plasmon polariton (SSPP) in this paper. The SSPP transmission line (TL) is etched with periodically arranged circular patches, which converts the slow-wave mode into the fast-wave region for radiation. The proposed LWA is designed, fabricated, and tested. The simulated results imply that the proposed LWA not only achieves a high radiation efficiency of about 81.4%, and a high scanning rate of 12.12, but also has a large scanning angle of 176° over a narrow operation bandwidth of 8.3–9.6 GHz (for |S 11| < –10 dB). In addition, the simulated average gain of the LWA can reach as high as 10.9 dBi. The measured scanning angle range is 175° in the operation band of 8.2–9.6 GHz, and the measured average gain is 10.6 dBi. The experimental results are consistent with the simulation, validating its performance. An antenna with high radiation efficiency, wide scanning angle range, and high scanning rate has great potential for application in radar and wireless communication systems.

Multi-dimensional and large-sized optical phased array for space laser communication

In this study, we propose a novel multi-dimensional and large-sized optical phased array theory for space laser communication that addresses the theoretical limitations of the conventional optical phased array. We theoretically analyzed the principle of this phased array technology. The results of simulation and laboratory experiment clearly showed it can realize the large scanning angle and high optical gain required for communication. The novel optical phased array theory is of great significance to the revolution of miniaturization and networking in the field of space laser communication.

Scanning Angle Magnification with Compact Reflective Optics for Light Detection and Ranging

The function of lidar requests a large scanning angle for a wide field of view and a well calibrated collimation of the laser beam for distant sensing. Besides meeting the required functionality, the compact form factor of the whole optical system is also highly desirable for the ease of being installed in mobile systems. In corresponding to the currently developed phase array laser which can achieve beam scanning without mechanical movement but still with a small scanning angle, a compact optics consisting of only two reflective surfaces has been proposed to magnify the scanning angle of a laser beam up to seven times while keeping the divergence of the laser beam smaller than 8 mrad for some short distance applications. The prototype has been prepared and evaluated with the expected performance.

Scanning optimization of an electrothermally-actuated MEMS mirror for applications in optical coherence tomography endoscopy

Probe is an important component of the optical coherence tomography (OCT) system. Electrothermally-actuated micro-electromechanical (MEMS) mirrors are especially suitable for OCT endoscopic imaging due to their large scan angle, low driving voltage and high fill factor. However, endoscopic OCT imaging quality would be seriously affected by the nonlinear scanning characteristics of electrothermal MEMS mirrors as well as the distortion due to the need of placing the MEMS mirror on a 45° slope. In this work, an open-loop control method based on the transfer function of the MEMS mirror is proposed to optimize the overall optical trajectory scanned on the sample under a MEMS OCT probe. The transfer function of the electrothermal MEMS mirror is established and the relation between the MEMS mirror’s tilt angle and the final scanning trajectory on the sample is calculated. A PID control model based on the transfer function is developed and employed to generate the driving voltage signals that can be applied to the MEMS mirror for obtaining undistorted scanning trajectories on the sample. Experiments show that the proposed method can correct the scanning nonlinearity and the distortion without adding extra hardware. For instance, the linear scanning ratio is improved from 72% up to 98%; the fan-shaped distortion is reduced by a factor 3–5. This method is also applied to a swept-source OCT system and the image distortions are compensated effectively.