Maximum Scan Angle Research Articles

A Large-Scan-Range Electrothermal Micromirror Integrated with Thermal Convection-Based Position Sensors.

This paper presents the design, simulation, fabrication, and characterization of a novel large-scan-range electrothermal micromirror integrated with a pair of position sensors. Note that the micromirror and the sensors can be manufactured within a single MEMS process flow. Thanks to the precise control of the fabrication of the grid-based large-size Al/SiO2 bimorph actuators, the maximum piston displacement and optical scan angle of the micromirror reach 370 μm and 36° at only 6 Vdc, respectively. Furthermore, the working principle of the sensors is deeply investigated, where the motion of the micromirror is reflected by monitoring the temperature variation-induced resistance change of the thermistors on the substrate during the synchronous movement of the mirror plate and the heaters. The results show that the full-range motion of the micromirror can be recognized by the sensors with sensitivities of 0.3 mV/μm in the piston displacement sensing and 2.1 mV/° in the tip-tilt sensing, respectively. The demonstrated large-scan-range micromirror that can be monitored by position sensors has a promising prospect for the MEMS Fourier transform spectrometers (FTS) systems.

Design of an Electromagnetic Micro Mirror Driving System for LiDAR.

Electromagnetic micro mirrors are in great demand for light detection and ranging (LiDAR) applications due to their light weight and low power consumption. The driven frequency of electromagnetic micro mirrors is very important to their performance and consumption. An electromagnetic micro mirror system is proposed in this paper. The model of the system was composed of a micro mirror, an integrated piezoresistive (PR) sensor, and a driving circuit was developed. The twisting angle of the mirror edge was monitored by an integrated PR sensor, which provides frequency feedback signals, and the PR sensor has good sensitivity and linearity in testing, with a maximum of 24.45 mV/deg. Stable sinusoidal voltage excitation and frequency tracking was realized via a phase-locked loop (PLL) in the driving circuit, with a frequency error within 10 Hz. Compared with other high-cost solutions using PLL circuits, it has greater advantages in power consumption, cost, and occupied area. The mechanical and piezoresistive properties of micro mirrors were performed in ANSYS 19.2 software. The behavior-level models of devices, circuits, and systems were validated by MATLAB R2023a Simulink, which contributes to the research on the large-angle deflection and low-power-consumption drive of the electromagnetic micro mirror. The maximum optical scan angle reached 37.6° at 4 kHz in the behavior-level model of the micro mirror.

Wide-Angle Scanning and High Isolation Dual-Polarized Base Station Antennas for Sub-6 GHz Applications

This paper presents a wide-angle scanning and high isolation base station antenna array. The antenna element employs a compact dual-polarized umbrella-shaped printed dipole with a small size of 0.23λ0 × 0.23λ0 × 0.26λ0, which provides the possibility for a small element spacing array. The antenna element possesses wide 3 dB beamwidth of 84.6∘ benefiting from the pulling down of the dipole arms. Then, a dual-layer metal superstrate structure and metal wall is adopted to mitigate different kinds of mutual coupling between the dual-polarized antenna elements in the array. Owing to the wide beamwidth of the element and the low mutual coupling between the elements, the final 4×6 antenna array can achieve a good beam-scanning capability with maximum scanning angle up to ±55∘ and a small gain variation of less than 3 dB over the operation band 3.3-3.8 GHz. The fabricated array shows the measured isolation between all ports of the antennas is increased to more than 20 dB. Scanning characteristics also agree well with the simulated results. With the merits of wideband, low-cost (simple design and easy fabrication), wide-angle beam-scanning capacity, and good radiation performance, the proposed design has potential for application in 5G base stationsystems.

Wide-angle scanning and Wideband millimeter-wave phased array with Enhanced Isolation using Novel Triple-function Electric Walls

A wide-angle scanning millimeter-wave (mm-wave) phased array with enhanced bandwidth and isolation using novel triple-function electric walls (TEWs) is presented in this work. First, a novel concept for element beamwidth broadening is proposed by using a suspended horizontal magnetic current (SHMC) with a conical pattern. Then, based on this concept, an antenna element is designed using the proposed TEWs. TEWs not only broaden the element beamwidth by forming a suspended horizontal magnetic current(SHMC), but also widen the element bandwidth by introducing a new mode. Meanwhile, the proposed TEWs can be used as a band-stop filter in the array to reduce the mutual coupling. Based on the three beneficial functions of the proposed TEWs, a wide-angle scanning mm wave phased array with enhanced bandwidth and isolation is designed. Measured results show that the phased array achieves an active impedance bandwidth of 19.3% (24.7-30 GHz) and a good isolation of more than 15 dB. Meanwhile, a wide 3 dB scanning angle larger than ±74° is achieved by the proposed array with the maximum scanning angle of ±80° at 27 GHz.

Wide-Angle Beam Steering Closed-Form Pillbox Antenna Fed by Substrate-Integrated Waveguide Horn for On-the-Move Satellite Communications

Wide-angle mechanical beam steering for on-the-move satellite communications is presented in this paper based on a closed-form pillbox antenna system. It includes three main parts: a fixed-feed part, which is a substrate-integrated waveguide (SIW) horn with an extended aperture attached to a parabolic reflector; a novel quasi-optical system, which is a single coupling slot alongside and without spacing from the parabolic reflector; and a radiating disc, which is a leaky-wave metallic pattern. To make the antenna compact, pillbox-based feeding is implemented underneath the metallic patterns. The antenna is designed based on a substrate-guided grounded concept using leaky-wave metallic patterns operating at 20 GHz. Beam scanning is achieved using mechanical rotation of the leaky-wave metallic patterns. The proposed antenna has an overall size of 340 × 335 × 2 mm3, a gain of 23.2 dBi, wide beam scanning range of 120°, from −60° to +60° in the azimuthal plane, and a low side lobe level of −17.8 dB at a maximum scan angle of 60°. The proposed antenna terminal is suitable for next-generation ubiquitous connectivity for households and small businesses in remote areas, ships, unmanned aerial vehicles, and disaster management.

Piezoelectric 1D MEMS scanning micromirror fabricated with bulk PZT laminated on stainless steel plate

In this research, a piezoelectric metal scanning micromirror with a large reflective surface area is presented. Unlike conventional scanning micromirrors fabricated with single-crystal silicon, stainless steel plate is used as the structural layer material. Two distinct device models, varying in cantilever and connector geometry, were conceptualized and experimentally assessed. These fabricated devices utilized the strain induced in bulk PZT (lead zirconate titanate) plates affixed to the cantilevers on opposing sides of the reflective surface. A 5 mm-diameter gold-coated silicon mirror plate served as the reflective surface. We evaluated the performance of two bulk PZT plates, PZT-5H and PZT-8. Our experimental results reveal that model #1, driven by PZT-5H with a sinusoidal input voltage of 200 Vpp, achieved a maximum optical scan angle of 26°, while model #2 exhibited a more substantial maximum scan angle of 44°. The average resonant frequency of the PZT-5H samples was 1264 Hz for model #1 and 995 Hz for model #2. These findings underscore the viability of stainless steel plates as a robust structural layer for piezoelectric scanning micromirrors. The proposed design holds potential for integration into a 3D LiDAR system when combined with an additional slow vertical scanner.

Tightly coupled arrays with time-domain beam scan for the radiation of high-power ultrawideband electromagnetic pulses.

In this paper, a kind of tightly coupled array (TCA) with time-domain beam scan is developed for the radiation of high-power ultrawideband (UWB) electromagnetic pulses, and the peak-power pattern is proposed to characterize the directivity. First, the active voltage standing wave ratio (AVSWR) bandwidth of the TCA is optimized, which is the precondition for the beam scan. It indicates that the lower-cutoff frequency (LCF) is inversely proportional to the total length of the whole array; an increase in the distance between the array and the ground plane could remarkably reduce the LCF; and an increase in the element number can also decrease the LCF because of the increase in length, but more elements would make the center elements difficult to match in the low-frequency range, so there is a limitation on the number of elements for a certain LCF. Based on these results, a six-element linear array is designed. Then, the definition of the peak-power pattern is proposed to characterize the directivity of the UWB pulsed antenna. Finally, the optimized six-element array is developed, and the measured working band is 276 MHz-6.4GHz (AVSWR < 3). The effective potential gain is 1.76, and it improves by 51.7% with a reduction in the aperture area by 68.4% compared with the previous TCA, which means that the aperture efficiency is remarkably improved. The half-power beam width of the developed TCA with the scan angle of 0° is 45°. The time-domain beam scan could be performed with time-delay feeding lines, and the maximum scan angle is over ±30° in the E-plane. The developed TCA can be applied for the generation of high-power electromagnetic environments for the study of intentional electromagnetic interference.

Analysis of tightly-coupled dipole phased array antennas with metasurface superstrate

Tightly coupled dipole arrays, including connected arrays, and capacitively coupled arrays, are one of the best solutions for wideband phased array antenna designs. However, to increase bandwidth and maximum scan angle, we can use a metasurface superstrate. We propose an analytical model to compute the scan impedance of a tightly coupled dipole array loaded with a metasurface. This analytical model helps us to simplify the calculation of the scan impedance of the array and speeds up the design process of these array antennas. It is shown that the metasurface superstrate improves the bandwidth and beam scanning angles of the array. Using the proposed general transmission line model, the computation of the scan impedance of tightly coupled dipole arrays is done very fast with minimum error. The semi-analytical model is about 7 times faster than a full-wave simulation.

A Compact Two-Dimensional Varifocal Scanning Imaging Device Actuated by Artificial Muscle Material.

This paper presents a compact two-dimensional varifocal-scanning imaging device, with the capability of continuously variable focal length and a large scanning range, actuated by artificial muscle material. The varifocal function is realized by the principle of laterally shifting cubic phase masks and the scanning function is achieved by the principle of the decentered lens. One remarkable feature of these two principles is that both are based on the lateral displacements perpendicular to the optical axis. Artificial muscle material is emerging as a good choice of soft actuators capable of high strain, high efficiency, fast response speed, and light weight. Inspired by the artificial muscle, the dielectric elastomer is used as an actuator and produces the lateral displacements of the Alvarez lenses and the decentered lenses. A two-dimensional varifocal scanning imaging device prototype was established and validated through experiments to verify the feasibility of the proposed varifocal-scanning device. The results showed that the focal length variation of the proposed varifocal scanning device is up to 4.65 times higher (31.6 mm/6.8 mm), and the maximum scanning angle was 26.4°. The rise and fall times were 110 ms and 185 ms, respectively. Such a varifocal scanning device studied here has the potential to be used in consumer electronics, endoscopy, and microscopy in the future.

Wide-angle reflectarray controllable by rotational and tilt angles for 28GHz communication systems

Arbitral control of reflection direction of a reflectarray for the mobile communication system is a key technology to amplify the coverage area. Here, we examined the correlation between the tilt and rotational angles of the reflection wave acquired by a reflectarray. Simulation results showed that changing the reflection rotation angle up to 75° reduces the radar cross section (RCS) by only a few dBsm. Furthermore, the maximum scanning angle up to ±60° was achieved by appropriate design of a reflectarrray. The reflection characteristics of the reflectarray will pave the way for the design guideline for a wide-angle reflectarray.

Design and development of 1D torsional spring resonant scanner

This paper presents the design and dynamic response of a proposed non- Micro-Electro Mechanical Systems (MEMS) 1D torsional spring resonant scanner. The torsional spring was selected as the compliant structure of the device, and it was fabricated using aluminum with dimensions of 49 x 3.50 x 0.18 mm (L x W x T). An Analysis of Variance (ANOVA) test was performed to determine the difference in mean between the operating resonant frequency and the three types of materials, which are aluminum, stainless steel, and carbon steel. The device operates at a resonant frequency of 80.65 Hz, yielding a maximum scanning angle of 58.06 ˚. Hysteresis was observed from the frequency response chart of the system. By comparing the resonant frequency of the experimental results with the dynamic analysis of this device, the percentage error of the resonant frequency and optical scanning angle was found to be 6.67% and 16.84%, respectively.

Two-Dimensional Beam Steering Based on Compact Programmable Coding Metasurface

A programmable coding metasurface provides unprecedented flexibility to manipulate electromagnetic waves dynamically. By controlling the peculiarity of subwavelength artificial atoms, devices with metasurfaces perform various functionalities. In this paper, a compact programmable coding metasurface with PIN diodes is proposed to realize the beam steering in the Ka band. The phase distribution on the metasurface can be actively controlled by switching the states of each meta-atom. By tuning the phase gradient along the metasurface plane, the reflective beam can scan all directions in the upper half-plane. In addition, the compact metasurface is easier to integrate, which could expand the fields of applications. The full-wave simulation results show that the radiation direction of the main lobe is consistent with the theoretical calculation results, and the maximum steering angle of simulation is 60°. As experimental verification, a prototype was processed and the functionality of beam steering in the xoz plane and in the yoz plane was tested. Experimental results show that the designed metasurface can achieve beam steering in both planes, and the maximum scan angle is 45° in the xoz plane. The proposed metasurface opens a new way of beam steering in half space, which may have potential applications in sensing and wireless communications in millimeter waves.

Novel Coupling Cancellation Method by Loading Planar Path for Wideband High-Isolation Wide-Scanning Millimeter-Wave Phased Array

A novel coupling-cancellation method by loading planar path is proposed and applied in the millimeter-wave phased array for wide-angle scanning. By employing the improved decoupling stubs with weak radiation first, an extra introduced wideband equal-magnitude and anti-phase path is generated to cancel the inherent coupling path. The principle of the proposed method is investigated by the equivalent circuits and the full-wave simulation. Based on this method, a high-isolation 1-D phased array using low-temperature-cofired ceramic (LTCC) process is designed and fabricated. The planar paths are placed symmetrically between the subarrays and its radiation polarization is coincident with the antenna elements, resulting in high isolation and enhanced boresight radiation null-fill of subarrays. The measured isolation is below 20 dB within the relative bandwidth of 16.7% and the maximum scanning angle is ±60°. Moreover, the proposed method can be expectedly extended to large-scale arrays.

Millimeter-Wave Wideband Dual-Polarized LTCC Antenna Array Based on Metasurfaces for Beam-Scanning Applications

This communication presents a millimeter-wave wideband dual-polarized low-temperature cofired ceramics (LTCC) antenna array based on metasurfaces (MSs) for beam-scanning applications. Benefiting from the wideband and large-freedom property of MS-based structures, a novel ±45° dual-polarized wideband MS-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a crosslike dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline–slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ &lt; 0.5\lambda$ </tex-math></inline-formula> ) to construct a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with a maximum scanning angle up to ±55° and a small gain variation of less than 3 dB. Meanwhile, the active <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> parameters almost always remain below −10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems.

Dual-Band Beam-Scanning Antenna at Ka-Band by Rotation of Two Transmitarrays

A dual-band beam-scanning antenna by rotation of two transmintarrays (TAs) operating at 20 and 30 GHz has been presented in this letter. TA's unit cell has three metal layers and demonstrates almost completely independent performance at two frequency bands. Two designed TAs have unit cells of different sizes to achieve dual-band with different linear phases. By rotating the two TAs synchronously around the axis orthogonal to the planes of the TAs, it enables two-dimensional (2-D) beam scanning with maximum scanning angles of ±40°. The achieved simulated peak gains are 19.9 dBi, 20.5 dBi and 22.5 dBi, 23.2 dBi at phi = 0°, phi = 90° at 20 and 30 GHz, respectively. The maximum beam scanning losses are 1.7 dB, 2.6 dB and 1.5 dB, 2.7 dB. Moreover, the two beams at the two frequencies can basically point to the same direction at the same time. To validate the design, a prototype is fabricated and tested. The measured results are in good agreement with the simulated results.

Static High Voltage Actuation of Piezoelectric AlN and AlScN Based Scanning Micromirrors

Piezoelectric micromirrors with aluminum nitride (AlN) and aluminum scandium nitride (Al0.68Sc0.32N) are presented and compared regarding their static deflection. Two chip designs with 2 × 3 mm2 (Design 1) and 4 × 6 mm2 (Design 2) footprint with 600 nm AlN or 2000 nm Al0.68Sc0.32N as piezoelectric transducer material are investigated. The chip with Design 1 and Al0.68Sc0.32N has a resonance frequency of 1.8 kHz and a static scan angle of 38.4° at 400 V DC was measured. Design 2 has its resonance at 2.1 kHz. The maximum static scan angle is 55.6° at 220 V DC, which is the maximum deflection measurable with the experimental setup. The static deflection per electric field is increased by a factor of 10, due to the optimization of the design and the research and development of high-performance piezoelectric transducer materials with large piezoelectric coefficient and high electrical breakthrough voltage.

Terahertz liquid crystal programmable metasurface based on resonance switching.

A programmable metasurface based on liquid crystal is of great significance to versatile dynamic wave manipulation such as beamforming and beam steering. One of the biggest obstacles currently is the lack of a simple way to multi-bit programming scheme for massive electrically addressable arrays, which limits its application and magnifies drawbacks like unavoidable symmetrical beam diffraction. Here, we put forward the concept of a liquid crystal metasurface based on a resonance switching mechanism for quasi-2-bit coding control, which is established upon interdigital structure electrodes. This enables a more elaborate control of meta-unit and a quasi-2-bit modulation based on a universal binary coding system to be realized. Our design could suppress unwanted -1 diffraction order with a maximum single-beam scanning angle of ± 21° under active beam manipulation. This concept paves the way for a feasible and robust multi-bit coding scheme of a liquid crystal metasurface, which is promising for THz applications such as spatial light modulators and wireless communication.

Millimeter Wave Wide-Angle Scanning Circularly Polarized Antenna Array With a Novel Polarizer

A wide-angle scanning circularly polarized (CP) antenna array based on a novel polarizer is proposed. The working mechanism is that the linear polarization (LP) substrate integrated waveguide (SIW) slot antenna array can be converted into CP antenna array through the proposed hybrid polarizer. Specifically, the proposed hybrid polarizer consists of a dipole array polarizer with <inline-formula> <tex-math notation="LaTeX">$6\times $ </tex-math></inline-formula> 6 elements and a metasurface polarizer with <inline-formula> <tex-math notation="LaTeX">$19\times19$ </tex-math></inline-formula> elements. The metasurface polarizer can realize the LP&#x2013;CP conversion of the beams with a scanning angle range (&#x2212;55&#x00B0;, 55&#x00B0;) and the dipole array polarizer can realize LP&#x2013;CP conversion of beams with scanning angle ranges (&#x2212;60&#x00B0;, &#x2212;40&#x00B0;) and (40&#x00B0;, 60&#x00B0;) through reasonable design. Based on the complementary characteristics of the metasurface polarizer and dipole array polarizer for different scanning angles, the proposed hybrid polarizer gives the designed CP antenna array have good AR characteristics in the scanning angle range (&#x2212;70&#x00B0;, 70&#x00B0;). Then, a <inline-formula> <tex-math notation="LaTeX">$6\times $ </tex-math></inline-formula> 6 Butler matrix is designed to feed the proposed wide-angle scanning CP antenna array. Finally, a prototype of the wide-angle scanning CP antenna array is fabricated. The test results show that the AR of the proposed wide-angle scanning CP antenna array is less than 3 dB, the maximum scanning angle is &#x2212;60&#x00B0;, and the maximum gain is more than 16.5 dBi in the operating frequency range 27.9&#x2013;28.4 GHz.

A MIMO Radar System based on Fractal Antenna Arrays for Level Measurement Applications

Abstract. In this contribution, the design of a multiple-input multiple-output (MIMO) radar system in 77–81 GHz range with 18 transmitting antennas and 24 receiving antennas for measuring the height profile of bulk solids in silos, is presented and discussed. The antenna array topologies are optimized by utilizing space filling fractals in order to approximate a circular shaped antenna array on a hexagonal grid. The proposed MIMO radar system achieves an angular resolution of 3.1∘ for a maximum scanning angle of ±45∘ and a side lobe suppression of 12.6 dB. The performance of the system has been evaluated by test measurements on a sand heap, showing an improved measurement accuracy compared to conventional radar level systems.

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.