Beam Scanning Mechanism Research Articles

Design of Alvarez Beam Scanning Reflectarray With Inversely Proportional Focal Length

In this letter, a beam scanning Alvarez reflectarray (RA) metasurface with its focal length ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> ) inversely proportional to the phase distribution on the Alvarez RA aperture is presented for ±45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> beam scanning coverage and less than 3-dB gain loss. The beam scanning mechanism is based on mechanically tilting the Alvarez RA panel to the desired direction to steer the beam. Compared to a conventional RA where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> is directly proportional to the parabolic phase distribution, the proposed Alvarez RA shows a wider 1-dB and 3-dB gain bandwidth, higher aperture efficiency (AE <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">)</i> , and wider scanning range with less than 3-dB gain loss. The proposed RA has adopted an Alvarez phase distribution which is a summation of two shifted cubic phase profiles. Pancharatnam- Berry (PB) meta-atoms of sub-wavelength periodicity were utilized to provide the 360 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> phase range and to enhance the bandwidth of the RA. An Alvarez RA consisting of 38 × 38 PB meta-atoms has been designed, fabricated, and tested for ±45 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> beam scan coverage with less than 3-dB gain loss. The simulated and measured results show that the gain of the proposed Alvarez RA metasurface is 29.1 dBi at 19.5 GHz, which corresponds to an AE of 44.2%. The 3-dB gain variation of the Alvarez RA is from 15 GHz to 23.4 GHz, which corresponds to a 3-dB gain bandwidth of 43.7%. The 1-dB gain bandwidth was 27.8% from 17.3 GHz to 22.9 GHz.

A Novel Comb-line Leaky-wave Antenna for 77 GHz FMCW Automotive Radar System and Comparison with Buttler Beamformers

For a typical frequency modulated continuous wave automotive radar system, a design using a novel leaky-wave antenna is proposed that has a simple, cheap and easy manufacturing structure whose performance is compared with two different antenna arrays. The software used were MATLAB and CST Microwave Studio. The first antenna system was an inset-fed patch array, and the second antenna system was a circular patch array with a Buttler beamforming network as a beam scanning mechanism. The simulation results of the three proposed designs are obtained using the range-Doppler method for multi-target scenarios. The proposed leaky-wave antenna excels the antenna arrays, which offer cheaper and simpler solutions for the automotive industry.

Optimised design design & analysis of high gain 3×3 square patch array antennas with six ports for airborne application in S-Band

The design and characteristic analysis of high isolation of 3×3 series feed square microstrip patch antenna array, having six ports, compromised with 3×3 edge feed square patches interconnected with each other are discussed in this paper. A sequential and simultaneous excitation occurs to each port/plane to achieve the beam scanning mechanism. Phase has varied each port to visualise the beam scanning phenomenon from −29.5° to +29.5°. The simulated and measured return loss result, gain profile, and radiation pattern are verified to prove the beam scanning range is ± 29.5°. The surface current distribution of each port of the proposed antenna array and the E-field and H-field radiation patterns was studied to evaluate the parameters such as reflection coefficient, individual port total gain, SLL (side lobe label),HPBW (half-power beamwidth) and FBR (front to back ratio). All vertical and horizontal ports were researched individually and together to understand the beam scanning mechanism.

Compact Slotted Waveguide Antenna Array Using Staircase Model of Tapered Dielectric-Inset Guide for Shipboard Marine Radar.

This paper presents a new configuration of a slotted waveguide antenna (SWA) array aimed at the X-band within the desired band of 9.38~9.44 GHz for shipboard marine radars. The SWA array, which typically consists of a slotted waveguide, a polarizing filter, and a metal reflector, is widely employed in marine radar applications. Nonetheless, conventional slot array designs are weighty, mechanically complex, and geometrically large to obtain high performances, such as gain. These features of the conventional SWA are undesirable for the shipboard marine radar, where the antenna rotates at high angular speed for the beam scanning mechanism. The proposed SWA array herein reduces the conventional design’s size by 62% using a tapered dielectric-inset guide structure. It shows high gain performance (up to 30 dB) and obtains improvements in radiation efficiency (up to 80% in the numerical simulations) and weight due to the use of loss and low-density dielectric material.

Lidar for Autonomous Driving: The Principles, Challenges, and Trends for Automotive Lidar and Perception Systems

Autonomous vehicles rely on their perception systems to acquire information about their immediate surroundings. It is necessary to detect the presence of other vehicles, pedestrians and other relevant entities. Safety concerns and the need for accurate estimations have led to the introduction of Light Detection and Ranging (LiDAR) systems in complement to the camera or radar-based perception systems. This article presents a review of state-of-the-art automotive LiDAR technologies and the perception algorithms used with those technologies. LiDAR systems are introduced first by analyzing the main components, from laser transmitter to its beam scanning mechanism. Advantages/disadvantages and the current status of various solutions are introduced and compared. Then, the specific perception pipeline for LiDAR data processing, from an autonomous vehicle perspective is detailed. The model-driven approaches and the emerging deep learning solutions are reviewed. Finally, we provide an overview of the limitations, challenges and trends for automotive LiDARs and perception systems.

Complex beam steering from substrate integrated waveguide leaky wave antenna array

A wideband single-beam/dual-beam leaky wave antenna (LWA) system based on periodic composite right-left handed substrate integrated waveguide is presented in this article. The proposed array can be a good candidate for tracking applications and intelligent protection systems. The system is contributed by installing in parallel two different antenna structures. The first antenna transmits in the frequency band 6.9-11 GHz where the second antenna radiates in the band 8.9-13.8 GHz, the frequencies of the broadside radiation are allocated at 7.8 and 10.2 GHz for the first and the second LWA, respectively. The results demonstrate the potential of the proposed system to continuously steer a single or a dual beams from −72° to 73°. The antenna system has a flexible beam scanning mechanism, good radiation efficiency, and maximum gain of 15.2 dBi. The simulation and the measurement results match well with the theoretical analysis described in the article.

Dual-axis optical coherence tomography for deep tissue imaging.

We have developed dual-axis optical coherence tomography (DA-OCT) which enables deep tissue imaging by using a novel off-axis illumination/detection configuration. DA-OCT offers a 100-fold speed increase compared with its predecessor, multispectral multiple-scattering low coherence interferometry (ms2/LCI), by using a new beam scanning mechanism based on a microelectro-mechanical system (MEMS) mirror. The data acquisition scheme was altered to take advantage of this scanning speed, producing tomographic images at a rate of 4 frames (B-scans) per second. DA-OCT differs from ms2/LCI in that the dual axes intersect at a shallower depth (∼1 mm). This difference, coupled with the faster scanning speed, shifts the detection priority from multiply scattered to ballistic light. The utility of this approach was demonstrated by imaging both ex vivo porcine ear skin and in vivo rat skin from a McFarlane flap model. The enhanced penetration depth provided by the DA-OCT system will be beneficial to various clinical applications in dermatology and surgery.

Study of 2D Scanning LIDAR Optics for Planetary Explorer

LIDAR(LIght Detection And Ranging) that measures distance by the laser pulse is a necessary sensor of navigation for a deep space explorer that doses a planetary exploration. Two dimension of LIDAR scanning is required from both sides of the navigation control and the science observation in order to make a 3D map of surface efficiently. This paper proposes a novel method on the beam scanning mechanism for a receiver telescope with big aperture by using MEMS technology. In addition, it reports on the result of executing the basic function experiment of the beam scanning mechanism. The scanning optics system is composed of a telecentric telescope, and a micro shutter array. This optical system has achieved a narrow viewing angle corresponding to aperture of the shutter by limiting the view of the telescope that has a wide viewing angle with the shutter. We experimented by using the shutter array of 6mm×6mm size. As a result, it succeeded that the scanning angle in the achievement of azimuth angle 8.8deg, elevation angle 8.1deg, and the field of view angle of azimuth angle 1.8deg and elevation angle 0.6deg.

Two-axis-scanning laser Doppler vibrometer for precision engineering

Laser Doppler vibrometer (LVD) has been the most favorite instrument for precision dynamics measurement due to its non-contact, high accuracy and high resolution. However, LDV can only give the dynamic data of a particular location on the entire feature. In order to get the whole field data, a laser beam-scanning mechanism has to be implemented. Currently, motor-driven scanning mirror is used to move the measurement probe from one point to another. The mechanical vibrations of the scanning mirror will reduce the measurement accuracy. This paper introduces a novel scanning LDV optical system embodied in an acousto-optic deflector scanning mechanism. It can improve the measurement accuracy since there is no mechanical motion involved. One main advantage of this system is that it generates a laser scanning beam in parallel that is different from the beam scanning in the conventional scanning laser Doppler vibrometer (SLDV). The new system has a board scanning range. The measurement target size ranges from few tens of millimeters down to 10 μm. We have demonstrated the capability of the novel system on scanning measurements of features as big as ultra-precision cutting tool to features as tiny as AFM cantilever. We believe that the novel SLDV will find profound potential applications in the precision engineering field.

Scanning laser vibrometer for dynamic study of small features

The laser Doppler vibrometer (LVD) has been the favorite instrument for precision dynamics measurement due to its noncontact nature, high accuracy, and high resolution. However, LDV can give only the dynamic data of a particular locate on the entire feature. To acquire the whole field data, a laser beam scanning mechanism must be implemented. Currently, a motor-driven scanning mirror is used to move the measurement probe from one point to another, and the mechanical vibrations of the scanning mirror reduce the measurement accuracy. We introduce a novel scanning LDV optical system embodying an acoustooptic deflector scanning mechanism, which can improve the measurement accuracy since there is no mechanical motion involved. One main advantage of this system is that it generates laser scanning in parallel, which is different from the beam scanning in a conventional scanning LDV. Promising results are obtained from the preliminary experiments carried out for measurement of a hard disk suspension.

Ferro-Fluid Lubricated Bearings for a Polygon Mirror Motor

Laser printers, which feature quiet, fast, high-quality printing, are evolving towards digital copiers with even faster and higher quality printing performance. This trend requires faster and more precise rotation of the polygon mirror motor of the laser beam scanning mechanism. Thus, bearings are becoming a key technology for the advancement of laser printers. This report proposes an integrated bearing unit that employs ferro-fluid for the bearing lubrication and seals in a new concept of leakage-free high-speed bearings. The intention is to take advantage of hydrodynamic oil-film bearings with high stiffness and damping characteristics to solve the oil leakage problem, and use them in place of ball-bearings or air bearings to get highly precise rotation. Leakage is completely prevented by using a compound seal of a ferro-magnetic seal and a viscous seal. The structural features of these bearings and experimental results concerning their lubrication and sealing performance and rotation accuracy when applied to a polygon mirror motor operating from 10000 to 30000 r/min are presented. The ferro-fluid bearings provide satisfactory friction torque and stiffness characteristics and the proposed bearing unit can be utilized with the polygon mirror motor.

ZT imaging system for layered thin wall structures

Abstract : Phase I demonstrated the feasibility of using a one-sided x-ray backscatter imaging technique called ZT to display very small delaminations, cracks, porosity, and chemical species differences in a variety of objects. Using both supplied carbon composites materials, some with known defects, and custom built phantoms, a series of experiments was performed to measure the sensitivity limits of the ZT technique to the various anomalies. The equipment consisted of ZT imaging system. During the execution of the program, we modified both the focussing collimator, the detectors and the X-ray beam scanning mechanism were modified to observe the differences in image quality caused by parametric changes in these items. Delaminations as small as 127 microns (0,005 in.) deep and 0.05 in. in diameter were imaged with the laboratory system. In the porosity phantom, holes as small as 787 microns in diameter were visualized. Our density investigations showed the ability to detect density differences as small as 2%. Also uncovered during the density experiments was the sensitivity of ZT to chemical species variations. A mathematical model is constructed which accurately predicts total system performance, including the backscatter process and the human detection probability.