Beam Scanning Angle Research Articles

Wide-Angle Beam-Scanning Reflectarray With Mechanical Steering

A novel wide-angle beam-scanning phase synthesis method, namely, multibeam phase matching method is introduced in this paper. It takes full advantage of angle sensitivity characteristic of reflectarray elements to improve the beam-scanning performance of reflectarrays. In the process of reflectarray aperture synthesis, the beam deviation factors and reference phases are optimized to minimize the total phase error, and the geometries of each element are optimized to match the desired phase shifts at multiple beam-scanning angles after taking into account the real incident angles. Then, a $16 \times 16$ -element reflectarray antenna with square patch elements operating at 12 GHz has been designed, simulated, and fabricated. The measured results show that a gain variation less than 1.7 dB across the scan coverage from −45° to +45° can be achieved by mechanically rotating the feed antenna, which shows a considerable improvement in beam-scanning performance as compared to the reflectarrays designed using conventional single-focus and bifocal methods.

Double-layered microstrip metamaterial beam scanning leaky wave antenna with consistent gain and low cross-polarization

In this paper, a novel double-layered microstrip metamaterial beam scanning leaky wave antenna (LWA) is proposed and investigated to achieve consistent gain and low cross-polarization. Thanks to the continuous phase constant changing from negative to positive values over the passband of the double-layered microstrip metamaterial, the proposed LWA, which consists of 20 identical microstrip metamaterial unit cells, can obtain a continuous beam scanning property from backward to forward directions. The proposed LWA is fabricated and measured. The measured results show that the fabricated antenna obtains a continuous beam scanning angle of 140° over the operating frequency band of 3.80–5.25 GHz (32%), the measured 3 dB gain bandwidth is 30.17% with maximum gain of 11.7 dB. Besides, the measured cross-polarization of the fabricated antenna keeps at a level of at least 30 dB below the co-polarization across the entire radiation region. Moreover, the measured and simulated results are in good agreement with each other, indicating the significance and effectiveness of this method.

Ultra-Wideband Scanning Antenna Array With Rotman Lens

An ultra-wideband (6-18 GHz) phased-array antenna with a beam scanning angle of ±28° is proposed. A step-by-step design procedure consisting of beamforming network (BFN), end-launcher feed adapter, and the radiating element is presented. Microstrip Rotman lens has been designed to act as the BFN, and optimized to achieve minimum phase-error over the whole frequency range. In order to satisfy the condition needed for avoiding grating lobes, as well as achieving a wide radiation bandwidth and a high power handling capability, an E-plane double-ridged horn antenna is used as the radiating element. A novel wideband end-launcher coaxial to double-ridged waveguide transition has also been developed for connecting the BFN to the antenna array. Extensive optimization procedures have been applied to the end-launched adapter together with the antenna to achieve the best return loss over the frequency band of operation. The whole system has been simulated using CST full-wave simulator. An excellent agreement between the measurements of the fabricated system and the simulated results is observed.

Improved Model for Depth Bias Correction in Airborne LiDAR Bathymetry Systems

Airborne LiDAR bathymetry (ALB) is efficient and cost effective in obtaining shallow water topography, but often produces a low-accuracy sounding solution due to the effects of ALB measurements and ocean hydrological parameters. In bathymetry estimates, peak shifting of the green bottom return caused by pulse stretching induces depth bias, which is the largest error source in ALB depth measurements. The traditional depth bias model is often applied to reduce the depth bias, but it is insufficient when used with various ALB system parameters and ocean environments. Therefore, an accurate model that considers all of the influencing factors must be established. In this study, an improved depth bias model is developed through stepwise regression in consideration of the water depth, laser beam scanning angle, sensor height, and suspended sediment concentration. The proposed improved model and a traditional one are used in an experiment. The results show that the systematic deviation of depth bias corrected by the traditional and improved models is reduced significantly. Standard deviations of 0.086 and 0.055 m are obtained with the traditional and improved models, respectively. The accuracy of the ALB-derived depth corrected by the improved model is better than that corrected by the traditional model.

SOIMUMPs micromirror scanner and its application in laser line generator

A SOIMUMPs 1-D rotation micromirror is presented. The micromirror is driven by electrostatic vertical comb-drive actuators to work at resonant mode to scan a laser beam. The residual stress in the metal film coated on the SOI device layer is used to generate vertical offset in the comb-drive actuators with the combs located far from the rotation axis to increase the torque. A concave lens is designed to put after the micromirror to amplify the laser beam scanning angle, as well as to compensate for the curvature of the micromirror. A micromirror-based scanning system is used to build a laser line generator with a continuously adjustable fan angle, which solves the limitation of a fixed fan angle in conventional laser line generators. Prototypes of the micromirror and the laser line generator are fabricated and measured. A driving circuit that can generate a high-voltage square wave driving signal with adjustable amplitude and frequency is designed. All the parts are integrated in a 44 mm×88 mm×44 mm box and powered with a single 5-V power supply. The optical scanning angle under 100 V with or without the concave lens is 27 deg and 12 deg, respectively, at a resonant frequency of 900 Hz.

A Wide-Angle and Circularly Polarized Beam-Scanning Antenna Based on Microstrip Spoof Surface Plasmon Polariton Transmission Line

In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.

Novel improved metamaterial transmission line and its application in wideband leaky-wave antenna with wide beam-scanning angle range and low cross-polarization

In this paper, a novel-improved metamaterial transmission line (MTM TL) is investigated and applied to design periodic leaky-wave antenna (LWA) with wide beam-scanning angle range and low cross-polarization. The improved MTM TL consists of metallic holes and interdigital fingers (which embedded in the main microstrip line). By introducing the metallic holes loaded in the interdigital fingers, the parasitic resonant modes of conventional MTM TL can be eliminated effectively. Considering the continuous phase constants changing from negative to positive values of the improved MTM TL under the balanced condition, a continuous beam-scanning property from backward to forward directions of the resultant periodic LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the improved MTM TL, is fabricated and measured. The measured and simulated results are in good agreements with each other in all condition. According to the measured results, the fabricated periodic LWA operates from 3.38 to 4.60 GHz with a bandwidth of 30.57%, and achieves a continuous beam-scanning property from backward –65° to forward +71° (including broadside radiation) over the operating frequency band. Moreover, the measured cross-polarization remains at a level of more than 30 dB below the co-polarization across the entire radiation region. The presented LWA should find promising applications in modern wireless communication systems due to these wonderful electromagnetic performances.

Wide-angle nonmechanical beam steering using liquid lenses.

Nonmechanical beam steering is a rapidly growing branch of adaptive optics with applications such as light detection and ranging, imaging, optical communications, and atomic physics. Here, we present an innovative technique for one- and two-dimensional beam steering using multiple tunable liquid lenses. We use an approach in which one lens controls the spot divergence, and one to two decentered lenses act as prisms and steer the beam. Continuous 1D beam steering was demonstrated, achieving steering angles of ±39° using two tunable liquid lenses. The beam scanning angle was further enhanced to ±75° using a fisheye lens. By adding a third tunable liquid lens, we achieved 2D beam steering of ±75°. In this approach, the divergence of the scanning beam is controlled at all steering angles.

Estimation of current velocity using circular SAR data

A method of current velocity estimation using airborne sea data is proposed. The sea data are collected by circular synthetic aperture radar. The range Doppler image can be acquired after range and azimuth compression for each beam scan angle. The corresponding average Doppler spectrum can be obtained and fitted to Gaussian shape well. Hence, the Doppler centre shift can be represented by the mean of Doppler spectrum. It is observed that the Doppler centre varies with the beam scan angle and the variation is approximately a sinusoid-shape function. The velocity and direction of current in a local area are fixed so the radial velocity caused by the current is a harmonic function of the scan angle. Therefore, the current velocity can be obtained by the amplitude of the harmonic. Actually, the radial velocity does not only include the current, but also includes the surface wave motion. However, the method presented can obtain the real current velocity directly, avoiding adopting the radial velocity of the scatterer, so the estimation of the current velocity is accurate.

Wideband leaky-wave antenna with consistent gain and wide beam scanning angle based on multilayered substrate integrated waveguide composite right/left-handed transmission line

In this article, a wideband leaky-wave antenna is designed for consistent gain and wide beam scanning angle by using the proposed multilayered substrate integrated waveguide (SIW) composite right/left-handed transmission line (CRLH TL). The proposed SIW CRLH structure consists of two parts: an interdigital fingers slot of rotating 45° etched on the upper ground of the SIW, and a rotated parasitic patch beneath the slot. Due to the continuous phase constants change from negative to positive values of the proposed SIW-CRLH under the balanced condition, the designed LWA can achieves a continuous beam-scanning property from backward to forward over the operating frequency band. The designed antenna is fabricated and measured, the measured and simulated results are in good agreements with each other, indicating that the designed antenna obtains a measured continuous main beam scanning from backward −78° to forward +76° over the frequency range from 7.7 to 12.8 GHz with a consistent gain of more than 9.5 dB. Besides, the designed antenna also exhibits a measured 3-dB gain bandwidth of 45.1% with maximum gain of 15 dB. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:731–738, 2016.

A Simple Low-Cost Shared-Aperture Dual-Band Dual-Polarized High-Gain Antenna for Synthetic Aperture Radars

This paper presents a novel shared-aperture dual-band dual-polarized (DBDP) high-gain antenna for potential applications in synthetic aperture radars (SARs). To reduce the complexity of SAR antennae, a DBDP high-gain antenna based on the concept of Fabry–Perot resonant cavity is designed. This antenna operates in both $C$ - and $X$ -bands with a frequency ratio of 1:1.8. To form two separate resonant cavities, two frequency selective surface layers are employed, leading to high flexibility in choosing desired frequencies for each band. The beam-scanning capability of this proposed antenna is also investigated, where a beam-scanning angle range of ±15° is achieved in two orthogonal polarizations. To verify this design concept, three passive antenna prototypes were designed, fabricated, and measured. One prototype has broadside radiation patterns, while the other two prototypes have frozen beam scanned to +15°. The measured results agree well with the simulated ones, showing that the high gain, high port isolation, and low cross-polarization levels are obtained in both the bands. Compared with the conventional high-gain DBDP SAR antennae, the proposed antenna has achieved a significant reduction in the complexity, mass, size, loss, and cost of the feed network.

Design of leaky‐wave antenna with wide beam‐scanning angle and low cross‐polarisation using novel miniaturised composite right/left‐handed transmission line

In this study, a novel periodic leaky-wave antenna (LWA) with wide beam-scanning angle and low cross-polarisation is proposed by using miniaturised composite right/left-handed transmission line (CRLH TL). By introducing the metallic holes loaded in the interdigital lines of the miniaturised CRLH TL, not only the parasitic resonant modes can be eliminated, but also the miniaturisation is realised. Considering the continuous phase constants from negative to positive values of the balanced CRLH TL, a continuous beam-scanning property from backward to forward of the resultant LWA can be obtained. For verification, a periodic LWA, which consists of 20 unit cells of the balanced CRLH TL, is fabricated and measured; the measured and simulated results are in good agreements with each other, indicating that the fabricated LWA operates from 3.90 to 4.90 GHz (a bandwidth of 22.7%), and has a wide continuous beam-scanning capability from backward −61° to forward 67° (including the broadside) within the operating band. Moreover, it also has very low cross-polarisation, which remains at a level of at least 25 dB below the co-polarisation across the entire radiation region. As a result, the presented LWA should find promising applications in modern wireless communication systems and the high-resolution radar system due to these wonderful electromagnetic performances.

Broadband impedance-matched near-zero-index metamaterials for a wide scanning phased array antenna design

We present broadband near-zero-index metamaterials composed of dielectric resonators and metallic rods, whose permittivity ε and permeability μ are near-zero simultaneously. It is notable that the values of permittivity ε are equal to those of permeability μ over a broadband frequency range of 8.45 GHz to 10.5 GHz, indicating the impedances of the proposed near-zero-index metamaterials match vacuum in this broadband. The broadband near-zero-index metamaterials for manipulating radiation sources are analyzed. We also demonstrate numerically that such near-zero-index metamaterials can offer a unique grating condition in a phased array antenna, with the beam scanning angle range beyond the critical angle limit of the grating lobe.

A Three-Band Substrate Integrated Waveguide Leaky-Wave Antenna Based on Composite Right/Left-Handed Structure

In this communication, the design and implementation of a three-band substrate integrated waveguide (SIW) leaky-wave antenna (LWA) based on the composite right/left-handed (CRLH) structure is presented. CRLH unit cell of the proposed antenna is composed of two adjacent interdigital slots with two vias between them. Two CRLH bands along with a new right-handed (RH) band between them are achieved through this structure. The first CRLH band (7.1–10.75 GHz) is balanced and the second one (15.1–21.75 GHz) is unbalanced with 0.25-GHz stop band. Beam scan angle in the first CRLH band is from $- 78^\circ $ to $+ 78^\circ $ , in the second one from $- 40^\circ $ to $+ 20^\circ $ and in the new RH band (12.6–13.4 GHz) from $+ 22^\circ $ to $+ 54^\circ $ . Antenna radiation efficiency in the first CRLH band is about 90%. Simulated and measured results are compared and there is a good agreement between them.

Leaky-wave antenna with high gain and wide beam-scanning angle range based on novel SIW-CRLH transmission line

A leaky-wave antenna (LWA) with high gain and wide beam-scanning angle is proposed in this article using a novel substrate integrated waveguide (SIW) composite left/right-handed transmission line (CRLH TL). The novel SIW-CRLH TL is analyzed and the equivalent circuit model is also provided. Considering the continuous phase constant of the balanced SIW-CRLH TL from negative to positive values, the proposed LWA can obtain a continuous beam steering property from backward to broadside to forward. For verification, a periodic LWA, which is comprised of 10 unit cells of the balanced SIW-CRLH TL, is fabricated and measured. The measured and simulated results agree well, showing that the proposed periodic LWA operates from has continuous beam-scanning capabilities of about 90° from backward to forward (including the broadside) with gains of better than 10 dB within the operating band. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:36–41, 2016.

Monte Carlo Simulation of the Carbon Beam Nozzle for the Biomedical Research Facility in RAON

‡§ The purpose of the Monte Carlo simulation study was to provide the optimized nozzle design to satisfy the beam conditions for biomedical researches in the Korean heavy-ion accelerator, RAON. The nozzle design was required to produce C 12 beam satisfying the three conditions; the maximum field size, the dose uniformity and the beam contamination. We employed the GEANT4 toolkit in Monte Carlo simulation to optimize the nozzle design. The beams for biomedical researches were required that the maximum field size should be more than 15×15 cm 2 , the dose uniformity was to be less than 3% and the level of beam contamination due to the scattered radiation from collimation systems was less than 5% of total dose. For the field size, we optimized the tilting angle of the circularly rotating beam controlled by a pair of dipole magnets at the most upstream of the user beam line unit and the thickness of the scatter plate located downstream of the dipole magnets. The values of beam scanning angle and the thickness of the scatter plate could be successfully optimized to be 0.5o and 0.05 cm via this Monte Carlo simulation analysis. For the dose uniformity and the beam contamination, we introduced the new beam configuration technique by the combination of scanning and static beams. With the combination of a central static beam and a circularly rotating beam with the tilting angle of 0.5 o to beam axis, the dose uniformity could be established to be 1.1% in 15×15 cm 2 sized maximum field. For the beam contamination, it was determined by the ratio of the absorbed doses delivered by C 12 ion and other particles. The level of the beam contamination could be achieved to be less than 2.5% of total dose in the region from 5 cm to 17 cm water equivalent depth in the combined beam configuration. Base d on the results, we could establish the optimized nozzle design satisfying the beam conditions which were required for biomedical researches.

A Wideband Widebeam Tapered Slot Array Antenna for Active Electronically Scanned Array Antenna

Phased arrays when mounted on aircraft and missiles will be capable of allowing only the desired signals to be received and simultaneously suppress all other unwanted ones incident from hostile sources. This in turn will make them invisible for the radars at the enemy base or on their aircraft. This paper discusses about the design of Phased array antenna for military airborne radar applications. A milllimeter wave active phased array antenna has been developed that is capable of wide scanning angle in both Eand H-planes. In order to achieve wide angle scanning over X-band frequency, a linear tapered slot antenna (LTSA) element has been designed and the resulting element is capable of scanning out to 60 o from broadside in all scan planes for a bandwidth of 11-14GHz and an active reflection coefficient less than -10 dB. Beam scanning angles of above ±45 degrees in the E-plane and ±60 degrees in the H-plane were obtained for an isolated element. An end fire array pattern with half power beamwidth of 14 degrees in E-plane is achieved over 11-14GHz frequency. This design was implemented on linear array antenna consisting of 7-elements and planar array antenna consisting of 49 (7x7) elements. The predicted performance of the antenna was verified by simulation of element patterns, array radiation patterns and S-parameter plot using commercially available electromagnetic simulator HFSS. Since the radar antenna is intended for applications where stealth is important. The antenna aperture consists many radiating elements used for beam-forming and hence through the adjustment of elemental phases steer the beam efficiently. Moreover, they are capable of rejecting all the unwanted components of the received signals while maintaining at the same time sufficient pattern gain in the desired directions. These characteristics can be implemented for stealth applications.

Gain Enhancement of Beam Scanning Substrate Integrated Waveguide Slot Array Antennas Using a Phase-Correcting Grating Cover

In this paper, planar beam scanning substrate integrated waveguide (SIW) slot leaky-wave antennas (LWAs) are proposed for gain enhancement using a metallic phase correction grating cover. Unlike conventional Fabry-Perot (FP) cavity antennas, the proposed antenna is fed by the SIW beam scanning LWA instead of a feeding antenna. The beam scanning angle range is enlarged by meandering the entire feeding structure and the gain is enhanced by a metallic grating cover acting as a 1-D lens. Two kinds of the gratings with different metal strip parameters are designed and analyzed. The proposed antennas operating at the center frequency of 25.45 GHz are designed and experimentally verified for an automotive collision avoidance radar with a gain enhancement of about 4 ~ 6 dB. The proposed SIW LWAs have the advantages of high gain, low profile, easy fabrication and beam-scanning capability good for millimeter wave radar applications.

Frequency scannable stacked patch antenna for beam‐steering applications

ABSTRACTA single element wideband antenna that has a stacked structure and provides beam‐steering characteristic according to the operating frequency is presented. Without requirements of phase shifters and associated circuits, the proposed antenna is composed of a circular patch electromagnetically coupled by a meandered‐strip feeder and a slotted conducting plane to have a compact size. The beam direction of the designed antenna can be mainly controlled by the operating frequency with a large beam scanning angle. From fabricating and testing the antenna, an operating bandwidth of 2.3 GHz (3.8–6.1 GHz) and an average gain of about 3.8 dBi have been obtained, and in addition, the beam‐steering characteristic has also been verified. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1506–1509, 2014

Liquid crystal based phased array antenna with improved beam scanning capability

A phased array antenna is presented, including a 1-by-4 dielectric resonator antenna (DRA) array, liquid crystal (LC) based phase shifters, RF-feeding and biasing networks. The dielectric resonators are used as waveguide radiating elements. The RF signal coupled between the phase shifters and DRAs are guided and then radiated from the top face of the DRAs. This reduces the effects of the surface waves since the radiation is away from the ground plane. Hence, the gain losses at wide scan angles are reduced, enlarging the antenna's beam scan angle, compared to that of a conventional microstrip patch antenna array. The LC phase shifters are realised in inverted microstrip line topology, with a phase shifter figure-of-merit of 70°/dB at 10 GHz. The far-field power patterns of the antenna were measured in an anechoic chamber for different beam directions. These results confirm that the gain losses are <;1.5 for a beam scanning range of ±30° for the broadside.