Showing papers on "Reflector (antenna) published in 2021"

Quasi-Optical Multi-Beam Antenna Technologies for B5G and 6G mmWave and THz Networks: A Review

Abstract: Multi-beam antennas are critical components in future terrestrial and non-terrestrial wireless communications networks. The multiple beams produced by these antennas will enable dynamic interconnection of various terrestrial, airborne and space-borne network nodes. As the operating frequency increases to the high millimeter wave (mmWave) and terahertz (THz) bands for beyond 5G (B5G) and sixth-generation (6G) systems, quasi-optical techniques are expected to become dominant in the design of high gain multi-beam antennas. This paper presents a timely overview of the mainstream quasi-optical techniques employed in current and future multi-beam antennas. Their operating principles and design techniques along with those of various quasi-optical beamformers are presented. These include both conventional and advanced lens and reflector based configurations to realize high gain multiple beams at low cost and in small form factors. New research challenges and industry trends in the field, such as planar lenses based on transformation optics and metasurface-based transmitarrays, are discussed to foster further innovations in the microwave and antenna research community.

Antenna Designs for CubeSats: A Review

Abstract: Cube Satellites, aka CubeSats, are a class of nano satellites that have gained popularity recently, especially for those that consider CubeSats as an emerging alternative to conventional satellites for space programs. This is because they are cost-effective, and they can be built using commercial off-the-shelf components. Moreover, CubeSats can communicate with each other in space and ground stations to carry out many functions such as remote sensing (e.g., land imaging, education), space research, wide area measurements and deep space communications. Consequently, communications between CubeSats and ground stations is critical. Any antenna design for a CubeSat needs to meet size and weight restrictions while yielding good antenna radiation performance. To date, a limited number of works have surveyed, compared and categorised the proposed antenna designs for CubeSats based on their operating frequency bands. To this end, this paper contributes to the literature by focusing on different antenna types with different operating frequency bands that are proposed for CubeSat applications. This paper reviews 48 antenna designs, which include 18 patch antennas, 5 slot antennas, 4 dipole and monopole antennas, 3 reflector antennas, 3 reflectarray antennas, 5 helical antennas, 2 metasurface antennas and 3 millimeter and sub-millimeter wave antennas. The current CubeSat antenna design challenges and design techniques to address these challenges are discussed. In addition, we classify these antennas according to their operating frequency bands, e.g., VHF, UHF, L, S, C, X, Ku, K/Ka, W and mm/sub-mm wave bands and provide an extensive qualitative comparison in terms of their size, −10 dB bandwidths, gains, reflection coefficients, and deployability. The suitability of different antenna types for different applications as well as the future trends for CubeSat antennas are also presented.

Visible Light Communications via Intelligent Reflecting Surfaces: Metasurfaces vs Mirror Arrays

Abstract: We propose two types of intelligent reflecting systems based on programmable metasurfaces and mirrors to focus the incident optical power towards a visible light communication receiver. We derive the required phase gradients for the metasurface array reflector and the required orientations of each mirror in the mirrors array reflector to achieve power focusing. Based on which, we derive the irradiance expressions for the two systems in the detector plane to characterize their performance in terms of aiming and focusing capabilities. We show analytically that the number of reflecting elements along with the relative source - reflector dimensions determine the system power focusing capability. Moreover, we quantify analytically the received power gain compared with reflector-free systems. In addition, we introduce a new simple metric to assess the relative reflectors’ performance for a given source, detector, reflector layout. Finally, we verify the analytical findings regarding absolute and relative reflectors’ performance via numerical simulations.

Coplanar Dual-Band Base Station Antenna Array Using Concept of Cavity-Backed Antennas

Abstract: In this article, we propose a novel reflector-back cavity-low-band (LB)/high-band (HB) configuration for the dual-band dual-polarized base station antenna array design. The HB antennas are embedded in the opening sections of the loop radiating arms of the LB antennas. Clear and independent radiating environments are fulfilled by using two different types of reflectors (large planar reflector and back cavity). The mutual effects between the LB and HB antennas help to acquire good impedance matching and stable radiation patterns. Loop-like LB radiators work as directors in the HB, thereby effectively suppressing the side and back radiations of the HB antennas. Dual-function open slots are loaded on the ground stubs of the LB baluns, serving as impedance transformer in the LB but filtering structures in the HB. The experimental results validate that the proposed antenna array successfully covers bandwidths of 0.69–0.96 and 3.3–3.8 GHz (VSWR < 1.5) for 4G/5G applications. The port isolations are higher than 38 and 25 dB in the LB and HB, respectively. With the two independent radiating environments formed in the two bands, both LB and HB antennas exhibit stable unidirectional radiation patterns. The antenna gains and HPBWs are also satisfactory in both bands.

Chronological development of innovations in reflector systems of parabolic trough solar collector (PTC) - A review

Abstract: The parabolic trough collector (PTC) technology is the most mature and cost-effective of solar thermal technologies. Given its importance in the use of solar power for electricity and industrial heating, this review presents a chruonological review of important innovations and improvements in reflector structure design and tracking system over a century of development. The fastest evolution is in the support structure of the PTC which has evolved from the old torque tube to the modern space tube. The space tube design is considered better for cost effective performance. The tracking systems have evolved from the conventional light-and-shadow sensing feedback loops to modern image-processing artificial-intelligence based systems with tremendous increases in tracking accuracy. This work also touches on reflective and structural materials. There has not yet been found a material to beat glass reflectors for specular reflectivity and durability. Considerable effort has gone into developing metal/polymer sheet reflectors, but their durability under cyclic weathering conditions is an open question. Similarly, there have been very few alternatives tried for steel as a support structure and most of these have experimented with aluminum. Only two types of actuators have been investigated: the geared motor and the hydraulic so far, and the geared motor has been the most favored. The optimization of all the components namely the reflector structure, tracking system, and reflector can lead to a design of PTC at a cost of 75–100$/m2 of aperture.

Hybrid Absorptive-Diffusive Frequency Selective Radome

Abstract: This article proposes a hybrid absorptive–diffusive frequency-selective radome (AD-FSR) that has a broadband transmission window with wide absorption and diffusion bands located at two sidebands, respectively. The proposed hybrid AD-FSR consists of a resistive sheet and a bandpass frequency-selective surface (FSS) integrated with a coding metasurface separated by a certain distance. The wide absorption band is realized by the combined effect of the resistive sheet and the FSS integrated with a metasurface as a reflector in its lower stopband, while a broad passband is obtained when the electromagnetic (EM) wave penetrates through the resistive sheet in the passband of the FSS. In the upper side of the passband, the EM wave is diffused to reduce the radar cross section (RCS) of the surface by arranging the unit cell of the AD-FSR and its mirror based on the phase cancellation theory. Equivalent circuit and relevant theoretical formulas are utilized to better comprehend the physical mechanism of the proposed hybrid AD-FSR. A design example is then fabricated and measured, and the experimental results show that a broad transmission band is achieved from 6.92 to 13.12 GHz with a minimum insertion loss of 0.43 dB in a wide low reflectivity ( $\pmb {|S_{11} |} dB) band from 2.24 to 18 GHz.

A Dual-Polarized 2-D Monopulse Antenna Array for Conical Conformal Applications

Abstract: A dual-polarized 2-D monopulse conical conformal antenna is proposed in this article. First, a method for implementing dual-polarized monopulse beams is presented. A novel array arrangement and a dual-polarized monopulse comparator suitable for conformal arrays are developed. Then, a wideband endfire element based on the double rhombic dipole is designed with directors and a reflector to obtain a stable high-gain endfire radiation. A conformal feeding network consisting of four rat-race couplers is employed to excite four conformal elements. The sum and difference beams of horizontal and vertical polarizations are realized on the azimuth and elevation planes. To verify the design concept, a prototype of the antenna array was designed, fabricated, and measured. The experimental results show that the proposed monopulse array achieves a shared bandwidth of 22.2% from 8.96 to 11.2 GHz on four ports, with the sum-beam gain of 9–11 dBi, the difference-beam gain of 5.8–7.7 dBi, and the null-depth of around −25 dB. To the best knowledge of the authors, the design concept of combining dual-polarized 2-D monopulse array with conical conformal antenna is proposed for the first time, which is a promising candidate as target detection and tracking antennas for various aircraft applications.

A CPW-fed wearable antenna at ISM band for biomedical and WBAN applications

Abstract: In this paper, a Mercedes-Benz logo antenna with a metal plate located at an optimized distance from the proposed antenna is introduced as a wearable antenna to operate in the industrial, scientific, and medical band with center frequency of 2.45 GHz. The metal plate is integrated with the antenna as an isolator and a reflector to improve the radiation performance of the proposed design, reduce the back radiation and reduce the specific absorption rate, when loaded on the human body. The front-to-back ratio improves by 18.2 dB, by adding a metal plate to the structure. The proposed antenna with coplanar waveguide-fed with dimensions of 35 mm × 35 mm × 0.508 mm is printed on a Rogers 4003C substrate, and has an impedance bandwidth from 2.20 to 2.56 GHz, the gain of 7.3 dBi at 2.45 GHz, and SAR levels is less than the criteria set by the FCC and ICNIRP. Nowadays, attention to health as product quality assurance factor along with other technical specifications is the requirements of industrial productions, especially in competition with superior brands. Based on comparisons made with similar works, the proposed wearable antenna structure can be used for wireless body area network.

TEMPEST-D Radiometer: Instrument Description and Prelaunch Calibration

Abstract: The Temporal Experiment for Storms and Tropical Systems Technology Demonstration (TEMPEST-D) instrument is a five-frequency millimeter-wave radiometer operating from 87 to 181 GHz. The cross-track scanning radiometer has been operating on a 6U CubeSat in low Earth orbit since September 5, 2018. The direct-detection architecture of the radiometer reduces its mass and power consumption by eliminating the need for a local oscillator and mixer, also reducing system complexity. The instrument includes a scanning reflector and ambient calibration target. The reflector rotates continuously to scan the antenna beams in the cross-track direction, first across the blackbody calibration target, then toward the Earth over the full range of incidence angles, and finally to cosmic microwave background radiation at 2.73 K. This enables precision end-to-end calibration of the millimeter-wave receivers during every 2-s scan period. The TEMPEST-D millimeter-wave radiometers are based on 35-nm indium phosphide (InP) high-electron-mobility transistor (HEMT) low-noise amplifiers. This article describes the instrument and its characterization prior to launch.

Time-Domain Digital-Coding Active Frequency Selective Surface Absorber/Reflector and Its Imaging Characteristics

Abstract: Switchable active frequency selective surface (AFSS) absorber/reflector can work in opposite scattering state and be widely applied in the stealth field. At present, abundant researches on material design have been conducted to obtain excellent electromagnetic (EM) properties. However, there are few studies on the modulation effect of switchable AFSS absorber/reflector on the EM wave. In this article, a time-domain digital-coding AFSS absorber/reflector is proposed to manipulate the spectral distribution of harmonic. The accurate control of each harmonic is achieved through AFSS modulating parameters. Then, a simple controller based on FPGA is designed. By coding “0” and “1” elements with controlled sequences, the AFSS can be switched flexibly in both absorbing and reflection states. On this basis, the imaging characteristics of time-domain digital-coding AFSS absorber/reflector are further analyzed, and distance transformation phenomena are described in detail. The synthetic aperture radar (SAR) experiments are performed to demonstrate the required function of distance transformation.

A Novel Dipole Configuration With Improved Out-of-Band Rejection and its Applications in Low-Profile Dual-Band Dual-Polarized Stacked Antenna Arrays

Abstract: In this communication, a novel dipole configuration with reactive loadings is proposed for the design of low-profile dual-band dual-polarized stacked antenna arrays. For lower band (LB1, 3.3–3.6 GHz) dipole, its inductive loadings are implemented at the end of each dipole arm to suppress the basic resonant mode for band rejection at higher frequencies. For higher band (HB2, 4.8–5.0 GHz) dipole, its LC loadings are implemented at the beginning of each dipole arm, where the inductor and the capacitor, respectively, increase the $Q$ -factor for improving the out-of-band rejection and balance the impedance matching. Hence, LB1 and HB2 dipoles can be closely stacked with high isolation. Moreover, a dual-band artificial magnetic conductor (AMC) reflector is adopted for reducing the distance between the antenna and the ground plane. Consequently, the overall height of the proposed one is only 0.16 $\lambda _{L}$ ( $\lambda _{L}$ being the free-space wavelength at the center frequency of LB1), which is smaller than the previous dual-band stacked designs. The measurement results demonstrate that the array achieves good impedance matching, high isolation, and stable radiation patterns simultaneously, indicating it as a promising candidate for sub-6 GHz base-station services.

Wideband Gain Enhancement of High-Isolation Fabry–Pérot Antenna Array With Tandem Circular Parasitic Patches and Radial Gradient PRS

Abstract: A high-isolation Fabry–Perot (FP) antenna array with wide bandwidth and high gain is proposed for Ku -band vehicle satellite communications. Each antenna element consists of a pair of tandem circular parasitic patches (TCPPs), a radial gradient partially reflective surface (PRS), and a reflector, respectively, separated from the ground plane with a double-dumbbell-shaped slot (DDSS) by air layer and foam dielectric. The slot radiator steers the TCPPs to create multiple resonant frequencies and then the impedance bandwidth is widened. The impedance matching could be improved by adjusting four circular slot diameters of the DDSS. The gain is raised by TCPPs and radial gradient PRS, which function to guide the electromagnetic field and uniformize the aperture near-field, successively. The reflector with several resonator elements is used to reduce the backside radiation. As proof of concept, the FP antenna array prototype with a height of $0.613\lambda _{0}$ has been fabricated and measurements confirming simulations are provided. Experimental results show that the impedance bandwidth ranges from 13.48 to 16.95 GHz [22.8% fractional bandwidth (FBW)], and the realized gain is up to 21.59 dBi. A decoupling metallic strip could achieve over 40.8 dB isolation. The proposed antenna element is easily extended for the multiple-input multiple-output (MIMO) and beamforming antennas, further improving the directivity.

Low-RCS and Wideband Reflectarray Antenna With High Radiation Efficiency

Abstract: This communication presents a wideband high-efficiency reflectarray antenna with a low radar cross section (RCS) based on metal pillars inserted absorptive frequency-selective reflector (AFSR). The AFSR is realized by the bent resistor-embedded metal strip, whose multimode resonance is utilized to obtain the wideband absorption-reflection-absorption performance. In addition, the realized AFSR is with compact lattice spacing characteristics, which enhances the antenna’s radiation efficiency. Then, the metal pillars with variable heights are inserted into the AFSR serving as a phase shifter to flexibly control the reflection phase within the wide reflection band. Simulated and measured results show that the proposed reflectarray antenna has a pencil-beam radiation pattern from 6 to 8 GHz with an aperture efficiency up to 60.4%. Additionally, two RCS reduction bands with the fractional bandwidth of 66.7% and 32.3% are obtained.

Wideband Gain Enhancement of a Dual-Polarized MIMO Vehicular Antenna

Abstract: A compact dual-polarized multiple-input-multiple- output (MIMO) Vivaldi antenna with a wide bandwidth, high gain, and high isolation is proposed for wireless communications in intelligent Internet of Vehicles (IoV). It consists of four identical orthogonally-crossed Vivaldi radiators, crossed-fishbone-shaped slot, metasurface lens, parasitic stubs, electromagnetic (EM) wave reflector, and three-dimensional (3D) printed radome with dielectric resonator (DR) array. These functional modules jointly contribute to optimized antenna performance. Four identical antenna elements are rotationally symmetrical. To reduce the inter-element mutual coupling, the crossed-fishbone-shaped slot is etched to reduce the surface current flowing in adjacent radiators. To raise the gain, the metasurface lens, parasitic stubs, and DR array are loaded to guide the EM wave in the frontward radiation. An EM wave reflector located underneath the Vivaldi radiators could increase the boresight gain and reduce the influence of the vehicle body on the antenna performance. Diversity performance analysis indicates the proposed antenna could offer better MIMO capability. Besides, the impact of weather conditions on the antenna is analyzed. As a proof of concept, an expanded 8-element antenna array prototype is designed, fabricated, and tested. A good agreement is observed between measured and simulated results. It achieves an -10-dB impedance bandwidth of 7.55–22.85 GHz (100.66% FBW) with port isolation of higher than 18.05 dB. The realized gain is 6.98–11.54 dBi, and the radiation efficiency is 85.05–90.27%. The proposed antenna could be used in wireless communications between vehicles and the satellite/infrastructure.

Angularly Stable Linear-to-Circular Polarizing Reflectors for Multiple Beam Antennas

Abstract: In this article, a new concept to improve the angular stability of linear-to-circular polarizing reflectors is presented. It is first explicitly demonstrated that existing design approaches heavily rely on the adjustment of the design stack-up, namely, the substrate height and relative permittivity, to the desired operating frequency. An approach is then proposed for decoupling the performance from the substrate parameters. The proposed approach provides increased design flexibility, resulting in performance improvement. Insight on the operating principle is provided resorting to equivalent circuit models. Subsequently, the benefits of the angularly stable reflection polarizer are demonstrated by a practical example involving a multiple beam antenna implemented using materials and processes compatible with satellite missions. The antenna exploits an innovative quasi-optical beamformer as primary feed combined with a cylindrical polarizing reflector. Numerical and experimental results from this antenna architecture are presented to confirm the improvements achieved with the proposed concept over existing designs. The close comparison of simulations with measurements that are achieved validates the concept and the design approach.

Spectral engineering of ultrathin germanium solar cells for combined photovoltaic and photosynthesis

Abstract: In densely populated areas, ground mounted photovoltaic power plants compete with agriculture for cultivable land. Agrivoltaic systems allow the combination of these two forms of land use by deliberately designed light sharing. In this contribution, we present a spectrally selective solar cell, for use in agrivoltaic systems, greenhouses, and photo-bioreactors. Our concept benefits from a solar cell with a transmission spectrum which can be easily tuned for the specific absorption requirements of algae and plants. This is achieved by a Fabry-Perot-type multilayer resonator as a back reflector, which determines the transmission and absorption spectrum of the solar cell. We demonstrate the extent of how this transmission spectrum can be engineered by varying the layer thicknesses of the reflector and we show how the reflecting metal layers in the back reflector influence the transmission and photocurrent generation of the spectrally selective solar cell. Finally, we analyze the optical loss mechanisms of the solar cell layer stack to address further optimization potential. Our work offers a spectrally selective solar cell which can be easily adjusted for the requirements of combining photovoltaic and photosynthesis.

A High Gain Millimeter-Wave Circularly Polarized Fabry–Pérot Antenna Using PRS-Integrated Polarizer

Abstract: This communication introduces a new structure of polarizer for generating millimeter-wave (MMW) circular polarization (CP) in a Fabry–Perot cavity (FPC) antenna. It is the first of its kind, which integrates a 3D-printed polarizer with an inserted partially reflective surface (PRS), which contributes to a wideband CP operation with high antenna gain. The realization of CP and gain enhancement can be controlled independently by optimizing the structures of the dielectric part and the PRS of the polarizer, respectively. The proposed antenna consists of a feeding source, a substrate-integrated quasi-curve reflector, and the proposed polarizer. The feeding source and the reflector are able to be fabricated by the conventional PCB technology which is low-cost and convenient in circuitry integration. For validation, a prototype of the FPC antenna with the proposed polarizer operating at 60 GHz has been designed, fabricated, and measured. The peak gain of the antenna reaches to 20 dBic. The antenna achieves an impedance bandwidth of 20% from 54.5 to 66.7 GHz for the reflection coefficient of less than −10 dB. The axial ratio (AR) bandwidth is 12.7% from 56.5 to 64 GHz for AR ≤3 dB. The experimental results confirm a good agreement between simulation and measurement.

Compact wideband hybrid fractal antenna loaded on AMC reflector with enhanced gain for hybrid wireless cellular networks

Abstract: A wideband hybrid fractal monopole antenna loaded with artifical magnetic conductor (AMC) is proposed. Using a hybrid fractal generator, the monopole antenna achieves self-similarity compactness, reduced size and good wideband performances. The ground is semi-elliptic and has defected steps aiming to improve impedance matching and X-pol. reduction. The AMC reflector has 3 × 3 array of cesaro shaped unit cells looped in a square metallic conductor. The AMC enhances radiation gain with back-lobe reduction. The AMC unit cell produce a 0 0 phase reflection at f AMC = 4.5 GHz and then loaded to optimize antenna performance. To validate the design, a prototype antenna is fabricated and measured. The antenna operates from (3.7–7.0) GHz with 61.68% impedance bandwidth, realized gain of (8.7–13.8) dBi, and radiation efficiency > 82.5%. The proposed antenna leverages on compactness, low-profile AMC height and good boresight radiation gain, which shows its potential for hybrid wireless cellular networks.

An S-/Ka-Band Shared Aperture Tracking Reflector Antenna With Polarization Diversity

Abstract: A dual-band dual-polarized tracking reflector design approach has been explored, and successfully demonstrated the $S$ - and Ka -band tracking with enhanced performance. The antenna works in Cassegrain mode at Ka -band and the prime focus configuration at $S$ -band. A frequency selective subreflector isolates the two feeds, permits $S$ -band transmission, and reflects the Ka -band signal. The antenna is dual linearly polarized at $S$ -band and dual circularly polarized at Ka -band. It capitulates an impedance bandwidth wider than 23.9% with isolation superior to 24 dB at the $S$ -band ports. At the Ka -band, it also displays an axial ratio ≤3 dB with isolation above 23 dB over the entire operating bandwidth of ≥12.4%. Monopulse tracking bandwidths of ≈13% at the $S$ -band and ≈8% at the Ka -band have been established. It reveals a gain of 53 dBi at Ka -band and 29 dBi at $S$ -band. The antenna demonstrates improved features, and measured results are enhanced compared to the earlier reported investigations.

A Wideband High-Gain Multilinear Polarization Reconfigurable Antenna

Abstract: In this communication, a wideband low-profile antenna with switchable multilinear polarizations (MLPs) is proposed. An odd number of dipoles with trapezoidal-shaped arms printed on both sides of a substrate are adopted as reconfigurable radiators, which provides a much smaller polarization interval than using an adjacent even number of dipoles. The p-i-n diodes with simple dc biasing lines are loaded to reconfigure the polarization states. A circular-contoured artificial magnetic conductor (AMC) reflector using hexagon-patch cells is employed to reduce the antenna profile. The whole multiple dipole structure is rotationally invariant, which provides almost rotationally invariant antenna performance for different LPs. In addition, the antenna can be easily redesigned when adjusting the number of dipoles for different LPs. A seven-LP reconfigurable antenna working in 2.85–3.40 GHz is used as an example to give the detailed parameters’ study and performance analysis. Three antennas with five, seven, and nine reconfigurable LPs are designed and measured. With $0.035\lambda $ height, they achieve the measured overlapped bandwidths of 20.6%, 17.6%, and 15.9% for five, seven, and nine LPs, respectively, and their measured peak gains are ranging from 8.3 to 8.5 dBi.

3D Beam Steering End-Fire Helical Antenna With Beamwidth Control Using Plasma Reflectors

Abstract: In this article, a beam steerable antenna based on plasma reflectors is presented. The proposed antenna consists of an axial mode helical antenna surrounded by an array of plasma reflector elements forming a cup-shaped ground. In this configuration, the elements of the reflector array can be individually switched on or off to achieve different radiation characteristics for the helical antenna. Specifically, it is shown that the symmetric activation of a specified number of elements of the plasma array can be used to control the beamwidth of the antenna. Moreover, the plasma reflectors can be asymmetrically configured to steer the endfire beam pattern of the helical antenna in 3-D space. To validate the concept, the proposed antenna is designed and numerically simulated. The simulation results show that using the proposed method, the beamwidth of the proposed antenna can be changed from 37° to 50° while the beam direction can be altered in 3-D space within a solid angle of ±6°. Finally, a prototype of the designed antenna is fabricated and its radiation characteristics for various configurations of the plasma reflectors are measured. Good agreement between the simulation and measurement results validates the proposed method.

Millimeter-Wave Radar Scheme With Passive Reflector for Uncontrolled Blind Urban Intersection

Abstract: Modern millimeter-wave automotive radars are employed to keep a safe distance between vehicles and reduce the collision risk when driving. Meanwhile, an on-board radar module is supposed to operate in the line-of-sight condition, which limits its sensing capabilities in intersections with obstructed visibility. Therefore, this paper investigates the scheme with passive reflector, enabling the automotive radar to detect an approaching vehicle in the non-line-of-sight (blind) urban intersection. First, extensive radar measurements of the backscattering power are carried out with the in-house assembled millimeter-wave radar equipment. Next, the measured data is employed to calibrate an accurate analytical model, deduced and described in this paper. Finally, the analytical models are deployed to define the optimal parameters of the radar scheme in the particular geometry of the selected intersection scenario. Specifically, it is found that the optimal angular orientation of the reflector is 43.5 $^\circ$ , while the 20 m curvature radius shows better performance compared to a flat reflector. Specifically, the curved convex shape increases scattering power by 20 dB in the shadow region and, thus, improves the detection probability of the vehicle, approaching the blind intersection.