Beam-steering Antenna Research Articles

A Low-Profile, Risley-Prism-Based, Beam-Steerable Antenna Employing a Single Flat Prism

We present a low-profile, mechanically beam-steerable antenna that implements the Risley prism beam-steering concept using only a single flat prism. The proposed antenna achieves 2-D beam steering and consists of two parts: a holographic leaky-wave antenna and a phase-shifting surface (PSS) that acts as a flat prism. The lower holographic leaky-wave antenna acts as the feed for the prism and provides a phase-shifting gradient over its output aperture. When paired with the flat prism, the system can provide 2-D beam steering by mechanically rotating the two layers against each other. Unlike conventional Risley-prism-based beam-steerable antennas, the proposed approach results in a very low-profile antenna and does not need spatial illumination of a two-prism system with a separate feed antenna. The flat prism is implemented using a PSS consisting of low-pass, hexagonal-shaped, spatial phase shifters. A prototype antenna with an overall thickness of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.1\lambda _{0}$ </tex-math></inline-formula> at 10 GHz was designed, fabricated, and experimentally characterized. Measurement results agree well with theoretical predictions and both show wide-angle beam scanning ranging from 0° to 57° in the elevation plane and 0° to 360° in the azimuth plane. The proposed antenna system has an equivalent aperture diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.1\lambda _{0}$ </tex-math></inline-formula> and a measured peak gain of 22.3 dBc at 10 GHz corresponding to an aperture efficiency of 34.5%. The proposed concept is expected to be useful in designing low-profile, beam-steerable antennas in which the scanning speed can be traded off to reduce system complexity.

Static and Reconfigurable Huygens’ Metasurfaces: Use in Antenna Beamforming and Beam Steering

In this article, we review recent advances in static and reconfigurable Huygens’ metasurfaces (HMSs) for antenna beamforming and beam steering. First, the fundamental theory of HMSs is summarized along with basic approaches for their physical realization. Subsequently, precise antenna beamforming without feeding networks by utilizing static HMSs is described. This is followed by the description of using HMSs as radomes for extending the scan range of phased arrays. Finally, several strategies are described for realizing reconfigurable HMS by means of electronic control devices.

K-Band Circularly Polarized Beam Steerable Reflectarray Enabling Internet of Space: Conceptualization and Validation

Low-cost and lightweight CubeSats have opened new possibilities to realize Internet of Space (IoS), a vision that aims to provide global network access, particularly for remote areas. A key challenge for IoS realization is the development of an antenna that can meet the gain, bandwidth, and polarization requirements for IoS while complying with the small form factor of CubeSats. The challenge is further magnified by the need to dynamically reconfigure the antenna’s beam location to maintain connectivity as the satellite orbits. This work addresses these challenges by proposing a beam steerable reflectarray antenna that can potentially be integrated with CubeSats to enable IoS. A novel reflectarray unit cell containing multiple Archimedean spiral arms is designed to support broadband circularly polarized (CP) operation, and its operational principle is discussed in depth. The unit cell provides four states of phase shift that are electronically switchable, allowing the reflectarray to achieve the required aperture phase for the desired beam scan. Representative reflectarray prototypes are designed, fabricated, and measured. CP beam scan up to 60° in the plane of offset across the targeted frequency band of 17.8–20.2 GHz is achieved.

Design of Coupled-Resonator Array Antenna for Steering Beam With Extremely High Scanning Rate

An extremely high scanning-rate beam-steering antenna based on coupled resonators is proposed in this communication. Coupling resonators in a controlled manner provides a sharp phase variation across a narrow frequency band, which contributes to the extremely high scanning rate. To steer the beam across broadside, alternating +90° and −90° impedance inverters are employed in the topology. Such a coupled-resonator array antenna is modeled and analyzed by coupling matrix technique, which was conventionally used in filter design. To illustrate the proposed technique, two examples with 50 and 100 MHz bandwidths are designed. Experimental validation is also provided for the 50 MHz bandwidth example, which demonstrates that the proposed antenna reaches a high relative scanning rate of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$52.8^{\circ }/\%BW$ </tex-math></inline-formula> with efficiency of 75%.

High gain and circularly polarized beam-switching 8 × 8 Vivaldi antenna array for X-band application

AbstractAn 8 × 8 butler Vivaldi beam-steering antenna array is introduced for X-band application. Circularly polarized array is made of eight Vivaldi elements with 1×8 platform and an 8×8 beam feeding network. Vivaldi radiating element is used in array form to enhance impedance bandwidth and overall efficiency such as gain. Using microwave passive components, for instance, 3 dB branch line couplers and crossover help to have orthogonal modes for feeding each of the elements, hence circular polarization property is achieved. Extracted results show that the array has an impedance bandwidth over 7–12.7 GHz (~58%) for VSWR≤2 and an axial-ratio bandwidth of 3.15 GHz that is between 8.15 and 11.3 GHz (~33%). The peak gain of antenna array is 18 dBi at 10 GHz. The proposed beam-steering antenna with compact size and good operation is capable to cover an angle range from −42 to 55 degree in whole operation frequency.

LiDAR integrated IR OWC system with the abilities of user localization and high-speed data transmission.

By using narrow infrared (IR) optical beams, optical wireless communication (OWC) system can realize ultra-high capacity and high-privacy data transmission. However, due to the point-to-point connection approach, a high accuracy localization system and beam-steering antenna (BSA) are required to steer the signal beam to user terminals. In this paper, we proposed an indoor beam-steering IR OWC system with high accuracy and calibration-free localization ability by employing a coaxial frequency modulated continuous wave (FMCW) light detection and ranging (LiDAR) system. In the meantime, benefitting from the mm-level ranging accuracy of the LiDAR system, a useful approach to assess the feasibility of the link alignment between beam-steering antenna and users is first demonstrated. With the assistance of the LiDAR system, we experimentally achieved the localization of user terminals with a 0.038-degree localization accuracy and on-off keying (OOK) downlink error-free transmission of 17 Gb/s in free space at a 3-m distance is demonstrated. The highest transmission data rate under the forward error correction (FEC) criterion (Bit error rate (BER) <3.8×103) can reach 24 Gb/s.

Dual-Band Phased Array 5G Mobile-Phone Antenna with Switchable and Hemispherical Beam Pattern Coverage for MIMO-Diversity Communications

A new design of dual-band antenna array with 3D-coverage beam steering characteristic for millimeter-wave (MM-Wave) communications is proposed in this manuscript. The antenna covers frequency bands of 18 GHz and 28 GHz. Its configuration contains three subarrays of patch radiators along the edge area of the smart phone printed circuit board (PCB). Each sub-array contains eight elements of dual-band patch antennas with C-shaped slots. The resonant frequencies of the single element radiator can be adjusted by tuning the sizes of the embedded C-shaped slot and the main patch radiator. The beam-steerable antenna is designed on an N9000 PTFE dielectric. In order to achieve high gain beams and also for covering wider beam-steering area, each sub-array is deployed in different top-sides of the PCB with a dimension of 55××110 mm22. Using three uniform linear eight element sub-arrays, hemispherical beam pattern coverages can be achieved. The proposed antenna provides good performances in terms of gain, radiation and total efficiencies, and beam steering properties which make it suitable for use in the fifthgeneration (5G) mobile-phone platforms.

Accurate optimization technique for phase-gradient metasurfaces used in compact near-field meta-steering systems

Near-Field Meta-Steering (NFMS) is a constantly evolving and progressively emerging novel antenna beam-steering technology that involves an elegant assembly of a base antenna and a pair of Phase-Gradient Metasurfaces (PGMs) placed in the near-field region of the antenna aperture. The upper PGM in an NFMS system receives an oblique incidence from the lower PGM at all times, a fact that is ignored in the traditional design process of upper metasurfaces. This work proposes an accurate optimization method for metasurfaces in NFMS systems to reduce signal leakage by suppressing the grating lobes and side lobes that are innate artifacts of beam-steering. We detail the design and optimization approach for both upper and lower metasurface. Compared to the conventionally optimized compact 2D steering system, the proposed system exhibits higher directivity and lower side-lobe and grating lobe levels within the entire scanning range. The broadside directivity is 1.4 dB higher, and the side-lobe level is 4 dB lower in comparison. The beam-steering patterns for the proposed 2D compact design are experimentally validated, and the measured and predicted results are in excellent concurrence. The versatile compatibility of truncated PGMs with a low gain antenna makes it a compelling technology for wireless backhaul mesh networks and future antenna hardware.

Ultrawideband Beam Steering at mm-Wave Frequency With Planar Dielectric Phase Transformers

In this article, a new method to design an ultrawideband beam-steering antenna system is presented. The system is completely passive and suitable for millimeter-wave applications, including some in defense, where both discrete beam steering and continuous beam steering in two dimensions (elevation and azimuth) are required at a reasonably fast speed. The beam-steering capability is achieved using a pair of distinct low-profile and planar phase transformers (PPTs) placed in the near-field region of a fixed-beam radiating source. The antenna system demonstrates a steering and impedance-matching bandwidth of 28.6&#x0025;, from 30 to 40 GHz. A prototype of the new antenna system, including a pair of thin PPTs and a completely automated mechanical system to rotate each of the PPTs around the antenna axis, has been fabricated and tested. The pair of rotating PPTs, equivalent to a pair of 3-D dielectric PTs (DPTs), introduces a precalculated phase gradient to the input near field from the fixed-beam antenna and creates an output near field that will radiate toward a selected direction, which can be varied within a large conical region with a maximum apex angle of 108&#x00B0;. The system exhibits the predicted and measured peak gains of 21.5 and 21.7 dBi, respectively, and the measured gain variation over 2-D beam steering is less than 2.2 dB. This beam-steering method obviates the need for expensive phase shifters and distribution networks, which are also lossy at mm-wave frequencies. The measured results validate the predicted wideband matching and steering performance of the system with a close agreement.

A compact size wide‐angle 3 × 3 substrate integrate waveguide Butler matrix for Ku‐band applications

In this paper, an array antenna fed by a novel double layer 3 × 3 Butler matrix for Ku-band application was presented. An antipodal Vivaldi antenna (AVA) with dielectric lens was suggested as radiating elements. AVA has a broadband specification along with directive stable patterns at operational bandwidth. Combinational structure of substrate integrated waveguide topology by modified radiating element (AVAs) results to miniaturized size and acceptable radiation efficiency in whole of Ku-Band. Presented array covers frequency range of 13–17.5 GHz (30%) with average gain of 14.2 dBi. The proposed beam-steering antenna with compact size and good performance is capable to cover an angle range from −39 to 38° in whole operation frequency. This structure with unique configuration and specification can be a good candidate for beam-forming application for wireless devices.

Achieving Continuous Stable Beam Steering with Gain Enhancement Using a Graded-Index Metasurface Lens

In this paper, the design of an ultrathin highly transmissive angular graded-index metasurface (AGIMS) lens is proposed, and a beam steerable high-gain low-profile lens antenna is designed using AGIMS lens and microstrip patch antenna (MPA) radiator operating at 10.10 GHz. An ultrathin graded-index metasurface lens is designed using fundamental unit cells and their modulated forms. The direction and gain control of the microwave radiator’s beam, using a designed modulated metasurface lens with doubled-sided double circular ring resonator as a fundamental unit cell, is presented. The uniform radial and linear movement of AGIMS in the step of 12 mm steer the radiated main beam of MPA continuously in a conical plane from −40° to +40° with a maximum measured broadside gain of 13.15 dBi and minimum broadside gain of 11.80 dBi at 10.10 GHz frequency, indicating maximum and minimum gain enhancement of 8.40 and 7.0 dB in −40° and 0° direction, respectively. The angular movement of AGIMS over the MPA radiator at the centre point results in beam steering from −25° to +25° continuously with a maximum gain variation of 2 dB and a maximum measured gain from 10.00 dBi to 12.00 dBi, indicating gain enhancement of 5.25 dB to 7.25 dB. Using AGIMS, the stable broadside radiation characteristic with beam steering and continuous gain enhancement is achieved. The measured and simulated results are in good agreement.

Design and implementation of a beam-steering antenna array using butler matrix feed network for X-band applications

This article proposes the design, simulation, fabrication and testing of a beam steerable antenna array using a 4 × 4 Butler Matrix feed network technique. The proposed antenna is developed to operate at the X band frequency range. The integrated antenna array and the Butler Matrix feed network operating at 10 GHz has a bandwidth of approximately 2 GHz with an achieved gain of 12 dBi. The main beam pattern of the antenna array is switched between four directions (+10°, −38°, +38°, −10°) providing an effective coverage of over 100°. The proposed antenna has the advantages of low cost, easy fabrication, and simplicity.

A Millimeter-Wave 2D Beam Steering Antenna Using Extended Hemispherical Dielectric Lens Antenna Subarrays

Recent work has proposed that millimeter-wave beam steering antennas consisting of lens antenna subarrays (LASs) reduce hardware complexity. This manuscript extends the concept to 2D beam steering with extended hemispherical dielectric lenses (EHDLs). To accomplish this, we introduce a design process to maximize scan range and side lobe level (SLL) performance. The design process first employs the solution of the geometric disk covering problem to identify the initial positions of the feed antennas such that the subarray size, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> , is minimized. This process is followed by systematic 3D full-wave simulation-based parametric sweeps of lens geometry and feed antenna positions to maximize scan range and minimize SLL. Finally, we demonstrate this process with a 38 GHz antenna consisting of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> = 7 LASs and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> = 17 feed antennas per LAS. The resulting antenna has a ±36° field of view, -9.5 dB SLL, 5° half-power beamwidth, and ~20 dBi maximum realized gain. Compared to the existing literature on subarray-based beam-steering antennas, this antenna performs with a more extensive scan range while offering a comparable SLL performance.

Reconfigurable Pattern Patch Antenna for Mid-Band 5G: A Review

New requirements in communication technologies make it imperative to rehash conventional features such as reconfigurable antennas to adapt with the future adaptability advancements. This paper presents a comprehensive review of reconfigurable antennas, specifically in terms of radiation patterns for adaptation in the upcoming Fifth Generation (5G) New Radio frequency bands. They represent the key of antenna technology for materializing a high rate transmission, increased spectral and energy efficiency, reduced interference, and improved the beam steering and beam shaping, thereby land a great promise for planar antennas to boost the mid-band 5G. This review begins with an overview of the underlying principals in reconfiguring radiation patterns, followed by the presentations of the implemented innovative antenna topologies to suit particular advanced features. The various adaptation techniques of radiation pattern reconfigurable planar antennas and the understanding of its antenna design approaches has been investigated for its radiation pattern enhancement. A variety of design configurations have also been critically studied for their compatibilities to be operated in the mid-band communication systems. The review provides new insights on pattern reconfigurable antenna where such antennas are categorized as beam steering antenna and beam shaping antennas where the operation modes and purposes are clearly investigated. The review also revealed that for mid-band 5G communication, the commonly used electronic switching such as PIN diodes have sufficient isolation loss to provide the required beam performance.

A Small Metaline Array Antenna for Circularly Polarized Dual-Band Beam-Steering

A circularly polarized (CP), small, beam-steerable antenna is realized using bent metalines. The antenna has the following features: (i) dual-band operation at low frequency <i>f</i>_LOW (wavelength &#x03BB;_LOW) and at high frequency <i>f</i>_HIGH (wavelength &#x03BB;_HIGH), (ii) a small antenna volume of less than 0.01&#x03BB;³_LOW, (iii) a small antenna height on the order of &#x03BB;_LOW/100, (iv) a small conducting antenna footprint of 0.62&#x03BB;_LOW &#x00D7; 0.49&#x03BB;_LOW, and (v) a phased array antenna consisting of minimum array elements (two elements). Firstly, the antenna characteristics of straight and bent metalines are briefly summarized. Secondly, it is shown that an array antenna composed of two bent metalines forms a CP broadside beam at <i>f</i>_LOW using an equal-amplitude/in-phase excitation mode. This is also shown to be true at <i>f</i>_HIGH. Thirdly, each of the obtained CP broadside beams at <i>f</i>_LOW and <i>f</i>_HIGH is steered within the H-plane. The array antenna is found to have a CP beam that is steerable across a region of &#x03B8; = -40&#x00B0; to &#x03B8; = +30&#x00B0; at <i>f</i>_LOW and &#x03B8; = -40&#x00B0; to &#x03B8; = +25&#x00B0; at <i>f</i>_HIGH, with an axial ratio of less than 3 dB. During the beam steering, the gain deviation from its maximum value is found to be small: 1.7 dB at <i>f</i>_LOW and 1.4 dB at <i>f</i>_HIGH.

When Satellites Work as Eavesdroppers

This paper considers <i>satellite eavesdroppers</i> in uplink satellite communication systems where the eavesdroppers are randomly distributed at arbitrary altitudes according to homogeneous binomial point processes and attempt to overhear signals that a ground terminal transmits to a serving satellite. Non-colluding eavesdropping satellites are assumed, i.e., they do not cooperate with each other, so that their received signals are not combined but are decoded individually. Directional beamforming with two types of antennas: fixed- and steerable-beam antennas, is adopted at the eavesdropping satellites. The possible distribution cases for the eavesdropping satellites and the distributions of the distances between the terminal and the satellites are analyzed. The distributions of the signal-to-noise ratios (SNRs) at both the serving satellite and the most detrimental eavesdropping satellite are derived as closed-form expressions. The ergodic and outage secrecy capacities of the systems are derived with the secrecy outage probability using the SNR distributions. Simpler approximate expressions for the secrecy performance are obtained based on the Poisson limit theorem, and asymptotic analyses are also carried out in the high-SNR regime. Monte-Carlo simulations verify the analytical results for the secrecy performance. The analytical results are expected to be used to evaluate the secrecy performance and design secure satellite constellations by considering the impact of potential threats from malicious satellite eavesdroppers.

Metamaterial-Inspired Flat Beamsteering Antenna for 5G Base Stations at 3.6 GHz.

In this paper, a metamaterial-inspired flat beamsteering antenna for 5G applications is presented. The antenna, designed to operate in the 3.6 GHz at 5G frequency bands, presents an unique flat form factor which allows easy deployment and low visual impact in 5G dense scenarios. The antenna presents a multi-layer structure where a metamaterial inspired transmitarray enables the two-dimensional (2D) beamsteering, and an array of microstrip patch antennas is used as RF source. The use of metamaterials in antenna beamsteering allows the reduction of costly and complex phase-shifter networks by using discrete capacitor diodes to control the transmission phase-shifting and subsequently, the direction of the steering. According to simulations, the proposed antenna presents steering range up to , achievable in both elevation and azimuth planes, independently. To prove the concept, a prototype of the antenna has been built and experimentally characterised inside an anechoic chamber. Although constructed in a different substrate (FR4 substrate) as initially designed, beamsteering ranges up to in azimuth and in elevation, limited to the proposed case-studies, are reported with the prototype, validating the antenna and the usefulness of the proposed design.

Circularly polarized beam steering array antenna fed by low magnitude and phase error response of Butler matrix to use pattern stabilization applications

In this work, a novel circularly polarized (CP) Fabry–Perot resonator beam-steering antenna array with capability covering C-band applications is introduced. The proposed antenna array caters to a relatively constant high gain at a broadband impedance bandwidth in comparison with conventional arrays. The presented antenna is designed based on a broadband Butler matrix feeding network which is able to stabilize direction patterns at different frequencies for each of the ports for the sake of phase distribution in whole operation frequency with low phase error.

Design of a liquid crystal beam‐steerable antenna with characteristic mode analysis

A novel liquid crystal beam-steerable antenna is presented. It is a conventional liquid crystal microstrip patch antenna with a bending slot in the middle of the H-plane. Owing to the introduction of the bending slot, this antenna can work at even mode and odd mode within a frequency band. To obtain the resonant frequencies and radiation characteristics of the two modes, the method of characteristic mode analysis is utilised. It indicates that the resonant frequency of even mode is lower than that of odd mode. Therefore, by choosing liquid crystal as its substrate, this antenna can alter its operating modes by varying the permittivity of liquid crystal. Furthermore, beam steering can be realised since the radiation patterns of the two modes are divergent. An antenna prototype at Ka-band has been designed, fabricated and measured. The measured results show that the maximum radiation direction can scan from −30° to −2° continuously at 26.5 GHz in the H-plane.

Enabling the Internet of Things With CubeSats: A review of representative beamsteerable antenna concepts

The advent of CubeSats has empowered the vision of using a satellite constellation to provide seamless Internet coverage across the globe. This vision, known as the Internet of Space (IoS), is the key enabler of the Internet of Things (IoT). One of the major challenges in making IoS a reality is the development of an antenna system that can sustain a high data-rate link while being amenable to integration with the small CubeSat form factor. This challenge is further magnified by the requirement that the antenna dynamically reconfigures its radiation pattern to illuminate geographical areas that demand more coverage. The aim of this article is to provide an overview of antenna concepts developed by representative researchers that can overcome these challenges. If properly tailored for specific CubeSat applications, these concepts can make CubeSat-based IoS a realizable vision. We also highlight the open challenges and technology gaps that future research must address to make IoT a reality.