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A beam-steering fed array antenna has been proposed for radar and mm-Wave applications operating from 22.6 to 26.89 GHz and 30–45 GHz with B.W % of 17.34 % and 40 % respectively having size of 12.11 × 25.58 × 0.8 mm3 (0.96λo × 2.01λo × 0.06λo). For radar, this antenna covers 24.15 GHz as police radar, 24.25–25.25 GHz & 31.8–33.4 GHz as navigation radar, and 33.4–36 GHz as high-resolution radar for airport surveillance. This antenna also covers mm-wave bands for different countries (Brazil-40 GHz, China- 34–42.5 GHz, Mexico- 33 GHz and 37 GHz, and USA- 24 GHz, 37 & 39 GHz). At initial stage, a monopole antenna with DGS has been designed with an operating band of 20.2–31.2 GHz and 36.6–42.2 GHz. Proposed antenna shifts the beam pattern at 90° with each other after exciting each port in alternative order with a scanning angle of ±45°, ±75° & ±180°. Peak gain for 1st band ranges from 7.1 to 9 dBi and for the 2nd band ranges from 8.8 to 10.2 dBi and has a radiation efficiency of 88 %. Other diversity parameters such as ECC, DG, MEG, and isolation get analysed to observe the coupling effects. Design, development, and analysis of all antenna parameters is done by using HFSS 19 platform. [ABSTRACT FROM AUTHOR]

ABSTRACT This paper introduces a 4‐channel 24‐ to 28‐GHz RF front‐end MIMO system designed for 5G applications. The transmitter (Tx) and receiver (Rx) chips are fabricated using 130‐nm SiGe BiCMOS technology. The chips contain a 6‐bit phase shifter (PS), 1‐bit attenuator (ATT), 3‐bit variable gain amplifier (VGA), serial peripheral interface (SPI), Wilkinson combiner, power amplifier (PA), and low noise amplifier (LNA). The designed vector‐sum PS, employing a current DAC for semi‐digitization, achieves a 6‐bit phase resolution with minimal root‐mean‐square (RMS) phase error. This design choice allows for the high bit control of the current DAC within a compact chip area. Four‐bit amplitude control is obtained with VGA and ATT. The VGA provides 8‐dB amplitude range while ATT enlarges overall amplitude control with additional 8 dB. L‐R‐L phase compensation technique is utilized to reduce the phase error that arises from ATT. The sub‐blocks are designed to operate with low DC power such that the DC power consumption of overall RX and TX is 50 and 97 mW, respectively. The measurement results of a single‐channel indicate a gain of 15.5‐dB and −25‐dBm IP1dB for the RX chip and 26.5‐dB and 10‐dBm OP1dB for the TX chip while each chip occupies 0.83 mm2$$ {}^2 $$. The RX chip exhibits a measured noise figure (NF) of 4.3 dB at 26 GHz. Both Tx and Rx chips achieve 6‐bit phase control and 4‐bit amplitude control with low RMS phase error of 2.6° and gain error of 0.3 dB. Low RMS gain and phase errors over a wide bandwidth are attributed to the high precision DAC employed in the control of VGA and PS. Both chips are flip‐chip packaged and undergo upconversion/downconversion via external mixers on a printed circuit board (PCB). System‐level tests with 64‐quadrature amplitude modulation (QAM) show an error vector magnitude (EVM) of 2.72% at 27 GHz for RX and 5.02% at 24 GHz for TX, with a 50‐MBaud modulated signal applied at a data rate of 300 MBps. [ABSTRACT FROM AUTHOR]

In this paper, a multifunctional transmit-array antenna with beam steering and polarization conversion capabilities for the X-band is presented. The proposed design offers advantages in terms of scalability, faster development and deployment, and ease of maintenance owing to its modular design, which is configured by a receiver, an active circuit, a DC bias control line, and a transmitter. The proposed design is capable of 2D beam scanning of up to ±45° for azimuth and elevation while converting vertical or horizontal polarization by electronic control. To verify its performance, a 16×16 array transmit-array antenna is fabricated and tested using a near-field measurement system. It exhibits a maximum gain of 23.7 dBi, the sidelobe level of 14 dBc, the polarization conversion loss of below 1 dB, and the polarization isolation of above 10 dB. The measurement results agree well with the simulation. [ABSTRACT FROM AUTHOR]

In this paper a beam steering 2 × 2 microstrip array antenna is proposed and simulated for the 5G sub-6 GHz frequency band. The array antenna is designed at the resonant frequency of 3.5 GHz. The antenna has four patches excited by two microstrip lines. Microstrip lines on top of teflon substrate of 0.8 mm height and slot line in the ground plane makes a hybrid junction. The design uses both sided microwave integrated circuit (MIC) to feed signal to the patch elements. This designed array antenna has the beam steering capability of maximum -17 to +17 while keeping the side lobe gain below 10 dB. The simulation results show that the array antenna is designed through good input impedance matching. The antenna has a return loss of -43 dB at center frequency 3.5 GHz. The results also show that the array antenna has a high gain of 12.57 dBi and directivity of 25.11 dB. The maximum gain of this antenna is 24.1 dB at -17 and +17. The proposed work is simulated on keysight technologies advanced designed system (ADS). [ABSTRACT FROM AUTHOR]

A circuit-based calibration system is presented for active phased arrays. In particular, to achieve the desired (and corrected) consecutive phase differences and relative magnitudes between RF channels, a computer controlled circuit system was developed for dynamic adjustment. The proof-of-concept demonstrator uses a phase sensor, phase shifters (PSs), and variable gain amplifiers, along with other active hardware, to realize a self-calibrating circuit system which achieves the required magnitude and phase for each array element. In addition, measured magnitude and phase imbalances are less than 0.10 dB and 3$^\circ$, respectively. The computer-controlled feed network is then used to demonstrate that the system can automatically calibrate an active antenna array for various beam steering examples. Also, the S-band feed system can self-calibrate due to any monitored magnitude and phase drifts due to temperature changes and practical component ageing, or, other general channel offsets. This can be considered advantageous and simpler when compared to more established approaches which characterize the coupling between elements or the response of the entire array in the near- or far-field for example.

A methodology for beam-steering using operational amplifiers (Op-amps) is presented. Continuous steering is required in various advanced applications and its implementation necessitates additional efforts since singularly control of the feeding of the radiators is mandatory for both phase and amplitude. The present work proposes a technique for generating the required sequence of the feeding signal using two Op-amps for each input port. It leads to generating incremental phases with sequential Op-amps without any limitation in the value of the phase differences, controlled by the bias voltage applied to the Op-amps, hence giving rise to a continuous beam-steering capability. The study case consists of a four-stage oscillator designed for creating a sequence of signals with progressive phase shifts between consecutive outputs. The general scheme allows continuous control of the phase differences here applied for generating a uniform, i.e., constant signal magnitude, feeding sequence. This set of signals is then used to feed a four-element microstrip array operating at 1.2 GHz. The effectiveness of the method is validated by numerical simulation of the array performances. Additionally, the low power consumption of active Op-amps, easy implementation, and high sensitivity are characteristics of the presented paradigm.

This paper presents a Ka-band beam steering transmitter exploiting a coupled varactor loaded transmission line (VLTL) phase shifter and a CMOS transmitter chip with an integrated frequency multiplier. The short-coupled line couplers placed along a single VLTL provides multi-phase outputs while minimizing the impedance mismatch and unequal power distribution along the VLTLs. The inherent phase-accumulating nature along the VLTL reduces the burden of wide phase control range required for using separate phase shifters for each channel. Additionally, the frequency multiplier with a multiplication ratio of 8 reduces the required amount of phase change at the reference frequency and therefore the tuning range of the varactor, which also minimize a change of line characteristic impedance to ensure the impedance matching of the VLTL. Hence, a 32 GHz phased array transmitter is implemented using a single VLTL phase shifter operating at a low reference frequency of about 4 GHz. The fabricated $1\times 4$ phased array transmitter achieves a continuous beam steering range of ±20° in the E-plane using a single control voltage. The sidelobe level is below -10 dB at all scan angles and the peak effective isotropic radiated power (EIRP) is 38.1 dBm at 31.6 GHz and the 3-dB bandwidth of 2.4 GHz is achieved.

A 3-D printable, planar, metal-dielectric metasurface-based, 2-D beam-steering system for aperture-type antennas is presented in this paper. This beam-steering system, also known as the near-field meta-steering system, comprises two fully passive phase-gradient metasurfaces placed in the antenna’s near-field region to steer the radiation beam. To address the non-uniform electric field phase of the aperture antenna, phase correction is also incorporated into the bottom metasurface placed on top of the antenna aperture in its near-field to enhance the far-field radiation of the antenna. Near-field phase transformation and phased array antenna theory concepts are applied to design the proposed metasurfaces. Two types of metal-dielectric unit cells are implemented to provide a phase range of 360°. The height of each metasurface is only 6.25 mm ( $0.25\lambda _{0}$ ), and the height of the whole system is only $1.56~\lambda _{0}$ at 12 GHz. The proposed beam-steering system with a resonant cavity antenna can steer the beam to a maximum of ±44° in the elevation plane and 360° in the azimuth plane with only a 1.4 dB (17 dB - 15.6 dB) deviation in directivity over the full steering range.

In this paper, we propose a reconfigurable intelligent surface (RIS) that can dynamically switch the transmission and reflection phase of incident electromagnetic waves in real time to realize the dual-beam or quad-beam and convert the polarization of the transmitted beam. Such surfaces can redirect a wireless signal at will to establish robust connectivity when the designated line-of-sight channel is disturbed, thereby enhancing the performance of wireless communication systems by creating an intelligent radio environment. When integrated with a sensing element, they are integral to performing joint detection and communication functions in future wireless sensor networks. In this work, we first analyze the scattering performance of a reconfigurable unit element and then design a RIS. The dynamic field scattering manipulation capability of the RIS is validated by full-wave electromagnetic simulations to realize six different functions. The scattering characteristics of the proposed unit element, which incorporates two p-i-n diodes have been substantiated through practical implementation. This involved the construction of a simple prototype and the subsequent examination of its scattering properties via the free-space measurement method. The obtained transmission and reflection coefficients from the measurements are in agreement with the anticipated outcomes from simulations. [ABSTRACT FROM AUTHOR]

High‐performance beam‐steering devices play a crucial role for optical wireless communication (OWC), which can meet the demand for increasing number of wireless mobile devices and emerging high‐speed multimedia applications. Conventional beam‐steering optical components like spatial light modulator and digital micromirror device are limited to realize a small steering angle (typ. several degrees), thus dramatically limits the spatial scope of OWC. Herein, a beam‐steering metadevice utilizing an ultracompact metasurface assisted with a spatial light modulator is presented, which can significantly increase the beam‐steering angle without at the cost of complicated optical setup like conventionally used angle magnifier. Based on the actively tunable beam‐steering metadevice, an intelligent bidirectional optical broadcasting communication system is designed and experimentally demonstrated, which exhibits nine broadcasting areas covering a large field‐of‐view of 20° × 20°, with user‐defined dynamic beam‐steering ability in each area, and each user has a data rate of 10 Gbps for both upstream and downstream transmission. The proposed metadevices can meet the demand of intelligent optical wireless communication which requires both high‐performance and low‐cost for practical purpose, under currently available technical architectures. [ABSTRACT FROM AUTHOR]

In this work, beam-steering in THz MIMO antennas has been demonstrated using two different types of graphene-based intelligent reflective surface. Equivalent circuit models of intelligent reflective surface unit cells have been proposed for demonstrating their reflection characteristics. Two types of microstrip patch-based THz MIMO in side-by-side configuration and orthogonal configuration have been designed to exhibit S11 lower than − 15 dB and radiation efficiency greater than 95%. Band-stop FSS has been employed to reduce the mutual coupling of MIMO antennas which are arranged in side-by-side configuration. The MIMO antennas have been integrated with graphene-based intelligent reflective surface for simultaneous steering of four beams radiated by the antenna elements. The reflectivity of the intelligent reflective surface relies on the conductivity of graphene which can be modified by changing its bias voltage. A digital 1-bit coded metasurface has been designed using graphene-based intelligent reflective surface. By varying the bias voltage on the graphene-based unit cells, the pattern of the digital code is modified on the intelligent reflective surface, which causes beam-steering of MIMO antennas placed above it. Gain improvement of 4 dB takes place when the intelligent reflective surface behaves as an AMC for the MIMO in linear configuration. Maximum gain improvement of 10 dB is obtained for the intelligent reflective surface integrated MIMO in orthogonal configuration with radiation efficiency greater than 90%. Numerical simulations using finite integration technique have been performed for illustrating the rotation of beam in MIMO antennas. [ABSTRACT FROM AUTHOR]

This paper provides an overview of broadband terahertz antenna elements and arrays for integrated communication systems. The fundamental challenges of integrated on-chip and off-chip antenna design, the trade-offs between performance metrics, and the impact of interface between the chip and off-chip antennas are studied in detail. The limitations and benefits of various interface technologies are discussed. The deployment of printed circuit boards (PCB) and flexible printed circuits (FPC) technologies for implementation of efficient broadband antennas is compared against on-chip counterparts. As a proof of concept, an off-chip antenna for the 91–134 GHz is presented.

The design of a reflective surface operated in the GHz range is proposed to enable beam-steering and polarization conversion simultaneously. The concept presented in this work relies on plasma-based Intelligent Reflecting Surfaces (IRS) in which the plasma is magnetized. Plasma-based IRSs have been introduced recently and consist of rectangular plasma discharges placed on top of a metallic ground plane. The reflected signal can be reconfigured electronically by varying the plasma parameters (e.g., density). First, a theoretical model is exploited to evaluate the capability of a plasma-based IRS to implement beam-steering and polarization conversion simultaneously. Second, the preliminary design of two plasma-based IRSs is presented to combine beam-steering with 1) cross-polarization or 2) linear-to-circular polarization conversion. According to the numerical results, the proposed concepts are feasible assuming the plasma density can be reconfigured in the range $4.9\times 10^{17}$ - $13.7\times 10^{17}\,\,\text{m}^{-3}$ and the intensity of the magnetostatic field in the range 60–183 mT; these values are consistent with the plasma technology at the state-of-the-art. The operation frequency is 10 GHz, and the bandwidth is between 0.5-0.8 GHz for the two plasma-based IRSs presented in this work.

This article reviews the latest developments of beam steering antennas that are entirely passive to realize interference-free, power-efficient, and highly secured end-to-end wireless communication. We briefly introduce metamaterials and metasurfaces, a timely advanced topic in electromagnetics (EM) and optics. Mathematical formulas associated with the design of beam steering metasurfaces have been numerically explained. In addition, reflect and transmit array antennas are also discussed for an in-depth understanding of beam scanning principles in elevation and azimuth planes. We then provide intuitive design examples and discuss three broad classes of the latest beam scanning antenna systems, namely 1) Reflectarrays (RAs); 2) Transmitarrays (TAs); and 3) Near-Field Meta-Steering (NFMS) antennas that are available in up-to-date literature. The third category’s unprecedented scanning performance and aesthetically compact size are elucidated compared to previous antenna systems, such as reflector dishes or large phased arrays. Alongside the working principles, the trade-offs for the scanning techniques, operation, and physical size of each antenna type are also discussed. Towards the end, an evaluative conclusion with a comparative discussion on the beam-steering antenna systems is provided. Future research directions considering mass-market demands are also indicated.

This paper presents an effective excitation synthesis algorithm of phased arrays of antennas to optimize the radiation patterns under minimum mutual coupling/induction interferences between two nearby arrays. The optimization goal is to minimize the inter-array interferences in an attempt to retain their radiation beam characteristics. Furthermore, a cost function is defined to reduce the inter-array reaction and the excitation weighting deviations from the desired ones for directional beam radiations by embedding a coupling reduction factor (CRF). The resulting solutions are in a simple closed-form for easy implementation. Besides, the mutual coupling/induction mechanisms are effectively interpreted using the singular-value decomposition (SVD) method to create an eigenspace for signal representations and the complementary null space. Finally, theoretical and numerical full-wave simulation examples are presented to validate the proposed mutual coupling/induction suppression method.

Visible light communication (VLC)-enabled unmanned aerial vehicle (UAV) networks have emerged as a novel approach for simultaneous illumination and communication. Among the prominent challenges in VLC are shadowing and low reflected energy. Light-emitting diode (LED) beam-steering is a promising technique to overcome these challenges. In this paper, we consider the problem of joint UAV deployment, LED beam-steering, cell association, and power allocation to satisfy a set of illumination and data rate requirements for stochastically distributed users. Towards addressing this problem, we develop SteerVLC, a novel scheme for UAV networks equipped with steerable LEDs that jointly optimizes UAV deployment, LED beam-steering, cell association, and power allocation. While accounting for illumination interference, SteerVLC minimizes the number of UAVs needed to satisfy the illumination and data rate requirements of stochastically distributed users and minimizes the total transmission power of the steerable LEDs. Using an $\epsilon $ -controlled two-stage mixed-integer linear programming approach, SteerVLC can effectively manage the tradeoff between the required number of UAVs and the required transmission power. SteerVLC is evaluated under various system parameters, user demands, and user distributions. Our results demonstrate the superiority of SteerVLC in managing the resources of a VLC-enabled UAV network and optimizing its performance.

The effect of load-pull on 3rd order intermodulation (IM3) radiation characteristics of a transmitting active phased array is studied and a general model for predicting the spatial distribution of fundamental tones and intermodulation products is introduced. The used data is obtained from a load pull measured amplifier prototype and a simulated linear antenna array, which are used in co-simulation of the system behavior. The system is optimized for maximum main tone beam powers with a two-tone excitation while satisfying a signal-to-IM3 ratio (SI3R) of 40 dB. In this paper, we demonstrate the case, where two separate beams are scanned independently from each other. The used load-pull system model achieves on average an improvement of 10.4 dB for SI3R, when compared to traditional small-signal modelling, while decreasing the main beam power densities by only 0.3 dB when compared to traditional small-signal modelling. Optimizing for SI3R degrades beam pattern by increasing beamwidths and decreasing sidelobe levels (SLL).

A novel metasurface reflector unit cell based on two coupled resonators is proposed and demonstrated for real-time reconfigurable beamforming in the X-band (8-12 GHz). The unit cell is composed of a split-ring resonator (SRR) with tunable capacitance and a dipole-ring resonator (DRR) with tunable resistance, whose collective variations allow for control over the complex reflectance at a desired frequency. To gain physical insight into its working mechanism, the proposed unit cell is modeled as a coupled Lorentz oscillator using the surface susceptibility description of the unit cell. Thereafter, a metasurface reflector based on the proposed unit cell is demonstrated in full-wave simulations to achieve various beamforming examples, such as beam-steering, side-lobe level control, beam-steering with amplitude control, and multi-beam patterns, from a single normally-incident plane wave excitation. Three metasurface reflectors are fabricated to experimentally demonstrate the proposed concept; the first is based on an SRR with a varactor diode, the second is based on a DRR with a PIN diode, and the third is based on the proposed coupled SRR-DRR configuration with both varactor and PIN diodes, for simultaneous magnitude and phase control. The metasurface reflector based on the coupled resonator unit cell is experimentally demonstrated to achieve versatile beam transformations including beam-steering with amplitude control and multi-beam patterns.

Background: To fully quantify arterial wall and plaque stiffness, acoustic radiation force impulse (ARFI)-induced wave-tracking along the entire vessel circumference is desired. However, attenuation and guided wave behavior in thin vessel walls limits wave-tracking to short trajectories. This study investigated the potential of beam-steered ARFI and wave-tracking to extend group velocity estimation over a larger proportion of the circumference compared to conventional 0° ARFI-induced wave-tracking. Methods: Seven vessel-mimicking polyvinyl alcohol cryogel phantoms with various dimensions and compositions and an ex vivo human carotid artery were imaged in a dedicated setup. For every 20⁰ phantom rotation, transverse group wave velocity measurements were performed with an Aixplorer Ultimate system and SL18–5 transducer using 0⁰/20⁰/−20⁰-angled ultrasound pushes. Transmural angular wave velocities were derived along 60⁰-trajectories. A 360⁰-angular velocity map was composed from the top-wall 60⁰-trajectories 0°-data, averaged over all physical phantom rotations (reference). For each phantom rotation, 360⁰-angular velocity maps were composed using 0°-data (0⁰-approach) or data from all angles (beam-steered approach). Percentages of rotations with visible waves and relative angular velocity errors compared to the reference map as function of the circumferential angle were determined for both approaches. Results: Reference 360°-angular velocity maps could be derived for all samples, representing their stiffness. Beam-steering decreased the proportion of the circumference where waves were untraceable by 20% in phantoms and 10% ex vivo, mainly at 0° push locations. Relative errors were similar for both approaches (phantoms: 10–15%, ex vivo: 15–35%). Conclusion: Beam-steering enables wave-tracking along a higher proportion of the wall circumference than 0⁰ ARFI-induced wave-tracking.

In this work, a metasurface-based, 1-bit electronically reconfigurable reflectarray antenna (RRA) is proposed for dual-polarization beam-steering applications. The proposed RRA consists of $16\times16$ Jerusalem cross-shaped unit cells loaded with PIN diodes, which are used as active and reconfigurable devices to generate a reflection phase difference of 180° between their on- and off-states. An optimal focal length to diameter ratio $(f/D)$ for the feed antenna is determined to maximize its radiation coverage on the RRA. Microcontroller-based shift registers are used to resolve the complexity of the individual DC bias networks for the PIN diodes. The proposed RRA is designed, fabricated, and measured to evaluate its beam-steering performance. The measurement results show that the proposed RRA can achieve beam-steering of ±60° for x- and y-polarizations in both azimuth and elevation planes. Moreover, the proposed RRA is further verified by full-wave simulations to evaluate its additional functions, such as the generation of sum and difference beams for monopulse radar systems. The proposed RRA is anticipated to have significant potential in areas such as wireless communications, imaging, and radar systems, and is a particularly suitable candidate for reconfigurable intelligent surfaces (RISs) due to its adaptability and capability of dynamically generating different radiation patterns.

High‐performance beam‐steering devices play a crucial role for optical wireless communication (OWC), which can meet the demand for increasing number of wireless mobile devices and emerging high‐speed multimedia applications. Conventional beam‐steering optical components like spatial light modulator and digital micromirror device are limited to realize a small steering angle (typ. several degrees), thus dramatically limits the spatial scope of OWC. Herein, a beam‐steering metadevice utilizing an ultracompact metasurface assisted with a spatial light modulator is presented, which can significantly increase the beam‐steering angle without at the cost of complicated optical setup like conventionally used angle magnifier. Based on the actively tunable beam‐steering metadevice, an intelligent bidirectional optical broadcasting communication system is designed and experimentally demonstrated, which exhibits nine broadcasting areas covering a large field‐of‐view of 20° × 20°, with user‐defined dynamic beam‐steering ability in each area, and each user has a data rate of 10 Gbps for both upstream and downstream transmission. The proposed metadevices can meet the demand of intelligent optical wireless communication which requires both high‐performance and low‐cost for practical purpose, under currently available technical architectures.

In this paper, a sub-6 beam-steerable antenna array system is introduced. The main radiating element in the proposed array is a gain-enhanced Vivaldi antenna, whose overall realized gain is improved by introducing near-zero-index metamaterial (NZIM) with broadband characteristics at 3.6 GHz. The proposed system is intended to be integrated with fifth-generation automotive applications. The 4 × 4 butler matrix is resonating at 3.6 GHz to feed the designed antenna array elements and steer the radiating beam. When altering the phase of the input signal, the primary beam direction is steered at an angle from 45° to 135°. So, by choosing the butler matrix input port, the phase of each radiating element is changed, which leads to precise beam direction control. All the system components, including antenna elements and the [4 × 4] butler matrix, are designed, simulated, and optimized. In order to verify the proposed design, the system is fabricated using the photolithographic technique. The experimental results show very good agreement with the simulated ones. The NZIM-loaded antenna element achieves a − 10 dB bandwidth of 2.9 GHz, while the overall array system achieves a 600 MHz bandwidth. The steered beam of the proposed system has an overall realized gain of 11.2 dB. [ABSTRACT FROM AUTHOR]

This paper presents a compact coaxial-fed square microstrip patch antenna integrated with a beam-steering Partially Reflective Surface (PRS). The proposed design has a two-dimensional (2-D) Fabry-Perot Cavity (FPC) antenna acting as a radiator and the PRS as a beam-steering superstrate operating at 5.5 GHz. The PRS consists of 6 × 6 reconfigurable unit cells etched on Rogers 5880 with a thickness of 1.57 mm. By controlling the switching of PIN diodes in different sections of PRS, beam steering can be achieved up to ±47° in the azimuth plane with a gain of 9.1 dB and 10.2 dB and ± 15° steering in an elevation plane with a measured gain of 9.3 dB and 8.9 dB, respectively. The antenna prototype is 2.56 λ × 2.56 λ at 5.5 GHz, and the measured gain values are around 10 dBi for all the states. The beam is able to radiate at boresight or tilted to 42° in two azimuthal directions and 45° in elevation direction by adjusting the PIN diodes ON/OFF states. The 10 dB impedance bandwidth of 5.4–5.52 GHz is achieved. [ABSTRACT FROM AUTHOR]

In this article, beam‐steering orbit angular momentum (OAM) beams by mechanical rotating transmitarray, which is formed by three layer metasurfaces (MSs), is proposed. It is the first time to achieve steering OAM beams based on mechanical rotating transmitarray in microwave region. By mechanically rotating the middle and bottom MSs, different phase distributions are obtained, and then OAM beams in corresponding directions are generated. OAM beam can be dynamically generated and independently controlled to steer toward any horizontal direction, and from −40° to 40° in vertical direction. As example, two transmitarrays with mode l = 1 or 2 are designed. To validate the method, one of the transmitarray is fabricated and measured. The measured peak gain is 18.3 dBi. [ABSTRACT FROM AUTHOR]

In this article, a transmissive metasurface has been designed using five different types of unit cells with linearly varying phase for 5G communication system operating at 28 GHz. The phase gradient profile is responsible for alteration of transmission phase of electromagnetic waves at each unit cell, which causes tilting of the radiated beam when vertically placed above a microstrip patch antenna. Passive beam‐steering from −30 to +30° is achieved with the change in orientation of the metasurface which reverses the sequence of unit cells. This novel technique is an efficient means of beam‐steering, which does not require the employment of active elements or bulky multilayered structures. The proposed antenna operating at the same frequency as that of the phase shifting surface exhibits 2 dB gain enhancement when integrated with it. A prototype has been fabricated and measured as a proof of concept. The measured results are consistent with the full–wave simulation results. [ABSTRACT FROM AUTHOR]

We present a 24–30-GHz 256-element dual-polarization transceiver (TRX) phased array based on a 16-element beamformer integrated circuit (BF-IC), 2-element frequency conversion integrated circuit (FC-IC), liquid crystal polymer (LCP)-based combiners and filters, and a tileable package with 64 embedded dual-polarized (dual-pol) antennas. The phased array presented in this work overcomes three key challenges in current 5G millimeter-wave (mmWave) antenna arrays: 1) it supports a dramatic increase in the number of supported fast-access beams; 2) it offers improved power efficiency; and 3) it provides a path to lower solution cost. 1) We enable fast switching among >30000 beams—orders of magnitude improvement over prior work—by employing an on-chip beam calculator in the BF-IC, achieving 200-ns beam setup and 8-ns over-the-air (OTA)-switching time. 2) We enable a module-level transmitter (TX) mode peak power added efficiency (PAE) of 20% using a modular architecture that preserves power amplifier (PA) linearity and efficiency as well as receiver (RX) mode low noise amplifier (LNA) noise figure (NF). The module achieves Psat effective isotropically radiated power (EIRP) of 68.5 dBm and BF-IC NF < 3.9 dB. 3) We lower the solution cost by enabling a wider steering range to reduce the number of phased arrays required in a sectorized coverage scheme, by reducing the IC and package area, and by avoiding calibration. The wider steering range is enabled by using an in-package magnetoelectric dipole antenna (for the first time in silicon-based phased arrays), resulting in steering over ±70° in H- and V-pol in both E- and H-planes without requiring any calibration. Moreover, the module achieves >20-dB cross-polarization isolation across the entire ±70° beam steering range. [ABSTRACT FROM AUTHOR]

Metasurfaces have emerged as game-changing technology ranging from microwaves to optics. This article provides a roadmap to the evolution of electromagnetic metasurfaces with a focus on their synthesis techniques, materials used for their design and their recent and futuristic applications. A broad classification is provided, and the design principle is elaborated. The efficient and economical use of available computational resources is imperative to work with state-of-the-art metasurface systems. Hence, optimization becomes an integral part of metasurface design. Several optimization methodologies reported to date have been discussed. An extensive study on the current research database gathered a comprehensive understanding of meta-atom topologies and the preferred fabrication technologies. The study concludes with a critical analysis and highlights existing and future research challenges to be addressed. [ABSTRACT FROM AUTHOR]

A 1-bit folded reflectarray (FRA) based on characteristic modes-inspired polarization twisting metasurface element is proposed. The element is inspired by a 2×2 patch-based metasurface where a corner patch is removed and a pair of the patch is connected to break the symmetry for polarization twist and reduce the number of switches with the assistance of the characteristic mode analysis. On this basis, only two switches are required in each element for 1-bit phase encoding. To verify the proposed metasurface element, two 1-bit FRA in the Ka-band with beam directions of 0° and 60° are designed and fabricated where the metal stubs/open circuits are employed instead of real switches. The measured peak gains reach 27.4 dBi at 30 GHz with an aperture efficiency of 21.2% and a 3 dB bandwidth of 16.2%. This FRA exhibits good beam scanning characteristics with high gain and wide fractional bandwidth, which shows great potential in the application of low-cost electronically beam-steerable antennas. [ABSTRACT FROM AUTHOR]

A miniaturized, vertically polarized (VP), pattern switchable/beam-steering antenna based on a metamaterial radiator is presented for sub-6 GHz applications. Different from the traditional split-ring resonator (SRR), the proposed T-shaped SRR can work as a miniaturized VP omnidirectional radiator. To steer the radiation beam, a novel switchable mushroom reflector with a low profile and low loss is explored and utilized. Multiple switchable mushroom reflectors are loaded around the T-shaped SRR radiator to obtain various steerable beams. To verify the proposed design principle, a VP beam-steering SRR-based antenna with a compact size of 0.36 λ0 × 0.36 λ0 × 0.07 λ0 is designed by loading four mushrooms. By controlling the off/on states of four switches, the proposed reconfigurable antenna can realize beam-steering in the horizontal plane (eight states with 45°-step). The measured overlapped −10 dB impedance bandwidth is wider than 3.40–3.80 GHz (11.1%), and the realized peak gain is larger than 5.3 dBi. Therefore, the proposed antenna is a good solution for the widely deployed fifth generation (5G)-NR and smart antenna applications due to its compact size, flexible beam-steering capacity, broad bandwidth, and good scanning coverage. [ABSTRACT FROM AUTHOR]

A 1‐bit reconfigurable transmitarray (RTA) is studied in this article for wireless power transmission (WPT). The type of the RTA is micro‐element embedded active frequency selective surface (AFSS). First, parameters of the 1‐bit RTA unit‐cell are obtained at 5.8 GHz through equivalent circuit analysis and HFSS simulation. After optimization, the maximum insertion loss of the unit‐cell at 5.8 GHz is 0.96 dB, a 180‐degree phase difference can be got when pin diodes reverse and forward biased, and the size of the unit‐cell is about 0.42λ0. Second, composing the unit‐cell to 11 × 11 AFSS, the beam‐steering of ±40° in XOZ‐plane and YOZ‐plane can be achieved, while feeding layer effect is to be discussed. Finally, the beam‐steering performance of this AFSS is verified through testing. The dimensions of each FSS board are 260.9 × 260.9 × 0.8 mm3 and 0/1 distribution is controlled by field‐programmable gate array (FPGA). The measured results are basically consistent with the simulation ones in beam steering. The difference of the peak gain in the main direction is analyzed. [ABSTRACT FROM AUTHOR]

Smart Antennas are important to provide mobility support for many enhanced 5G and future wireless applications and services, such as energy harvesting, virtual reality, Voice over 5G (Vo5G), connected vehicles, Machine-to-Machine Communication (M2M), and Internet of Things (IoT). Smart antenna technology enables us to reduce interference and multipath problems and increase the quality in communication signals. This paper presents a number of nonlinear configurations of dipole arrays for forming a single beam in any desired direction. We propose three, four, six, and eight-element array structures to perform this single beam-steering functionality. The proposed array configurations with multiple axes of symmetry (in the azimuthal plane) decrease the computational repetitions in optimizing respective weight factors for beam-steering. The optimized weight factors are obtained through the Least Mean Square (LMS) method. MATLABTM is used to calculate optimized weight factors as well as to determine the resulting radiation patterns. Since antennas are bidirectional elements, beamforming in one direction means that the antenna will also have high receiving gain in that direction. Performances of differently configured models are compared in terms of their directivity, sidelobe reduction, and computational complexities for beam-steering. [ABSTRACT FROM AUTHOR]

The work aims to theoretically and experimentally investigate the radiation characteristics of the plasma window antenna for beam-steering applications. The antenna system consists of a wire antenna in the center, surrounded by a circular array of 22 cylindrical plasma columns. The research reveals that the radiation pattern of the antenna system can be simply controlled by exploiting the variable parameters, such as working frequency, driving current, and plasma configurations. It implies that the beam narrows as the plasma antenna aperture decreases, implying a greater directivity. By electrically tuning the plasma, a maximum directivity of 9.09 dBi and a minimum half-power beam width of 35.86∘ emerged for a specific configuration. The results show that higher currents prevent radiation from escaping from the plasma shell, while higher frequency microwaves are more likely to penetrate the plasma blanket. [ABSTRACT FROM AUTHOR]

Summary: A new leaky wave antenna (LWA) based on wire‐loaded metagratings (MGs) is proposed, with the capability of successfully employing MGs for leaky modes. Periodic capacitive‐wired and inductive‐wired MGs are located on a dielectric substrate in the LWA framework and backed by a perfect electric conductor (PEC) layer. These MGs are partial radial surfaces to radiate energy using equivalent surface impedance with a local value of the complex wavenumber. A theoretical analysis has created a model for the equivalent electromagnetic fields produced via loaded‐wire MGs and generated the Z‐matrix and S‐matrix for a two‐port structure from the electromagnetic fields. As a result, a beam‐scanning range of 53° for the operating bandwidth of 9.9–11.9 GHz is achieved with a scanning sensitivity of 26.5°/GHz. Meanwhile, the realized gain is obtained up to 12.9 dB. The measurement and simulation results indicated that the MGs LWA was consistent. The proposed antenna performed admirably in beam‐steering communication systems. [ABSTRACT FROM AUTHOR]

Single sideband suppressed carrier (SSB-SC) modulation enables high efficiency and dispersion-tolerant shifting of light that is of great interest for many optical systems and applications. Herein, the design procedure of a spatiotemporal reflective metasurface is proposed to realize SSB-SC modulation in near-infrared spectral regime. The metasurface consists of a periodic array of plasmonic nanostrips integrated with indium-tin-oxide (ITO) in metal-insulator-metal configuration, wherein two sets of time-varying biasing signals are independently applied to the metasurface for modulating the permittivity of ITO in space and time. The spatiotemporal metasurface features a sawtooth phase profile with linear span over $2\pi$ and a constant amplitude in time domain, that can be obtained by judicious adjustment of the biasing waveforms. It is established that such spatiotemporal metasurface allows for spurious-free frequency conversion by transforming the incident signal into the first-order up-modulated sideband and suppressing all the undesired mixing products. The normalized conversion efficiency of more than 99% is achieved for the metasurface, while the peak levels of the largest undesired mixing product and the fundamental frequency are reduced down to $-39$ dB and $-44$ dB, respectively. The proposed spatiotemporal metasurface is exploited for multi-channel and multi-beam scanning via pixelated control over the modulation phase delays assigned to the constituent elements of the spatially-interleaved sub-arrays, rendering a shared-aperture metasurface in space-time. In this case, the crosstalk between the channels with identical operating frequencies is substantially reduced. In addition, spatiotemporal redirection of light based on frequency gradient metasurface is demonstrated, which enables ultrafast, all-angle, and continuous beam-scanning as progressing in time. [ABSTRACT FROM AUTHOR]

Steerable antenna beam capability is an outstanding expectation for the development of automatic tracking systems and target detection. A switched beam array antenna, which can generate multiple fixed beams with enhanced sensitivity, emerges as a solution for beamforming tracking. On the other hand, it is known that the target can be detected with high‐range resolution thanks to ultra‐wideband (UWB) systems. In this work, a compact switched beam Vivaldi array antenna based on a Butler matrix for a UWB application capable of target detection with accurate target tracking is presented to meet the high gain and low side lobe level requirements. Based on a three‐element antenna array, two methods have been applied to obtain small grating lobes and it has been shown that significant improvements can be achieved. Designed with a 3 × 3 UWB Butler matrix, the UWB array antenna can direct its beams in three directions in a direction range from −42 to 42°. The measured result showed that the group delay was less than about 4.5 ns with variation of less than ±0.7 ns over the entire operating frequency band. [ABSTRACT FROM AUTHOR]

We investigate the aptness of various $4^{th}$ order (90°) rotationally symmetric phase-transforming cells for the upper phase-gradient metasurface, which always receives an oblique incidence wave from the lower metasurface in a Near-Field Meta-Steering system. A comprehensive study on the behavior of various phase-transforming cells and corresponding supercells when a rotating oblique plane wave impinges on them is presented. First, we select the supercell with high transmission in the desired output Floquet modes, for both TE and TM input modes, when an oblique incidence wave is rotated. The selected supercell is then optimized using Floquet analysis in conjunction with particle swarm optimization (PSO). All the undesired modes are successfully suppressed below −32 dB in the optimized supercell, and the predicted broadside radiation pattern is free of spurious grating lobes. A Near-Field Meta-Steering system with an aperture diameter of $7.3\lambda _{0}$ (110mm @ 20 GHz) is presented. It has a pair of optimized phase-gradient metasurfaces and a dipole antenna array. A maximum peak directivity of 24.2 dB is achieved when the beam is in the broadside direction. The proposed steering system is capable of scanning a conical range with an apex angle of 126° when a 6 dB reduction in peak directivity is allowed. For a 3 dB variation in the peak directivity, the corresponding apex angle is 103°.

A new $1\times $ 4 phase distribution network (PDN) featuring a fully controllable progressive phase shift between outputs is proposed for continuous beam-scanning arrays. The PDN is made up of two parts: a modified $2\times $ 4 Butler matrix integrated with four phase shifters (PSs), and a tunable power divider (TPD) whose power division ratio can be controlled over a wide tuning range. The synthesis equations show that the relative phase shift between PDN outputs can be fully controlled by the TPD and embedded PSs without using an external single-pole quad-throw (SP4T) switch. The proposed PDN is demonstrated at 2.4 GHz as the feed network of a 4-element linear array. The experimental results display a fully controllable progressive phase shift (from −180° to 180°) between PDN outputs over a 20% bandwidth with good performance of matching, power division, and relative phase shifts. A spatial coverage of 116° with the feature of continuous beam scanning and negligible dc power consumption is achieved. Benefitting from the single-input topology, a planar 16-element phased array for 2D beam scanning is then realized by simply stacking and cascading five instead of eight PDN modules. It removes the high-cost and bulky SP16T switch. Experimental results demonstrate the uniqueness of the proposed designs.

A novel fixed frequency beam-steering leaky-wave antenna (LWA) is presented in this manuscript. Radiation occurs through thin offset longitudinal slots etched on a substrate integrated waveguide (SIW). The beam-steering is achieved by implementing GaAs varactor diodes on the backside of the antenna. Sweeping the bias voltage from 1V to 15V causes the phase constant variation, leading to the 25° beam-steering at 28.5 GHz. The key novelties of the proposed reconfigurable antenna are the low-profile and electronic beam-steering capability using a single varactor diode per cell located on the antenna’s backside. Moreover, placing the components on the backside reduces the unwanted blockage effects on the radiation. The antenna’s thickness, length, and width are 0.32 mm, 95 mm, 24 mm, respectively. The measured peak realized gain of the proposed antenna at 28.5 GHz is 9 ± 0.8 dBi. Low-profile, small gain variation, ease of fabrication, and electronic beam-steering capability make the proposed LWA suitable for the 5G beam-steering applications. A detailed sensitivity analysis along with the experimental validations were performed to prove the validity of the proposed novel design.

Fiber-wireless-Fiber links require alignment between the transmitter and receiver to a high degree of precision (typically ~ 0.01° for a link of a few meters), and channel coding can be used for mitigating the link margin reduction caused by the limited precision of the beam-steering and tracking system. This paper reports results from an experimental study of the misalignment tolerance attained by channel coding. Explicitly, the received power penalties imposed by misalignment are characterized, and then forward error correction techniques are adopted for mitigating the performance degradation inflicted, which is quantified experimentally. Our results characterize trade-offs between coding rate, decoding complexity and the degree of misalignment. Overall, an improvement of the tolerance to misalignment up to ~50% was attained for coded links compared with the uncoded counterpart.

The theoretical analysis of beam-steerable, broadside-radiating Huygens dipole antenna arrays (HDAAs) is presented. Linear HDAAs with different numbers of elements are investigated and compared with full-wave simulations. Their attractive performance characteristics for wirelessly powered IoT applications are emphasized. Each Huygens dipole antenna (HDA) is an electrically small, linearly polarized, efficient, unidirectional radiating element. Linear HDAAs are confirmed to achieve high directivity beams in one principle plane and significantly broad beamwidths in the orthogonal principle plane. Very stable gain variation when their main beam is steered is demonstrated. A practical beam-steerable, broadside-radiating, linear HDAA is developed that employs an experimentally-verified HDA and is facilitated by a microstrip power-divider feed network. The entire HDAA design is ultrathin ( $\lambda _{0}/240.87$ ), lying only on a single piece Rogers Duroid $^{TM}~5880$ copper-clad substrate. A proof-of-concept 3-element HDAA prototype excited with a $3\times 3$ Butler matrix centered at 2.45 GHz was designed, fabricated and measured. The measured results, in very good agreement with their simulated values, demonstrate the efficacy of the linear HDAA designs and their potential usefulness for wireless power transfer (WPT) systems dedicated to emerging IoT applications that require power be directed towards terminals in multiple specified directions with broad area coverage at each one.

In this article, beam‐steering of microstrip antenna (MSA) is demonstrated in a cost‐effective manner using a single‐layer, low‐loss passive frequency selective surface (FSS) based on a phase‐shifting surface (PSS). A quasi‐periodic spatial PSS is constructed by arranging four rows of eight split‐ring resonators (SRR) shaped unit cells having different geometrical parameters but identical dimensions and placed adjacent to each other with a periodicity (p) of 0.18λ, where λ is the wavelength corresponding to the resonant frequency (4.5 GHz) of the fundamental unit cell. The geometrical parameters of the SRRs are tailored to control the surface impedance and the transmission phase across the surface area to reshape the phase front of the transmitted waves. A directive MSA operating at 5.5 GHz, is also designed and integrated with this PSS to demonstrate the beam‐steering capability. On rotating/shifting the PSS over the MSA, beam‐steering in the elevation plane is accomplished across −30° to +30° without degrading its reflection coefficient characteristics, with a maximum gain of 8.9 dBi. The best antenna performance in terms of beam tilt and gain is achieved when the PSS is vertically placed and fixed above the MSA. The MSA integrated with the non‐uniform metasurface exhibits 75% radiation efficiency with a front to back ratio of 55.5 (17.4 dB). A prototype is fabricated and measured as a proof of concept. The measured results are consistent with full–wave simulation results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article presents 28 GHz circular polarized antenna arrays designed in an embedded wafer level ball grid array (eWLB) package for 5G applications. The antenna arrays are realized on a re‐distribution layer (RDL) in the fan‐out region of the chip package. Two separate but identical arrays perform RX and TX operations where a crossed dipole is used as a building block of the array. These 4‐element arrays have <−10 dB impedance bandwidth covering 25.3–29.8 GHz (4.5 GHz bandwidth) while presenting 10 dBi maximum realized gain. The measurement results show <3 dB axial ratio in the band 26–29.5 GHz, and the main beam can be steered in ±50∘ in the azimuth plane when array elements are fed by appropriate phases from the chip. The radio frequency module provides 31 dBm maximum equivalent isotropic radiated power (EIRP). [ABSTRACT FROM AUTHOR]

The shared aperture antenna is regarded as one of the promising approaches to support new frequencies with very efficient space utilization. To the best of the authors’ knowledge, there are few shared aperture antennas that include both the sub-6 GHz antenna and the millimeter-wave (mm-wave) beam-steering array for broadside applications. In this article, a broadside sharing aperture technique is developed so that a 2 $\times4\,\,26$ GHz beam-steering substrate-integrated DRA (SIDRA) array can be integrated into a 3.5 GHz bandwidth enhanced perforated patch antenna in a coplanar and aperture-shared way. The proposed solution benefits from several aspects. First, the 3.5 GHz antenna features a compact size as this part is built on the substrate (where the mm-wave SIDRA is constructed) with a high permittivity. Second, the mm-wave SIDRA is a 3-D-type device, and in the case of coplanar integration, its height can be freely adapted to the thickness of 3.5 GHz antenna without concerning the impact from surface waves as many 2-D-type antennas have to do. Third, the antenna can be implemented with the multi-layer printed circuit board (PCB) process, yielding a high integrity level. The dual-frequency antenna was designed, fabricated, and measured. The performances of the antenna are reported with reasonable agreement between the measured and simulated results observed. [ABSTRACT FROM AUTHOR]

A novel reflectarray (RA) with ultralow-profile and 2-bit phase quantization beam-steering ability is presented in this article. To reduce the profile, a Leaky-wave feed is used to excite the RA with enhanced illumination efficiency. Moreover, simultaneous sum and difference patterns are also obtained to provide beam flexibility. The entire thickness of the proposed RA is less than 3% of that of the conventional front-fed RA with the same aperture. To increase the efficiency of the RA, a novel unit cell consisting of a polarizer layer and a reflection layer is developed, which is configured to provide polarization rotation and 2-bit phase shifts by using a hybrid of tunable polarization and discrete resonator. The operation principle, theoretical explanation, and implementation of the proposed antenna are elaborated in this work. To prove the design concept and beam scanning performance, an array with $9 \times 7$ unit cells operating at Ka-band is designed and simulated first. Two-dimensional beam scanning within the range of ±30° has been verified. Then, a passive prototype with $9\,\,\times67$ unit cells is designed, fabricated, and measured. Experimental results show aperture efficiency of 35.1% and illumination efficiency of 43.4%. The developed RA is scalable, and it provides a viable low-cost solution to develop low-profile, high-gain and beam-steering array antennas for satellite applications. [ABSTRACT FROM AUTHOR]

A modified ant lion optimization (MALO) algorithm is proposed in this article, for the synthesis of Chebyshev-based arrays by optimizing amplitudes and phases of excitations, and element spacings. Modification in ant lion optimization is achieved by hybridizing it with chaotic particle swarm optimization. The optimization process is employed to obtain an array pattern with the least possible sidelobe level. Close-in sidelobe level minimization for optimum pattern synthesis is suggested. Instead of only steering the main beam towards the desired direction presented by some popular optimization methods, the beam steering along with null positioning in other specified direction is also achieved employing MALO. Considering the arrays with the same design parameters and the results of other optimization algorithms, the performance of MALO is evaluated. The results show that MALO provides considerable improvements in an array pattern compared to the arrays optimized using other optimization algorithms and the uniform array. [ABSTRACT FROM AUTHOR]

This paper presents a 60 GHz connected slots linear-phased array feeding a high-gain semi-symmetric lens antenna. This design provides high gain, broadband, and beam-steering capabilities for gigabit rate access and backhaul communications. The connected slots antenna array (CSAA) is excited at 16× equidistant points which not only yields spatial power combining but also allows the progressive phase changes to steer the beam in ±45° in azimuth plane. To characterize the CSAA-fed lens antenna, four different power splitters are fabricated which steer the main beam in 0, 15, 30, and 45°. The lens is designed in a way to overcome the scan loss and get comparatively higher gain when beam is steered away from the broadside. The measured results show 25.4 dBi maximum gain with 3 dB gain bandwidth covering the full band 57–66 GHz whereas 3 dB beam-steering range is ±45° for all frequencies. Besides, the half power beamwidth is 6 and 10° in elevation (E-plane) and azimuth plane (H-plane), respectively. [ABSTRACT FROM AUTHOR]