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A novel low-profile beam-switchable antenna operating in the Extended Global System for Mobile Communications band of 5G sub-6 GHz for vehicular communication is proposed in this paper. The proposed work has a centre patch that connects with four parasitic radiators and encompasses a tapered patch to R1, R2, R3 and R4 which are slotted loop rectangular patches. The main lobe switching is achieved for Extended GSM by switching between the states of PIN diode circuits, which affects the overall performance of the antenna. With the dimensions of 0.346 λe × 0.346 λe, the presented work exhibits a very-low-profile antenna, having an impedance bandwidth of 14.7% and a peak gain of 1.27 dBi. The proposed beam-switchable antenna incorporates four similar radiators facing different directions affixed to the central square patch director. Each PIN diode is incited eventually to obtain the same resonant frequency at each radiator. The pattern of the proposed antenna can be switched using different states of PIN diodes in the angles of 81°, 171°, 261° and 351°. The prototype is fabricated, and the measured results are in agreement with the simulated results. For the validation of the practicability of the proposed antenna, the far-field analysis is done on the vehicle. [ABSTRACT FROM AUTHOR]

With the rapid advancement of wireless communication technologies, efficient utilization of the spectrum has become more complex and competitive. Millimeter-waveand Terahertz are considered to be one of the key technologies for next-generation wireless communication systems. However, high-frequency LOS links are sensitive to occlusions, which may lead to blocking problems during signal transmission. Therefore, in this study, we propose a recommendation system based on the knowledge graph of adaptive smart radio environment, which aims to solve the blocking problem that is prone to occur in the new generation of communication. The system utilizes deep learning and knowledge graph techniques, as well as sensing and understanding of the radio environment, to provide users with personalized communication services. First, it obtains information about the user's location, network state, and surroundings by sensing and understanding the wireless environment, second, it constructs a knowledge graph using the sensed information, and then, it extracts effective feature representations from the knowledge graph, including the user's communication history, device type, and network congestion, using deep learning techniques. Based on these features, the system generates personalized recommendations, such as optimizing the allocation of communication resources or selecting the best communication policy. By continuously learning and optimizing the wireless environment, the recommender system can provide more efficient and reliable communication services to solve the blocking problem in the new generation of wireless communications. [ABSTRACT FROM AUTHOR]

In low earth orbit (LEO) satellite constellations, when earth-fixed footprint mode is used, the switching of beams between coverage regions affects the elevation angle of the coverage, which in turn affects the communication quality. A coverage region switching method was proposed to address the coverage region switching problem in earth-fixed footprint mode. Firstly, a coverage region division mechanism was designed to keep the coverage region topology regular. Then, a switching time selection mechanism and a target coverage region selection mechanism were designed with the objective of maximizing the minimum elevation angle of the beams. The proposed method takes the differences between polar and inclined orbit constellations into account and supports both constellations. The OneWeb and Telesat constellations are used as simulation scenarios to validate the proposed method. The simulation results show that the proposed method can effectively improve the minimum elevation angle of the beams, which helps to improve the link quality.

We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a beam-transformation region featuring an on-chip metalens layer, and a tapered waveguide array serving as the output ports. The PM array, engineered to effectively manipulate multiple phases for a waveguide array using a single voltage, utilizes metal strips of varying lengths to streamline operation. The on-chip metalens, characterized by varying slot lengths, facilitates the wavefront manipulation of the fast Fourier transform, resulting in beam deflection with a focusing length of 20 µm. The simulated validation of the proposed compact optical switch demonstrated efficient beam deflection, yielding a 1 × 8 beam switching at a wavelength of 1550 nm. Combinations of diverse OPAs and metalens configurations resulted in potential scalability, allowing for the realization of optical switches with pathway numbers ranging from 4 to 16. This development of a metalens-assisted optical switch on a compact chip presents significant practical implications for enhancing data transmission efficiency and scalability in photonic integrated circuits. [ABSTRACT FROM AUTHOR]

THz technology has the potential to revolutionize various fields, including high-speed wireless communication, medical imaging, and spectroscopy. One challenge facing THz technology, however, is the limited output power (on the order of microwatts) of photonic THz sources (e.g., uni-traveling-carrier photodiode). Researchers are therefore exploring THz beam steering techniques to maximize their power effectiveness. To this end, we propose a photonic THz beam steering method that utilizes fiber chromatic dispersion, eliminating the need for energy-consuming active electronics. This paper explains its basic operating principle, fabrication and performance analysis of the associated THz array antenna, and demonstrates the feasibility of achieving a 300 GHz beam steering within 10 ∘ by means of dispersion-varied polarization-maintaining fibers. In conclusion, the present scheme can greatly enhance the power efficiency of photonic THz sources, and enable the potential advantages of seamless integration with fiber-optic networks, including reduced complexity, simplified operation, low power consumption, and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Fifth Generation (5G) Millimeter cellular networks are particularly interesting within the Industry 4.0 paradigm. mmWaves provide flexibility to the industrial use case, as well as enable specific application requirements, e.g. robots needing high data rates and low latency communication. Coverage at mmWaves, however, is challenged by additional attenuation and blocking effects, requiring the use of beamforming to overcome this by steering transmissions towards specific directions. Reliability is a key requirement as well, and requires, e.g, seamless beam switching during movement. Here, the resulting directivity of the antennas makes the beam switching procedures key to maintain the connectivity as the users move by. The present work aims to analyze the beam switching performance in a real-world indoor industrial scenario with high clutter to identify potential failures and propose optimization strategies. Firstly, this work has gathered insights into how beamforming operates under specific situations, identifying unused beams, relating the beam switching to the User Equipment (UE)’s movement, and collecting statistics from the beam switchings. Finally, a refined beam switching criteria is proposed based on radio metrics and location information, which outperforms the current criteria used by the network. This is evaluated based on the Reference Signal Received Power (RSRP) and the number of beam switchings under different criteria.

This paper proposes a design of a multilayer controlled beam horn antenna for the D-band. The multilayer design can achieve easy to control, low cost, and compact structure. The designed structure achieves the effect of a conventional horn antenna by stacking multiple layers and realizes the effect of beam switching by modifying the multi-layer plate structure. The widest bandwidth can be obtained when stacking 4 layers of boards, covering 24.7% (110-141GHz) of the bandwidth with a simulation gain of approximately 13.5dBi. By replacing the third plate structure, beam switching of ±30 degrees can be achieved, and the gain after beam switching can also reach 11.5 dBi.

The paper proposes a four-directional beamforming switched antenna system based on Butler matrix for 28 GHz mmWave. It is made up of a 90-degree coupler, a crossover, and a 45-degree phase shifter. A $4\times 4$ Butler matrix is combined with a 28 GHz patch antenna to form a Butler network antenna. Four directions of the radiation beam can be changed when the input position is changed. From the simulation and measurement results, the measured reflection coefficients cover 27.9-29.3 GHz at all four ports with a standard reflection coefficient of -10 dB and four different angles of 15°, -46°, +44° and -13° for switching beam direction. The antenna’s compact size of $39.1\times 45.6\,\,{\mathrm {mm}}^{2}$ ( $3.65\lambda _{0}\times 4.26\lambda _{0}$ ) makes it ideal for use in millimeter wave bands for 5G NR n258, and n261 applications, while also providing a high gain of 11.5 dBi.

Shared aperture antennas are versatile structures that can fulfill the demand for multi-band compact antennas in multi-standard emerging communication systems. However, the requirement of operation at widely separated frequency bands, such as sub-6-GHz band and mm-wave band in 5G, poses a challenge. This paper introduces a novel Encapsulated Dielectric Resonator Antennas (E-DRAs) designed for operation at sub-6-GHz and mm-wave bands for 5G and beyond applications. The DRA part of the antenna consists of an array of small cylindrical DRAs (cDRA) encapsulated in a larger cylinder. At mm-wave band, the small cDRAs are radiating elements while the larger cylinder acts as a lens to enhance the gain and provide beam switching at discrete angles by switching the feed between the small cDRAs. At sub-6-GHz band, the large cylinder is the main radiator. The antenna is realized with a 3D printing process using two distinct ABS materials with different infills. Measurements of the fabricated antenna show a maximum gain of 7.8 dBi at 3.35 GHz and 19.7 dBi at 27 GHz. The measured bandwidth is 20.2% centered at 3.45 GHz and 28.7% centered at 28.5 GHz. The array of small cDRAs with five elements enables beam switching within ±30°.

Multichannel orbital angular momentum (OAM) generation based on metasurfaces has brought significant advancements in expanding communication capacity. However, the realization of truly integrated optics is still challenging and important aspects such as beam scanning and rapid electronic switching among OAM channels, which are crucial for broad‐area communication coverage, have received little attention until now. Herein, a novel concept for multichannel OAM vortex beams generation and switching is proposed, realized by a guided‐wave‐excited metasurface (GWEM) in conjunction with a single pole five throws (SP5T) RF switch. A holography‐based theory is developed and employed to complete the array synthesis and analysis procedure without the need for a 2π phase modulation. As a proof of concept, a prototype of the GWEM is experimentally demonstrated with high qualities, including the generation of five channels of OAM vortex beams with a scanning range of ±35° in the elevation plane, a measured OAM mode purity of up to 84.5%, and consistent maintenance of the topological charge l = 2 state from 25 to 27 GHz. The proposed strategy features cost‐effectiveness, compactness, and fast nanosecond‐scale electronic switching for multichannel OAM vortex beams, making it highly applicable in space‐limited automotive radar, imaging, and communication systems. [ABSTRACT FROM AUTHOR]

In this article, a beam steering millimeter-wave antenna array operating in ka-band frequency has been proposed for 5G applications. Thus, to achieve a beam switching and to ensure a low side lobe level (SLL), a 4 × 4 Butler matrix (BM) and a Chebyshev array are used respectively. Moreover, to minimize the antenna array dimensions, a multilayer structure is used, where the BM and the antenna array are printed on the bottom and the upper layers respectively. The two radio frequency structures are connected by using via connectors. Furthermore, to reduce the mutual coupling between the antenna elements, we have used a metamaterial surface (metasurface) composed by periodic complementary split ring resonators (CSRRs) printed on the back side of the top layer. As a result, enhancements of the radiation pattern in the E-plane and an impedance matching improvement have been achieved. In addition, a beam steering in the range of − 6° to + 27°, with a variation of the main lobe magnitude from 11.5 to 13.5 dB, and a multi-band behavior in the frequency range 25–40 GHz, have been achieved. [ABSTRACT FROM AUTHOR]

We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a beam-transformation region featuring an on-chip metalens layer, and a tapered waveguide array serving as the output ports. The PM array, engineered to effectively manipulate multiple phases for a waveguide array using a single voltage, utilizes metal strips of varying lengths to streamline operation. The on-chip metalens, characterized by varying slot lengths, facilitates the wavefront manipulation of the fast Fourier transform, resulting in beam deflection with a focusing length of 20 µm. The simulated validation of the proposed compact optical switch demonstrated efficient beam deflection, yielding a 1 × 8 beam switching at a wavelength of 1550 nm. Combinations of diverse OPAs and metalens configurations resulted in potential scalability, allowing for the realization of optical switches with pathway numbers ranging from 4 to 16. This development of a metalens-assisted optical switch on a compact chip presents significant practical implications for enhancing data transmission efficiency and scalability in photonic integrated circuits.

We present an electrically switchable, compact metasurface device based on the metallic polymer PEDOT:PSS in combination with a gel polymer electrolyte. Applying square-wave voltages, we can reversibly switch the PEDOT:PSS from dielectric to metallic. Using this concept, we demonstrate a compact, standalone, and CMOS compatible metadevice. It allows for electrically controlled ON and OFF switching of plasmonic resonances in the 2–3 µm wavelength range, as well as electrically controlled beam switching at angles up to 10°. Furthermore, switching frequencies of up to 10 Hz, with oxidation times as fast as 42 ms and reduction times of 57 ms, are demonstrated. Our work provides the basis towards solid state switchable metasurfaces, ultimately leading to submicrometer-pixel spatial light modulators and hence switchable holographic devices.

This article provides for the first time a detailed discussion of the optimal assignment of adjacent output phase differences in terms of matrix performance out of all possible combinations in generalized one-dimensional parallel switching matrices with four beams. In this specific case, the topology of the proposed matrix reduces to that of a single-layer Butler matrix, connecting hybrid couplers and crossovers with adequate phase shifters. The values of the phase shift required are dependent on the assignment of the output phase differences, which in turn is shown to have an impact on the radiation characteristics of the linear array fed by such networks when imposing constraints on the matrix layout for a more generic implementation. The configuration having the smallest phase difference with reference to the transmission phase of a straight waveguide with the same length as the coupled region of the crossover is chosen and compared with the conventional well-known Butler matrix. The two matrix configurations are implemented using post-wall waveguides designed to operate over the band 20 GHz – 24 GHz. The prototypes are manufactured and tested, using transitions to standard waveguide WR42. The measured results confirm the benefits of the identified optimal adjacent phase difference assignment in terms of transmission coefficients, reflection coefficients, phase differences between adjacent output ports, and frequency dependence of the array factor. These results will also benefit the design of larger generalized one-dimensional parallel switching matrices.

Ensuring a seamless connection with various types of mobile user equipment (UE) items is one of the more significant challenges facing different generations of wireless systems. However, enabling the high-band spectrum – such as the millimeter wave (mmWave) band – is also one of the important factors of 5G networks, as it enables them to deal with increasing demand and ensures high coverage. Therefore, the deployment of new (small) cells with a short range and operating within the mmWave band is required in order to assist the macro cells which are responsible for operating long-range radio connections. The deployment of small cells results in a new network structure, known as heterogeneous networks (HetNets). As a result, the number of passthrough cells using the handover (HO) process will be dramatically increased. Mobility management (MM) in such a massive network will become crucial, especially when it comes to mobile users traveling at very high speeds. Current MM solutions will be ineffective, as they will not be able to provide the required reliability, flexibility, and scalability. Thus, smart algorithms and techniques are required in future networks. Also, machine learning (ML) techniques are perfectly capable of supporting the latest 5G technologies that are expected to deliver high data rates to upcoming use cases and services, such as massive machine type communications (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communications (uRLLC). This paper aims to review the MM approaches used in 5G HetNets and describes the deployment of AI mechanisms and techniques in ″connected mode″ MM schemes. Furthermore, this paper addresses the related challenges and suggests potential solutions for 5G networks and beyond.

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Ensuring a seamless connection with various types of mobile user equipment (UE) items is one of the more significant challenges facing different generations of wireless systems. However, enabling the high-band spectrum -- such as the millimeter wave (mmWave) band -- is also one of the important factors of 5G networks, as it enables them to deal with increasing demand and ensures high coverage. Therefore, the deployment of new (small) cells with a short range and operating within the mmWave band is required in order to assist the macro cells which are responsible for operating long-range radio connections. The deployment of small cells results in a new network structure, known as heterogeneous networks (HetNets). As a result, the number of passthrough cells using the handover (HO) process will be dramatically increased. Mobility management (MM) in such a massive network will become crucial, especially when it comes to mobile users traveling at very high speeds. Current MM solutions will be ineffective, as they will not be able to provide the required reliability, flexibility, and scalability. Thus, smart algorithms and techniques are required in future networks. Also, machine learning (ML) techniques are perfectly capable of supporting the latest 5G technologies that are expected to deliver high data rates to upcoming use cases and services, such as massive machine type communications (mMTC), enhanced mobile broadband (eMBB), and ultra-reliable low latency communications (uRLLC). This paper aims to review the MM approaches used in 5G HetNets and describes the deployment of AI mechanisms and techniques in "connected mode" MM schemes. Furthermore, this paper addresses the related challenges and suggests potential solutions for 5G networks and beyond. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leaky-wave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (ɛr = 2.2 and h = 1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement.

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]

A novel array antenna with reconfigurable polarizations and radiation pattern agility is presented in this paper. The digital-controllable array antenna has the functional capabilities of reconfigurable polarization and switching beam, which consists of cavity-backed antenna element based on substrate integrated waveguide (SIW) technique, parasitic patch array, power dividers and phase shifters. Polarization modes and radiation patterns can be dynamically controlled by means of Microcontroller Unit (MCU) with the different feeding ports and phase difference. To validate this proposal, the performance of the fabricated device was measured at the operating frequency of 5.4 GHz. Measured results indicate that the 10 dB impedance bandwidths and 3 dB axial ratio (AR) bandwidths cover from 5.25 to 5.6 GHz, and the measured gains range from 7.9 to 10.1 dBic. The experimentation and simulation verify that the proposed antenna can achieve two polarization states and five radiation beams of each polarization state, which indicate a good performance of the polarization reconfigurable and beam switching antenna array.

This article presents an electronically beam‐switching conformal microstrip array antenna for 5G applications. The 1 × 2 array microstrip antenna is used as a radiating element. They are placed on a hexagonal shape‐holding structure to form the conformal geometry. The radiating elements are excited with a six‐faced feeding network. It consists of one 3‐way power divider and two 2‐way power dividers. These power dividers (PDs) are serially connected and formed a six‐faced regular structure with 12 output ports. To obtain the beam switching mechanism, the uniform PD is then loaded with RF switched PD. Six angular separation beams (Sectors I–VI) are obtained (each 60°) with RF switches (1 SP3T and 3 SPDT). The response of the feed network is verified experimentally with a conformal array structure. The impedance bandwidth is well below −10 dB and measured for all switched sectors. The measured isolation among different output ports of the device is below −20 dB. The simple microstrip design technique makes the device suitable for beam switching in a large array configuration for 5G applications. [ABSTRACT FROM AUTHOR]

In this work, a novel leaky-wave antenna (LWA) with Archimedean spiral slots is proposed for realizing high radiation efficiency and stable gain performance in both frequency-controlled and fixed-frequency beam-scanning applications. The structural feature of the proposed Archimedean spiral slot privileges LWA with properties of easy impedance matching and high leakage rate, because it avoids the strong reflection from large-size slots that commonly used in LWA design for high leakage rate. The bandwidths of the final designed Ka-band LWA defined by radiation efficiency larger than 90% and 80% are 13% and 25%, respectively, while the bandwidth defined by return loss less than −10 dB is 29%. And the gain fluctuations between different scanned beams are less than 2.4 dBi in the whole broadband. The LWA is further applied in designing a new-type antenna with double-layer substrate-integrated waveguide (SIW) structures, which has four feeding ports at the ends and a coupling plane in the middle interface and can realize the fixed-frequency beam switching between directions of −46°, −36°, 34°, and 45° at 28 GHz through changing the excitation port. The proposed LWAs are potential candidates for applying in future millimeter wave communication systems where multifunction integrated and multifrequency adaptive antennas are required. [ABSTRACT FROM AUTHOR]

In this paper, an antenna array for the X-band aerial landing system has been proposed. The proposed antenna is an ellipse-shaped leakywave array radiating in slow mode wave and has a scanning range of 75° for different inter-element spacing. Four antenna arrays were designed: two with 60 elements and two with 30 elements each, all operating from 9.3 GHz to 12.3 GHz providing a gain of 30 dBi and 20 dBi, respectively. To verify the performance, a 15-element sub-array having an overall size of 210 mm × 30 mm and achieving a total gain of 17 dBi was fabricated and tested. The proposed sub-array was fabricated using Rogers Duroid5880 (εr=2.2 and h =1.575 mm). It has been shown through comparison of radiation patterns that measured and simulation results are in good agreement. [ABSTRACT FROM AUTHOR]

This paper introduces on-chip patch antenna with electronic beam switching using graphene strip array for wireless communications at 415 GHz. The on-chip patch antenna is printed on silicon/on-chip ground/silicon-oxide multilayer structure for simple integration with system electronic components. Groups of graphene strip arrays are placed parallel to the arms of polygon patch antenna fed by microstrip line connected to its base arm. When the group of N-graphene strips is biased by 15 V, it behaves as conductor strips which act as directors in Yagi-Uda antenna. The radiated beam is directed along with the biased group of graphene strips. When the graphene strips are unbiased 0 V, it behaves as dielectric strips and un-affect the beam direction. An equilateral triangular on-chip patch loaded with two groups of graphene strips is investigated. The effect of a number of graphene strips and their separation gap on the matching bandwidth and beam directivity is studied. It produces impedance bandwidth of 44% with maximum gain of 8.4 dBi and high radiation efficiency of 74%. A single directive beam is electronically switched in directions φ = 45° or φ = 135° by alternate biasing ON the two groups. Dual beams in both directions are achieved when the two groups are biased ON at the same time. A pentagonal-shaped patch loaded with four groups of graphene strips is studied. The single beam is switched in four different directions 0, 45°, 135°, and 180° based on the biased group. Dual, triple, and quad directive beams are radiated from the pentagonal patch with high gain of 7.85 dBi according to the number of biased groups. [ABSTRACT FROM AUTHOR]

A 2-D beam switching dipole antenna working at 60 GHz is proposed. To realize this, a folded electric-field coupled (ELC) resonator is designed to achieve a high-refractive-index medium in the band of 57–64 GHz. By integrating an array of ELC resonators in the off-center of a printed dipole antenna in the E- and H-planes forming high-refractive-index medium lenses (metalenses) in each plane, the main beam direction is manipulated to generate 2-D beam switching at 60 GHz. In the final configuration, six slabs each containing three folded ELC inclusions are incorporated vertically in front of the dipole antenna in the azimuth plane to tilt the radiation beam by 25° in the H-plane. In addition, a $2\times5$ array of folded ELC resonators is added into the elevation plane of the antenna substrate to deflect the radiated beam in the E-plane by 20°. The measurement results confirm that the radiated beam is tilted by 25° and 20° in the H- and E-planes, respectively, over a frequency band of 57–64 GHz. The measured antenna gain is 10.7 dBi at 61 GHz, the measured reflection coefficient is below −10 dB over 57–64 GHz, and the measured radiation efficiency of the antenna is 82% at 60 GHz. [ABSTRACT FROM AUTHOR]

Integrated lens antennas are widely used in high gain and beam steering applications at millimeter-wave frequencies. The ILA has often large height and suffers from significant scan loss. In this article, we demonstrate a low-profile, efficient, and scanloss-reduced integrated metal-lens antenna (IMLA). An IMLA is a combination of a dielectric lens and metal–plate lens. A 16- $\lambda _{0}$ diameter IMLA is designed using the HDPE and 58 stainless steel plates to achieve the $f/d$ of 0.69. The simulated aperture and radiation efficiency of the IMLA are 73% and 92%, respectively. At 76 GHz, the simulated and measured realized gains of the fabricated IMLA are 31.24 and 31 dBi, respectively. The IMLA is designed to steer the main beam to ±30°. The scan loss is reduced by tilting the radiation pattern of the feeds at offset positions along the focal plane. The radiation pattern of the square waveguide feed is tilted using asymmetrical dielectric pins. The asymmetrical dielectric pins reduce the simulated gain scan loss of the IMLA by more than 1.5 dB at 30° steering angle. The simulation results show that the inclination of the feed radiation pattern helps limit the scan loss of the IMLA to 4.1 and 4.3 dB in the H- and E-planes for 30° steering angle, respectively. The measured scan loss of the manufactured IMLA is 3.8 and 6.2 dB in the H- and E-plane, respectively. [ABSTRACT FROM AUTHOR]

We present a photonically-excited antenna array at E-band for scanning by beam switching in wireless links. First, we discuss the proposed technique applied to photonic-enabled (sub)millimeter-wave transmitters. Next, we present our implementation; it consists of two sub-arrays of stacked patches as primary feeds of a Polytetrafluoroethylene (PTFE) lens, with one photodiode feeding each sub-array. To validate the assembly, the return loss and radiation patterns have been measured for one of the sub-arrays excited with a coplanar probe. In turn, the lens illuminated by one of the sub-arrays yields a directivity of 27 dBi. The radiation patterns measured for the transmitter module (including the lens) are in very good agreement with full-wave simulations, and they show that excitation of one of either sub-arrays allows beam switching between $\pm 2.7^\circ$ with a beam crossover at $-3\, \mathrm{dB}$. Finally, we have tested the transmitter in a 0.6 m wireless link. Depending on the position of the detector and on which sub-array is excited, we have accomplished 5 Gbps transmission for on-off-keying modulation and direct detection (BER $=10^{-11}$). The system constitutes an initial proof of photonic-assisted beam switching for mm-wave transmitters enabling broadband operation with a directive and switchable beam. [ABSTRACT FROM AUTHOR]

Many operators have been bullish on the role of millimeter-wave (mmWave) communications in fifth-generation (5G) mobile broadband because of its capability of delivering extreme data speeds and capacity. However, mmWave comes with challenges related to significantly high path loss and susceptibility to blockage. Particularly, when mmWave communication is applied to a mobile terminal device, communication can be frequently broken because of rampant hand blockage. Although a number of mobile phone companies have suggested configuring multiple sets of antenna modules at different locations on a mobile phone to circumvent this problem, identifying an optimal antenna module and a beam pair by simultaneously opening multiple sets of antenna modules causes the problem of excessive power consumption and device costs. In this study, a fast antenna and beam switching method termed Fast-ABS is proposed. In this method, only one antenna module is used for the reception to predict the best beam of other antenna modules. As such, unmasked antenna modules and their corresponding beam pairs can be rapidly selected for switching to avoid the problem of poor quality or disconnection of communications caused by hand blockage. Thorough analysis and extensive simulations, which include the derivation of relevant Cramér-Rao lower bounds, show that the performance of Fast-ABS is close to that of an oracle solution that can instantaneously identify the best beam of other antenna modules even in complex multipath scenarios. Furthermore, Fast-ABS is implemented on a software defined radio and integrated into a 5G New Radio physical layer. Over-the-air experiments reveal that Fast-ABS can achieve efficient and seamless connectivity despite hand blockage. [ABSTRACT FROM AUTHOR]

This paper presents designs and prototypes of low cost multiple input multiple output (MIMO) antennas for 5G and millimetre-wave (mm-wave) applications. The proposed MIMOs are fabricated using 3D printing and are able deliver beams in multiple directions that provide continuous and real time coverage in the elevation of up to F300 without using phase shifters. This equips the proposed MIMO with a superior advantage of being an attractive low cost technology for 5G and mm-wave applications. The proposed MIMO antennas operate at the 28 GHz 5G band, with wide bandwidth performance exceeds 4 GHz and with beam switching ability of up to F300 in the elevation plane. The direction of the main beam of the single element antenna in the MIMO is steered over the entire bandwidth through introducing 3D printed walls with different heights on the side of the 3D printed radiating antenna. Unlike all other available beam steering techniques; the proposed wall is not only able to change the direction of the beam of the antenna, but also it is able to increase the overall directivity and gain of the proposed antenna and MIMO at the same time over the entire bandwidth.

Millimeter wave antennas have applications in several sensing and communication systems. Such antennas, designed for modern miniaturized devices and systems, must be low profile, flexible, and low cost. Some applications also require beam steering for detection purposes. Combining all these features into an antenna system and delivering decent antenna performance is challenging. In this study, we combined a partially reflective surface with a parasitic patch array to create a simple beam-switching, low-profile, and flexible wearable detection system. To ensure lower costs as well as compatibility with wearable systems, screen printing was utilized on a flexible substrate. The antenna array was optimized for the 77 GHz band and had a high gain of 11.2 dBi. The designed system has three independent beams, which can be oriented from bore-sight to ±32° through a simple switching mechanism. The antenna array maintains its performance in both flat and flexed conditions. Finally, the antenna array was tested in the field to successfully detect objects moving in three different directions.

A novel fixed-frequency beam switchable dual-beam antenna array is presented, which consists five dual-beam leaky-wave antenna (LWA) elements designed on substrate integrated waveguide (SIW) and integrated together on a common substrate. The LWAs work on fundamental wave and -1th spatial harmonic wave simultaneously and excite two symmetrical radiation beams in forward and backward direction respectively. In order to realize beam switching, three voltage-driven radio frequency chip switches (CSW-RFs) are used and integrated behind the antenna aperture. Since the periodic slot in LWA causes open stopband at the operating frequency, so the staggered radius amplification of local vias in the via walls of SIW is performed to suppress the open stopband. In addition, electromagnetic band-gap (EBG) structures, capable of reducing coupling between neighboring antenna elements, are embedded in between LWAs. The proposed dual-beam antenna array with beam switching capability between ±35, ±45, ±55, ±65 and ±75 degrees at 28 GHz are simulated, fabricated and measured. Both analysis and measurement results show that the proposed antenna array exhibits an excellent performance, which can be used in fixed-frequency beam-switching millimeter wave communication.

This study proposes a cylindrical conformal array antenna (CCAA) for fifth-generation (5G) micro base station applications. The CCAA is composed of five Chebyshev flexible linear array antennas (LAAs) with a circumferentially uniform arrangement on the cylindrical surface. The LAA with a logarithmic periodic arrangement is constructed by synthesizing the current amplitude distribution coefficients in elements with the Chebyshev method. The LAA with a half-power bandwidth (HPBW) wider than 76° (-8.41° to 38.58°) and a peak gain greater than 10 dBi is fabricated via the micro-electromechanical system process. Cost-performance analysis shows that five is the best number of linear arrays. To achieve omnidirectional switching scanning of the circumferential section, five LAAs wrapped on the cylindrical surface are individually excited by connecting a radio frequency semiconductor switch to the exciting ports of an eight-way power divider. Moreover, beam-switch scanning of the CCAA is measured with the aid of a standard anechoic chamber. The irradiated performance with low mutual coupling and high realized gain is verified to be irrelevant to the structural variation of various flexible experiments of LAAs wrapped around a cylindrical surface. The CCAA with beam-switch scanning operates at 26 GHz and belongs to the 5G millimeter-wave band. Results show the proposed antenna achieves omnidirectional scanning property in the H plane and has a HPBW of only 9.08° in the E plane. The performances of the CCAA present potential advantage in flexible terminal equipment wireless communication.

Collaborative beamforming (CB) enables uplink transmission in a wireless sensor network (WSN) composed of sensors (nodes) and far-away access points (APs). It can also be applied to the case where the sensors are equipped with beam-switching structures (BSSs). However, as the antenna arrays of the BSSs are randomly headed due to the irregular mounting surface, some sensors form beams that do not illuminate a desired AP and waste their limited energy. Therefore, to resolve this problem, it is required to switch the beams toward the desired AP. While an exhaustive search can provide the globally optimal combination, a greedy search (GS) is utilized to solve this optimization problem efficiently. Simulation and experimental results verify that under certain conditions the proposed algorithm can drive the sensors to switch their beams properly and increase the received signal-to-noise ratio (SNR) significantly with low computational complexity and energy consumption. [ABSTRACT FROM AUTHOR]

A wideband pattern reconfigurable bow-tie antenna on an inductive reflector is presented. The antenna consists of three bow-tie structures printed on an FR-4 substrate and controlled by six p-i-n diodes. The excited bow-tie at each operating state acts as the driven antenna, while the other bow ties act as the parasitic elements. To achieve low profile and high gain with directional radiation, a 5 × 5 metallic mesh-grid structure is designed as an inductive reflecting surface. It is located at a distance of $0.08{\lambda _0}$ (where ${\lambda _0}$ is the wavelength at the lower operation frequency) from the radiator. The antenna is able to steer the radiation pattern at the angles −25°, 0°, and +25° in the azimuth plane. Moreover, it is capable of electronically switching polarization along the diagonal section of the antenna's surface. It has a compact size of $0.6{\lambda _0} \times 0.6{\lambda _0} \times 0.08{\lambda _0}$ , measured fractional bandwidth of 37% at 0.8–1.16 GHz for tilted states, peak measured gain of 9 dBi, and maximum measured front-to-back ratio of 12 dB with ±1 dBi gain variations and ±3° peak pattern's direction variations across the whole bandwidth in all operational states. [ABSTRACT FROM AUTHOR]

This letter presents a circular lens antenna for wide-angle beam steering and for dual-polarized operation at millimeter-wave (mm-wave) frequencies (27–30 GHz). The lens consists of a dielectric disc and two parallel plates, whose vertical spacing is varied linearly to achieve a suitable effective refraction index profile for the polarization parallel to the plates. The desired refraction profile is that of the Luneburg lens. The variation in plate spacing has negligible effect on the polarization perpendicular to the plates, and therefore, the dielectric material is selected such that the circular shape of the lens approximates the dimensions of the extended hemispherical lens. This way, the lens provides focusing or collimation for both linear polarizations. The lens is fed with square waveguides supporting both polarizations. Several feeding waveguides allow beam switching over a wide angular range. The designed lens antenna was fabricated, and the simulation and measurement results agree well and show that the proposed antenna concept is a valid solution for the upcoming 5G technologies, for instance as the access-point antenna. The antenna provides a $\pm \text{50}{^\circ }$ beam-scanning range in both polarizations, and the realized gain is mostly between 9 and 12 dBi for the main beam. The measured reflection coefficient is mainly below $-$ 10 dB for both polarizations across the whole frequency band. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate a fast fiber mode converter in a short piece of special passive fiber. The switching mechanism relies on selective wavelength resonance between the core and a high index surrounding ring in the fiber. Beam switching at 530 kHz from a Gaussian beam shape to an expanded beam with a ring with corresponding M2 from 1.4 to 3.5 is demonstrated in a modified industrial pulsed fiber laser at power levels in the excess of 15 W. [ABSTRACT FROM AUTHOR]

Collaborative beamforming (CB) enables uplink transmission in a wireless sensor network (WSN) composed of sensors (nodes) and far-away access points (APs). It can also be applied to the case where the sensors are equipped with beam-switching structures (BSSs). However, as the antenna arrays of the BSSs are randomly headed due to the irregular mounting surface, some sensors form beams that do not illuminate a desired AP and waste their limited energy. Therefore, to resolve this problem, it is required to switch the beams toward the desired AP. While an exhaustive search can provide the globally optimal combination, a greedy search (GS) is utilized to solve this optimization problem efficiently. Simulation and experimental results verify that under certain conditions the proposed algorithm can drive the sensors to switch their beams properly and increase the received signal-to-noise ratio (SNR) significantly with low computational complexity and energy consumption.

A beam-sweeping antenna utilizing a novel active frequency-selective surface (FSS) is developed in this letter. It is comprised of a simple dipole and a cylindrical FSS formed by six columns of unit cells. The dipole used as a radiating source is situated at the center of the cylindrical FSS. The radiation pattern of the antenna could be reconfigured by controlling the states of the PIN diodes in the FSS. The dimension of the whole antenna is 0.75 λg × 0.75 λg × 1.57 λg (λg is the guided wavelength at its resonant frequency). Experimental results demonstrate that the presented beam-steering antenna can operate at 2.45 GHz and the main beam can be swept across the whole azimuth plane with a peak gain of 8.15 dBi. [ABSTRACT FROM AUTHOR]

This letter presents a design for three-dimensional polymeride printing, printed circuit board fabrication, and a full experimental verification of a conical conformal array antenna (CCAA) with wide solid angle switching beam by a radio frequency semiconductor switch (RFSS) configuration. The CCAA consists of eight linear array antennas (LAAs) with uniform circumferential arrangement around a conical surface. Only one LAA out of the eight arrays is individually excited, operating each time by the RFSS connected to the ports of 1–8 power dividers in order to achieve the requirement of beam switching. The CCAA with beam-switching feeding network operates at 4.8 GHz according to the fifth-generation (5G) band requirements. Both a wide solid scanning angle of 0°–218° in the H-plane and a half-power bandwidth less than 16° in the E-plane are achieved. When the realized gain of each LLA is over 10 dBi, the measured peak gain of the final antenna can reach about over 11 dBi and the average radiation efficiency can reach 59.5%. This CCAA with wide solid angle beam switching and high-gain property has the potential to reduce the signal-to-noise ratio and integrate with 5G communication systems. [ABSTRACT FROM AUTHOR]

Pattern-reconfigurable antennas with multiple switchable beams, especially with both boresight and endfire directions, are highly desired for wireless communications. In this letter, a novel pattern-reconfigurable antenna is proposed that provides an efficient solution. By reconfiguring parasitic striplines placed around a radiating dipole and reflecting metal pieces under the dipole using p-i-n diodes, the antenna main beam can be switched to five directions in the elevation plane, approximately from $-90^{\circ }$ (left endfire), $-45^{\circ }$ , 0 $^{\circ }$ (boresight), $+45^{\circ }$ , to $+90^{\circ }$ (right endfire). The proposed antenna operates at 2.45 GHz with dimensions of about 0.57 $\lambda$ $\times\, 0.45\lambda$ $\times\, 0.28\lambda$. An antenna prototype is fabricated and measured. For all five directional beams, the measured $|S_{11}|$ values are below $-$ 13 dB, and the measured realized gains range from 5.2 to 6.5 dBi. They agree reasonably well with the simulated ones. [ABSTRACT FROM AUTHOR]

This letter presents a 28 GHz switched five-beam antenna system based on a rectangular waveguide and a reconfigurable semiconductor circuit (RSC) with slots. Surface p-i-n diodes are used to close or open slots in order to achieve required configuration of an aperture. The RSC with a modified WR28 waveguide composes a reconfigurable radiating structure (RRS), which provides three beams directed toward 0°, 30°, and 45°. Beam switching is achieved by reconfigurable arrangement of a set of slots. Complementary RRSs connected to the electromechanical RF switch is used to generate remaining −30° and −45° beams. The gain of each generated beam is similar because different numbers of slots are opened, i.e., three, five, and nine slots for beams directed toward 0°, 30°, and 45°, respectively. Aperture of the antenna is controlled by a unit composed of high-current operational amplifiers. Measured results validate the performance of designed millimeter-wave reconfigurable antenna. [ABSTRACT FROM AUTHOR]