Multibeam Antenna Research Articles

Millimeter-Wave High-Gain Dual-Polarized Flat Luneburg Lens Antenna with Reflection Cancellation

Because of its good beam coverage and beam scanning abilities, the Luneburg lens (LL) is a promising multibeam antenna for the fifth-generation (5G) wireless communications. However, the conventional LL has a spherical formfactor, exhibiting a large volume, large weight, and curvature surface, all of which limit the adoption of an LL in practice. To alleviate the problem, a flat LL is proposed, with transformation optics to convert the conventional spherical structure into a flat one. However, a high permittivity distribution is usually required in a transformed flat LL, causing of server reflections, which further degenerates the performance of the LL in terms of both gain and efficiency. In this article, a millimeter-wave dual-polarized flat Luneburg lens antenna (FLLA) is proposed following the transformation of optics, and implemented using multilayer PCBs, where a reflection cancellation method is introduced to optimize the multilayer structure to improve its gain and efficiency. The designed FLLA is exemplified in the Ka-band and fed using a dual-polarized patch antenna. The measured results show that the designed FLLA has an impedance bandwidth (|S11| ≤ −10 dB) of 27.5–32.6 GHz, a gain of 16.8–18.8 dBi over the operating band, and a beam scanning range up to ±25°/±24° with a gain loss of 1.72 dB/1.7 dB in either E- or H-plane, respectively.

Design and Development of Multibeam Antenna Technologies for 5G Wireless Communications

Multibeam antenna (MBA) systems operating in the millimeter-wave frequency bands have drawn significant attention from researchers and are being effectively studied due to the demanding system needs for the fifth-generation (5G) wireless communication systems and the drastic spectrum scarcity at the existing cellular frequency range. To enable a greater transmission speed, an enhanced signal-to-interference-plus-noise ratio, an enhanced spectral and energy performance, and flexible beam shaping, they serve as the primary antenna technology. They offer tremendous potential for serving as the crucial infrastructure for facilitating beamforming and massive multiple-input multiple-output (MIMO) which uplift the 5G. To achieve this, a novel beamforming design and optimization approach based on the Convex Time Modulated Particle Swarm Optimization (CTM-PSO) algorithm is suggested for 5G communication networks, offering multiple concurrent transceivers to support efficient beamformed interactions whereas a second beam concurrently detects the atmosphere around the base-station. The suggested beamforming method combines the optimization of the transmitter and receiver beamforming weights to increase sensor performance, reduce potential intervention resulting from the communication beams, and ensure the communications link's target beamforming gains. Comprehensive numerical assessments are used to evaluate the effectiveness of the recommended method, showing that it may provide significant improvements over more conventional beamforming methods.

A 3D-Printed Subterahertz Metallic Surface-Wave Luneburg Lens Multibeam Antenna

This letter presents an experimental realization of a sub-terahertz metallic gradient index (GRIN) lens multi-beam antenna operating at 355 GHz. The antenna is composed of a surface-wave Luneburg lens based on a bed of nails and a feeder array of nine WR-2.2 waveguides. The lens and the feeding structures are fabricated by the same high-precision 3D printing technique and are metalized using magnetron-sputtering gold coating. The antenna has been measured, showing good reflection coefficients below -12.5 dB at all ports and multiple independent beams covering a range of ±60°, which agree very well with the simulation. The measured gains are above 16 dBi and the scan loss is below 1.2 dB. This work demonstrates a novel manufacture and implementation approach for metallic multi-beam lens antennas at sub-terahertz frequencies.

Design and Simulation of Transceiver Antennas in FSO Technology within the 5G Networks

There is an urgent need for high-capacity connection with high data transfer rate in densely populated areas due to the rapid growth of mobile communication technologies and the explosion of data traffic. Multi beam antennas have generated a lot of research interest and have been extensively explored for base station applications due to their ability to boost communication capacity and sustain a high data transfer rate. Multi-beam antennas based on Butler matrices (MABBMs) are also appropriate for base station applications because to their advantages of high gain, simple design, and low profile. This paper's goal is to give a summary of the current MABBMs. The presentation of MABBMs includes its specifications, operating principles, design methodology, and implementation. In the final section, the difficulty of MABBMs for 3G/LTE/5G/B5G base station applications is discussed. The paper is divided into six sections, in the first section an introduction, in the second section base station application standards are presented, the design strategy and operating principles of MABBMs in the third section, and the latest developments in MABBM research for mobile communication systems are addressed in the fourth section, and challenges are presented in fifth Section, and conclusions are presented in the sixth Section.

Low-Complexity Online Calibration for Large-Scale Multi-Beam Antennas

High-throughput satellite communication based on large-scale multi-beam antennas is a promising technology for sixth-generation (6G) mobile networks. Conventional online calibration methods for large-scale antennas after satellite launch are restricted by communication signals. This paper proposes an online calibration method of amplitude and phase errors without disturbing the normal communication traffic. Two important aspects of calibration are discussed, i.e., closed-form expressions of calibration accuracy and hardware complexity. Simulation results show that theoretical approximation results are close to simulation results when the number of antennas is less than half of the code length. The relative amplitude and phase performance deteriorate by 6.12 dB and 40.96 deg, respectively, when the power is lower than the reference 20 dB. Finally, a calibration experimental system with eight beams is built for verification.

Wideband and High-Efficiency Parallel-Plate Luneburg Lens Employing All-Metal Metamaterial for Multibeam Antenna Applications

A parallel-plate Luneburg lens (LL) based on all-metal metamaterial is presented in this paper. To achieve the required refractive index distribution of the LL, an all-metal unit cell with a separated cuboid is proposed, whose height is related to its refractive index. This inserted cuboid is attached to neither the top plate nor the bottom plate of the parallel plate. Compared with traditional bed of nail design, the proposed metamaterial unit cell exhibits a wider bandwidth. The operation principle of such a unit cell is investigated using the transverse resonance technique. To construct the all-metal metamaterial LL into one body, a cruciform cuboid is added to each unit cell such that adjacent unit cells can connect to each other. Based on the designed metamaterial LL, a multibeam antenna is developed by providing seven inputs, which can generate seven predefined beams. Several parts of the prototype are separately fabricated and assembled, and good agreement is observed between simulation and measurement. The designed LL based multibeam antenna has several advantages, including wide bandwidth, high aperture efficiency, and high radiation efficiency.

3D Printed Multi-Beam OAM Antenna Based On Quasi-Optical Beamforming Network

In this paper, a multi-beam orbital angular momentum (OAM) antenna is proposed. By employing 3D printed millimeter-wave quasi-optical beamforming network (BFN), the emitted OAM wave can realize passive beam scanning capability. The antenna is composed of a pillbox BFN, a slotted waveguide antenna (SWA) array, and several full-dielectric phase elements (PEs) on the top of the SWA array. The required phase distribution of the OAM beams is turned by the phase shifts of the PEs. The pillbox BFN can generate the input waves with different phase gradients for the SWA array, and thus steer the beam direction. Moreover, the folded structure of the pillbox BFN can greatly decrease the size of the antenna. The proposed topology can be easily expanded to realize more beam number, higher directivity, and other OAM modes for its periodical structure. To verify the performance of the proposed antenna, a prototype is fabricated and measured. Two types of 3D printing technology are used, i.e., selective laser melting (SLM) for the pillbox BFN and the SWA array, and fused deposition modeling (FDM) for the PEs. The application of the 3D printed method greatly helps to decrease the fabrication difficulty. The measured results show that the antenna can achieve five +1 mode beams with ±20° 3 dB beam coverage range. Moreover, due to the full-metal structure of the BFN and the SWA array, the proposed design can achieve the minimum efficiency of 83.2%, which is much better than the other printed circuit broad (PCB) based OAM antennas. The advantages of low-cost beam scanning capability and the extensibility make the proposed antenna topology a good choice for future OAM communication and sensor systems.

Sub-6-GHz Uplink Massive MIMO System Using Holographic Beamforming Metasurfaces: A Conceptual Development

We propose an uplink massive MIMO system using an array of holographic metasurfaces as a sector antenna operating at 3.5 GHz. The antenna consists of a set of rectangular waveguide-fed metasurfaces combined along the elevation direction into a planar aperture, each with subwavelength-sized metamaterial elements as radiators. The metamaterial radiators are designed such that the waveguide-fed metasurface implements a holographic solution for the guided (or reference) mode, generating a directional beam towards a prescribed direction, thereby forming a multibeam antenna system. We demonstrate that a narrowband uplink massive MIMO system using the metasurfaces can achieve the sum capacity close to that offered by the Rayleigh channel. We show that metasurfaces supporting multiple beams can achieve high spatial resolution in the azimuth directions in sub-6 GHz channels, and thereby form uncorrelated MIMO channels between the base station and users. Also, the proposed metasurface antenna is structurally simple, low-cost, and efficient, and thus is suitable to alleviate RF hardware issues common to massive MIMO systems equipped with a large antenna system.

Design and Extension of Modified Butler Matrix Based on Three-Way Directional Coupler and Its Multibeam Application

A new topology of modified Butler matrix (BM) based on three-way directional coupler (TWDC) is proposed in this brief. The two TWDCs are regarded as two submatrices, by alternately arranging the output ports of the two submatrices and introducing a front network consisting of 3dB/90∘ hybrid couplers, 3dB power divider and phase shifters, a topology of modified five-input six-output (5×6) BM is constructed. In order to verify the design method, a prototype of microstrip 5×6 BM operating at 5.5 GHz is implemented and it is used as a beamforming network (BFN) for multibeam antenna array (MAA) to generate five radiation beams including a boresight beam. The measured and simulated results coincide well with each other. And according to the design method, a topology of extended 9×12 BM is designed based on the 5×6 BMs, which validates the capacity of building a modified BM with a higher number of the input and output ports.

Spaceborne Multibeam Phased Array Antennas for Satellite Communications

Multibeam phased array antenna is one of the core payloads of the satellite communication system, which has the potential to realize the transformation of the satellite communication system from application-adapted satellite to satellite-adapted application. This article provides a brief overview of the beamforming technologies used in spaceborne multibeam phased array antennas from three perspectives: analog beamforming, digital beamforming, and optical beamforming. The application status of multibeam phased array antennas in satellite communication is then classified and explained. Finally, the development trend of spaceborne multibeam phased array antenna is analyzed.

Optimization design of feed array structure for space-borne synthetic multi-beam antenna

To reduce the difficulty of engineering realization as much as possible on the premise of ensuring the performance of the feed network, a new design method of the multi-feed composite multi-beam antenna feed array is proposed. In the design process, the method of longitudinal subdivision and layering is used to solve the processing problem of complex large-scale electrical and small-sized devices. Then the multi-objective and multi-variable differential evolution algorithm is used to optimize the distribution position of each mounting hole to realize the optimal interface layout. The method is used to optimize the design of a multi-beam antenna feed array and the product object is produced and tested. The test results show the effectiveness of the design method. This method can be used to guide designers to carry out actual engineering design, shorten the design cycle, and improve the design quality.

A Miniaturized Planar Multibeam Antenna for Millimeter-Wave Vehicular Communication

Existing millimeter-wave beamforming network-based multibeam antennas usually suffer from complex configuration and bulky size, which limit their applications on a vehicle. To address these issues, in this paper, a symmetrical series-fed array topology is proposed for eliminating the conventional beamforming network. The topology is constructed by applying two unequal main transmission lines (TLs) to symmetrically feed a linear antenna array in series. To effectively suppress the mutual coupling between two TLs, an antenna element exhibiting co-polarized in-band full-duplex performance is implemented. When the four terminals are excited, respectively, four groups of excitation signals with different phase differences will be delivered to antennas to implement the desired beam steering characteristics. For validation, an antenna array operating at 28 GHz is designed, fabricated, and measured. Thanks to the simplicity of topology, the overall size of the proposed multibeam antenna is only 5.57 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a radiation efficiency of 85.6%. Meanwhile, a comparable performance is obtained when compared to a conventional beamforming network-based multibeam antenna. All of these results demonstrate the potential of the proposed topology in miniaturized millimeter-wave vehicular communication.

Ka-Band Multibeam Patch Antenna Array Fed by Spoof-Surface-Plasmon-Polariton Butler Matrix

A novel Ka-band spoof-surface-plasmon-polaritons (SSPPs) Butler-matrix-fed multibeam patch antenna array is proposed. An SSPPs-fed single-layered microstrip patch antenna with suppressed cross-polarization is investigated acting as the radiator. By using SSPPs etched on both sides of a substrate, a 3 dB coupler, a crossover, two phase shifters, and a vertical interconnection with compact geometries and promising performance are designed and investigated. By connecting the devices together, an SSPPs Butler matrix is realized, whose topology is modified in order to compensate for the phase influence of the SSPPs couplers that are different from traditional results. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times4$ </tex-math></inline-formula> multibeam patch array fed by the SSPPs Butler matrix is fabricated and measured. An impedance bandwidth of 15.4%, a gain of up to 12 dBi, and stable radiation beams are obtained. Benefitting from the small ratio between the metal area and the overall array area and the promising operating performance, the proposed SSPPs fed multibeam array may find potential applications in millimeter-wave systems where the absence of a large ground is preferred.

Compact Cylinder Luneburg-Lens Antennas Based on 3-D-Printing Technology

The Luneburg-lens is a prospective candidate for implementing multibeam antennas. However, the size of the conventional configuration is bulky, and most reported works are linearly polarized (LP), leading to some inconvenience in the practical applications. To deal with these problems, a new approach to realize a compact LP Luneburg-lens antenna is proposed first, and then, a method for implementing circular polarization (CP) property is further proposed. An air-coated dielectric cylinder is rotated around the center axis to form different layers of an equivalent cylindrical Luneburg-lens. The corresponding theoretical model to calculate the equivalent permittivity is given. Based on this approach, a Luneburg-lens is constructed using one dielectric cylinder and nine dielectric rings with the same permittivity but different dimensions. The proposed lens can be easily fabricated through the 3-D printing technology with low manufacturing complexity. For validation, an LP and a CP Luneburg-lens antenna operating at the Ka-band were designed, fabricated, and measured. A good consistency between simulated results and measured ones can be found. The LP antenna achieves a wide-scanning range of 174° and a bandwidth of 28.6%. Also, the CP one exhibits a scanning range of 134° and an AR bandwidth of 17.4%.

Design of broadband microstrip three‐way directional coupler for multibeam antenna application

AbstractIn this letter, a design of broadband microstrip three‐way directional coupler (TWDC) is presented. The broadband performance of the microstrip TWDC is realized by the method of cascading multi‐section. The broadband TWDC is designed to achieve equal power division and −120°, 0°, and +120° phase differences between output signals. To verify the broadband design, a prototype of three‐section microstrip TWDC operating at C‐band is designed, fabricated and measured. The measured results show that the power division error of the designed broadband TWDC is less than ±0.7 dB and phase error is less than ±12° at a relative bandwidth of 16%. To verify its performance in multibeam application, the designed TWDC is used as a beamforming network for multibeam antenna array to generate three orthogonal beams.

Electrodynamic Modeling of a Morgan Double-Layer Lens

A multibeam antenna based on a Morgan double-layer lens in the form of plane waveguides coupled via a frequency-periodic array is investigated. The lens synthesis problems are considered. The analytical model of coupled plane waveguides is constructed. The model uses the equivalent boundary conditions. It is verified using the electromagnetic modeling in the HFSS system. An approximate electromagnetic model of the antenna is proposed. The model is based on the representation of the structure electromagnetic field inthe form of radial waves of coupled plane waveguides of the fundamental type. It is shown that, in the doublelayer lens, the effect of its shading by irradiators is substantially attenuated. This fact makes it possible to form the system of rays with fan-shaped patterns, which provides for the space view in the azimuth angle sector of 360°. The possibility of formation of narrow rays with the low level of the side and back irradiation is demonstrated.

A Method for Estimating the Changes in the Directions of the Main Maxima of the Directional Pattern of a Multibeam Antenna in the Problem of Passive Direction Finding

A Method for Estimating the Changes in the Directions of the Main Maxima of the Directional Pattern of a Multibeam Antenna in the Problem of Passive Direction Finding

A 7 × 8 Butler Matrix-Fed Multibeam Antenna Based on Substrate Integrated Waveguide Technology

In this letter, a novel 7 × 8 Butler matrix (BM) operating in the millimeter-wave band is presented. It is composed of a 3 × 4 BM, two 3 × 4-like BM, two phase shifters and two couplers, achieving equal amplitude output distribution and seven output phase differences (0°, ±45°, ±90°, ±135°). The proposed 7 × 8 BM can be realized by dual-layer substrate integrated waveguide structure easily, which is difficult for merging the two central ports of the traditional 8 × 8 BM. To verify the concept, a multibeam antenna fed by the proposed BM is designed and fabricated, achieving seven beams in the frequency range of 26.5–29.5 GHz. Compared with counterparts, the proposed antenna features compact size, broadside radiation, and relatively wide bandwidth.

Distributed Satellite Cluster Laser Networking Algorithm with Double-Layer Markov DRL Architecture

Considering the demand of distributed satellite clusters for high-speed information communication in the future, this paper establishes a laser network model based on optical multibeam antenna. At present, there are still some networking and reconstruction problems, such as network connectivity, duration, and stability. To address them, the paper develops a multiobjective optimization model for the laser networking of distributed satellite clusters, which aims to maximize network connectivity and network duration and minimize the perturbation of the network connection matrix. The model is constructed under the constraints of multibeam antenna capability, the visibility of satellites in clusters, and network connectivity. From the perspectives of the optimization effect and timeliness of the optimization algorithm, a deep reinforcement learning algorithm is proposed, which is based on a double-layer Markov decision model, to meet the needs of on-orbit intelligent networking and dynamic reconstruction of distributed satellite clusters. Simulation results show that the algorithm features flexible architecture, excellent networking performance, and strong real-time performance. When the optimization results are similar, the proposed algorithm outperforms the nonsorted genetic algorithm II algorithm and the particle swarm optimization algorithm in terms of solution speed.

Optimization of Multibeam Antennas Employing Generalized Joined Coupler Matrix

Currently, there is increasing interest in analog multibeam antennas whose beams can be flexibly steered to arbitrary directions. In a previous paper, we presented the theoretical framework for synthesizing individually steerable multiple beams using generalized joined coupler (GJC) matrices. The synthesis method was to optimize the array excitation vectors to approximate known distributions. In this article, we present a more robust optimization method to optimize the multibeams directly in order to control the half-power beamwidth, the sidelobe levels, and nulls for mitigating system interference. The effectiveness of the proposed method is demonstrated by numerical examples. We reveal how the quality of the multiple beams is inherently determined by the dimensions of the GJC matrix. Experimental results of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\,\, \times10$ </tex-math></inline-formula> Nolen-like GJC matrix are presented for the first time to validate the proposed method in realizing low sidelobe multibeams.