Multibeam Antenna Research Articles

Steerable Simultaneous Multibeam Antenna Based on Reconfigurable Reflectarray

Multi-beam system is a core part for wireless concurrent communication and massive MIMO applications. Traditional concurrent communication techniques, like phased-array or digital beam-forming (DBF) system, suffer from massive RF frontends or power-hungry high speed ADCs, which makes them complex and expensive in fabrication. Inheriting the advantages of reflectarray and passive multi-beam system, we reported in this letter a novel and cost-effective concept of steerable simultaneous multi-beam antenna (SMBA). New features and the practicality of it are fully verified with theoretical analysis and experimental implementation of a prototype working at 7GHz with 300MHz bandwidth. With multiple beams steered simultaneously, the SMBA can eliminate the crossover regions between adjacent beams of passive multi-beam antenna. Experimental results indicate its potential in the design of diverse concurrent communication systems such as base stations and point-to-point links.

Low-Profile Multibeam Antenna Based on Modulated Metasurface

Linearly polarized (LP) multi-port multi-beam antennas (MBAs) based on modulated metasurface (MTS) are presented in this paper. A key challenge for MTS to generate multiple independent beams is the mutual interference of different impedance modulations. This interference can lead to reduced directivities of main beams and high side lobe levels (SLLs). A full-wave based optimization for a large number of beams is significantly time consuming and practically ineffective. The source locations are optimized here by employing the aperture field calculated from a zeroth-order approximation (ZOA) of the currents on the surface. This provides a good preliminary accuracy without any full-wave analysis. The relevant design method is verified by two examples of 3-beam and 7-beam MTS antennas. Furthermore, the 7-beam MTS antenna is fabricated and successfully measured. The measurements show a measured realized gain of 20 dBi at 14.10 GHz with a beam coverage (10-dB overlap) up to ±36°. It is seen that the same performance requires larger areas with conventional summation of apertures.

E-Plane-Focused Partial Maxwell Fish-Eye Lens Antenna for Multibeam Wide-Angle Scanning

This letter presents a multi-beam wide-angle scanning antenna based on the E-plane-focused partial Maxwell fish-eye (PMFE) lens operating in Ka-band. The gradient equivalent refractive index distribution of the lens is realized by the parallel plate waveguide (PPW) partially filled with dielectric material, which can support the E-plane focus. The lens is fed by a series of rectangular waveguides arranged along the straight cut line to realize the multiple beams. To improve the impedance matching, the dielectric wedges are loaded in the interface between the feeders and the lens. The E-plane broadening of waveguide feeding ports effectively alleviates the gain drop of wide-angle scanning. The measured results of the prototype show a beam scanning range more than ±90° with the aperture efficiencies between 57% and 85.7%. The good impedance matching is also obtained in the operating band. The proposed PMFE lens antenna has the application potential in the low-cost millimeter wave (MMW) multi-beam systems.

A Compact Circularly Polarized Multibeam Antenna Using Defected Polarization Conversion Metasurface

In this letter, a four-beam circularly polarized (CP) antenna at Ku band based on metasurface (MS) is proposed. It consists of a defected polarization conversion metasurface (PCM) and a feeding structure. The PCM is composed of centrosymmetric units, each of which contains a pair of square patches and a pair of L-shaped patches. When it is placed above the feeding structure, the linearly polarized (LP) wave is converted into CP wave, and the gain is also enhanced. Furthermore, through loading stubs on the microstrip feeding lines and modifying the PCM as a defected PCM by removing some units from the MS, both the back and side lobe levels are reduced. The realized antenna has a compact dimension of 1.05 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 1.05 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.12 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . It has a -10 dB impedance bandwidth from 12.69 to 13.38 GHz (5.3%) and a 3 dB axial ratio (AR) bandwidth from 12.69 to 13.88 GHz (9.1%). When the four ports are excited, the four beams point at ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">θ</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">φ</i> ) = (40°, 105°), (40°, 165°), (40°, 285°) and (40°, 345°), respectively. The four beam directions may be altered by readjusting the coupling slots in the ground plane. The gain in the working band reaches 8.27 dBi.

A High-Gain Dual-Band Multibeam Antenna System for MIMO Wi-Fi Application

A compact dual-band multibeam antenna system with high gain is presented for multiple-input-multiple-output (MIMO) Wi-Fi application. The antenna system is composed of four rotationally symmetric antenna panels occupying a compact size of 60 × 200 × 7.2 mm3. Two series-fed microstrip patch antenna (MPA) arrays are proposed to operate at the 5-GHz band. They are fed with ±90° phase difference signals for two directional radiation patterns with about 45° horizontal 3-dB beamwidth and distinct radiation directions. Two dual-function metasurface based on periodically loaded parallel lines is designed and compactly placed between the two MPA arrays. The metasurface works as a 2.4-GHz antenna with about 90° 3-dB beamwidth in the azimuth. Besides, the application of metasurface improves the gains at the 5-GHz band. Then, four antenna panels are placed in a rotating arrangement with an electric size of 0.59λL × 0.59λL × 1.57λL (λL is the free-space wavelength at the lowest operating frequency). The antenna system was manufactured and demonstrated the characteristics of 360° pattern coverage in azimuth and high gain. The measured average gains are respectively higher than 8 dB and 12 dB at the 2.4-and 5-GHz bands.

Design of Broadband 9×9 Butler Matrix and its Extension for Multibeam Application

In this brief, a broadband 9×9 Butler Matrix (BM) and its extension for multibeam antenna array (MAA) application are presented. Based on the configuration of 3×3 beamforming network (BFN) comprised of three couplers and two 90∘ phase shifters, the topology of 9×9 BM is built, which can provide in-phase signals at output ports. And a broadband 9×9 BM is implemented to verify the design by adopting broadband components. The results indicate that the designed broadband 9×9 BM achieves equal power division and 9 uniformly distributed progressive phases (PPs) between output signals in a relative bandwidth of 40% when the 9 input ports are excited, respectively. And the fabricated 9×9 BM is applied in MAA for producing 9 beams including a boresight beam. In addition, according to the design method of 9×9 BM, the topology of the extended 27×27 BM is built and presented, which validates that an extended BM with higher order can be realized by the design method, and the extended BM can also provide in-phase signals at output ports.

Wideband multibeam mushroom antenna array with low‐temperature cofired ceramic‐integrated pillbox transition for millimetre‐wave applications

AbstractThis article presents a millimetre‐wave (MMW) wideband multibeam antenna array with a pillbox transition using multilayer low‐temperature cofired ceramic (LTCC) technology. The mushroom structure with dual resonant modes offers wideband performance for radiating array, while an integrated pillbox reflector achieves multibeam scheme. To reduce the design complexity of electrically large pillbox system, two popular pillbox transitions are investigated with a unit model method. The proposed unit model can be used to predict the transmission performance of pillbox reflector in any incident angle. Moreover, the mushroom antenna array and power divider fed by quasi‐TEM wave are also designed using unit model, greatly simplifying the design of electrically large pillbox antenna array. In the final design, the long‐slot pillbox transition, rather than multi‐slot transition, is selected due to its ultrawideband performance and simple structure. The proposed LTCC prototype is analysed and fabricated, obtaining a good agreement between simulation and measurement. The measured results show a −10 dB impedance bandwidth of 17.6% from 31 to 37 GHz, and five beams with ±45° scanning range is achieved with sidelobe level lower than −10 dB.

An ultra-low profile reconfigurable multi-beam antenna based on impedance modulated metasurface

ABSTRACT A new ultra-low profile reconfigurable multi-beam antenna is proposed. It is based on impedance modulated metasurface fed with a one-divide-four electronically controllable feed network. By properly arranging the feed network, six beams at different azimuth planes are formed by controlling four diodes. The gain is enhanced through loading a cross metal strip in the middle of metasurface. The results indicate that the realized antenna has dimensions of 126 mm × 126 mm × 4 mm (equal to 2.1λ0 ×2.1λ0 ×0.067λ0, λ0, wavelength at 5 GHz). Its −10-dB bandwidth is larger than 30.0% (4.28 GHz − 5.79 GHz) when diodes I-V are turned on successively. And it can radiate beams pointing to (0°, 33°), (20°, 44°), (150°, 36°), (180°, 35°). Furthermore, the beams can be steered to (0°, 43°) and (180°, 43°) in case that diodes I&II or III&IV are switched on simultaneously.

Многолучевая антенна с полным азимутальным углом обзора на основе многослойной геодезической линзы с осевой симметрией

A multibeam antenna with a full azimuthal survey based on a cylindrical lens with axial symmetry in the form of a set of layers, each of which is a metal-dielectric geodesic lens with a shell, is proposed and investigated. A cylindrical lens converts the fields of feeds located on a circle centered on the axis of symmetry in the plane of its base into directed beams in the same plane. The analysis of a multibeam lens antenna with metal horn and metal-dielectric feeds was carried out by numerical simulation using the finite element method.

Peculiarities of adaptive signal processing in circular antenna arrays

Formulation of the problem. Today, antenna arrays are often used as directional antennas of different radio systems. The main advantages of the such antennas over the mechanically steered directional antennas are the ability to steer the main lobe (beam) of the Radiation Pattern (RP) without the rotation of the array, and also the ability to control the shape of the RP. However, the antenna arrays also have some drawbacks. For example, a drawback of the linear and the planar antenna arrays is the varying beamwidth. This width increases as the orientation of the beam moves from the normal to the aperture to the plane of the aperture. This feature is due to the fact that when the beam is deflected, the effective aperture of the antenna array decreases, and this is the reason of the beam increase. If it is required to steer the beam in a wide range of angles while maintaining its width, then this restricts the usage of a linear and flat antenna arrays as the directional antennas. This disadvantage is practically absent in the circular antenna arrays. Therefore, such arrays are attractive for the usage, for example, in the radio communication systems, because they allow the beam to move within 360° in azimuth plane while maintaining its width practically fixed. If the antenna array is built using a digital beamforming architecture (digital array), then such an array can also be easily made as a multi-beam one, that will provide a parallel view of space. In multibeam digital antenna arrays, the same analog portion of each channel from the antenna to the digital output is used to form all the beams. And only in digital form, the separate devices for the forming of these beams are required, which multiply the channel output signal samples by the weights and add the weighted signals together to form the output signals of the antenna array. The access to the signals from the outputs also allows such an antenna array to easily become adaptive, because these signals are used to calculate the weights in all the adaptive algorithms. The adaptive signal processing allows to suppress the interferences. The suppression of the interference signals in the output signal of the antenna array is achieved due to the creation of the dips (low levels) in the RP towards the sources of these interferences. Such a change in the shape of the RP is provided by the changing weights calculated using an adaptive algorithm. Target. The paper deals with the circular adaptive antenna arrays with digital beamforming. The features of the such adaptive antenna arrays and their performance are considered. Results. The architecture of a single beam and a multibeam adaptive antenna array is considered, as well as a procedure (algorithm) for the calculation of its weights. It is also demonstrated the efficiency of a circular adaptive antenna array in terms of maintaining its beamwidth regardless of its direction and simultaneously suppressing interferences, that practically does not affect this beamwidth. Practical significance. The considered adaptive antenna array can be used as a directional antenna in radio systems where it is required to form a several beams simultaneously, to maintain their width regardless of steering directions, and also to suppress the interference signals in the output signal.

Multimode CRLH SIW Transmission Lines for Wideband Multiport Directional Couplers and Miniaturized Beamforming Networks

In this article, a multimode composite right/ left-handed (CRLH) substrate-integrated waveguide (SIW) transmission line technology is proposed, which aims to broaden the operating bandwidth of the multiport directional couplers (DCs) and solve the oversize of the beamforming network (BFN). Its core is to etch multiple interdigital slots (IDSs) on the conductor surface of the multimode SIW transmission line, which can control the electromagnetic fields of different modes in the transmission line under the condition of less electromagnetic energy leakage. By adjusting the position and size of the IDSs, the desired phase constants and electromagnetic field distributions of different modes can be obtained simultaneously. Based on the proposed multimode CRLH SIW transmission line, the six-port, the eight-port, and the ten-port DCs are designed, respectively. Compared with the traditional multiport DCs based on the SIW, the bandwidth of the proposed six-port and eight-port DCs is broadened by about 87.3%. Based on the proposed multiport DCs, the miniaturized BFNs and the miniaturized multibeam array antennas (MBAs) can be realized by adding appropriate fixed phase shift. Finally, to verify the feasibility of applying multiport DCs based on the multimode CRLH SIW transmission lines to the miniaturized BFNs and the miniaturized MBAs, a 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 3 BFN, a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 4 BFN, and a three-port MBA are fabricated, measured, and discussed. Their sizes are reduced by 58%, 49%, and 60%, respectively, compared with their SIW butler matrix (BM) counterparts.

Green Joint Communications and Sensing Employing Analog Multi-Beam Antenna Arrays

Joint communications and sensing (JCAS) is potentially a hallmark technology for the sixth generation mobile network (6G). Most existing JCAS designs are based on digital arrays, analog arrays with tunable phase shifters, or hybrid arrays, which are effective but are generally complicated to design and power inefficient. This article introduces the energyefficient and easy-to-design multi-beam antenna arrays (MBAAs) for JCAS. Using pre-designed and fixed analog devices, such as lens or Butler matrix, MBAA can simultaneously steer multiple beams yet with negligible power consumption compared with other techniques. Moreover, MBAAs enable flexible beam synthesis, accurate angle-of-arrival estimation, and easy handling/ utilization of the beam squint effect. All these features have not been well captured by the JACS community yet. To promote the awareness of them, we intuitively illustrate them and also exploit them for constructing a multi-beam JCAS framework. Finally, the challenges and opportunities are discussed to foster the development of green JCAS systems.

Compact Amplitude-Only Direction Finding Based on a Deep Neural Network with a Single-Patch Multi-Beam Antenna

In this paper, a compact direction-finding system based on a deep neural network (DNN) with a single-patch multi-beam antenna is proposed. To achieve multiple beams, the patch is divided into four sectors by metal vias, and the pattern is tilted in the theta direction due to the coupled mode of the divided patch structure. This design allows a single-patch multi-beam antenna to generate eight beams using a combination of four excitation ports assigned to the four-divided sectors. This approach increases the amount of training data required for DNN-based direction finding without requiring multiple antennas, thus improving the accuracy of estimation probability. Furthermore, compared to our previous work, the parasitic elements are applied to improve the estimation probability by reducing the beamwidth of the antenna. The size of the antenna for the proposed direction-finding system is 0.44λ × 0.44λ × 0.008λ with a 97.7% estimation probability. The direction-finding performance has been validated and compared through the experiment to show higher accuracy with compactness than previously studied works.

Bifocal Dual Reflectarray with Curved Main Surface

This paper presents a novel approach to synthesizing curved reflectarrays using Geometrical Optics (GO). It introduces the concepts of virtual normal and path length shift, which enable a vector-based formulation of the problem that can be solved using ray tracing techniques. The formulation is applied for the design of two different versions of a Dual Bifocal Reflectarray with a parabolic main surface and a flat subreflectarray. The first version aims to enhance the performance of the multibeam antenna by providing a focal ring located at the feed cluster plane. The second version focuses on improving the scanning characteristics of the antenna in the horizontal plane by incorporating two foci. The synthesis procedure yields samples of the path length shift or its derivatives. To reconstruct the phase distribution, an interpolation scheme is employed and described in this paper. Numerical results are presented for both the focal-ring and two-foci configurations, demonstrating the feasibility of this solution for multibeam or scanning satellite antennas operating in the Ka.

Reflector‐based highly isolated dual‐polarized multibeam antenna

AbstractIn this paper, a dual‐polarized multibeam antenna in X‐band is designed and physically fabricated using a parabolic reflector. The antenna consists of a feed array and a metal reflector. A dual‐polarized microstrip antenna array combining two design approaches, T‐coupled feed and defective ground structure, is adopted as the feed array to improve polarization isolation. In addition, the electromagnetic bandgap structure is loaded between the antenna units to reduce the mutual coupling and improve the isolation between the units. A nine element of the highly‐isolated dual‐polarized microstrip antenna array is designed to be placed on the focal plane of the parabolic reflector as the feed, and the beam deflection is realized by using the lateral defocus effect of the parabolic plane, which can finally realize nine single beams covering a 30° scanning range in both horizontal and vertical polarization modes. Based on the scanning state of multiple point beams, this paper uses the Fourier series for beam assignment to form a flat‐top beam with a wide scanning angle. The application of the antenna with two operating modes of wide beam and multibeam to navigational satellite systems can greatly improve the accuracy and efficiency of navigation.

A Leay Wave Antenna With Dielectric Superstrate on Perforated Dielectric Spacer

In this paper, a leaky wave antenna with dielectric superstrate (LWADS) on the perforated dielectric spacer is proposed. The LWADS has an asymmetric structure with a half-filled dielectric spacer and with a non-filled spacer to make a quasi-cutoff region. The half-filled dielectric spacer is periodically perforated, and the beam direction of leaky wave is controlled by changing the hole radius. Generally, the unwanted radiation is occurred in the broadside direction when the beam of leaky wave is tilted with large angle, this unwanted radiation is avoided by providing these perforated dielectric spacers. The proposed design is validated by measurements at X-band, and it is shown that a high gain tilted beam pattern with peak gains of 14 dBi is obtained not only at θ = 20°, 40°, but also at the wide-angle of θ = 60°. Since the effective permittivity can be controlled by the hole radius, an array of LWADS with different beam angles can be realized with the same height, and a multi-beam antenna with switched feeding can be realized.

Multibeam Antenna with a Full Azimuth Field Angle Based on a Layered Metal-Dielectric Cylindrical Lens

A multibeam antenna based on a layered lens with axial symmetry in the form of a set of dielectric disks with a refractive index gradient along the radius, which are located between metal disks, is proposed and investigated. A layered lens converts the fields of feeds located on a circle centered on the axis of the lens in the plane of its base into highly directed beams in the same plane. A synthesis of a layered lens is carried out, the layers of which are made in the form of a set of dielectric rings of variable thickness. The analysis of a multibeam lens antenna with metal-dielectric feeds was carried out by numerical simulation using the finite element method.

A Passive Metasurface for Gain Enhancement of Wide-Angle Millimeter-Wave Multibeam Array Antenna

In this letter, a passive metasurface for gain enhancement of the wide-angle millimeter-wave (mm-wave) multibeam array antenna (MBA) is proposed, and its core includes the wide-angle huygens' unit cell and the point-to-point phase compensation (PPC) method. The huygens' unit cell can achieve high transmission performance of the TM-wave in the range of ±70°. The PPC is to map all the beams of the MBA onto the phase modulation plane (PMP), and then block the PMP, that is, each beam corresponds to an independent block region, and each block region can adjust the phase of associated beam independently. Based on the proposed metasurface, the application for improving the beam performance of the MBA is implemented. It can realize the gain enhancement in the range of the beam pointing angle from −55° to +57°. The gain difference between the central beam and the edge beam is 2.69 dBi, and the gain enhancement range is 7.53 to 8.04 dBi.

Optimal Multicasting in Millimeter Wave 5G NR With Multi-Beam Directional Antennas

Optimal Multicasting in Millimeter Wave 5G NR With Multi-Beam Directional Antennas

Dual-Polarized Multi-Beam Fixed-Frequency Beam Scanning Leaky-Wave Antenna.

A fixed-frequency beam-scanning leaky-wave antenna (LWA) array with three switchable dual-polarized beams is proposed and experimentally demonstrated. The proposed LWA array consists of three groups of spoof surface plasmon polaritons (SPPs) LWAs with different modulation period lengths and a control circuit. Each group of SPPs LWAs can independently control the beam steering at a fixed frequency by loading varactor diodes. The proposed antenna can be configured in both multi-beam mode and single-beam mode, where the multi-beam mode with optional two or three dual-polarized beams. The beam width can be flexibly adjusted from narrow to wide by switching between multi-beam and single-beam states. The prototype of the proposed LWA array is fabricated and measured, and both simulation and experimental results show that the antenna can accomplish a fixed frequency beam scanning at an operating frequency of 3.3 to 3.8 GHz with a maximum scanning range of about 35° in multi-beam mode and about 55° in single-beam mode. It could be a promising candidate for application in the space-air-ground integrated network scenario in satellite communication and future 6G communication systems.