Multiple Beam Antenna Research Articles

Design of multiple-beam microstrip smart antenna for massive MIMO applications

To improve the capacity of a radio communication system, MIMO (multiple input, multiple output) wireless technology is used, where multiple antennas are installed at both the transmission and reception ends. At the receiving end, by combining the received signals from all antennas, the fading effect can be reduced, which increases signal-to-noise ratio (SNR) and minimizes the error rate. Wireless networks in multi-user environments need massive MIMO (MMIMO) systems as multiple antenna networks. The MMIMO installs large antenna arrays in the base stations, using a large number of transceivers with other RF modules to produce a very narrow and targeted radiation beam with reduced interference. This paper describes the method of producing multiple targeted radiation beams using an MMIMO smart antenna system with a microstrip array. The sub-6 GHz band of 5 GHz is used for the design of multiple beam smart antennas. The adaptive signal processing algorithm least mean square (LMS) is used for the beamforming of microstrip smart antennas. The number of antenna elements in the smart antenna is varied from 30 to 45. In case of three beam formation, the achieved maximum side lobe level (SLL) is -13 dB and minimum null depth is -27 dB. In case of four beam formation, the achieved maximum side lobe level (SLL) is -12 dB and minimum null depth is -25 dB. There was no deviation of the generated beam directions from the target user directions.

Compact and Lightweight Additive Manufactured Parallel-Plate Waveguide Half-Luneburg Geodesic Lens Multiple-Beam Antenna in the K$_{\mathrm{a}}$-Band

In this letter, a parallel-plate waveguide half-Luneburg geodesic lens multiple-beam antenna optimized for additive manufacturing is designed and validated experimentally in the K <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{\mathrm{a}}$</tex-math></inline-formula> -band. Two prototypes were manufactured in AlSi <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{10}$</tex-math></inline-formula> Mg through laser powder-bed fusion and measured in an anechoic chamber. The compact and lightweight prototype optimized for additive manufacturing demonstrates excellent RF performance while significantly reducing mass and mechanical complexity. Specifically, misalignment errors present in previous studies are solved, improving sidelobe level by up to 10 dB. A maximum realized gain of 22.1 dBi is measured at 28 GHz. This single-piece, compact, and lightweight design is particularly attractive for applications having mass restrictions and limited space like millimeter-wave systems on board small satellites.

Ray-Tracing Model for Generalized Geodesic-Lens Multiple-Beam Antennas

geodesic-lenses are a compelling alternative to traditional planar dielectric lens antennas, as they are low loss and can be manufactured with a simple mechanical design. However, a general approach for the design and analysis of more advanced geodesic-lens antennas has been elusive, limiting the available tools to rotationally symmetric surfaces. In this article, we present a fast and efficient implementation built on geometrical optics and scalar diffraction theory. A numerical calculation of the shortest ray path (geodesic) using an open-source library helps quantify the phase of the electric field in the lens aperture, while the amplitude is evaluated by applying ray-tube power conservation theory. The Kirchhoff-Fresnel diffraction formula is then employed to compute the far field of the lens antenna. This approach is validated by comparing the radiation patterns of a transversely compressed geodesic Luneburg lens (elliptical base instead of circular) with the ones computed using commercial full-wave simulators, demonstrating a substantial reduction in computational resources. The proposed method is then used in combination with an optimization procedure to study possible compact alternatives of the geodesic Luneburg lens with size reduction in both the transverse and vertical directions.

Broadband Coding Metasurfaces with 2-bit Manipulations

Due to their limited number of units but outstanding ability to control rather complex wave-propagation phenomena, acoustic coding metasurfaces (ACMs) as two-dimensional metamaterials show a stronger competitiveness in metamaterial applications. However, hindered by their narrow-band modulation capability, the previously reported ACMs do not exhibit a broadband applicability. To address the frequency-based coding capability, in this paper we report broadband acoustic coding metasurfaces (BACMs) whose units are designed by the bottom-up topology optimization method. Subsequently, by utilizing our optimization strategy, we design the 1-bit coding units ``0'' and ``1'' with out-of-phase responses and the 2-bit coding units ``00'', ``01'', ``10,'' and ``11'' with four different phase shifts of 0\ifmmode^\circ\else\textdegree\fi{}, 90\ifmmode^\circ\else\textdegree\fi{}, 180\ifmmode^\circ\else\textdegree\fi{}, and 270\ifmmode^\circ\else\textdegree\fi{}. The topological features show constant phase differences, and in the following analysis, we attempt to explain this phenomenon by the related mechanisms of the internal resonances and the bianisotropy effect. The optimized BACMs are beneficial to improve the functions of a fixed coding metasurface in the frequency range. This idea provides an inspiration for fabricating fast-sector-scanning sound antenna. In combination with the convolution method, we also present the design strategy for the broadband fast-scanning multiple-beam antenna. The design of the acoustic antenna is a fixed coding sequence, and its scanning and echolocation mode does not depend on the reconfiguration of the coding units. Furthermore, we also demonstrate a pair of opposite functions, namely the broadband sound focusing and diffusion-scattering characteristics, which have potential applications in ultrasonic therapy, low-scattering target design and noise control, and so on.

Geodesic Lens Antennas for 5G and Beyond

This article summarizes the recently discovered opportunities of geodesic lenses for producing high-performing antennas for 5G/6G communications. First, we explain the operation of these lenses based on Geometrical Optics with rays that follow “the shortest optical path” on the geodesic surface. Also, we explain the connection between geodesic lenses and rotationally symmetric graded-index lenses. Generally, geodesic lenses can be implemented without the need of dielectric materials, resulting in very efficient devices constructed with a fully-metallic configuration. When combined with a feeding network and a radiating transition, such as a flare or a leaky wave, they can produce a multiple-beam lens antenna, of interest for applications requiring one-dimensional (e.g., azimuthal) coverage diversity such as in cell tower communication systems. Prototypes of these antennas have been recently tested, demonstrating remarkable performance in the Ka-band, part of which is considered for 5G. At high operational frequencies allocated for 5G/6G, geodesic lenses offer an opportunity to produce cost-effective antenna solutions with high directivity, high efficiency and spatial diversity through multiple beams.

Recent Developments of Butler Matrix From Components Design Evolution to System Integration for 5G Beamforming Applications: A Survey

Beamforming networks for multiple beam antennas are believed to be in the vanguard of technological developments in mmWave for 5G wireless applications. The basic idea of beamforming technique is the application of multiple antenna elements radiating the same signal at an identical phase and wavelength, into one strong signal pointed to a specific direction. For low cost and power consumption, radio frequency beamforming networks (RF-BFNs) such as Blass matrices, Butler matrices, and Nolen matrices will play a critical role in achieving the ever-increasing demands in wireless technology. Therefore, this study aims to present a comprehensive survey and developments of RF-BFNs with (particular focus in Butler matrices). From the fundamental perspectives of the beamforming techniques and progress over time, component evolution includes branch-line coupler (BLC), Phase shifter (PS), and Crossovers to complete system Butler matrix (BM) integration. Different design techniques to improve bandwidth, size reduction, multi-band, and other performance characteristics are discussed extensively. Furthermore, the paper also discusses different geometry of Butler matrices in open microstrip transmission lines, substrate integrated waveguide (SIW) and gap waveguide (GWG) technologies highlighting key developments and research challenges from single band to dual-band operations.We expect this paper to provide more profound insights into the designs processes and suggest suitable ways to facilitate further developments of RF-beamforming networks at mmWave and sub-mmWave frequency ranges.

Circuit Type Multiple Beamforming Networks for Antenna Arrays in 5G and 6G Terrestrial and Non-Terrestrial Networks

To support the ever-increasing demand on connectivity and datarates, multiple beam antennas are identified as a critical technology for the fifth generation (5G), the sixth generation (6G) and more generally beyond 5G (B5G) wireless communication links in both terrestrial networks (TNs) and non-terrestrial networks (NTNs). To reduce the cost and power consumption, there is a marked industrial interest in adopting analogue multiple beam antenna array technology. A key sub-system in many of such antenna arrays is the circuit type multiple beamforming network (BFN). This has led to a significantly renewed interest in and new technological developments of Butler matrices, Blass matrices, and Nolen matrices as well as hybrid structures, mostly at millimeter-wave frequencies. To the best of the authors' knowledge, no comprehensive analysis and comparison of circuit type multiple BFNs have been properly reported with focus on 5 G and 6 G applications to date. In this paper, the principle of operation, design, and implementation of different circuit type multiple BFNs are discussed and compared. The suitability of these sub-systems for 5 G and B5G antenna arrays is reviewed. Major technology and research challenges are highlighted. It is expected that this review paper will facilitate further innovation and developments in this important field.

Optimal Design of Shaped Multiple-Beam Antenna Based on Artificial Bee Colony Algorithm

In order to maximize the multiple-beam performance in a specific service area, a new optimization design method of shaped single-aperture single-feed multiple-beam antenna was proposed. The contradiction between the layout of satellite platform and the performance of specific service area was solved by comprehensively optimizing the reflector and feed position. As the reflector surface and the feed position were taken as optimization variables, the objective function was constructed by the gain and XPD in the service area, and then the artificial bee colony algorithm was used for optimization, so as to obtain the optimal performance of the whole service area. Finally, an optimization design example was given, and the simulation results indicated the effectiveness of the optimization method.

Compact Orthogonal Multiple-Beam Antenna With Shared Aperture

In this letter, a planar array antenna with multiple-beams in orthogonal planes is proposed and investigated. A shared aperture is deployed for achieving a compact size, which is based on a cross transmitting network consisting of the substrate integrated waveguide (SIW) and the stripline. Two 1-D passive beamforming networks (BFNs) consisting of folded SIW Cassegrain reflectors are designed and integrated independently with the shared aperture. For demonstration, an 8 × 8 slot array at 26.0 GHz is designed and measured. In orthogonal planes, i.e., the xz plane and yz plane, six radiation beams have been achieved within ±40°, respectively. The proposed antenna is a good candidate for the millimeter-wave fifth-generation (5G) wireless applications.

Angularly Stable Linear-to-Circular Polarizing Reflectors for Multiple Beam Antennas

In this article, a new concept to improve the angular stability of linear-to-circular polarizing reflectors is presented. It is first explicitly demonstrated that existing design approaches heavily rely on the adjustment of the design stack-up, namely, the substrate height and relative permittivity, to the desired operating frequency. An approach is then proposed for decoupling the performance from the substrate parameters. The proposed approach provides increased design flexibility, resulting in performance improvement. Insight on the operating principle is provided resorting to equivalent circuit models. Subsequently, the benefits of the angularly stable reflection polarizer are demonstrated by a practical example involving a multiple beam antenna implemented using materials and processes compatible with satellite missions. The antenna exploits an innovative quasi-optical beamformer as primary feed combined with a cylindrical polarizing reflector. Numerical and experimental results from this antenna architecture are presented to confirm the improvements achieved with the proposed concept over existing designs. The close comparison of simulations with measurements that are achieved validates the concept and the design approach.

Adaptive Array Processing based Wireless Energy Transmission for IoT Applications

Rechargeable energy sources are essential for the extreme deployment of Internet-of-Things (IoT) sensors with the massive growth in smart systems. In order to meet these requirements, wireless energy transmission (WET) provides demand based power to the sensors. Temporary energy storage is done using supercapacitors. This overcomes the drawback of release of hazardous wastes released by IoT connected disposables after their working life. WET is made possible through adaptive array processing. The system consists of a transmitting side with multiple antennas and a receiving side with a programmable energy harvester. Several far-field adaptive processing schemes such as conventional beamformers, multiple sidelobe canceller (MSLC), multiple beam antenna system, regenerative hybrid array, digital beamformer, and generalized sidelobe canceller are tested and compared with the proposed modified beamforming model for superior performance. As the number of antennas increases, the gain increases. Gain and cumulative distribution function are analyzed over multiple distances for multiple iterations. The received signal strength indicator (RSSI) is also estimated to validate the performance of the proposed model.

Multi-beam Antenna Array Operating Over Switch On/Off Element Condition

In this work, is presented the design of a linear multi-beam antenna. The designed procedure is focused on the possibility of switching off a part of antenna array elements, in active antenna systems, in order to preserve resources (power and heat dissipation). The behavior of the original multi beam antenna design is investigated on the radiation pattern alteration due to the switched off elements. The choice of switching on/off antenna elements requires less computational effort from the algorithms incorporated in the active antenna system. Antenna array beam design using progressive phase shifts permits beam orthogonality which is valuable over use multiple beam antenna. In this work, turning off part of antenna elements will inevitably change the beam orthogonality conditions. Despite this, the case presented in this paper, shows beam space discrimination better than 10dB. To rank the behavior of modified antenna, with the turned off elements, are used both Euclidean and Hausdorff distances to measure the changes resulted from the modified array performance. The obtained solutions show the applicability of binary operation on existing antenna array. The metric showed in here can be effectively used as ranking criteria.

A Compact Millimeter-Wave Planar Directional Coupled Crossover With a Wide Bandwidth

A compact planar directional coupled crossover with a wide fractional bandwidth is proposed in this letter, which is composed of overlapping planar 3-dB couplers based on the substrate integrated waveguide (SIW) and stripline techniques. In the proposed structure, the TE10 mode and TEM mode can be transmitted simultaneously without any interaction, which is helpful to design and integrate the SIW and stripline couplers for realizing a wideband directional coupled crossover with a compact footprint. A prototype with a center frequency of 26 GHz for 5G applications is designed and fabricated. The experimental results show that the measured crossover has high isolation among all ports and good directional coupling performance in orthogonal directions. The proposed crossover has a compact footprint and low loss, which can be a good candidate for developing the miniature feeding networks for multiple beam antennas.

A Dimension-Reduction Multibeam Antenna Scheme With Dual Integrated Butler Matrix Networks for Low-Complex Massive MIMO Systems

In this letter, a multiple-beam antenna (MBA) scheme with reduced port dimension is proposed for low-complex massive multiple-input–multiple-output (MIMO) systems. From practical scenario consideration, two 2-port and 8-element subarrays with dual 2-to-8 Butler matrix networks are designed for 3 dB beam coverage within 60° sector. Based on channel capacity analysis of an 8-subarray (8 × 8-element) antenna system, it is proved that only 25% number of radio frequency (RF) chains are utilized in the proposed scheme to achieve a competitive data transmission rate, compared with a regular 8 × 8-element and 64-chain massive MIMO system, with the advantages of low cost, low system weight, and low complexity of signal processing. The proposed 8-subarray system is built and measured to verify the antenna performance. The proposed multibeam antenna scheme exhibits potential possibilities in low-complex and low-cost massive MIMO systems for the fifth-generation (5G) applications.

180° hybrid using a novel planar balun on suspended substrate for beam forming network applications

In this paper, a 180° hybrid consisting of a broadband balun and a T-junction in-phase power divider is proposed. The 180° hybrid is intended for operation in the C-band. The balun resembles a center tapped magnetic transformer where the coils are replaced by broadside-coupled lines. This new technique allows magnetic couplers to be realized by planar structures at microwave frequencies. The planar balun is broadband, and the size reduction is considerable. The broadside-coupled lines are on a suspended substrate. The proposed structure can be used in the beam forming networks of the multiple-beam antennas. It also prevents cross connections in the conventional beam forming networks. The planar balun is analyzed by the signal flow graph method. The scattering parameters of the 180° hybrid are calculated by the multiport connection method. Some design formulas for the construction of the balun are presented. The 3-dimensional model of the planar 180° hybrid is simulated by a full-wave simulator. Measurement results of the fabricated hybrid approve the simulation results. The 180° hybrid exhibits a relative bandwidth of 45% centered at 4.5 GHz. In the operating band, the amplitude and phase imbalance of the output ports are <0.6 dB and <10°, respectively.

Squint 빔 분할을 통한 고해상도 SAR 영상 구현

Airborne synthetic aperture radars(SARs) are vulnerable to geometric distortion when operated in the squinted mode. The polar format algorithm(PFA) is preferred owing to its convenient motion compensation, good image quality, and efficient computational performance. As a major drawback of the conventional PFA, the increase in data distortion under the forward-looking mode results in interpolation errors, thereby deteriorating image quality. In this paper, we propose a high-resolution SAR processing method based on the sub-aperture division PFA. In this approach, multiple antenna beams are imposed on extended areas divided by sub-aperture regions. Antenna beam steering is implemented from multiple platforms to simultaneously collect raw data from the sub-apertures. Thereafter, multiple sub-data images, each featuring low-resolution qualities, are processed in parallel to compensate for phase distortion and further merged to obtain a complete SAR image over an extended area. The results show that the synthesized SAR image yields an improved quality with enhanced resolution.

Design of a Multiple-beam Cassegrain Antenna with Quasi-optical Isolator at 200 GHz for Target Tracking

This letter proposes a multiple-beam Cassegrain antenna with quasi-optical isolator at 200 GHz for target tracking. The proposed antenna is designed with a special topology, in which a multichannel transceiver feed integrated with a quasi-optical isolator is designed and placed in the back of the main reflector, aiming to isolate the transmitting and receiving channels, and to avoid the aperture blockage. Four receiving feeds are laterally defocused to produce offset beams and each of them is received and sampled individually without comparators, which simplifies the structure and provides flexibility for signal processing. An optimization is performed to achieve the best compromise design considering the conflicts induced by its special structure. The fabricated antenna is measured and the results demonstrate an excellent radiation performance of the proposed antenna. Four well-performed offset beams are obtained as expected and the antenna works stably within a bandwidth of 10 GHz. The measured 3 dB beamwidths vary around 0.6° and the sidelobe levels are lower than −12.5 dB for all the beams. The superiorities of the proposed antenna show its potential application in high-performance tracking and imaging systems.

A Triple-Band High-Gain Multibeam Ambient RF Energy Harvesting System Utilizing Hybrid Combining

Overcoming the challenge of battery recharging and replacement in industry Internet-of-Things (IoT) applications is considered by proposing the design of a triple-band high-gain multibeam ambient radio frequency (RF) energy harvesting system utilizing hybrid combining. The novelty of the design is that it simultaneously exploits frequency, space, and polarization to maximize the harvested RF energy. Wideband hybrid combining is proposed, which enables the harvesting of energy at low RF power densities while maintaining the wide frequency and space coverage necessary for ambient RF energy harvesting. The antenna design consisting of 16-ports has an average area per port of 0.3λ × 0.3λ (where λ is the freespace wavelength at 1.8 GHz) and is demonstrated to achieve a wide relative bandwidth of 38.5% covering the GSM-1800, UMTS-2100, and WiFi frequency bands. Hybrid combining of the 16-port antenna provides multiple antenna beams each with up to 11 dBi antenna gain and these provide broad beam coverage. The design for the rectifiers, using multistub impedance matching, is also provided and these are shown to be efficient over the frequency bands of interest. Measurements in an anechoic chamber demonstrate that the proposed energy harvesting system can provide an output dc voltage of more than 755 mV, an output dc power of more than -6.4 dBm and RF-to-dc efficiencies greater than 40% when the power density is more than 1400 μW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . It is also shown that the proposed system can provide output dc power of 80 μW and 7.3 μW in real outdoor and indoor ambient environments, respectively.

Advanced Multibeam Antenna Configurations Based on Reflectarrays: Providing multispot coverage with a smaller number of apertures for satellite communications in the K and Ka bands

This article presents some recent developments in multiplebeam antennas (MBAs) based on reflectarrays for communication satellites in the Kurz (K) and Kurz-above (Ka) bands. The existing high-throughput satellites commonly employ four reflector antennas to provide cellular coverage that is formed by multiple spot beams in a four-color scheme. Reflectarray antennas are proposed as an attractive solution for the design of novel MBA configurations to produce multispot coverage, with a smaller number of apertures than conventional MBA systems based on reflector technology. Single and dual reflectarray configurations have been considered for the purpose of exploiting their ability to produce independent beams in different polarizations and frequencies.

Analytical Model and Study of Continuous Parallel Plate Waveguide Lens-like Multiple-Beam Antennas

An analytical model based on geometrical optics is proposed to design and analyze continuous parallel plate waveguide (PPW) lens-like antennas. The proposed design is based on a transversal PPW section working as a lens-like beamformer. By simplifying the propagation inside this transversal section, a bifocal constrained lens model is first defined; it provides a relevant starting point to design the proposed beamformer. A refined model based on ray tracing and with an enhanced performance prediction is achieved by accounting the wave propagation inside the transversal cavity. The numerical analysis of phase aberrations and radiation demonstrate the performance of the proposed beamformer. The results of the ray-tracing model are in a very good agreement with the corresponding full-wave model, while providing a significant reduction in the computational effort, making the proposed model more suitable for advanced optimization processes.