Multibeam Applications Research Articles

Compact SIW 2-D Butler Matrix and Its Multibeam Application

This letter presents a compact 2-D Butler matrix (BM) realized by multilayer substrate integrated waveguide (SIW) technology. The 2-D BMs in the open literature suffer from either bulky size or poor integration with the radiation portion. Facing this issue, a new SIW 2-D BM is developed and realized in planar configuration easily integrated with the slot antenna array. The key point of this letter is to design planar 2-D components, including 2-D couplers, 2-D crossovers, and 2-D phase shifters, of the proposed SIW 2-D BM, which can perform coupling, intersection, or phase shifting in both E- and H-planes. The proposed SIW 2-D BM also has the merit of ease integration with radiation portion and it is used to build a compact 2-D multibeam antenna in this letter. Simulation, fabrication, and experiments are conducted to verify the performance of the realized 2-D multibeam antenna.

3D Printing of a Monolithic K/Ka-Band Dual-Circular Polarization Antenna-Feeding Network

In this paper, a Ka/K-band antenna-feeding network in dual-circular polarization is reported. The design of the system was carried out in view of its monolithic manufacturing through selective laser melting in AlSi10Mg alloy. As a proof-of-concept for satellite telecommunication multi-beam applications, the feeding network operates in the K band (19.25, 20.75) GHz and in the Ka band (27.0, 29.0) GHz. The system provides four rectangular-waveguide ports and a common dual-polarized circular-waveguide port to be connected to the feed horn. The prototype exhibits measured values of in-band return loss better than 28 dB and a port-to-port isolation better than 19 dB (in polarization) and 50 dB (in frequency). The cross-polar discrimination is higher than 20 dB. In this regard, an elliptical-waveguide line was specifically designed and manufactured to recover a value higher than 30 dB in both frequency bands. The line can be easily integrated in the feed horn to be connected to the feeding-network thanks the ease of customization provided by 3D printing. The insertion losses are lower than 0.5 and 0.2 dB in the K and Ka bands, respectively. The weight of the prototype is approximately 130 g.

Exploitation of Triangular Lattice Arrays for Improved Spectral Efficiency in Massive MIMO 5G Systems

A thorough analysis of the performance of planar arrays with a regular periodic lattice is carried out and applied to massive multiple-input-multiple-output (MIMO) systems operating within 5G NR n257 and n258 frequency band. It is shown that, among different arrangements with uniform spacing, a triangular lattice guarantees the reduction of the Average Side Lobe Level (ASLL), a better angular scan resolution of the main beam within a predefined angular sector and a lower mutual coupling level among elements. Moreover, single beam and multibeam application scenarios are considered for the performance comparison and both cases assess the remarkable features offered by a triangular arrangement. Particular attention is paid to illustrate, for different propagation channel scenarios, the effects of the array lattice on overall system performance including average gain as well as Signal-to-Interference plus Noise Ratio (SINR) and Sum Spectral Efficiency (SSE). The obtained results prove that a regular and periodic triangular lattice is appealing for arrays to be adopted in massive MIMO 5G systems.

Design of 3D Printed Multi-Wavelength DRA

This paper presents the design and analysis of a portable multi-wavelength antenna for UWB, wireless data-link, electromagnetic sensor, and multi-beam applications. The antenna structure consists of an air suspended rectangular dielectric resonator antenna (DRA) loaded with a printed horn. The DRA is suspended in air using four supporting dielectric pillars. The overall antenna structure is fabricated using 3-D printing technology. Poly-Lactic Acid (PLA) is used for the implementation of the antenna system (i.e. DRA, horn and supporting pillars integrated with the substrate). It is a biodegradable thermoplastic composite polymer. The antenna shows multibeam characteristics at different frequencies. The radiation patterns are explained using the concept of multi-wavelength long dipole or monopole. The computed efficiency of the projected DRA is more than 70% and maximum peak gain is 12.15 dBi. The measured impedance bandwidth of the antenna is 122.6% (7.5 GHz to 31.3 GHz). The measured group delay is less than 1.5 ns in the band of operation.

Analysis of Electromagnetic Simulation Method for the Dielectric Lens Antenna

For the millimetre wave usage at 5G mobile communication system, a dielectric lens antenna will become a promising candidate for the base station antenna. In developing a dielectric lens antenna, antenna performance analysis by an electromagnetic simulator will be necessary. The structure of the proposed design is a hyperbolic dielectric lens antenna fed by a pyramidal horn at the operating frequency of 28GHz. In this paper, the abilities of a commercial electromagnetic simulator FEKO are investigated. Simulation methods of GO and MoM solvers are shown for electric field distributions on the antenna aperture and far field radiation patterns. The simulation results show that the optimum gain of lens antenna based on GO and MoM method are 26.68 dBi and 27.24 dBi, respectively. Moreover, multi beam radiation patterns and suitable feed positions are clarified for wide scanning angle. Good performance for multi beam application by using MoM is shown based on the off-focus characteristic where the antenna gain is only slightly reduced from 0.51 dBi to 4.03 dBi for 5.71° to 35.54°.

Mitigation of beam losses in LANSCE linear accelerator

The LANSCE accelerator has been in operation for nearly five decades. During this period, it was transformed from a 0.8 MW average proton beam power machine used primarily for the study of meson physics, to a multi-user high-power facility for fundamental research and national security applications, concurrently delivering beams to five distinct experimental areas. Minimization of beam losses in multi-beam application is a key issue for effective operation of accelerator facility. This paper summarizes recent experimental results in understanding and lowering of beam losses in LANSCE linear accelerator and high-energy beam transport lines.

Broadband Passive Two-Feed-Per-Beam Pillbox Architecture for High Beam Crossover Level

Multi-beam antennas based on quasi-optical systems feeding a single radiating aperture generate orthogonal beams with a low crossover level between adjacent beams (around −13 dB at most). To circumvent this limitation, we present a circuit architecture allowing the excitation of a quasi-optical system (pillbox system) with two feeds per beam to reach much higher beam crossover levels. To this end, a specific eight-beam passive circuit is designed to cover the 76–86 GHz frequency band. It is based on a single-layer substrate integrated waveguide (SIW) coupler followed by equiphase SIW lines. The maximum phase and amplitude imbalance between the sources are only 35° ( $\lambda _{g} / {1g}$ , with $\lambda _{g}$ the wavelength in the SIW lines at the design frequency) and 1.3 dB, respectively, and the isolation is better than −19 dB. The measured beam crossover level of the corresponding antenna is better than −3.2 dB, corresponding to an improvement of 16 dB with respect to single-feed-per-beam pillbox systems. The proposed passive architecture offers beam crossover levels suitable for low-cost electronically controlled multi-beam applications, as for next-generation 5G backhauling systems.

A Ka-Band Active Aperiodic Constrained Lens Antenna for Multibeam Applications: Active discrete lens antennas are promising alternative solutions for multibeam coverage using a single aperture

This article presents the design, manufacturing, and testing of a transmitting active discrete lens antenna demonstrator in the Ka band. These antennas permit generating multibeam coverage using only a single main aperture and exhibit excellent scanning capabilities and a large-frequency bandwidth. Because the beamforming is mainly achieved in the free space, the complexity and cost of the antenna grows marginally with the number of beams and radiating elements. For these characteristics, active discrete lens antennas are a promising alternative to more conventional antenna solutions that are based on phased arrays and reflectors antennas, especially for Ka-band and higher frequencies where the dimensions become smaller.

Proton array focused by a laser-irradiated mesh

We present a technique on focusing laser-driven proton beams in an array pattern by employing a copper mesh irradiated by a separate, intense laser pulse. Transient fields are generated on the mesh following the intense interaction. Under the combined effect of collisional scattering and electrical deflections from the mesh, a laser-driven proton beam is split into multiple focused beams with a high density of ∼4 × 109/cm2 after propagation through the charged-up mesh. The particle density within the focused beamlets is up to ∼11 times the initial density of the proton beam. Multiple beam focusing through this approach may open routes for proton beam conditioning, leading to opportunities for multi-beam applications, such as tomographic radiography and proton implantation.

Near-Field Focus Radiation of Multibeam Phased Array of Antennas Realized by Using Modified Rotman Lens Beamformer

This paper presents the design of 2-D phased array of antennas to radiate collinear multiple beams properly distributed for near-field (NF) focus (NFF) applications. In the design, the 2-D array is first decomposed into single-column subarrays, where each of the subarrays is identically excited to radiate a vertically NFF beam with the focal points located at a designated distance along the boresight direction of each subarray aperture. Afterward, the NFF column subarrays become the elements of a 1-D horizontal collinearly located array to radiate horizontally NFF multiple beams. The horizontal NFF beamforming network is implemented by extending the basic concept of conventional Rotman lens beamformer for directional NFF multibeam applications. Thus, three feeding points are selected to determine the lens’s profile such that the produced phases via the modified Rotman lens can be used to feed a planar array to radiate three NFF beams when the lens is excited at the three selected points, respectively. This antenna set is realized at 2.45 GHz for radio frequency identification applications to demonstrate the implementation concept. Both the simulation and experimental measurement results are shown to validate the feasibility.

Circumferentially conformal slot array antenna and its Ka‐band multibeam applications

A standing-wave slot array covered with a two-layer dielectric slab based on substrate integrated waveguide (SIW) technology, which is circumferentially conformed to a cylinder, is designed, fabricated and measured at Ka-band. The radiating part consists of seven slotted cylindrical SIWs, each of which has four-element longitudinal slots. Several such slot arrays fed by Rotman lenses are grouped on a cylinder along the circumferential direction to cover a 2D field of view. The microstrip Rotman lens is employed as the beamforming network with seven input ports, which can generate a corresponding number of beams to cover -35° to 35° along 1D ( E -plane). Another dimension ( H -plane) is covered from -52° to 52° with four beams generated by the slot arrays group. A prototype antenna is fabricated, the measured results demonstrate its ability of scanning over a 2D field of view with multiple beams. This type of multibeam conformal antenna is a good candidate for high-speed vehicles or communication base stations requiring electronic beam-scanning capabilities and considering conformal reasons.

A Flat Dual-Polarized Transformation-Optics Beamscanning Luneburg Lens Antenna Using PCB-Stacked Gradient Index Metamaterials

Based on a transformation optics method, a flat compact dual-polarized Luneburg lens antenna is proposed and implemented using the printed-circuit-board-stacked gradient-index metamaterials for beamscanning and multibeam applications at X-bands. The transformed material properties of the planar Luneburg lens are designed with 17-layered permittivity distribution of polynomials. Each layer is discretized into $41 \times 41$ pixels made of broadband and less polarization-dependent unit cells responsible for desired index distributions. The effects of transformation, approximation, and discretization on the lens performance are analyzed comprehensively. Also, to validate the implementation method, a flat Luneburg lens with a thickness of 14.1 mm, a focal length of 28 mm, and an aperture size of $98.9 \times 98.9$ mm2 is designed and tested. A stacked aperture-coupled patch antenna operating at 10 GHz is applied as a feeder. The measured results show that the proposed antenna can operate over a bandwidth of ~20% with an antenna efficiency of 32%, a cross-polarization level of <−17.1 dB, as well as the maximum gain of 15.9/16.35 dBi and a scanning angle of ±32°/±35° for two orthogonal polarizations, respectively. The presented flat Luneburg lens antenna featuring broad bandwidth, high gain, wide scanning angle, and easy fabrication has a high potential in 5G wireless communication, imaging, and remote sensing applications.

An Electronically Scannable Reflector Antenna Using a Planar Active Array Feed at &lt;italic&gt;Ka&lt;/italic&gt;-Band

This contribution presents the system design procedure and performance of an array fed reflector antenna. Combining the inherent benefits of a reflector antenna-high gain, low-cost, and simplicity-with the agility provided by a scannable active array feed, enables a new range of applications, for instance in commercial mobile antenna terminals. The whole arrangement features a restricted field of view for either scanning or multibeam applications. To minimize system cost, a planar patch antenna array in printed circuit board technology is used for the feed and the reflector diameter is restricted to 60 cm. To obtain optimal performance, both the reflector and the feed are specifically designed for the desired application, i.e., mobile satellite communication at Ka-band. A comprehensive study of various rotationally symmetric reflectors is carried out to determine arrangements maximizing the field of view and still complying with the respective regulations. For the feed, a 30 GHz transmit array with 49 elements is developed, enabling 2-D scanning in a ±6° conical sector. It includes a wideband signal distribution network and frontend electronics.

Direct radiating array design via convex aperture synthesis, pareto front theory, and deterministic sampling [antenna designer's notebook

A deterministic method for the design of direct radiating arrays for multibeam satellite applications is presented in the current work. The method embodies the following steps: First, we consider the problem of continuous aperture synthesis, subject to directivity-pattern mask constraints. We succeed in stating the problem as a convex magnitude antenna design that exhibits a second-order cone program form. The solution provides the optimum continuous aperture current-density distribution. Second, exploiting the optimum solution, analytical formulas, in the form of the Pareto front, are presented through which the proposed method determines the minimum number of radiating elements that must be used in the process of transforming the continuous aperture to an antenna array. Third, an effective deterministic sampling approach is contributed to produce a discrete array with the desired characteristics. Armed with the above, the current work provides a generalized framework for the design of direct radiating arrays for multibeam satellite applications. The method is validated by the provided design examples.

Development of Ray Tracing Algorithms for Scanning Plane and Transverse Plane Analysis for Satellite Multibeam Application

Reflector antennas have been widely used in many areas. In the implementation of parabolic reflector antenna for broadcasting satellite applications, it is essential for the spacecraft antenna to provide precise contoured beam to effectively serve the required region. For this purpose, combinations of more than one beam are required. Therefore, a tool utilizing ray tracing method is developed to calculate precise off-axis beams for multibeam antenna system. In the multibeam system, each beam will be fed from different feed positions to allow the main beam to be radiated at the exact direction on the coverage area. Thus, detailed study on caustics of a parabolic reflector antenna is performed and presented in this paper, which is to investigate the behaviour of the rays and its relation to various antenna parameters. In order to produce accurate data for the analysis, the caustic behaviours are investigated in two distinctive modes: scanning plane and transverse plane. This paper presents the detailed discussions on the derivation of the ray tracing algorithms, the establishment of the equations of caustic loci, and the verification of the method through calculation of radiation pattern.

Two-arm spiral antenna array with dual circular polarised radiations for multi-beam applications at Ku-band

The implementation and examination of a spiral antenna array to radiate dual circularly polarised radiations are presented. Each antenna element consists of two spiral arms, which are excited individually on the opposite terminals to produce dual circular polarisations. Its applications to create multiple directional beams are also examined.

ESPRIT with multiple-angle subarray beamforming

Abstract This article presents a new approach of implementing signal direction-of-arrival estimation, in which subarray beamforming is applied prior to estimation of signal parameters via rotational invariance techniques (ESPRIT). Different from the previous approaches, the beam-domain data from multiple adjacent pointing angles are combined in a way that the displacement invariance structure required by ESPRIT is maintained. It is intended to further obtain a sub-beamwidth resolution for a conventional multi-beam system already having small beamwidths. Computer simulations show that for typical multi-beam system applications the new approach provides improved estimation mean-square errors over the original ESPRIT, on top of reduced requirements for signal-to-noise ratio, number of snapshots, and computational time.

Theoretical Approach to Estimate Intermodulations in Wideband Active Transmit Phase-Array Antennas

In this article, an active phased-array multi-beam antenna model including the nonlinear model of the amplifier is developed and validated by experimental data. An amplifier model with frequency-dependent parameters is considered. To investigate nonlinearity effects in a phased-array antenna, a two-beam S-band array is analyzed, and the results of the proposed method are compared with measured data. It is shown that the presented model is able to precisely predict the intermodulation products with an accuracy of 1 dB. Therefore, the model can be used as a tool to accurately predict the intermodulation patterns for multi-beam satellite array applications, avoiding excessive system margin and reducing DC power consumption.

Investigations on the Efficiency of Array Fed Coherently Radiating Periodic Structure Beam Forming Networks

The concept of coherently radiating periodic structure beam forming network (C-BFN) has been introduced recently in the literature as a possible mean to feed linear or planar arrays. Losses are expected in such a structure as it produces non-orthogonal excitation laws, motivating the investigations on C-BFN efficiency presented in this paper to guide antenna designers. Mono- and multi-beam applications are considered, including also beam steering capability. These investigations help define some useful design rules depending on the application. Some evolutions are also proposed that may overcome some limitations of the original concept. All the presented results are supported by both simulations and measurements of various prototypes designed on printed technology at 6 GHz.

Offset Parabolic Reflector Antenna Fed by EBG Dual-Band Focal Feed for Space Application

A new design of a metallic dual-band electromagnetic band-gap (EBG) suitable to feed a reflector antenna for space multibeam applications is introduced in this letter. The EBG antenna is composed of double-layer frequency selective surfaces (FSS) arranged in the longitudinal direction and a square horn as a feed. First, we devise a technique to adapt the dual-band EBG antenna characteristics for this space application, which requires the same EBG phase center and the same radiation patterns for both frequency bands. Then, a dual-band EBG antenna has been designed. Finally, a prototype is realized, and the experimental measurements are compared with success to the simulated ones. The same phase center has been obtained at 5 and 7.5 GHz. This antenna is suitable to feed a reflector antenna with a focal-length-to-diameter (F/D) ratio of 1.2. The performances of the offset reflector fed by this antenna are good with a maximum efficiency about 77% and with sidelobes levels always better than -22 dB for both frequency bands.