Orbital Angular Momentum Antenna Research Articles

Frequency-adjustable OAM antenna with co-divergent beams for IoT applications

A frequency-tunable Orbital Angular Momentum (OAM)-generating antenna array system is introduced for the first time to provide high-data-rate and secure communication for Internet of Things (IoT) infrastructures and devices. Propagation of simultaneous OAM modes brings about the high-data-rate and frequency tunability leads to interference suppression for secure communication. Regarding the design evolution of the proposed structure, the novel Multiple-Input-Multiple-Output (MIMO) antenna consisting of two input ports creates a 2 × 2 UCA, resulting in two 2 × 2 sub-UCA. Feeding each 2 × 2 sub-array with [0°, 90°, 180°, 270°] phase gradients in clockwise and counterclockwise states gives rise to dual-mode OAM-carrying waves with simultaneous excitation capability. It should be mentioned that each MIMO element owns frequency tunability, resulting in a frequency-adjustable dual-mode OAM antenna array. A prototypes of the suggested MIMO antenna as well as the OAM array are fabricated and measured. Changing the applied DC-voltage to the varactor diodes embedded in capacitive stubs of the antenna elements shifts the operating frequency in the MIMO antenna and consequently in the OAM array. Concerning the unique radiation characteristics of the OAM antenna, vortex beams having helical phase fronts are observed, confirming the generation of expected OAM waves. Therefore, it is asserted that the introduced structure, for the first time, proposes new features of frequency-tunability, and co-divergent simultaneous OAM propagation using the MIMO-UCA technique to provide high-data-rate and secure communication in IoT applications.

Design of Orbital Angular Momentum Antenna Array for Generating High-Order OAM Modes

Orbital angular momentum (OAM) modes can offer high density and high-capacity communication. The traditional phased array antenna can only produce a limited number of OAM beam modes l, usually less than half of the number of array elements (N): −N/2 < lmax < N/2. An OAM antenna array for generating high-order OAM modes is proposed in this letter. The proposed antenna array consists of a ring patch antenna that can generate vortex waves with OAM mode l = 1 or −1 and a phase-shifting feeding network. By adding different feed excitation signals to each element, the generated beam carries a higher-order mode: l = N or −N, breaking the previous limitations. Near-field measurements were conducted on antenna arrays composed of 3, 4, and 5 elements, revealing a high degree of correspondence between their phase distribution and radiation patterns with numerical simulation results. This alignment further substantiates the practical efficacy of this approach in significantly enhancing the generation of high-order OAM modes within antenna arrays. This advancement improves component utilization efficiency, reduces system complexity, and meets the high demands for spectral resources and channel capacity in future communication applications.

Realization of circular polarized multiple band multi-mode OAM antenna using a ring patch for IoT applications

A multiband and multi-mode antenna with circular polarized conical patterns is suitable for achieving desired spectral efficiency, increased capacity, and spatial diversity for IoT applications. However, simultaneous excitation of such circular polarized multiple Orbital Angular Momentum (OAM) modes through a single patch antenna is challenging due to the complexity of simultaneously fulfilling distinct requirements of each mode. In this paper, a ring patch antenna is designed to excite different OAM states at different frequencies simultaneously. First, characteristic mode analysis is used to analyze the possibility of simultaneous excitation of multiple OAM modes at corresponding frequencies through a simple ring patch antenna. Then, a dual port ring patch antenna is designed and fabricated to verify the capability of generating multiple OAM states at corresponding frequencies. Furthermore, it also presents the guidance to suppress unwanted OAM modes.

A Circular-Polarized Vortex Beams Generation With Orbital Angular Momentum Based on a Leaky-Wave Antenna

A circular-polarized vortex beams generation with orbital angular momentum (OAM) based on a leaky-wave antenna with substrate integrated waveguide (SIW) is proposed in this letter. The loop leaky-wave antenna is designed to transmit vortex beams with various OAM modes controlled by the operating frequency. With the frequency change from 11GHz to 12GHz, the OAM modes change accordingly. The OAM antenna realizes a low profile by use of the leaky-wave structure. Meanwhile, two transverse slots and one longitudinal slot are utilized to realize circular polarization to improve the mode purity of OAM. Notably, the measured results demonstrate that the gain reaches 7.18 dBi with vortex beams generated by four OAM modes (+2, +1, 0, -1). And the axial ratio (AR) is good from 11GHz to 12GHz, indicating that circular polarization is achieved.

Generation of dual‐band OAM beam using planar uniform circular array for vehicular communications

AbstractIn this article, a novel compact dual‐band uniform circular array (UCA) is proposed to generate the conical‐shaped orbital angular momentum (OAM) beam with high azimuthal symmetry for vehicular communication. Most antenna designs proposed in the past for obtaining conical‐shaped radiation patterns have complex structures and are very expensive. However, the generation of conical‐shaped patterns by an OAM antenna provides simplicity in the structural realization and is compact for integrating with transceiver circuits. By selecting circularly polarized (CP) patches as array elements of a UCA, conical‐shaped OAM beams can be generated. The proposed UCA consists of a simple feed network with eight dual‐band CP elements. The required phase delay for generating OAM beam ( = +1 mode) is obtained by rotating the CP elements in clock wise direction. The UCA is 150 mm 140 mm in size, fabricated on a FR4 substrate, and experimentally tested. The measured results confirm that the generated OAM beam has conical‐shaped radiation patterns at 5.3 and 5.77 GHz. The generated OAM beam has a peak gain of 10 dBi with high mode purity and a divergence angle of in both simulated and measured findings.

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.

Generation of Mixed-OAM-Carrying Waves Using Huygens’ Metasurface for Mm-Wave Applications

Antennas that generate orbital angular momentum (OAM) have the potential to significantly enhance the channel capacity of upcoming wireless systems. This is because different OAM modes that are excited from a shared aperture are orthogonal, which means that each mode can carry a distinct stream of data. As a result, it is possible to transmit multiple data streams at the same time and frequency using a single OAM antenna system. To achieve this, there is a need to develop antennas that can create several OAM modes. This study employs an ultrathin dual-polarized Huygens' metasurface to design a transmit array (TA) that can generate mixed-OAM modes. Two concentrically-embedded TAs are used to excite the desired modes by achieving the required phase difference according to the coordinate position of each unit cell. The prototype of the TA, which operates at 28 GHz and has a size of 11 × 11 cm 2, generates mixed OAM modes of -1 and -2 using dual-band Huygens' metasurfaces. To the best of the authors' knowledge, this is the first time that such a low-profile and dual-polarized OAM carrying mixed vortex beams has been designed using TAs. The maximum gain of the structure is 16 dBi.

Synthesis of Orbital Angular Momentum Antennas for Target Localization

AbstractThe exploitation of Orbital Angular Momentum (OAM) is proposed to design circular‐support continuous aperture distributions and concentric‐ring arrays for target‐localization applications. The proposed approach allows generating a single isolated null of the field in the target direction, which is of interest with respect to common techniques leading to a line (or perpendicular lines) of power‐pattern zeroes in the spectral plane. In the presented design procedure, the optimal continuous aperture source is first identified by resorting to the most suitable OAM vortex and effective tools such as the Singular Value Decomposition of the involved operator and a smart Convex Programming optimization. Then, by exploiting fast deterministic algorithms, this continuous source is discretized into circular‐ring arrays emulating it at best. Relevant applications including equispaced arrays, sum‐difference reconfigurable arrays, and isophoric sparse arrays are presented. The proposed approach is also compared with the state‐of‐the‐art techniques and assessed through full‐wave electromagnetic simulations.

Generation of orbital angular momentum multiplexing millimeter waves based on a circular traveling wave antenna.

Orbital angular momentum (OAM) has recently attracted extensive attention in the radio frequency domain due to its potential applications in various areas. In the OAM-based communication system, the development of the OAM-generating antennas lies at the heart of the matter to generate and receive vortex beams. In this work, a multiplexing/demultiplexing millimeter-wave OAM antenna based on the traveling-wave circular loop structure is proposed and experimentally demonstrated. The feeding networks are implemented using waveguide ports which are inherent integration in millimeter wave communication systems. A prototype with OAM states l = ±3 carried by the z polarization and l = ±2 for the x and y polarizations at 60 GHz is fabricated and measured. Measured near-field distributions and far-field radiation patterns show excellent agreement with the simulated ones. Furthermore, based on the designer strategy, four coaxially propagating waves with OAM modes l = ±3 and ±5 for the z polarization component and l = ±2 and ±4 for the x, y polarization components are investigated, respectively. The antenna will have a positive effect on the application potential of OAM-based wireless communication.

A review of planar antennas for millimeter wave 5G network

In order that wide implement of 5G network is realizable in the future, special features in the propagation of millimeter wave is required, which are much different from that of current operating 4G network and still have great potential to explore. As a result, the antennas used in future 5G network will be much more sophisticated in design and will need a lot of frontier technologies. The key factors in 5G millimeter wave antenna design are reconfigurable antennas, beamforming, antenna array, orbital angular momentum antennas, meta-surface antennas and massive MIMO. The purpose of this work is to illustrate some designing idea of planar antennas used in 5G millimeter wave network by presenting some of the contemporary theoretical and practical design idea investigated by this paper. Since currently there is great amount of research ongoing in this field, this paper can serve as a brief guide and introduction for those who are interested in 5G planar antennas to get a picture of the latest theories and technologies used in those designs.

Characterization parameters for antennas generating orbital angular momentum waves

As one of the pivotal candidate technologies of 6G, orbital angular momentum (OAM) carrying radio waves have attracted much attention in wireless communication and sensing technology fields owing to the particular twisted phase fronts. Various kinds of antennas have been proposed to generate this kind of wave; however, the antenna performance has not been well analyzed in terms of the OAM carrying wave’s characteristics. In this paper, some dedicated characterization parameters termed as conjugated receiving pattern, purity related bandwidth, and mode phase linearity based on well-known properties of OAM carrying electromagnetic waves are proposed for the first time. These parameters can be used to characterize the performance of OAM antennas. As an example, the performance of a fabricated helical OAM antenna with a wide bandwidth is characterized by the proposed parameters, which proves the reasonableness and necessity of the proposed characterization parameters.

Shielding of Orbital Angular Momentum Waves by a Cavity With Apertures

In this article, for the first time, the shielding of orbital angular momentum (OAM) waves by a cavity with apertures is evaluated. This is particularly interesting because the distinguishing feature between the OAM modes is their phase distribution in space, and, hence, shielding effectiveness is a mode-dependent phenomenon. A perfectly electrically conducting cavity with multiple apertures and two OAM antennas, inside and outside the cavity, is investigated using a method of moments based tool. The behavior of OAM waves is analyzed by comparing the transmission between the OAM arrays for different cases, including their field patterns in front of and behind the apertures. The effects of the orientation and position of the transmitting antenna, the rotation, size, and form of the apertures and different cavities are explored. Additionally, the effect on the distance and the orientation angle of the outer antenna are studied. It is shown that the propagation of OAM waves through apertures is possible and that the resulting signal loss is similar to the loss of a plane wave or the field of a monopole. It is also shown that certain OAM waves penetrate the apertures better than others.

A Non-Uniform Travelling-Wave Current Source Model for Designing OAM Antenna: Theory, Analysis and Application

Orbital angular momentum (OAM) has become a research hotspot in radar, communication, and other fields because of its spatial spiral phase distribution in azimuthal domain. However, it encounters some problems in practical application scenarios owing to its inherent defects. Recently, several particular OAM waves and novel antenna structures have been proposed to make up for its defects or optimize its characteristics. However, there lack a universal and systematic theoretical analysis for these schemes. In this paper, the non-uniform travelling-wave current source (NTCS) model for OAM generation is proposed. This model is universal and suitable to be applied to many proposed antennas. The far field pattern and OAM spectrum distribution are theoretically derived based on the uniform travelling-wave source model. Bridged by the OAM spectrum analysis, an application-oriented antenna design process is presented. A PSOAM MG antenna optimal for the MIMO system is designed as an example. This work not only unifies the generation model of different OAM waves, but also provides a new view for the OAM based antenna design.

Millimeter-Wave and Terahertz OAM Discrete-Lens Antennas for 5G and Beyond

The incoming 5G and beyond 5G wireless communications provide unprecedented ultra-high-speed transmission data rates. This is enabled by driving the carrier frequency up to millimeter-wave (mmWave) and terahertz (THz) bands and developing advanced multiplexing technology to increase spectrum bandwidth and spectral efficiency. In this article, we present novel discrete lens antenna designs to solve the two leading open challenges of orbital angular momentum (OAM) applications in mmWave and THz bands: OAM multiplexing and the diffractive problem of OAM waves. For discrete lens antennas operating at THz frequencies, the emerging 3D printing technology and its superior geometric flexibility are utilized to design and implement OAM antennas. The successful demonstration of the mmWave and THz OAM discrete lens antennas can open avenues for future several-hundred-gigabits-per-second wireless communications.

A Wideband OAM Antenna Based on Chiral Harmonic Diffraction

An orbital angular momentum (OAM) antenna based on chiral harmonic diffraction of spoof surface plasmon polaritons (SSPP) is demonstrated in this letter. Due to the diffraction of the helical wire, SSPP is transformed into the high-purity OAM mode. The operation frequency is determined by SSPP, and the topological charge is manipulated by modulating the harmonic order. Additionally, this system achieves a frequency-controlled beam-scanning characteristic in a wide bandwidth from 7.8 to 12.6 GHz, and the measurement data agrees well with the theoretical analysis and the simulation results. Furthermore, the OAM antenna validated in this letter is compact, easy-fabricated, and robust.The underlying principle opens up a new train of thought for generating OAM mode and paves the versatile applications involving wireless communication.

Effects of Concentration, Temperature, and Geometry on Double Spiral Liquid Orbital Angular Momentum Antenna

This paper studies the relationship between liquid concentration, temperature and geometry and the performance of the double spiral liquid orbital angular momentum (OAM) antenna which has two nested spiral shells to excite multiple OAM modes. Distilled water and salt water are injected into the inner and outer spiral shells, respectively. Attractive simulation and measurement results are obtained by changing the concentration and temperature of injected solution and the radius of spiral shells. The bandwidth will increase 100 MHz by the geometry decreases, the center frequency will shift 500 MHz by the liquid temperature, and the radiation efficiency will improve 20% by the liquid concentration. The proposed double spiral liquid OAM antenna can generate OAM models of l = 1 and l = 3at 1.65 GHz and 5.4 GHz.

A Low-Divergence Circularly Polarized Dual-Mode OAM Antenna Based on Higher Order Laguerre–Gaussian Modes

An open resonator antenna for orbital angular momentum (OAM) generation and dual-mode application is proposed. The excitation of OAM mode is deduced by the open resonator theory and the circular array theory. In the cavity, eight aperture coupled patch antenna elements are used to excite two higher-order Laguerre-Gaussian HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> modes with a 90° phase difference. Verifying by simulation and experiment, the proposed low-profile antenna can radiate left-hand or right-hand circularly polarized waves of OAM modes l=±1, which have a relatively low divergence angle of ±9° and high gain of around 13 dBi.

Defining Effective Gain for Evaluation of Orbital Angular Momentum Links

In this paper, a communication link based on circular phased array antennas generating orbital angular momentum (OAM) beams at radio frequency is investigated. The presence of a null in the radiation pattern of OAM antennas is the main drawback of them. This problem makes it difficult to establish a telecommunication link using OAM systems and calculate the link budget for such a system. To solve this problem, we have defined two new gain parameters by using Friis Transmission Equation. The new formulas can help to calculate the effective gain of OAM antennas. Also, we have defined the effective OAM gain in detail for the first time in order to evaluate the performance of the OAM links. By using the proposed formulas, a capable and secure link based on the orthogonality of OAM beams can be designed.

High-Directivity Orbital Angular Momentum Antenna for Millimeter-Wave Wireless Communications

Although orbital angular momentum (OAM) millimeter-wave wireless communications have attracted much attention given their potential to provide an additional degree of freedom in channel capacity, they still face challenges for realization. For instance, the OAM beam diverges rapidly in free space, limiting the coverage of wireless communication. To increase the communication range, we propose a high-directivity broad-bandwidth OAM antenna, which consists of a nonlinear taper and a lens-integrated metamaterial structure (MMS). A linearly polarized TE (transverse electric) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode traverses through the antenna to generate two OAM modes with the low reflectance of the MMS and a low divergence angle (DiA). We evaluate these two factors separately and analyze the effect of reducing the OAM DiA. Then, we validate the OAM antenna using the CST Microwave Studio software and experimentally verify its performance. The measured mode patterns are quantitatively analyzed using a cross correlation function and by calculating the beam DiA from beam radius variations. The proposed OAM antenna provides a novel approach to effectively reduce the DiA of the OAM beam and may be suitable for realizing millimeter-wave wireless communications.

Throughput Performance of Wireless Multiple-Input Multiple-Output Systems Using OAM Antennas

This letter experimentally demonstrated the performance improvement of orbital-angular-momentum (OAM) based 2 $\times $ 2 MIMO communication by using the diversity of different OAM modes. The OAM antenna we used is an eight-arm Archimedean spiral antenna (ASA) capable of generating multiple high-quality OAM vortex waves individually or two types of two-mode mixed vortex waves simultaneously. Both of the two cases are investigated for MIMO communication by evaluating the throughput performance. For MIMO with two OAM modes (generated by two ASAs separately), the throughput improves upon traditional MIMO by up to 30.50%, while for MIMO with two-mode mixed vortex waves (generated by one ASA), 6.59% throughput improvement is obtained.