Flat plate for OAM generation in the millimeter band

International audienceThe use of electromagnetic waves carrying orbital angular momentum in the radio frequency range is a growing subject, and so is the design of antennas able to produce such waves. The aim of this paper is to present a new type of antenna (a flat plate) in order to generate an electromagnetic wave carrying orbital angular momentum in the millimeter frequency band

Measurements and Characterization of Twisted Radio Wave Multipath for Indoor Wireless Communication and Security System

This paper presents a novel twisted radio wave based wireless communication system that has the capability to discriminate against strong reflections in indoor multipath environment. The twisted wave transmitter is designed using a uniform circular array, which is capable of transmitting different OAM modes simultaneously and the receiver is designed to match to the transmitted OAM mode. The measurement results obtained from the experiments carried out in different indoor environments and different propagation scenarios show that our proposed twisted radio wave system can provide a stable transmission link even in the presence of existing ZigBee and Wi-Fi signals, which are operating in the same frequency band. A good general agreement between the simulations and measurement results shows the accuracy and applicability of our proposed wireless communication system in such indoor multipath environments

Orbital Angular Momentum Waves: Generation, Detection and Emerging Applications

Orbital angular momentum (OAM) has aroused a widespread interest in many fields, especially in telecommunications due to its potential for unleashing new capacity in the severely congested spectrum of commercial communication systems. Beams carrying OAM have a helical phase front and a field strength with a singularity along the axial center, which can be used for information transmission, imaging and particle manipulation. The number of orthogonal OAM modes in a single beam is theoretically infinite and each mode is an element of a complete orthogonal basis that can be employed for multiplexing different signals, thus greatly improving the spectrum efficiency. In this paper, we comprehensively summarize and compare the methods for generation and detection of optical OAM, radio OAM and acoustic OAM. Then, we represent the applications and technical challenges of OAM in communications, including free-space optical communications, optical fiber communications, radio communications and acoustic communications. To complete our survey, we also discuss the state of art of particle manipulation and target imaging with OAM beams

Novel Pseudo Magneto-electric Dipole Antennas

One of the major requirements for modern wireless communications is very high data transmission, so antennas with simple geometry, wide operation bandwidth and stable high gain features are in increasing demand. In this thesis, three novel pseudo magneto-electric (ME) dipole antennas operating in 5G Frequency Range 1 (FR1) sub-6GHz and Frequency Range 2 (FR2) millimeter-wave (mmW) band are introduced and analyzed. Comparing with conventional ME dipole antennas, which always require a vertical quarter-wave cavity to generate the magnetic dipole resonance, the pseudo-ME dipole designs proposed in this thesis do not rely on the cavity to provide the complementary magnetic dipole mode, therefore, they have extremely simple geometry. Meanwhile, it achieved wide bandwidth (50.30%) and high gain (average 8.74 dBi) the in-band gain variation is only ± 1dB. Based on the novel cavity-less Pseudo-ME dipole antenna geometry, a wide axial ratio bandwidth (54.1%) circularly polarized pseudo-ME dipole antenna is also designed to overcome the polarization misalignment problem in multipath-rich wireless environments, this antenna has two pairs of orthogonal electric dipoles and magnetic dipoles to achieve the wide axial ratio bandwidth performance. Finally, an aperture-coupled printed pseudo-ME dipole antenna is designed for operating in millimeter-wave band, it has 32.3% of impedance bandwidth and stable high gain 7.4 ± 0.8 dBi. Especially, there is none typical via-hole formed cavity in the geometry, so the fabrication of the mmW band antenna becomes simpler

Phase Quantized Metasurface Reflectors for X-band Laguerre Gaussian Vortex Beam Generation

From last two decade, there is an exponential growth in consumption of available bandwidth in the radio frequency spectrum. To challenge this issue, improvement in channel capacity is getting huge research attention. Laguerre-Gaussian vortex beams are one of the solution to challenge so-called Multi-Input-Multi-Output (MIMO) technology. However, designing compact portable antennas to generate vortex beams at radio frequencies is still a challenge. We proposed two metasurface reflector models (Track and sector-wise distribution) based on 3-bit phase quantized meta-element analysis to generate fundamental Orbital Angular Momentum (OAM) vortex modes. A microstrip antenna is used as feeding element instead of conventional horn to reduce overall reflector size. Simulated E-field distribution clarifies the spatial vortex mode behavior at X-band. Experimental results of fabricated prototypes at 9.5 GHz, 10 GHz, and 10.5 GHz agrees with simulated far-fields which indicates a broadband characteristic

ORBITAL ANGULAR MOMENTUM ORTHOGONALITY-BASED CROSSTALK REDUCTION: THEORY AND EXPERIMENT

Full duplex communication systems allow a single channel to be used for simultaneous two-way communication, increasing spectral efficiency. However, full duplex communication systems suffer from the issue of self-interference between local transmitter and receiver antennas. Analog subtraction and signal processing methods have previously been used to reduce this problem. This dissertation proposes the use of waves carrying orbital angular momentum (OAM) to mitigate the problem of self-interference by offering a means of additional isolation between local antennas. Orbital angular momentum has been widely studied both in the photonics and radio domain. The theoretically infinite orthogonal states of an OAM signal make it highly desirable in the field of communication. The application of OAM in a full duplex system, may be the answer to the problem of self-interference. This dissertation shows how the use of OAM waves may create an additional isolation between local antennas in a full duplex system. Motivated by the promise that OAM orthogonality holds, this dissertation explores the crosstalk reduction achieved through OAM. One of the main contributions of this dissertation is to provide insight into the nature of the effect. It motivates OAM orthogonality as a direction of research for use in future full duplex systems. The effect of OAM on crosstalk must be studied experimentally and theoretically. To this effect, a patch array antenna was designed using the High Frequency Simulation Software (HFSS), to generate OAM beams. The designed antennas are fabricated and characterized. This dissertation discusses the experiments carried out to determine the amount of crosstalk reduction achieved due to the OAM nature of the signal transmitted. The impact of the change in distance between the local transmitter and receiver antennas on crosstalk is also studied. The results obtained are verified through theoretical analysis using simulations in HFSS. This dissertation reports a maximum theoretical crosstalk reduction of 3.6dB, and a crosstalk reduction of 2.6 dB realized experimentally. Building on these results, a compact, more practical antenna configuration was designed. This nested design yields more than 60dB crosstalk reduction and provides for a more elegant system realization. The dissertation includes the design of a parabolic dish antenna to build a complete system, which is also studied in this dissertation. The symmetry of the nested antenna configuration allows for analytic theoretical study which is included herein. The study mathematically proves the orthogonality of OAM modes, and the isolation between two antennas with different OAM modes. A similar study is simulated in HFSS using coaxial based loop antennas, and the crosstalk in the nested design is investigated. The design offers a crosstalk isolation of more than 90dB, and further affirms the mathematical analysis. This dissertation provides a detailed analysis of the isolation offered by OAM orthogonality in local antennas which can be useful in a full duplex system. The work consists of practical, simulated, and mathematical investigation, and considers various antenna configurations and designs. Additionally, it presents and analyses a design for a full duplex system

Characterization of an eight element circular patch array for helical beam modes

This paper reports on a new method for characterizing inter-modal isolation, power penalty and reception zone area of Helical Beam antennas. As an example, an eight element circular patch array is fully characterized and its performance is critically assessed. Validation through beam measurements is accompanied with precise electromagnetic modeling using CFDTD computation on a GPU

A High-Gain Transmitarray for Generating Dual-Mode OAM Beams

This paper proposes a novel transmitarray antenna which can achieve high gain and produce dual-mode orbital angular momentum (OAM) beams in Ku band. Two back-to-back wideband dual-polarized microstrip antennas are employed as the unit cells, which are connected using metalized via holes. Full 360 o phase ranges can be obtained by varying the length of feeding lines in two orthogonal polarizations. Due to high isolation between the two orthogonal polarizations, dual-mode OAM beams can be formed simultaneously by tuning phase distributions in x- and y-polarizations, respectively. The approach for generating OAM beams is explained. To verify this concept, one prototype carrying 0 and +1 mode OAM beams is designed, fabricated and measured. Experimental results demonstrate that the both 0 and +1 mode OAM beams can be generated successfully, and the measured results agree well with the simulated results. Because of high directivity and focusing effects of transmitarray, the proposed +1 mode OAM beam has stable performance at a long propagation distance. The maximum gain reaches 26 dBi and 20 dBi in 0 and +1 mode OAM beams, respectively. Meanwhile, a narrow divergence angle of +/-5 o is obtained in +1 mode OAM beam. Compared to other OAM antennas reported, main advantages of the proposed antenna include high gain, narrow divergence angle?low cost, planar structure and the capability of producing dual-mode OAM beams