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Antenna array is one of the methods which can generate Orbital Angular Momentum (OAM) waves. However, OAM waves generated by different antenna arrays have different characteristics of Electric-field (E-field) components’ distribution and radiation patterns. In order to solve this problem, we derive E-field formulas of OAM waves generated by differe...
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... displayed in Fig. 2, the dipole antenna elements are placed by the radial direction around a circle and d n in formula (1) should be changed as r n to get the vector potential A 2n . It can be seen that the vector potential's direction of each antenna element is r n ¼ xcosφ n þ ysinφ n . Thus, in order to get the vector potential's three components r, θ ...
Citations
... The current distribution of the nth antenna element is I = ϕ n e ilϕn , where ϕ n is the unit direction vector, ϕ n = 2πn/N , and N is the total number of the antenna array. The E-field of the azimuthal dipole antenna array is E, as displayed in equation (1) [25]. and (x + e i π 2 y), which correspond to polarization [26], [27]. ...
Two patch antennas that can generate two or four orbital angular momentum (OAM) modes are designed and verified to work at frequency band from 2.2GHz to 2.7GHz. One antenna is composed of two single OAM mode monopole patch antenna systems with one common ground plane and it can generate two OAM modes: mode
l
=1 and mode
l
=-1. This antenna is designed, simulated, fabricated and tested. Its reflection coefficients, radiation patterns, phase distributions and isolation between two different OAM mode channels are obtained. Phase distributions of the two OAM modes are measured to show the effectiveness of the antenna to generate two OAM modes. Channel isolation between these two OAM modes is 25.72dB at 2.598GHz and more than 15dB at the frequency band from 2.585GHz to 2.62GHz. The measurement results have shown that this two-OAM-mode antenna can produce two isolated channels at the same frequency band. Another monopole patch antenna has been designed and verified by simulation to be able to generate four OAM modes. This four-OAM-mode antenna provides an example that this kind of multiplexed monopole patch antennas can multiplex more OAM modes together.
... The OAM multiplexing based on UCA has been analyzed in multiple research works. In [37], the UCA-OAM wave was theoretically analyzed, revealing that the antenna array in the same direction demonstrated the highest energy transmission efficiency. Additionally, a theoretical analysis was conducted to assess the channel capacity of UCA-OAM and UCA-MIMO systems [38]. ...
... Therefore, the near-fields of UCA-OAM waves need to be accurately analyzed. However, conventional analysis of UCA-OAM waves is derived under the assumption that each array element of UCA radiates a far-field [24], [31], [37], making it inaccurate for the near-field analysis. Therefore, fields of UCA-OAM waves need to be rigorously analyzed without the far-field assumption. ...
... In this section, UCA-OAM near-fields and EM energy densities are theoretically analyzed based on the conventional far-field assumption. We refer to [37] where N antenna arrays of the UCA are electrically short dipoles on the xy plane centered around the z axis. Additionally, it is assumed that there is no mutual coupling between antenna arrays. ...
This paper demonstrates the significance of employing the infinitesimal dipole modeling (IDM) in analyzing uniform circular array-orbital angular momentum (UCA-OAM) near-fields in terms of electromagnetic (EM) energy densities. The electric and magnetic field, and the EM energy densities of UCA-OAM waves are theoretically analyzed and numerically estimated where the spatial distribution of EM Lagrangian density and complex Helicity is visualized. It is validated that the IDM is more accurate than the conventional far-field assumption in evaluating the near-fields of UCA-OAM waves as the EM Lagrangian density and the complex Helicity are clearly depicted based on the IDM, while they are unobservable with the far-field assumption. The visualization of EM Lagrangian density and complex Helicity can be beneficial in designing UCA-OAM communication system as it suggests the mutual coupling between antennas by describing the regions of reactive EM energy densities and non-orthogonal EM fields in the near-field region.
... In this paper, simulated phase patterns of the radiated field of three different array configurations, i.e., unidirectional element array, radial array, and tangential array, respectively, are studied [17][18][19]. Different number of elements are arranged in these three configurations at different values of radius for generating various modes of OAM as a result. The presented results will be beneficial for future OAM ...
... In [18] Liu et al has demonstrated three kinds of arrays and their radiating field expressions. Those expressions work well theoretically but have limitations when those arrays are designed physically. ...
... The E-field equations in Cartesian co-ordinate system radiated by UCA configurations for the N number of short dipole elements at a detection point P(x, y, z) in the far field has been mentioned in [18]. The length of short dipole element 'd' is replaced with space factor as mentioned in expression (1) in the final E-field equation of all three configurations of half wave dipoles. ...
... The OAM is associated with the spatial phase of helical radio beams. Each helical radio beam has a spatial phase profile with jlϕ, where l is the mode number, also known as topological charge of OAM [31]. In the microstrip array technique, there are two commonly used methods for phase modulation and vortex beam generation: one is using the excitation phase from the feeding network [32,33]; the other is using Pancharatnam−Berry (PB) phase that is generated by element rotation [34,35]. ...
Achieving multiple vortex beams with different modes in a planar microstrip array is pivotal, yet still extremely challenging. Here, a hybrid method combining both Pancharatnam−Berry (PB) phase that is induced by the rotation phase and excitation phase of a feeding line has been proposed for decoupling two orthogonal circularly polarized vortex beams. Theoretical analysis is derived for array design to generate quad vortex beams with different directions and an arbitrary number of topological charges. On this basis, two 8 × 8 planar arrays were theoretically designed in an X band, which are with topological charges of l1 = −1, l2 = 1, l3 = −1, and l4 = 1 in Case I and topological charges of l1 = −1, l2 = 1, l3 = −1, and l4 = 1 in Case II. To further verify the above theory, the planar array in Case I is fabricated and analyzed experimentally. Dual-LP beams are realized by using rectangular patch elements with two orthogonally distributed feeding networks on different layers based on two types of feeding: proximity coupling and aperture coupling. Both the numerical simulation and experimental measurement results are in good agreement and showcase the corresponding quad-vortex-beam characteristics within 8~12 GHz. The array achieves a measured S11 < −10 dB and S22 < −10 dB bandwidth of more than 33.4% and 29.2%, respectively. In addition, the isolation between two ports is better than −28 dB. Our strategy provides a promising way to achieve large capacity and high integration, which is of great benefit to wireless and radar communication systems.
... The E-field of the radial direction arrays of antennas is shown in the following equation [21]. ...
This study evaluates the feasibility of using antenna array to detect crack defects in metal pipes. Antenna arrays are set at the port of a metal pipe in radial direction, and the microwave signal can be effectively coupled into the metal pipe. It can produce orbital angular momentum (OAM) waves. The cracks in the pipe will change the microwave transmission characteristics, and they can be inspected by time domain reflectometry (TDR) of vector network analyzer (VNA). By studying the transmission characteristics of current on the inner surface of the metal pipe, the feasibility of linearly polarized TE11 mode microwaves for crack inspection was preliminarily verified. Three galvanized metal pipes with an inner diameter of 8 cm and a total length of about 270 cm were used in the experiment. Axial slits and circumferential slits were used to simulate the crack, respectively. The slits penetrated the pipe wall with a breach of approximately 10 cm×0.7 cm. The experimental results demonstrated that the radial direction antenna array can detect both the axial slit and circumferential slit through TDR and standing wave ratio (SWR) at the port, especially effective for the axial slit. It provides a new inspection method for metal pipe defect evaluation.
... For instance, a standard algorithm assumes that the array is made up of two identical subarrays. Fortunately, for those not familiar with antennas, antenna arrays with defined characteristics are commercially available [43]. A helpful antenna array will ensure the collection of accurate IQ samples. ...
This paper presents an in-depth overview of the Bluetooth 5.1 Direction Finding standard’s potentials, thanks to enhancing the Bluetooth Low Energy (BLE) firmware. This improvement allows producers to create location applications based on the Angle of Departure (AoD) and the Angle of Arrival (AoA). Accordingly, it is conceivable to design proper Indoor Positioning Systems (IPS), for instance, for the traceability of resources, assets, and people. First of all, Radio Frequency (RF) radiogoniometry techniques, helpful in calculating AoA and AoD angles, are introduced in this paper. Subsequently, the topic relating to signal direction estimation is deepened. The Bluetooth Core Specification updates concerning version 5.1, both at the packet architecture and prototyping levels, are also reported. Some suitable platforms and development kits for running the new features are then presented, and some basic applications are illustrated. This paper’s final part allows ascertaining the improvement made by this new definition of BLE and possible future developments, especially concerning applications related to devices, assets, or people’s indoor localization. Some preliminary results gathered in a real evaluation scenario are also presented.
This paper investigates a trapezoidal Monopole Patch Antenna (MPA) with an Ultra-
Wideband (UWB) characteristic and a dual-stage notched band at fifth generation (5G) and
Wireless Local-Area Network (WLAN) bands. The 5G band is notched by inserting a U-shaped
slot on the trapezoidal UWB MPA. The WLAN band is notched using five-square metallicconductor
Electromagnetic Bandgap (EBG) patches that are installed on the surface of the
backside of the radiating patch and attached to the ground plane via a shorting pin. The small,
proposed antenna is built upon an FR4 substrate substance, having dielectric comparative
permittivity 𝜀𝑟= 4.7, and fed by a 50Ω coplanar waveguide. The antenna’s size is 32×42.90×0.8
mm3. The simulated results show that the antenna has an operating frequency range of 2.39–
14.72 GHz for |𝑆11|<-10 rejecting WLAN (5.15–5.825 GHz), as well as sub-6 GHz 5G (3.4–3.9
GHz) great-selectivity signals. A higher gain obtained by the UWB antenna is 6.4 dBi, while a
sharp decrease occurs in the rejected bands, reaching -8.29 dBi. This study also employs the
Orbital Angular Momentum (OAM) technique. However, OAM waves are generated using eight
trapezoidal UWB MPAs. Creating notches reduces the interference problem in UWB frequencies,
and merging the UWB with the OAM technique allows the OAM to operate on many frequencies.
Moreover, notches can be generated for specific frequencies inside the UWB bands. These
techniques, trapezoidal UWB MPA and OAM wave generation, can significantly increase the
spectrum range and improve the spectrum efficiency in wireless communications.
