Circular Antenna Array Research Articles

Near-field formation of the UCA-based OAM EM fields and short-range EM power flux profiles

Orbital angular momentum (OAM) multiplexing is a recently considered solution for enhancing wireless and free-space optical communications channel capacity, whether implemented separately or in combination with existing multiplexing techniques. The theoretically infinite number of paraxially propagating and mutually orthogonal OAM modes is expected to increase the channel capacity. However, the orthogonality for different OAM modes has been shown to decrease for far link range distances, and the paraxiality of the OAM beams is not very good for small radiating sources. Based on the current knowledge, OAM beams are most likely to be used for short-range communications. Many models of the electromagnetic (EM) fields carrying the OAM neglect the fact that the OAM beam sources could be electrically large or introduce other approximations that are appropriate for far-field analysis only. An in-depth analysis of the short-range properties of OAM EM fields is still lacking. To address this problem, we propose the use of the infinitesimal (Hertz) dipole method customized for the analysis of the OAM EM fields. This technique can model the positioning and basic radiation properties of separate antennas or antenna sub-arrays that are the building blocks of OAM arrays exactly and efficiently. Similar modeling can represent the OAM sources for free-space optical communications. We focus here on the uniform circular antenna arrays and provide an in-depth analysis of what can and cannot be expected, in the best case, in their utilization. We assume low losses, which is a common assumption for many methods, except for computationally much more demanding full-wave simulations. The obtained results indicate the need to simultaneously optimize the transmission of all planned OAM modes and allow estimates of the link distances that could provide adequate OAM wave reception in various cases.

Direction of arrival estimation for BLE: Antenna array design and evaluation

The use of smart antenna arrays in wireless communication systems is becoming increasingly popular, as they improve the performance of the radio link and allow the integration of communication and sensing functions. In this paper, we present the design and performance evaluation of a uniform circular antenna array (UCAA) with 12 monopole antennas and RF switches to select the active antenna for the signal direction of arrival (DoA) estimation. The antenna configuration was optimized through simulations for a different number of antennas and antenna array radius. The frequency tuning of the antennas considered the coupling of the active antenna with adjacent antennas. The performance of the antenna array was evaluated by (1) simulations that examined the proximity of the antenna to the edge of the antenna array and the influence of adjacent antennas on the performance of the active antenna, and (2) measurements in outdoor and indoor environments. The results of the simulations show that antenna coupling can cause nulls in the radiation pattern, which affects the DoA estimation by reducing the signal-to-noise ratio. In a semi-controlled environment, we achieved a DoA estimation error of less than 1 degree by using the Bluetooth Low Energy (BLE) Angle of Arrival feature.

Polarization singularities in planar electromagnetic resonators with rotation and mirror symmetries

In this work, we apply the group representation theory to systematically study polarization singularities in the in-plane components of the electric fields supported by a planar electromagnetic (EM) resonator with generic rotation and reflection symmetries. We reveal the intrinsic connections between the symmetries and the topological features, i.e., the spatial configuration of the in-plane fields and the associated polarization singularities. The connections are substantiated by a simple relation that links the topological charges of the singularities and the symmetries of the resonator. To verify, a microwave planar resonator with the D8 group symmetries is designed and numerically simulated, which demonstrates the theoretical findings well. Our discussions can be applied to generic EM resonators working in a wide EM spectrum, such as circular antenna arrays, microring resonators, and photonic quasi-crystals, and provide a unique symmetry perspective on many effects in singular optics and topological photonics.

Multiband Pattern Synthesis of Time-Modulated Conformal Array with Quadratic Convex Optimization Algorithm

Aiming at the multiband pattern synthesis problem of time-modulated conformal array antenna, a quadratic convex optimization algorithm is proposed for sum and difference beamforming with low sidelobe levels. This articles method synthesizes a difference beam with a low sidelobe level by generating nulls at the center frequency band and optimizing the switch-on duration time of array elements. And the sum beamforming and sidelobe suppression of the first-order sideband are realized by optimizing the switch-on instant time of the array elements. The proposed algorithm has excellent properties of sidelobe suppression and angular sweep. The simulation results of circular and satellite array antenna verify the effectiveness of the algorithm.

Detection and position determination of the signal source in the near-field zone of the circular antenna array

Detection and position determination of the signal source in the near-field zone of the circular antenna array

Optimization of the size of the circular antenna array in the problem of determining the direction to the radiation source in the far-field zone

Optimization of the size of the circular antenna array in the problem of determining the direction to the radiation source in the far-field zone

Main-Lobe Recognition for Sum-Delta Monopulse of Single-Ring Circular Array Antenna

The target must be located within the main-lobe of the antenna in order to measure the direction of the target by using sum-delta monopulse technique. The most common way if the target is located within the main-lobe is to compare the amplitude of the sum channel received signal with the delta channel received signal. However, in the case of the single-ring circular array antenna, it is difficult to apply the conventional method due to its structural limitation where antenna elements do not exist in the center of the array. In this paper, we proposed a novel method to identify whether a target is located within the main-lobe by appropriately adjusting the feeding amplitude of each element constituting the single-ring circular array antenna through the particle swarm optimization method. Simulation results showed that the proposed method can determine whether the target is located within the main-lobe of the single-ring circular array antenna.

Photonic Radio Frequency Orbital Angular Momentum Generation and Beam Steering

Orbital angular momentum (OAM) is a fundamental property of electromagnetic waves and is inherently carried by all frequencies of waves. In particular, OAM applications at radio frequencies (RFs) have attracted much attention due to their unique functionalities in communications. Enabled by the present wireless communication system, employing a circular antenna array (CAA) is a highly compatible and cost-effective approach for generating RF-OAM beams. In this paper, recent progress on RF-OAM communication systems with CAAs from the transceiver to the controller is summarized. A new scheme for RF-OAM generation and beam steering systems is proposed based on dual-wavelength control using CAA with the energy-conserved feature, where an integrated chip incorporating an arrayed waveguide grating (AWG) structure is introduced. Either microwave photonic phase shift or optical true time delay (OTTD) can be operated by this chip, benefiting from the phase amplification concept and the design of delay channels. Utilizing their combination, RF-OAM beams with arbitrary OAM states can be achieved for multiplexing and steered simultaneously. Furthermore, RF-OAM beam steering can be achieved without distortion in the desired transmission direction. This photonics-assisted method with an integrated chip is a potential strategy for improving the signal quality and reducing the system complexity of RF-OAM transmission systems.

Impact of antenna directivity on compressed sensing-based DOA estimation employing UCA antenna

This letter investigates the impact of the antenna element directivity on compressed sensing (CS)-based direction of arrival (DOA) estimation employing the uniform circular array (UCA) antenna. In the CS-based approach, the reconstruction accuracy of sparse signals is determined by a sensing matrix, which depends on the array antenna configuration in the DOA estimation. In our study, we analyze the cross-correlation between column vectors of the sensing matrix and clarify the estimation accuracy for various antenna element radiation patterns.

Design and Analysis of 1x4 and 1x8 Circular Patch Microstrip Antenna Array for IWSN Application

A 1x4 and 1x8 circular micro strip patch antenna array operating at 2.4GHz are simulated for Industrial Wireless Sensor Network (IWSN) applications using CST studio suite and MATLAB based simulator software. The circular patch antenna designed on a FR4 substrate with dielectric constant of 4.4 and a substrate height of 1.6mm is fed using inset-fed technique. Several antenna characteristics such as return loss, radiation pattern, bandwidth, directivity, antenna gain, radiation efficiency isanalyzed. The compact size and higher directivity help to improve the network performance by alleviating contention, increasing communication range, and mitigating interference of the system. Hence, the advantages gained, make the system more useful for IWSN applications as achieved in this research

Synthesis of Reconfigurable Multiple Shaped Beams of a Concentric Circular Ring Array Antenna Using Evolutionary Algorithms

The approach described in this paper uses evolutionary algorithms to create multiple-beam patterns for a concentric circular ring array (CCRA) of isotropic antennas using a common set of array excitation amplitudes. The flat top, cosec2, and pencil beam patterns are examples of multiple-beam patterns. All of these designs have an upward angle of θ = 0◦. All the patterns are further created in three azimuth planes (φ = 0◦, 5◦, and 10◦). To create the necessary patterns, non-uniform excitations are used in combination with evenly spaced isotropic components. For the flat top and cosecant-squared patterns, the best combination of common components, amplitude and various phases is applied, whereas the pencil beam pattern is produced using the common amplitude only. Differential evolutionary algorithm (DE), genetic algorithm (GA), and firefly algorithm (FA) are used to generate the best 4-bit discrete magnitudes and 5-bit discrete phases. These discrete excitations aid in lowering the feed network design complexity and the dynamic range ratio (DRR). A variety of randomly selected azimuth planes are used to verify the excitations as well. With small modifications in the desired parameters, the patterns are formed using the same excitation. The results proved both the efficacy of the suggested strategy and the dominance of DE over GA as well as FA.

Design of Linear and Circular Antenna Arrays for Side Lobe Reduction Using a Novel Modified Sparrow Search Algorithm

Design of Linear and Circular Antenna Arrays for Side Lobe Reduction Using a Novel Modified Sparrow Search Algorithm

Smart Gateway for Healthcare Networks Based on Beam Steering Technology

To ensure high-reliability communication in healthcare networks, this paper presents a smart gateway system that includes an angle-of-arrival (AOA) estimation and a beam steering function for a small circular antenna array. To form a beam toward healthcare sensors, the proposed antenna estimates the direction of the sensors utilizing the radio-frequency-based interferometric monopulse technique. The fabricated antenna was assessed based on the measurements of complex directivity and the over-the-air (OTA) testing in Rice propagation environments using a two-dimensional fading emulator. The measurement results reveal that the accuracy of the AOA estimation agrees well with that of the analytical data obtained through the Monte Carlo simulation. This antenna is embedded with a beam steering function employing phased array technology, which can form a beam spaced at 45° intervals. The ability of full-azimuth beam steering with regard to the proposed antenna was evaluated by beam propagation experiments using a human phantom in an indoor environment. The received signal of the proposed antenna with beam steering increases more than that of a conventional dipole antenna, confirming that the developed antenna has great potential of achieving high-reliability communication in a healthcare network.

Direct Adaption Methods for Linear and Circular Antenna Arrays

Introduction. The mitigation of interferences that degrade the performance of navigation systems constitutes one of the most significant problems of contemporary satellite navigation. This problem is conventionally solved using digital adaptive space filters. Depending on a particular radio technical system, the mathematical description of digital signal processing methods may involve specific calculation structures implemented using specific calculation algorithms. For example, the use of centrosymmetric linear and circular antenna arrays in a radio navigation system allows the description of such systems in terms of Toeplitz and circulant sample covariance matrices, respectively, and the inversion of such matrices by means of special numerical methods in order to design a digital filter.Aim. A comparative analysis of the performance of space signal processing algorithms is carried out along with an estimation of Toeplitz and circulant sample covariance matrices and numerical methods of their inversion. The previously obtained results in this field are clarified.Materials and methods. An analysis of algorithm performance was carried out in the MATLAB environment using experimental recordings of satellite navigation signals and jammers obtained by an actual radio technical system.Results. A new expression was derived for estimating circulant sample covariance matrices. Formulae that describe a modification of the Bareiss numerical Toeplitz matrix inversion algorithm for the case of complex Hermitian matrix were introduced. An analysis of the results of computer simulation allowed the algorithms with the highest performance to be indicated. The amount of time taken by the algorithms based on Toeplitz and circulant matrices did not exceed 2.5 10⋅ −3 s and 0.04 s, respectively. The carrier-to-noise ratio in the processed signal was at least 46 dB. Conclusion. The formulae obtained and the algorithms analyzed can be used when implementing adaptive digital filtering of satellite navigation signals.

Reducing the Mutual Coupling of Cylindrical Circular Microstrip Antennas (CCMAs) Array Using EBG Structure

A theoretical study to design a conformal microstrip antennas was introduced in this work. Conformal microstrip antennas define antennas which can be conformed to a certain shape or to any curved surface. It is used in high-speed trains, aircraft, defense and navigation systems, landing gear and various communications systems, as well as in body wearable. Conformal antennas have some advantages such as a wider-angle coverage compared to flat antennas and low radar cross-sectional (RCS) and they are suitable for using in Radome. The main disadvantage of these antennas is the narrow bandwidth. The FDTD method is extremely useful in simulating complicated structures because it allows for direct integration of Maxwell's equations depending on time. The 1x2 cylindrical circular microstrip antennas array is designed and simulated vertically via Finite Difference Time Domain (FDTD) method where can directive antenna be achieved through antennas array design. Mutual coupling between the antennas in the array and the different separation between them were studied. The circular patch is excited by a probe feed method for several reasons including providing less spurious radiation from the probe current, in addition to the simplicity in theoretical engineering installation and practical manufacturing. It is well known that the values of the coupling are decreased as the distance separation increased. Cylindrical circular microstrip antenna with resonant frequency operating is 3.5GHz for mode, several parameters like return loss, band width, and input impedance are calculated. Also, for isolated coupling, mutual coupling coefficients, directivity gain, for different separations between the centers of the two adjacent circular patches in terms the wave length operating are calculated. Moreover, the electromagnetic band gap EBG structure is used for reducing the mutual coupling created by the surface waves in order to enhance the antenna's performance in an array has become smaller than before. The proposed EBG is a three triangular-shape equal sides metallic structure, utilizing the inter-element spacing in an array. The less value of for the spacing between the two centers of patches is . BW percentage increased to 34.3% and the directivity is enhanced also. Additionally, simulations were done using MATLAB 2017b.

Retracted: Design and Performance Evaluation of OAM-Antennas: A Comparative Review

For many communication systems, including wireless networks, mobile, satellite, radar, remote sensing, and many more applications, antenna arrays are very necessary. Utilizing effective beamforming techniques, antenna arrays have recently played a major part in driving data rates and system capacity to extremely high levels. The beamforming capabilities and system performance are both greatly influenced by the array configuration. Numerous array structures, including linear, two-dimensional, circular, conical, cylindrical, spherical, and even non-uniform array shapes, can be used in different applications. Modern communication systems pay a lot of attention to reconfigurable antennas because of the many applications they may serve and the added functionality they provide. A single structure that has the ability to change between one or a number of features, such as frequency, pattern, and polarization, is referred to as a reconfigurable antenna. Utilizing a specific circular phased microstrip antenna array, the orbital angular moment (OAM) vortex electromagnetic wave is created, allowing for more effective and dependable data transmission. When propagating, the vortex electromagnetic wave has a spiral phase wavefront structure, and its many OAM modes are orthogonal to one another. The helical antenna offers the benefits of light weight, small size, and excellent circular polarization when compared to other OAM radio producing techniques. This paper reviews various state-of-the-art antennas for 5G applications. Specifically, the single microstrip, array, traveling wave and metasurface antennas have been discussed and their important aspects were elaborated. Finally, the applications and future prospects were described.

Design of Multiband Fractal Antenna Array for Wireless Communication

This work proposes a modified circular fractal antenna array for multiband applications, including WLAN (5.15–5.85 GHz), C-band applications (3.8–4.4 GHz), and X-band for satellite communication (7.1–7.76 GHz). High Frequency Structure Simulator (HFSS) is used to simulate the antenna. The substrate material is FR4 epoxy, which has a 4.4 relative permittivity and 1.6 mm of thickness. It is discovered that the antenna only covers a portion of the bandwidth of the aforementioned applications.

Sustainable Design of Multiband Antenna for Wireless Communication Applications

This work emphasises sustainability as a crucial component of the design process and offers a novel approach to antenna design. A miniature circular microstrip antenna array with 1800 hybrid coupler operating at different modes of frequency, specifically aiming for multiband wireless communication is presented. The Circular patch, two element broad side array and end fire array structures are designed and analysed by using High Frequency Software Simulator (HFSS) software. Measured results are also presented for validating the simulated results.

Generation of OAM Waves and Analysis of Mode Purity for�G燬ub-6燝Hz燗pplications

This article presents the generation of Orbital Angular Momentum (OAM) vortex waves with mode 1 using Uniform Circular Array (UCA) antenna. Two different designs, namely, UCA-1 (4-element array antenna) and UCA-2 (8-element array antenna), were designed and fabricated using FR-4 substrate to generate OAM mode 1 at 3.5 GHz (5G mid-band). The proposed antenna arrays comprised rectangular microstrip patch elements with inset fed technique. The elements were excited by a carefully designed feeding phase shift network to provide similar output energy at output ports with desired phase shift value. The generated OAM waves were confirmed by measuring the null in the bore sight of their 2D radiation patterns, simulated phase distribution and intensity distribution. The measurement results agree well with the simulation results. Moreover, a detailed mode purity analysis of the generated OAM waves was carried out considering different factors. The investigation found that the greater the number of elements, the higher the purity of the generated OAM wave. Compared with other previous works, the proposed antenna design of this paper is very simple to design and fabricate. In addition, the proposed antennas are compact in design even at lower frequency band with very wide bandwidth to meet the requirements of 5G mid-band applications.

MIMO Antenna Array in 5G Communication

The main topics of this study are the fundamental operation of a MIMO antenna array and the benefits of using MIMO technology for 5G communication. Three significant works are recognized as benchmarks by outlining the component sets and spatial reuse that designers should consider in MIMO antenna design. For 5G low and medium frequencies, these include an 8x8 large-scale MIMO antenna array and a circular binary MIMO antenna array. In these designs, the design of the MIMO antenna array will be carried out based on the introduction of the design and parameter selection of the antenna array elements as a priority. Additionally, this study conducts a performance analysis of a multi-cell, Massive MIMO antenna array system, which serves as a high reference point for the Analysis of this system. Numerous possible application domains exist for the study object of this work, including hotspot situations and 3D coverage scenarios. Campus, shopping malls, and halls are examples of hotspot environments.