Beam Coverage Research Articles

Exploring physical layer security in underwater optical wireless communication: A concise overview

Underwater wireless optical communications are a developing alternative to meet the increasing need for high-speed connections in oceans and seas. Optical wireless communications (OWCs) are more secure and less susceptible to eavesdropping compared to acoustic communications or radio frequency (RF) communications due to their narrow optical beam coverage and reliance on line-of-sight components. Nevertheless, the existence of a hostile eavesdropper can compromise the level of confidentiality achieved by OWC networks. This article provides a concise overview of the latest research conducted on physical layer security (PLS) in underwater optical wireless communication (UOWC). Furthermore, this work presents the relevant unresolved matters, approaches for enhancing secrecy performance, and potential areas for further research.

A single-feed circularly polarized antenna with a low vertical profile and hemispherical axial-ratio beam coverage

ABSTRACT A novel wide axial-ratio beamwidth (ARBW) circularly polarized (CP) antenna with a single layer substrate fed by a single probe is proposed. It consists of an inner annular slotted radiator containing eight outer sector units with arc branches, a ground plane, and eight grounded vias. The antenna has an ARBW covering the upper hemisphere and has a low vertical profile. The ultra-hemispherical ARBW is formed by ingeniously merging the endfire omnidirectional CP radiation pattern with the boresight CP radiation pattern. The two radiation patterns can be excited by a central coaxial probe without an additional feeding network. An antenna prototype of dimensions 1.15 × 1.15 × 0.02 (λ 0 3) is fabricated and measured to validate the design concept. Measured results show that the impedance bandwidth of the proposed antenna is 2.0% (3.328–3.394 GHz) and the 3 dB axial ratio (AR) bandwidth is 1.3% (3.332–3.374 GHz). The 3 dB AR beamwidth can cover more than 217° and the maximum gain is 0.79 dBic at 3.35 GHz. A good agreement between the simulated and measured results is obtained.

AcpAS: An Advanced Circularly Polarized Antenna Structure for an Airborne Relay Communication System

The airborne relay system is an important support for improving the stability of communication systems in complex electromagnetic environments. As a key component of the airborne relay system, the antenna needs to have characteristics such as high gain, dual circular polarization, wide beam coverage, and miniaturization. Based on the septum circular polarizer, this paper proposes a high-performance circularly polarized antenna structure suitable for airborne relay systems, named AcpAS. The structure consists of a coaxial feed port, a coaxial-to-waveguide transition, a septum circular polarizer, and a parabolic metal housing. Based on this structure, two antennas operating at 19.6 GHz to 21.6 GHz and 29.2 GHz to 31.2 GHz are designed in this paper. Simulated and measured results show that the two antennas have dual circular polarization characteristics, with beam coverage range of more than ±55° for gains higher than 0 dBi, and the radiation patterns exhibit good symmetry and wide-beam coverage characteristics.

Deep-learning-based speech enhancement under rough-focus conditions with optical laser microphone

Optical laser microphones have attracted attention for acoustic systems capable of recording the target speech from a distance. An optical laser microphone measures the speech-induced vibration by focusing the laser beam on the surface of the vibrating object. A recording method called rough-focus recording using an unfocused laser beam, enables wide-range recording and robust recording against changes in focal length. However, with rough-focus recording, the broad laser beam coverage leads to insufficient intensity of the reflected laser for accurate acoustical signal measurement, resulting in speech-quality degradation, such as the inclusion of noise, and attenuation of high-frequency components in the acquired speech. To solve this problem, deep-learning-based speech-enhancement methods for optical laser microphones have been proposed. Such methods require separate models for different focus settings, exhibiting a lack of adaptability to changing focus settings. We propose a speech-enhancement method for training a single model for various focus settings. This model is trained with speech signals recorded across different focus settings to enhance speech recorded in various focus settings. Experimental results indicate that the this model trained with the proposed method performs equivalent to or better than a model trained with the conventional models.

Isolation enhancement of a capacitively-fed MIMO antenna using a quasi-fractal parasitic element and defected ground structure

Vehicular Internet of Things (IoT) is facilitated by efficient RF front ends with suppressed mutual coupling for enhanced spatial diversity and increased channel capacity. This paper presents a mutual coupling suppressed MIMO antenna with a hybrid decoupling technique for Vehicle-to-Everything (V2X) communications, enabling IoT in automotive systems. The single elements consist of a radiating patch with a cleaving circular slot to introduce a capacitive effect on the radiating structure. Afterwards, the single-unit design is further extrapolated to a 2 × 2 MIMO antenna. The mutual coupling is suppressed between antenna elements by introducing a quasi-fractal parasitic element and a defected ground structure (DGS). The MIMO antenna is designed to conform to the requirements posed by V2X systems in Dedicated Short-Range Communications (DSRC) and Intelligent transportation system (ITS) scenarios. The proposed MIMO antenna offers measured |S11| < −10 dB of 200 MHz, ranging from 5.77 GHz to 5.97 GHz, fully covering the spectrum guided by the IEEE 802.11p standard. A physical prototype is fabricated and placed on a car roof to assess the congruency between measured and simulated results. The MIMO antenna exhibits exceptional diversity properties, such as enhanced isolation (>28 dB) between its individual elements, a diversity gain (DG) close to the ideal value of 10 dB (9.99 dB), peak realized gain of 6.5 dBi, an ECC below 0.001, and a beam coverage area of 180° in azimuthal and elevation plane by dynamic port switching. Thus, the proposed MIMO antenna module is a considerable candidate for future V2X communication paradigms.

Multi-Satellite Cooperative Load-Balancing Scheme Based on Dynamic Beam Coverage for LEO Beam Hopping Systems

Multi-Satellite Cooperative Load-Balancing Scheme Based on Dynamic Beam Coverage for LEO Beam Hopping Systems

A Balloon Conformal Heterogeneous Array Antenna with Ultrawide Bandwidth and Half-Space Beam Coverage

A Balloon Conformal Heterogeneous Array Antenna with Ultrawide Bandwidth and Half-Space Beam Coverage

Low-profile, low sidelobe array antenna with ultrawide beam coverage for UAV communication

This paper presents a design method to implement an antenna array characterized by ultra-wide beam coverage, low profile, and low Sidelobe Level (SLL) for the application of Unmanned Aerial Vehicle (UAV) air-to-ground communication. The array consists of ten broadside-radiating, ultrawide-beamwidth elements that are cascaded by a central-symmetry series-fed network with tapered currents following Dolph-Chebyshev distribution to provide low SLL. First, an innovative design of end-fire Huygens source antenna that is compatible with metal ground is presented. A low-profile, half-mode Microstrip Patch Antenna (MPA) is utilized to serve as the magnetic dipole and a monopole is utilized to serves as the electric dipole, constructing the compact, end-fire, grounded Huygens source antenna. Then, two opposite-oriented end-fire Huygens source antennas are seamlessly integrated into a single antenna element in the form of monopole-loaded MPA to accomplish the ultrawide, broadside-radiating beam. Particular consideration has been applied into the design of series-fed network as well as antenna element to compensate the adverse coupling effects between elements on the radiation performance. Experiment indicates an ultrawide Half-Power Beamwidth (HPBW) of 161° and a low SLL of −25 dB with a high gain of 12 dBi under a single-layer configuration. The concurrent ultrawide beamwidth and low SLL make it particularly attractive for applications of UAV air-to-ground communication.

Design of an ultrabroadband and compact H‐plane sectoral ridged horn‐reflector array

AbstractIn this paper, an ultrabroadband linear array in which horn‐reflector antennas are used as radiating elements by adding a central ridge to the rectangular waveguide, leading to an increased bandwidth of 3:1. With a reflector embedded in the H‐plane sectoral ridged horn, a desired narrow beam can be easily achieved. Moreover, due to the compact enclosed structure, the proposed reflector array can not only eliminate the illumination loss but also significantly reduce size compared with those of conventional array‐fed parabolic cylinder antennas. Good agreement between the calculated and measured results is obtained, showing that the proposed antenna array has a high aperture efficiency of about 80%, a ±45° scanning range in the E‐plane and 5° beam coverage with low side lobes in the H‐plane within the frequency range of 6–18 GHz.

Joint beam power and pointing management in multi‐beam low earth orbit and low earth orbit co‐existing satellite system

SummaryRecently, the low earth orbit (LEO) satellite has attracted much attention due to its advantages of low latency and construction costs. However, the scarcity of frequency spectrum resources has resulted in these satellites sharing the same spectrum to provide services for ground users. So, challenges such as overlapping beam coverage and inter‐beam interference occur in the multi‐beam LEO satellite coexistence scenario. Therefore, this paper focuses on the issue of interference coexistence in LEO and LEO (LEO–LEO) co‐existing scenario, where the initially established system is the primary system, and the later established system is the secondary system. The interference coexistence problem is modeled as a multi‐objective optimization problem. The joint beam power and pointing management (JBPPM) based on particle swarm optimization (PSO) is proposed. The power control is applied to the LEO satellites in the secondary system to reduce the interference to the primary system user. Meanwhile, beam pointing optimization is adopted by the LEO users in the secondary system to avoid interference from the primary system and ensure the minimum communication ability. The simulation results verify that the proposed technique can adapt to various coexistence conditions and outperform the existing method.

Reviewing the application of big data analytics in satellite network management to optimize performance and enhance reliability, with implications for future technology developments

The application of big data analytics in satellite network management has emerged as a transformative approach to optimize performance and enhance reliability in the satellite telecommunications industry. This paper reviews the current state of big data analytics in satellite network management, highlighting its key applications and benefits. By analyzing large volumes of data generated by satellite networks, big data analytics enables satellite telecommunications companies to gain valuable insights into network performance, identify potential issues, and take proactive measures to ensure optimal performance. One of the key applications of big data analytics in satellite network management is predictive maintenance. By analyzing historical data and equipment performance metrics, companies can predict when equipment is likely to fail and take preventive measures to avoid downtime. This not only improves network reliability but also reduces maintenance costs and improves overall operational efficiency. Another important application is network optimization. Big data analytics can analyze network traffic, weather conditions, and other factors to optimize satellite beam coverage, frequency allocation, and routing. This helps companies maximize bandwidth utilization, reduce interference, and improve service quality. The implications of big data analytics for future technology developments in satellite network management are significant. As the volume of data generated by satellite networks continues to grow, there is a need for advanced analytics tools and techniques to process and analyze this data efficiently. Future technology developments in areas such as AI, machine learning, and data visualization are expected to play a key role in enhancing the capabilities of big data analytics in satellite network management. In conclusion, the application of big data analytics in satellite network management offers significant benefits in terms of optimizing performance and enhancing reliability. By leveraging the insights provided by big data analytics, satellite telecommunications companies can improve operational efficiency, reduce costs, and deliver better services to their customers. Future technology developments will further enhance the capabilities of big data analytics, paving the way for more efficient and reliable satellite network management.

Dual-Band and Dual-Polarized Shared-Aperture Phased-Array Antennas With Enhanced Beam Coverage for 5G FR2 and 6G FR3

Dual-Band and Dual-Polarized Shared-Aperture Phased-Array Antennas With Enhanced Beam Coverage for 5G FR2 and 6G FR3

Validation of Optimal Imaging Conditions for Coronary Computed Tomography Angiography Using High-definition Mode and Deep Learning Image Reconstruction Algorithm

To verify the optimal imaging conditions for coronary computed tomography angiography (CCTA) examinations when using high-definition (HD) mode and deep learning image reconstruction (DLIR) in combination. A chest phantom and an in-house phantom using 3D printer were scanned with a 256-row detector CT scanner. The scan parameters were as follows - acquisition mode: ON (HD mode) and OFF (normal resolution [NR] mode), rotation time: 0.28 s/rotation, beam coverage width: 160 mm, and the radiation dose was adjusted based on CT-AEC. Image reconstruction was performed using ASiR-V (Hybrid-IR), TrueFidelity Image (DLIR), and HD-Standard (HD mode) and Standard (NR mode) reconstruction kernels. The task-based transfer function (TTF) and noise power spectrum (NPS) were measured for image evaluation, and the detectability index (d') was calculated. Visual evaluation was also performed on an in-house coronary phantom. The in-plane TTF was better for the HD mode than for the NR mode, while the z-axis TTF was lower for DLIR than for Hybrid-IR. The NPS values in the high-frequency region were higher for the HD mode compared to those for the NR mode, and the NPS was lower for DLIR than for Hybrid-IR. The combination of HD mode and DLIR showed the best value for in-plane d', whereas the combination of NR mode and DLIR showed the best value for z-axis d'. In the visual evaluation, the combination of NR mode and DLIR showed the best values from a noise index of 45 HU. The optimal combination of HD mode and DLIR depends on the image noise level, and the combination of NR mode and DLIR was the best imaging condition under noisy conditions.

A Low-Profile Circularly Polarized Antenna with Hemispherical Axial-Ratio Beam Coverage by DualMode Radiation Patterns Merging

A Low-Profile Circularly Polarized Antenna with Hemispherical Axial-Ratio Beam Coverage by DualMode Radiation Patterns Merging

Modeling and Analysis of Air-Ground Integrated Networks With Flexible Beam Coverage

Air platforms, such as unmanned aerial vehicles, airships, and balloons are expected to complement traditional ground networks to provide flexible coverage solutions. However, most existing models for air-ground integrated networks (AGINs) neglect the spatial dependence caused by the complementary deployment of the aerial and ground nodes. Accordingly, in this paper, we propose two AGIN models with horizontal dependence that differ in the vertical dimension, namely uniformly independent altitudes and location-dependent altitudes. The air platforms serve as aerial base stations, distributed as a marked Poisson hole process, and provide flexible beam coverage through varying altitudes. Under this setup, we propose a region-based user association scheme and derive the association probabilities as well as the serving distance distributions of an arbitrarily located user. Considering Nakagami fading and air-to-ground propagation properties, we characterize the signal-to-interference ratio and area spectral efficiency for each model. Using the proposed analytical framework, we demonstrate the importance of deploying the air platforms more sensibly to provide targeted services and flexible beam coverage in reducing the load of base stations and improving the user coverage and network capacity performance.

Interference analysis between NGSO systems based on the beam coverage and link angle

The existing interference assessment methods usually consider the special scenario of earth station coincidence. However, in practice, earth stations such as gate stations are sparsely distributed and often do not coincide. Aiming at the problem of how to efficiently calculate the co-frequency interference between Non-Geostationary Satellite Orbit (NGSO) systems with high complexity and a large amount of data, the influencing factors of interference scenes between NGSO systems with non-earth station coincidence are analyzed. The time-varying expression of the bit error rate (BER) of the interference evaluation index to measure the system performance is derived. An interference analysis method based on the beam coverage and link angle is proposed. In this method, four interference time-varying parameters are reduced to two. One of them is associated with the distance between earth stations, which is used to rapidly evaluate the probability of harmful interference between NGSO systems. It provides a reference for the construction of the spacing of earth stations.

Dual-Polarized Conformal Transparent Antenna Array With Hemispherical Beam Coverage

Dual-Polarized Conformal Transparent Antenna Array With Hemispherical Beam Coverage

Adaptive Beam Alignment and Optimization for IRS-Aided High-Speed UAV Communications

In the unmanned aerial vehicle (UAV) enabled wireless communication system, the rapid channel change caused by high-speed UAV may cause the beam misalignment problem. It is a challenge to fast establish and maintain the communications link between UAV and ground base stations. To address this challenge, an IRS-aided high-speed UAV adaptive beam alignment (IRS-UAV-ABA) scheme utilizing double-layer long short-term memory (DL-LSTM) spatial angle prediction model is proposed to improve the effectiveness and reliability of the UAV communication. Firstly, DL-LSTM enabled spatial angle prediction is modeled to facilitate the calculation of the beam coverage adapted to the UAV real-time flight trajectory. Secondly, the non-convex optimization problem for maximizing the received signal-to-noise ratio of moving UAV is formulated to obtain the suboptimal solutions of the BS’ beamforming vector and the IRS’ phase shift matrix. Finally, with the aforementioned beamforming vectors, the phase shift matrix and the adaptive beam coverage, the adaptive dual-beams alignment from BS to UAV and from IRS to UAV can be achieved by the proposed DL-LSTM-enabled IRS-UAV-ABA algorithm. Simulation results verify that the proposed scheme not only can effectively avoid the beam misalignment caused by the mobility and perturbation of UAV, but also has superior spectrum efficiency and stable beamforming gain.

Independently Polarization Manipulable Liquid- Crystal -Based Reflective Metasurface for 5G Reflectarray and Reconfigurable Intelligent Surface

This study presents a new class of independently polarization manipulable liquid-crystal (LC)-based reflective metasurface antenna. To the best of the authors’ knowledge, this study first introduces independent polarization controllability of the LC-based reflective metasurface in mmWave. Two LC layers are embedded into the proposed structure for independent manipulation of the polarization. Isolation topologies, such as rectangular patch shape and metal strip ground, are utilized to enhance polarization purity, achieving compact bias configuration. The independent polarization controllability and antenna performance, such as aperture efficiency, sidelobe level, and beam coverage, are validated as a reflectarray. The proposed antenna has a maximum aperture efficiency of 22.5% and beam coverage of over 120°. In addition, the proposed metasurface is employed to achieve link connectivity as a reconfigurable intelligent surface (RIS) at millimeter-wave 5G. The demonstration confirms a small aperture RIS concept, considering spillover and taper efficiencies.

Low-Profile Multibeam Antenna Based on Modulated Metasurface

Linearly polarized (LP) multi-port multi-beam antennas (MBAs) based on modulated metasurface (MTS) are presented in this paper. A key challenge for MTS to generate multiple independent beams is the mutual interference of different impedance modulations. This interference can lead to reduced directivities of main beams and high side lobe levels (SLLs). A full-wave based optimization for a large number of beams is significantly time consuming and practically ineffective. The source locations are optimized here by employing the aperture field calculated from a zeroth-order approximation (ZOA) of the currents on the surface. This provides a good preliminary accuracy without any full-wave analysis. The relevant design method is verified by two examples of 3-beam and 7-beam MTS antennas. Furthermore, the 7-beam MTS antenna is fabricated and successfully measured. The measurements show a measured realized gain of 20 dBi at 14.10 GHz with a beam coverage (10-dB overlap) up to ±36°. It is seen that the same performance requires larger areas with conventional summation of apertures.