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26 pages, 5101 KiB

Open AccessArticle

Federated Learning Augmented Cybersecurity for SDN-Based Aeronautical Communication Network

by Muhammad Ali, Yim-Fun Hu and Jian-Ping Li

Electronics 2025, 14(8), 1535; https://doi.org/10.3390/electronics14081535 - 10 Apr 2025

Viewed by 299

Abstract

With the requirements of government data protection regulations and industrial concerns regarding data protection and privacy, the security level required for data privacy and protection has increased. This has led researchers to investigate techniques that can train cybersecurity machine learning (ML) models without [...] Read more.

With the requirements of government data protection regulations and industrial concerns regarding data protection and privacy, the security level required for data privacy and protection has increased. This has led researchers to investigate techniques that can train cybersecurity machine learning (ML) models without sharing personal data. Federated Learning (FL) is a newly developed decentralized and distributed ML mechanism that emphasize privacy. In this technique, a learning algorithm is trained without collecting or exchanging sensitive data from distributed client models running at different locations. With the rapid increase in the number of cybersecurity attacks reported in the aviation industry in the last two decades, strong, dynamic, and effective countermeasures are required to protect the aviation industry and air passengers against such attacks, which can most of the time lead to catastrophic situations. This paper proposes and implements an FL model for identifying cyberattacks on a Software Defined Network (SDN)-based aeronautical communication networks. The machine learning model used in the FL architecture is a Deep Neural Network (DNN) model. The publicly available National Security Laboratory–Knowledge Discovery and Datamining (NSL-KDD) dataset was employed to train and validate the proposed FL model. The simulation results illustrated that the FL-based system can accurately and effectively identify potential cybersecurity attacks and minimize the risk of data and service exposure without degrading model performance. A comparison was also made between the FL and non-FL machine learning models. Preliminary results demonstrated that the FL model outperformed the non-FL machine learning approaches. FL reached an accuracy of 96%, compared to 76% and 83% for NFL. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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18 pages, 3238 KiB

Open AccessArticle

Multilayer Printed Circuit Board Design Based on Copper Paste Sintering Technology for Satellite Communication Receiving Phased Array

by Sicheng Sun, Yijiu Zhao, Sitao Mei, Naixin Zhou and Yongling Ban

Electronics 2025, 14(2), 322; https://doi.org/10.3390/electronics14020322 - 15 Jan 2025

Viewed by 785

Abstract

A 2048-element dual-polarized receive (RX) phased array for

K u

-band (10.7–12.7 GHz) satellite communication (SATCOM) is presented in this paper. The design of the multilayer printed circuit board (PCB) it uses adopts a novel copper paste sintering interconnection technology that allows for [...] Read more.

A 2048-element dual-polarized receive (RX) phased array for

K u

-band (10.7–12.7 GHz) satellite communication (SATCOM) is presented in this paper. The design of the multilayer printed circuit board (PCB) it uses adopts a novel copper paste sintering interconnection technology that allows for more flexibility in the design of vias and can reduce the PCB’s lamination number. This technology is more suitable for manufacturing multilayer and complex PCBs than traditional processes. The array is designed to consist of sixteen 8 × 16 element subarrays, each based on the silicon RX beamformer and multilayer PCB. Dual-polarized antenna elements are arranged in a regular rectangle with a spacing of 0.5 for a wavelength of 12.7 GHz, thus achieving a scanning range of ±70° in all planes. By adjusting the amplitude and phase of two line polarizations with cross-polarization levels better than −25 dB at boresight, the array can generate linear or circular polarization. Moreover, the antenna gain-to-noise temperature is above 12 dB/K (

T_{ant}

= 20 K) at boresight. The aperture of the 2048-element RX phased array is 768 × 450 mm. With its low profile, the array is appropriate for usage in

K u

-band SATCOM terminals. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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8 pages, 1529 KiB

Open AccessArticle

Double Resonance of Electromagnetically Induced Transparency of Rydberg Atom in Counter-Propagating Configuration

by Chao Li, Guo Ma, Mingwei Lei and Meng Shi

Electronics 2024, 13(22), 4391; https://doi.org/10.3390/electronics13224391 - 8 Nov 2024

Viewed by 705

Abstract

The double resonance phenomenon of EIT is studied through the ladder three-level Rydberg system. A probe laser with the wavelength

λ_{p} = 852.35

nm is used to coupling the ground state 6S_1/2 to the middle state 6P_3/2, and a [...] Read more.

The double resonance phenomenon of EIT is studied through the ladder three-level Rydberg system. A probe laser with the wavelength

λ_{p} = 852.35

nm is used to coupling the ground state 6S_1/2 to the middle state 6P_3/2, and a coupling laser with the wavelength

λ_{c} = 509.08

nm is implemented to couple the state 6P_3/2 to the Rydberg state 62D_5/2. A special optical scheme is designed, in which the co-propagating and counter-propagating configurations are both used. As a result, the double resonance of electromagnetically induced transparency (EIT) with the Rydberg atom is observed. By comparing the distance between the double peaks, it is found that the double resonance phenomenon comes from the Doppler effect, and the distance between the two resonance peaks in the absorption spectrum is related to the detuning of the resonant lasers. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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15 pages, 20922 KiB

Open AccessArticle

A Versatile Shared-Aperture Antenna for Vehicle Communications

by Mingtang Li, Yihong Su, Wenxin Zhang and Xianqi Lin

Electronics 2024, 13(20), 4009; https://doi.org/10.3390/electronics13204009 - 12 Oct 2024

Cited by 1 | Viewed by 1124

Abstract

This communication introduces a versatile, multi-service, shared-aperture antenna system for multiple vehicle applications. The design comprises three antenna elements: a rotatable microstrip antenna for global positioning system (GPS) communication, a cross-dipole circularly polarized antenna for satellite communication in the S-band, and a pattern [...] Read more.

This communication introduces a versatile, multi-service, shared-aperture antenna system for multiple vehicle applications. The design comprises three antenna elements: a rotatable microstrip antenna for global positioning system (GPS) communication, a cross-dipole circularly polarized antenna for satellite communication in the S-band, and a pattern reconfigurable antenna for V2V (vehicle-to-vehicle) communication. These antennas collectively support GPS, satellite communication (Satcom), and V2V communication in a single, shared-aperture design. This shared-aperture antenna system offers cost savings and occupies less space compared to using separate antennas for each service. The microstrip antenna covers the 1575 MHz frequency band used for GPS communication. The cross-dipole circularly polarized antenna provides continuous wideband coverage for S-band satellite communication. The pattern reconfigurable antenna, tailored for the specific application scenario, covers the 5.9 GHz V2V working frequency band (5.855–5.925 GHz). Practical testing and simulation results confirm the effectiveness of this antenna system for the intended applications. In summary, the microstrip antenna has a bandwidth of 1.565–1.578 GHz and a realized gain of 7 dBi with radiation efficiency of 81%, the cross-dipole antenna has a bandwidth of 2.2–3.8 GHz (53.3%) and a realized gain of 8.3 dBi with radiation efficiency of 90%, and the pattern reconfigurable antenna has a 5.8–6 GHz bandwidth and a realized gain of 3.7 dBi with radiation efficiency of 85%, and the isolation between antennas with different frequencies is 25 dB, 20 dB, and 30 dB in three frequency bands. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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12 pages, 2566 KiB

Open AccessArticle

A Wideband Polarization-Reconfigurable Antenna Based on Fusion of TM₁₀ and Transformed-TM₂₀ Mode

by Xianjing Yuan, Siyuan Zheng, Binyun Yan and Weixing Sheng

Electronics 2024, 13(18), 3760; https://doi.org/10.3390/electronics13183760 - 22 Sep 2024

Viewed by 1011

Abstract

A wideband polarization-reconfigurable microstrip antenna based on a mode-fusion mechanism is proposed. This simple antenna structure consists of a rectangular radiation patch and a ground, both with crossed slots. The slots crossing the ground are connected by eight PIN diodes and four capacitors [...] Read more.

A wideband polarization-reconfigurable microstrip antenna based on a mode-fusion mechanism is proposed. This simple antenna structure consists of a rectangular radiation patch and a ground, both with crossed slots. The slots crossing the ground are connected by eight PIN diodes and four capacitors such that two orthogonal linear-polarization radiation modes can be realized. The radiation patch is slotted such that a transformed

{TM}_{20}

mode is excited, realizing broadside radiation that the traditional

{TM}_{20}

mode is unable to. With fusion of the fundamental

{TM}_{10}

mode and the transformed-

{TM}_{20}

(T-

{TM}_{20}

) mode, a wide bandwidth of 30.1% is achieved in two reconfigurable polarizations. The measured results agree well with the simulation results. The total efficiency of the proposed antenna is more than 80.0% over the bandwidth. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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24 pages, 7011 KiB

Open AccessArticle

A Comprehensive Review of Traditional and Deep-Learning-Based Defogging Algorithms

by Minxian Shen, Tianyi Lv, Yi Liu, Jialiang Zhang and Mingye Ju

Electronics 2024, 13(17), 3392; https://doi.org/10.3390/electronics13173392 - 26 Aug 2024

Cited by 2 | Viewed by 2770

Abstract

Images captured under adverse weather conditions often suffer from blurred textures and muted colors, which can impair the extraction of reliable information. Image defogging has emerged as a critical solution in computer vision to enhance the visual quality of such foggy images. However, [...] Read more.

Images captured under adverse weather conditions often suffer from blurred textures and muted colors, which can impair the extraction of reliable information. Image defogging has emerged as a critical solution in computer vision to enhance the visual quality of such foggy images. However, there remains a lack of comprehensive studies that consolidate both traditional algorithm-based and deep learning-based defogging techniques. This paper presents a comprehensive survey of the currently proposed defogging techniques. Specifically, we first provide a fundamental classification of defogging methods: traditional techniques (including image enhancement approaches and physical-model-based defogging) and deep learning algorithms (such as network-based models and training strategy-based models). We then delve into a detailed discussion of each classification, introducing several representative image fog removal methods. Finally, we summarize their underlying principles, advantages, disadvantages, and give the prospects for future development. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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15 pages, 394 KiB

Open AccessArticle

User Scheduling and Path Planning for Reconfigurable Intelligent Surface Assisted MISO UAV Communication

by Yang Gu, Zhiyu Huang, Yuan Gao and Yong Fang

Electronics 2024, 13(14), 2797; https://doi.org/10.3390/electronics13142797 - 16 Jul 2024

Viewed by 980

Abstract

The high mobility of unmanned aerial vehicles (UAVs) enables them to improve system throughput by establishing line-of-sight (LoS) links. Nevertheless, in urban environments, these LoS links can be disrupted by complex urban structures, leading to potential interference issues. Reconfigurable intelligent surfaces (RIS) provide [...] Read more.

The high mobility of unmanned aerial vehicles (UAVs) enables them to improve system throughput by establishing line-of-sight (LoS) links. Nevertheless, in urban environments, these LoS links can be disrupted by complex urban structures, leading to potential interference issues. Reconfigurable intelligent surfaces (RIS) provide an innovative approach to enhance communication performance by intelligently reflecting incident signals. Recent studies suggest that utilizing multi-antenna transmission can increase system efficiency, while single-antenna transmission may be more prone to interference. To address these challenges, this article introduces a RIS-assisted multiple-input single-output (MISO) UAV communication system. Our objective is to optimize the minimum user rate, thereby guaranteeing equitable communication for all users. Nevertheless, the non-convexity inherent in this optimization problem complicates the pursuit of a direct solution. Hence, we decompose the problem into four subproblems: user scheduling optimization, RIS phase-shift optimization, UAV trajectory optimization, and UAV transmit beamforming optimization. To obtain suboptimal solutions, we have developed an alternating iterative optimization algorithm for addressing the four subproblems. Numerical results demonstrate that our algorithm effectively boosts the minimum user rate of the entire system. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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14 pages, 7922 KiB

Open AccessArticle

An Ultra-Thin Multi-Band Logo Antenna for Internet of Vehicles Applications

by Jun Li, Junjie Huang, Hongli He and Yanjie Wang

Electronics 2024, 13(14), 2792; https://doi.org/10.3390/electronics13142792 - 16 Jul 2024

Cited by 1 | Viewed by 1506

Abstract

In this paper, an ultra-thin logo antenna (LGA) operating in multiple frequency bands for Internet of Vehicles (IoVs) applications was proposed. The designed antenna can cover five frequency bands, 0.86–1.01 GHz (16.0%) for LoRa communication, 1.3–1.36 GHz (4.6%) for GPS, 2.32–2.71 GHz (16.3%) [...] Read more.

In this paper, an ultra-thin logo antenna (LGA) operating in multiple frequency bands for Internet of Vehicles (IoVs) applications was proposed. The designed antenna can cover five frequency bands, 0.86–1.01 GHz (16.0%) for LoRa communication, 1.3–1.36 GHz (4.6%) for GPS, 2.32–2.71 GHz (16.3%) for Bluetooth communication, 3.63–3.89 GHz (6.9%) for 5G communication, and 5.27–5.66 GHz (7.1%) for WLAN, as the simulation indicated. The initial antenna started with a modified coplanar waveguide (CPW)-fed circular disk monopole radiator. To create extra current paths and further excite other modes, the disk was hollowed out into the shape of the car logo of the Chinese smart EV brand XPENG composing four rhombic parasitic patches. Next, four triangular parasitic patches were inserted to improve the impedance matching of the band at 5.6 GHz. Finally, four metallic vias were loaded for adjusting resonant points and the return loss reduction. Designed on a flexible substrate, the antenna can easily bend to a certain degree in complex vehicular communication for IoV. The measured results under horizontal and vertical bending showed the LGA can operate in a bending state while maintaining good performance. The proposed LGA addresses the issue of applying one single multi-band antenna to allow vehicles to communicate over several channels, which relieves the need for a sophisticated antenna network. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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12 pages, 12837 KiB

Open AccessArticle

Improved Convolutional Neural Network for Wideband Space-Time Beamforming

by Ming Guo, Zixuan Shen, Yuee Zhou and Shenghui Li

Electronics 2024, 13(13), 2492; https://doi.org/10.3390/electronics13132492 - 26 Jun 2024

Viewed by 1692

Abstract

Wideband beamforming technology is an effective solution in millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems to compensate for severe path loss through beamforming gain. However, traditional adaptive wideband digital beamforming (AWDBF) algorithms suffer from serious performance degradation when there are insufficient signal snapshots, [...] Read more.

Wideband beamforming technology is an effective solution in millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems to compensate for severe path loss through beamforming gain. However, traditional adaptive wideband digital beamforming (AWDBF) algorithms suffer from serious performance degradation when there are insufficient signal snapshots, and the training process of the existing neural network-based wideband beamforming network is slow and unstable. To address the above issues, an AWDBF method based on the convolutional neural network (CNN) structure, the improved wideband beamforming prediction network (IWBPNet), is proposed. The proposed method increases the network’s feature extraction capability for array signals through deep convolutional layers, thus alleviating the problem of insufficient network feature extraction capabilities. In addition, the pooling layers are introduced into the IWBPNet to solve the problem that the fully connected layer of the existing neural network-based wideband beamforming algorithm is too large, resulting in slow network training, and the pooling operation increases the generalization ability of the network. Furthermore, the IWBPNet has good wideband beamforming performance with low signal snapshots, including beam pattern performance and output signal-to-interference-plus-noise ratio (SINR) performance. The simulation results show that the proposed algorithm has superior performance compared with the traditional wideband beamformer with low signal snapshots. Compared with the wideband beamforming algorithm based on the neural network, the training time of IWBPNet is only

10.6 %

of the original neural network-based wideband beamformer, while the beamforming performance is slightly improved. Simulations and numerical analyses demonstrate the effectiveness and superiority of the proposed wideband beamformer. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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13 pages, 7796 KiB

Open AccessArticle

Transformer-Based User Charging Duration Prediction Using Privacy Protection and Data Aggregation

by Fei Zeng, Yi Pan, Xiaodong Yuan, Mingshen Wang and Yajuan Guo

Electronics 2024, 13(11), 2022; https://doi.org/10.3390/electronics13112022 - 22 May 2024

Cited by 2 | Viewed by 1109

Abstract

The current uneven deployment of charging stations for electric vehicles (EVs) requires a reliable prediction solution for smart grids. Existing traffic prediction assumes that users’ charging durations are constant in a given period and may not be realistic. In fact, the actual charging [...] Read more.

The current uneven deployment of charging stations for electric vehicles (EVs) requires a reliable prediction solution for smart grids. Existing traffic prediction assumes that users’ charging durations are constant in a given period and may not be realistic. In fact, the actual charging duration is affected by various factors including battery status, user behavior, and environment factors, leading to significant differences in charging duration among different charging stations. Ignoring these facts would severely affect the prediction accuracy. In this paper, a Transformer-based prediction of user charging durations is proposed. Moreover, a data aggregation scheme with privacy protection is designed. Specifically, the Transformer charging duration prediction dynamically selects active and reliable temporal nodes through a truncated attention mechanism. This effectively eliminates abnormal fluctuations in prediction accuracy. The proposed data aggregation scheme employs a federated learning framework, which centrally trains the Transformer without any prior knowledge and achieves reliable data aggregation through a dynamic data flow convergence mechanism. Furthermore, by leveraging the statistical characteristics of model parameters, an effective model parameter updating method is investigated to reduce the communication bandwidth requirements of federated learning. Experimental results show that the proposed algorithm can achieve the novel prediction accuracy of charging durations as well as protect user data privacy. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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8 pages, 3108 KiB

Open AccessCommunication

A High-Gain Metallic-via-Loaded Antipodal Vivaldi Antenna for Millimeter-Wave Application

by Jun Li, Junjie Huang, Hongli He and Yanjie Wang

Electronics 2024, 13(10), 1898; https://doi.org/10.3390/electronics13101898 - 12 May 2024

Cited by 6 | Viewed by 1924

Abstract

This paper presents a miniaturized-structure high-gain antipodal Vivaldi antenna (AVA) operating in the millimeter-wave (mm-wave) band. A gradient-length microstrip-patch-based director is utilized on the flares of the AVA to enhance gain. Additionally, an array of metallic vias is incorporated along the lateral and [...] Read more.

This paper presents a miniaturized-structure high-gain antipodal Vivaldi antenna (AVA) operating in the millimeter-wave (mm-wave) band. A gradient-length microstrip-patch-based director is utilized on the flares of the AVA to enhance gain. Additionally, an array of metallic vias is incorporated along the lateral and horizontal edges of the antenna for further gain enhancement and bandwidth extension. Based on the proposed structure, the AVA can achieve a peak gain of 11.9 dBi over a relative bandwidth of 71.24% within 16.5–36.6 GHz as measured, while the electrical dimension is only 1.54 × 2.69 × 0.07

{λ_{c}}^{3}

. The measured results show good agreement with the simulated ones. Owning the characteristics of being high-gain and ultra-wideband, and having a compact size, the proposed AVA can be a competitive candidate for future millimeter-wave communication. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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18 pages, 31412 KiB

Open AccessArticle

Design of a 3-Bit Circularly Polarized Reconfigurable Reflectarray

by Zhe Chen, Chenlu Huang, Xinmi Yang, Xiaoming Yan, Xianqi Lin and Yedi Zhou

Electronics 2024, 13(10), 1886; https://doi.org/10.3390/electronics13101886 - 11 May 2024

Viewed by 1451

Abstract

In this paper, a 3-bit circularly polarized reconfigurable reflectarray is proposed. The array consists of 64 units in an 8 × 8 configuration, with each unit containing a circular metal patch loaded with phase-delay lines and eight PIN diodes. To independently control each [...] Read more.

In this paper, a 3-bit circularly polarized reconfigurable reflectarray is proposed. The array consists of 64 units in an 8 × 8 configuration, with each unit containing a circular metal patch loaded with phase-delay lines and eight PIN diodes. To independently control each unit, a corresponding DC control circuit was designed and tested with the array. In the bandwidth of 3.43–3.71 GHz, the circularly polarized reconfigurable reflectarray achieved a gain of 16 dB, an aperture efficiency of 27%, an axial ratio of ≤3 dB, an operating bandwidth of 8%, and a beam scanning range of ±60°. The circularly polarized reconfigurable reflectarray can also achieve a good dual-beam radiation performance after testing. The 3-bit circularly polarized reconfigurable reflectarray proposed in this paper offers several advantages, including low loss, high aperture efficiency, a wide beam scanning range, and excellent stability in wide-angle oblique incidence. It has potential applications in low-cost phased array, satellite communications, and deep space exploration. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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16 pages, 3903 KiB

Open AccessArticle

A Broadband Three-Way Series Doherty Power Amplifier with Deep Power Back-Off Efficiency Enhancement for 5G Application

by Xianfeng Que, Jun Li and Yanjie Wang

Electronics 2024, 13(10), 1882; https://doi.org/10.3390/electronics13101882 - 11 May 2024

Cited by 2 | Viewed by 1768

Abstract

This article presents a new broadband three-way series Doherty power amplifier (DPA) topology, which enables a broadband output power back-off (OBO) efficiency enhancement of up to 10 dB or higher. The proposed DPA topology achieves Doherty load modulation and three-way power combining through [...] Read more.

This article presents a new broadband three-way series Doherty power amplifier (DPA) topology, which enables a broadband output power back-off (OBO) efficiency enhancement of up to 10 dB or higher. The proposed DPA topology achieves Doherty load modulation and three-way power combining through a transformer, which requires only a low coupling factor, thus facilitating its implementation in double-sided PCBs or monolithic microwave integrated circuit (MMIC) processes. The design equations for the proposed DPA topology are proposed and analyzed in detail. A proof-of-concept PA at the 2.1–2.8 GHz band using commercial GaN transistors was designed and fabricated to validate the proposed concept. Within the operating frequency band, it achieves a saturated output power (

P_{sat}

) of 44.5–46.5 dBm with a peak drain efficiency (DE) of 60–72%, and 43–52% DE at 10 dB OBO. Moreover, under a 20 MHz long-term evolution (LTE)-modulated signal, the PA demonstrates a 36.8–37.5 dBm average output power (

P_{avg}

) and 47–53% average drain efficiency (

{DE}_{avg}

). Notably, the adjacent channel leakage ratio (ACLR) is as low as −35–−28.2 dBc without any digital predistortion (DPD). Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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20 pages, 1057 KiB

Open AccessArticle

Low-Resolution Optimization for an Unmanned Aerial Vehicle Communication Network under a Passive Reconfigurable Intelligent Surface and Active Reconfigurable Intelligent Surface

by Qiangqiang Yang, Yufeng Chen, Zhiyu Huang, Hongwen Yu and Yong Fang

Electronics 2024, 13(10), 1826; https://doi.org/10.3390/electronics13101826 - 8 May 2024

Viewed by 1022

Abstract

This paper investigates the optimization of an unmanned aerial vehicle (UAV) network serving multiple downlink users equipped with single antennas. The network is enhanced by the deployment of either a passive reconfigurable intelligent surface (RIS) or an active RIS. The objective is to [...] Read more.

This paper investigates the optimization of an unmanned aerial vehicle (UAV) network serving multiple downlink users equipped with single antennas. The network is enhanced by the deployment of either a passive reconfigurable intelligent surface (RIS) or an active RIS. The objective is to jointly design the UAV’s trajectory and the low-bit, quantized, RIS-programmable coefficients to maximize the minimum user rate in a multi-user scenario. To address this optimization challenge, an alternating optimization framework is employed, leveraging the successive convex approximation (SCA) method. Specifically, for the UAV trajectory design, the original non-convex optimization problem is reformulated into an equivalent convex problem through the introduction of slack variables and appropriate approximations. On the other hand, for the RIS-programmable coefficient design, an efficient algorithm is developed using a penalty-based approximation approach. To solve the problems with the proposed optimization, high-performance optimization tools such as CVX are utilized, despite their associated high time complexity. To mitigate this complexity, a low-complexity algorithm is specifically tailored for the optimization of passive RIS-programmable reflecting elements. This algorithm relies solely on closed-form expressions to generate improved feasible points, thereby reducing the computational burden while maintaining reasonable performance. Extensive simulations are created to validate the performance of the proposed algorithms. The results demonstrate that the active RIS-based approach outperforms the passive RIS-based approach. Additionally, for the passive RIS-based algorithms, the low-complexity variant achieves a reduced time complexity with a moderate loss in performance. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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15 pages, 4907 KiB

Open AccessArticle

Design of UWB Electrically Small Antenna Based on Distributed Passive Network Loading

by Zhe Chen, Xianqi Lin, Yuchen Luan, Xinjie Hao, Xiaoming Yan and Guo Liu

Electronics 2024, 13(5), 914; https://doi.org/10.3390/electronics13050914 - 28 Feb 2024

Cited by 1 | Viewed by 1921

Abstract

In this paper, an ultra-wideband electrically small antenna based on distributed passive network loading is proposed. Based on the Vivaldi antenna theory, magnetic dipole antenna theory, and distributed loading theory, the electrically small antenna achieves the purpose of being wideband using a three-dimensional [...] Read more.

In this paper, an ultra-wideband electrically small antenna based on distributed passive network loading is proposed. Based on the Vivaldi antenna theory, magnetic dipole antenna theory, and distributed loading theory, the electrically small antenna achieves the purpose of being wideband using a three-dimensional design of a planar Vivaldi antenna structure under limited space constraints. At the same time, the magnetic dipole antenna is introduced to effectively expand the low-frequency bandwidth of the electrically small antenna without increasing the aperture size. Finally, through the distributed passive network loading, the wideband-conjugated matching of the electrically small antenna is achieved without increasing the size of the electrically small antenna. The −6 dB bandwidth of the electrically small antenna is 0.2 GHz–3 GHz, and the overall size is 0.06 λ₀ × 0.05 λ₀ × 0.12 λ₀, where λ₀ is the wavelength of the lowest frequency of the antenna. One sample of the proposed UWB electrically small antenna is fabricated and tested. Good agreement between simulation results and measurement results are obtained. The design method of UWB electrically small antenna proposed in this paper can be applied to the base station antenna, low-frequency detection, microwave sensing, and microwave measurement. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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12 pages, 4621 KiB

Open AccessArticle

Ultrathin Antenna-in-Package Based on TMV-Embedded FOWLP for 5G mm-Wave Applications

by Yuhang Yin, Chenhui Xia, Shuli Liu, Zhimo Zhang, Chen Chen, Gang Wang, Chenqian Wang and Yafei Wu

Electronics 2024, 13(5), 839; https://doi.org/10.3390/electronics13050839 - 22 Feb 2024

Cited by 2 | Viewed by 2170

Abstract

In this paper, a novel through mold via (TMV)-embedded fan-out wafer-level package (FOWLP) technology was demonstrated to manufacture the well-designed Antenna in Package (AiP) with ultrathin thickness (0.04 λ₀). Double-sided redistribution layers (RDLs) were employed to build the patch antenna, while [...] Read more.

In this paper, a novel through mold via (TMV)-embedded fan-out wafer-level package (FOWLP) technology was demonstrated to manufacture the well-designed Antenna in Package (AiP) with ultrathin thickness (0.04 λ₀). Double-sided redistribution layers (RDLs) were employed to build the patch antenna, while a TMV interposer was used to connect the front and back RDLs. By optimizing the AiP’s parameters, the patch antenna can achieve a wide impedance bandwidth of 17.8% from 24.2 to 28.5 GHz, which can cover the 5G frequency bands. Compared with previous works, the proposed AiP has significant benefits in terms of its ultralow profile, easy processing, and high gain. Hence, the TMV-embedded FOWLP should be a promising technology for fifth generation (5G) millimeter wave (mm-Wave) applications. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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Review

Jump to: Research

18 pages, 4102 KiB

Open AccessReview

Research Progress on FSS Stealth Radome

by Yong-Xing Che, Shi-Ji Wu, Ming Li and Yong-Ling Ban

Electronics 2025, 14(6), 1132; https://doi.org/10.3390/electronics14061132 - 13 Mar 2025

Viewed by 538

Abstract

Radome stealth technology is a key research area in aircraft stealth design. Traditional aircraft stealth methods primarily focus on optimizing the shape to scatter radar waves and using absorbing materials to absorb radar waves. However, when these methods are applied to radomes, they [...] Read more.

Radome stealth technology is a key research area in aircraft stealth design. Traditional aircraft stealth methods primarily focus on optimizing the shape to scatter radar waves and using absorbing materials to absorb radar waves. However, when these methods are applied to radomes, they can negatively impact antenna performance. By combining Frequency-Selective Surface (FSS) technology with radome design, it is possible to ensure good transmission performance for the antenna within its operating frequency range while simultaneously reducing the radar cross-section outside the operating frequency range, achieving an integrated design for both transmission and stealth. This paper outlines the technical approaches for radome stealth, reviews the research status of scattering stealth radomes and absorbing stealth radomes based on FSS both domestically and internationally, and provides an outlook on the future development of FSS radomes from the perspectives of omnidirectional broadband, conformal design, and intelligent control. Full article

(This article belongs to the Special Issue Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems)

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Advanced Wireless Technologies for Next-G Networks: Antennas, Circuits, and Systems

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