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Design of a two-port UWB MIMO antenna with high isolation based on characteristic mode theory

JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS 2025年第8期39卷 898-917页

作者： You, Rui Nie, Wenyan Wang, Zhonggen Yang, Ming Wang, Mingqing Anhui Univ Sci & Technol Sch Elect & Informat Engn Huainan Peoples R China Huainan Normal Univ Sch Mech & Elect Engn Huainan 232001 Peoples R China West Anhui Univ Sch Elect & Commun Engn Luan Peoples R China

In this paper, a two-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is designed, fabricated, and tested based on characteristic mode theory. The MIMO design consists of two circular patches which are connected to the UWB unit with an I-shaped branch. Slots are opened in the circular patch to enhance the impedance matching performance, and in order to improve the isolation of the antenna while operating, metal strips are added to the patch, and a fence decoupling structure. The overall size of the proposed antenna is 77.5 x 39 x 1 mm(3), and the microstrip feed is used. Simulation results show that the antenna can cover the 2.68-11.85 GHz band with a return loss of -43.5 dB, an isolation of less than -20 dB, and an envelope correlation coefficient (ECC) of < 0.007. It possesses good directional radiation characteristics, and it can be used in 5G MIMO communication systems.

关键词： characteristic mode theory isolation multiple-input multiple-output Ultra-wideband

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Diversity gain in cylindrical vector beam multiplexing

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OPTICS AND LASER TECHNOLOGY 2025年 184卷

作者： Guan, Zhiwei Yang, Jing Ren, Jianjun Xie, Chuangxin Nong, Lvye Huang, Liyu Zuo, Tianyimei Dong, Ze Wang, Chaofeng Fan, Dianyuan Shenzhen Univ Inst Microscale Optoelect Int Collaborat Lab Mat Optoelect Sci & Technol 2D Minist Educ Shenzhen 518060 Peoples R China Minzu Normal Univ Xingyi Coll Phys & Engn Technol Xingyi 562400 Peoples R China Beijing Inst Technol Sch Informat & Elect Beijing Peoples R China

Cylindrical vector beam (CVB) provides an attractive prospect in enhancing the capacity density of optical communication via mode multiplexing. However, the mode coupling in few-mode fiber will disturb the mode power distribution of CVBs randomly, which causes crosstalk and signal fading, severely degrading the system performance and even interrupting communication. Here, we propose a diversity gain strategy to mitigate the crosstalk and signal fading in CVB multiplexing communication. By performing multi-input multi-output equalization on the receiving signals and estimating the channel matrix by solving the optimal mode channel weights, the diversity gain is performed to equalize the crosstalk-induced noise components and random signal errors, and the crosstalk and signal fading are mitigated. As a proof of concept, we experimentally demonstrate a multi-dimensional multiplexing communication (320 channels combined by 4 CVBs and 80 wavelengths), and 7.5 Tbit/s QPSK-OFDM signals are transmitted in 5 km few-mode fiber. We show that after diversity gain, the biterror-rate is improved by about 2-3 orders of magnitude, and the communication outage of 60 % is completely suppressed. These validate that the diversity gain effectively eliminates crosstalk and signal fading caused by mode coupling in CVB multiplexing transmission over few-mode fiber, which significantly enhances communication capacity while greatly improving the stability and reliability of the communication system. It provides an effective solution for future high-capacity and long-distance optical communication.

关键词： Cylindrical vector beam Mode-division multiplexing multiple-input multiple-output Diversity gain

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Self-Isolation in MIMO Array Using Mode Diversity

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IEEE ACCESS 2025年 13卷 45023-45036页

作者： Elahi, Manzoor Koziel, Slawomir Leifsson, Leifur Reykjavik Univ Engn Optimizat & Modeling Ctr IS-102 Reykjavik Iceland Gdansk Univ Technol Fac Elect Telecommun & Informat PL-80233 Gdansk Poland Purdue Univ Sch Aeronaut & Astronaut W Lafayette IN 47907 USA

A new isolation technique is proposed for multiple-input multiple-output (MIMO) microstrip patch antenna (MPA) arrays utilizing mode diversity. Typically, similar modes are excited in each element of the MIMO array. However, the proposed MIMO array uses two elements of different sizes excited in distinct modes at the same frequency. It is found that the TM01 mode excited in one MPA, a hybrid mode (TM 03+ TM21) is induced in the coupled MPA, while exciting the TM03 mode in another patch induces a quasi-TM11 mode in the coupled MPA. Both induced modes exhibit weak fields at the feeding points, reducing the mutual coupling between the two patch antennas without requiring extra decoupling structure. Additionally, the induced modes create a null in the broadside direction, reducing cross-polarization (x-pol) levels. An isolation level over 50 dB is achieved in 1x2 MIMO array at 5.8 GHz. The design is adaptable to larger array. Therefore, to validate the design technique, a 1x4 array is simulated, fabricated and measured, showing 30-45 dB isolation among the ports in the passband. Moreover, the design features an x-pol around -40 dB in broadside direction in both E- and H-planes, ensuring effective polarization diversity. The technique is applied to a MIMO dielectric resonator antenna (DRA) array, demonstrating excellent isolation and radiation pattern performance. Furthermore, the technique is versatile and can be applied to various MIMO configurations. Therefore, simulations have been performed for 2x4 MPA array, validating the effectiveness of isolation in both the E- and H-planes. This approach also optimizes space utilization, allowing for the inclusion of additional patch elements to form hybrid-coupled MIMO MPAs within confined spaces.

关键词： MIMO Mutual coupling Antenna arrays Antennas Resonant frequency Couplings Substrates Patch antennas Current distribution Scattering parameters Microstrip patch antenna multiple-input multiple-output isolation self-decoupling method mode's diversity cross-polarization

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A Delay-Oriented Joint Optimization Approach for RIS-Assisted MEC-MIMO System

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2025年第5期24卷 4263-4277页

作者： Jiang, Shanshan Wang, Xue Lin, Junhao Huang, Chongwen Qian, Zhihong Han, Zhu Jilin Univ Dept Commun Engn Changchun 130012 Peoples R China Yanbian Univ Coll Engn Yanji 133002 Peoples R China Zhejiang Univ Coll Informat Sci & Elect Engn Hangzhou 310027 Peoples R China Zhejiang Prov Key Lab Multimodal Commun Networks & Hangzhou 310027 Peoples R China Univ Houston Dept Elect & Comp Engn Houston TX 77004 USA Kyung Hee Univ Dept Comp Sci & Engn Seoul 446701 South Korea

In the paper, we propose a joint optimization algorithm based on the block coordinate descent (JOABCD) algorithm for reflective intelligent surface (RIS) assisted MEC-MIMO systems. First, we define the delay minimization function for both single user with multi-antenna and multiple users with single-antenna scenarios. Since the optimization function is an NP-hard problem, we decompose it into two subproblems: computing setting and communication setting using the block coordinate descent (BCD) iterative algorithm. The subproblem of resource allocation is solved using a bisection method, while the subproblem of transmit power and phase shift matrix is solved alternately. The optimal simulation results show that the JOABCD algorithm can realize a lower time latency and a higher sum achievable rate compared with the existing methods.

关键词： Delays Resource management Optimization Channel estimation Energy consumption MIMO Minimization Covariance matrices Computational efficiency Communication system security Multi-access edge computing reflecting intelligent surface multiple-input multiple-output delay

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Design of a Multiband Antenna Using Auxiliary Classifier Wasserstein Generative Adversarial Network for IoT Applications

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INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS 2025年第5期38卷

作者： Bessant, Y. R. Annie St Xaviers Catholic Coll Engn Dept Elect & Commun Engn Nagercoil Tamil Nadu India

The rapid expansion of Internet of Things (IoT) applications presents unprecedented challenges for antenna design, demanding solutions that are versatile, efficient, and capable of operating across multiple frequency bands. This paper addresses these challenges through the development of a design of a multiband antenna using Auxiliary Classifier Wasserstein Generative Adversarial Network for IoT applications (DMA-ACWGAN-IoT). Here, the Auxiliary Classifier Wasserstein Generative Adversarial Network (ACWGAN) is employed to generate synthetic data representing electromagnetic field distributions and antenna characteristics across various frequencies. The proposed metamaterial-based multiple-input multiple-output (MIMO) antenna contains four discrete elements, each provided by a micro strip feed. The structures overall width and length are 60 and 52 mm. The metamaterial is printed on a patch and dispersed from the fields with the most effective coupling. The proposed structures strong impedance bandwidth works at 8.3 GHz, 10.8 GHz, 12.3 GHz, 13.7 GHz, 16.1 GHz, and 18.1 GHz, fabricating the proposed antenna prototype using a substrate made of FR-4 material. The proposed DMA-ACWGAN-IoT design provides 6.5 dB maximum gain and 25.40%, 21.60%, and 20.05% higher efficiency compared to existing dual band antenna design with resonance frequency prediction under machine learning models (DBA-PRF-ML), machine learning verification depending on a distinctive SWB multiple slotted four-port high isolated MIMO antenna loaded with metasurface for the applications of IoT (SWB-MIMO-IOT-ML), and dual-band miniaturized composite right-left-handed transmission line ZOR antenna along machine learning method for microwave communication (DB-ZORA-MC-ML).

关键词： Auxiliary Classifier Wasserstein Generative Adversarial Network complementary split ring resonator internet of things multiband antenna multiple-input multiple-output

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End-to-End Deep Learning for TDD MIMO Systems in the 6G Upper Midbands

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2025年第3期24卷 2110-2125页

作者： Park, Juseong Sohrabi, Foad Ghosh, Amitava Andrews, Jeffrey G. Univ Texas Austin Res Ctr 6GUT Wireless Networking & Commun Grp Austin TX 78712 USA Nokia Bell Labs Radio Syst Res Murray Hill NJ 07974 USA Nokia Stand Strategy & Technol Naperville IL 60563 USA

This paper proposes and analyzes novel deep learning methods for downlink (DL) single-user multiple-input multiple-output (MIMO) and multi-user MIMO (MU-MIMO) systems operating in time division duplex mode. A motivating application is the 6G upper midbands (7-24 GHz), where the base station (BS) antenna arrays are large, user equipment array sizes are moderate, and theoretically optimal approaches are practically infeasible for several reasons. To deal with uplink (UL) pilot overhead and low signal power issues, we introduce the channel-adaptive pilot, as part of the novel analog channel state information feedback mechanism. Deep neural network (DNN)-generated pilots are used to linearly transform the UL channel matrix into lower-dimensional latent vectors. Meanwhile, the BS employs a second DNN that processes the received UL pilots to directly generate near-optimal DL precoders. The training is end-to-end which exploits synergies between the two DNNs. For MU-MIMO precoding, we propose a DNN structure inspired by theoretically optimum linear precoding. The proposed methods are evaluated against genie-aided upper bounds and conventional approaches, using realistic upper midband datasets. Numerical results demonstrate the potential of our approach to achieve significantly increased sum-rate, particularly at moderate to high signal-to-noise ratio and when UL pilot overhead is constrained.

关键词： Precoding Channel estimation Deep learning Artificial neural networks Array signal processing Antenna arrays 6G mobile communication Training MIMO Signal to noise ratio 6G mid-band multiple-input multiple-output deep learning time division duplex precoding channel state information feedback

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Spatial-Frequency Block Coding Automatic Recognition With Non-Gaussian Interference for Cognitive MIMO-OFDM Systems

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IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING 2025年第1期11卷 156-167页

作者： Zhang, Junlin Liu, Mingqian Chen, Yunfei Zhao, Nan Xidian Univ State Key Lab Integrated Serv Networks Xian 710071 Peoples R China Univ Durham Dept Engn Durham DH1 3LE England Dalian Univ Technol Sch Informat & Commun Engn Dalian 116024 Peoples R China

Space-time/frequency block coding (STBCs/SFBCs) scheme is a crucial technique for enhancing the effectiveness and reliability of multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems with cognitive radio (CR) capability. Automatic recognition of STBCs/SFBCs is a prerequisite for achieving dynamic spectrum sharing in cognitive MIMO-OFDM systems. In contrast to existing works, this paper proposes a weighted cross-correlation function-based algorithm to recognize SFBCs for cognitive MIMO-OFDM systems with Gaussian noise and non-Gaussian impulsive interference. The proposed algorithm extracts the space-frequency redundancy information of different OFDM subcarriers on different receiver antenna pairs by using weighted cross-correlation functions. Then, the weighted cross-correlation feature vectors are constructed by exploiting the multi-antenna system so as to design the detection statistics and thresholds based on the central limit theorem. Finally, a decision tree method is adopted to discriminate between several SFBCs. The proposed algorithm does not require prior information such as channel coefficients, modulation schemes, noise power, or interference power. Simulation results show that the proposed algorithm is robust against non-Gaussian impulsive interference and achieves high recognition performance in the case of a small number of samples and a low signal-to-noise ratio.

关键词： OFDM Interference Vectors Receiving antennas Symbols Noise MIMO communication Cognitive radio multiple-input multiple-output non-Gaussian impulsive interference orthogonal frequency division multiplexing parameter recognition space-frequency block coding

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Error performance analysis of generalized quadrature spatial modulation with labelling diversity

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SCIENTIFIC REPORTS 2025年第1期15卷 1-19页

作者： Sibanda, Nathael Xu, Hongjun Pillay, Narushan Univ KwaZulu Natal Sch Engn ZA-4001 Durban South Africa

multiple-input multiple-output (MIMO) generalised spatial modulation (GSM) systems represent a pivotal advancement in wireless communication technology. These systems have unlocked the potential for enhanced data rates and enhanced error performance (EP). Therefore, this research delves into a strategy aimed at elevating the EP within MIMO-GSM systems. This strategy involves the integration of MIMO-GSM systems with both generalised quadrature spatial modulation (GQSM) and the concept of labelling diversity (LD). Two schemes namely multiple active antenna generalised spatial modulation with labelling diversity (MAA-GSM-LD) and generalised complex quadrature spatial modulation with labelling diversity (GCQSM-LD) are proposed. The first scheme is MAA-GSM-LD, which builds on conventional generalised spatial modulation (C-GSM) by incorporating it with multiple active antennas and optimised labelling maps that have a maximised minimum product distance (M-MPD) between constellations. This M-MPD helps improve detection, thereby improving the EP of MIMO-GSM schemes. Four symbols are sent simultaneously per time slot in MAA-GSM-LD. The second scheme (GCQSM-LD), builds on MAA-GSM-LD by splitting the four symbols created in MAA-GSM-LD into the quadrature and in-phase dimensions, thereby avoiding inter-antenna synchronisation and improving the EP of MIMO-SM systems. In this study, analytical mathematical expressions were developed to determine both the union-bound and upper-bound average bit error rate (ABER) for the MAA-GSM-LD and GCQSM-LD schemes. These evaluations were conducted over independent and identically distributed Rayleigh frequency-flat fading channels. Monte Carlo simulations were utilised to validate the accuracy of these expressions. The findings suggest that as the signal-to-noise ratio (SNR) increases, the average bit error probability (ABEP) closely approximates the outcomes of the simulations. Moreover, the simulation results indicate enhancements in the EP o

关键词： Error performance Generalised quadrature spatial modulation Labelling-diversity multiple-input multiple-output

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Capacity Results for MIMO Optical Intensity Channels With Individual Intensity Constraints

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IEEE TRANSACTIONS ON COMMUNICATIONS 2025年第4期73卷 2505-2521页

作者： Chen, Ru-Han Li, Longguang Guo, Jia-Ning Yang, Xu Zhang, Jian Li, Lin Natl Univ Def Technol Res Inst 63 Nanjing 210044 Peoples R China Shanghai Jiao Tong Univ SJTU Paris Elite Inst Technol Shanghai 200240 Peoples R China Natl Digital Switching Syst Engn & Technol Res Ctr Zhengzhou 450002 Peoples R China

In this paper, we investigate the capacity of a multiple-input multiple-output (MIMO) optical intensity channel (OIC) with peak- and average-intensity constraints individually imposed on each transmitter. We first consider the case where the average input intensities are required to be equal to preassigned constants due to the requirement of illumination quality and color temperature. For the MIMO OIC with a strongly connected channel graph, we prove that its strongest eigen-subchannel must have positive channel gains, which reveals the underlying relationship between the MIMO OIC and the multiple-input single-output OIC. In the general case, we derive various capacity bounds by standard information theoretic tools and investigate several transceivers with certain architectures. In the special case where the channel rank is one less than the number of transmitters, we derive an equivalent capacity expression from the perspective of convex geometry, and new capacity lower bounds are derived based on this equivalent expression. Finally, the developed results are extended to another type of channels, where the average input intensities are required to be no larger than preassigned constants. These derived bounds are numerically verified to approach the capacity in the low or high signal-to-noise ratio regime.

关键词： Vectors Optical transmitters Optical receivers Radio frequency Optical modulation Signal to noise ratio Optical noise Channel capacity dimming control intensity-modulation and direct-detection (IM/DD) multiple-input multiple-output optical wireless communication per-aperture constraint visible light communication

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Empowering MIMO-FSO Systems: RIS Technology for Enhanced Performance in Challenging Conditions

IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY

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IEEE OPEN JOURNAL OF THE COMMUNICATIONS SOCIETY 2025年 6卷 2616-2641页

作者： Shakir, Wafaa M. R. Charafeddine, Jinan Al Furat Al Awsat Tech Univ Tech Inst Babylon Dept Comp Networks & Software Babil Iraq De Vinci Res Ctr De Vinci Higher Educ F-92400 Paris France

This paper presents a novel analytical framework to enhance the performance of reconfigurable intelligent surfaces (RIS)-integrated multiple-input-multiple-output (MIMO) free-space optical (FSO) communication systems. The study addresses critical challenges such as atmospheric turbulence, misalignment, and signal attenuation. It introduces a series-based approach to model the combined effects of Gamma-Gamma turbulence, generalized Rician pointing errors, and RIS size-related constraints. In contrast to previous studies, which often rely on oversimplified or idealized channel models, this framework provides closed-form expressions for the first time for the probability density function and cumulative distribution function of the end-to-end channel specifically designed for RIS-empowered (RIS-E) MIMO-FSO systems. These expressions capture the complex interactions between channel impairments and system parameters, enabling accurate performance evaluation in real-world deployments. The derived formulations provide key performance metrics, including outage probability, average bit error rate, ergodic capacity, data rate, and energy efficiency, for a variety of system configurations. Practical diversity combining techniques such as equal gain combining, maximal ratio combining, and selection combining are rigorously analyzed. In addition, asymptotic analyses at high signal-to-noise ratios offer simplified expressions that provide valuable insights into coding gain, diversity order, and system behavior under extreme conditions. A key contribution of this work is the investigation of the optimization of RIS placement, which improves signal alignment and reduces the outage probability, even under challenging atmospheric conditions. In addition, the study highlights the computational efficiency of the proposed framework through a detailed complexity analysis that confirms its feasibility for practical, large-scale applications. Monte Carlo simulations validate the theoretical

关键词： Reconfigurable intelligent surfaces MIMO Adaptive optics Diversity reception Atmospheric modeling Optical transmitters Wireless communication Optical variables control Optical receivers Energy efficiency multiple-input multiple-output free-space optical reconfigurable intelligent surface Gamma-Gamma turbulence non-zero boresight pointing errors atmospheric attenuation

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