Double Negative Metasurface Wideband Antenna Design Using TCM-Based Optimization for 5G Sub-6 GHz Applications

This communication presents a dual-band aperture-shared high gain antenna for millimeter-wave (mm-wave) multi-beam and sub-6 GHz applications by integrating transmitarray into Fresnel zone plate (FZP) lens. The transmistarray consists of two sets of unit cells (UCs), which can provide high transmission magnitude and [ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-\pi $ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> ] phase tuning at the mm-wave frequency band. Meanwhile, they show distinct transmission features at the sub-6 GHz band (one set of UC allows the electromagnetic (EM) wave to pass while the other prohibits the EM wave from passing). Then, by properly arranging the two kinds of UCs into the transparent and opaque region of the FZP lens respectively, the sub-6 GHz FZP lens and the mm-waveband transmitarray are integrated into the same aperture seamlessly. A waveguide-integrated patch antenna is adopted as the feed. The patch antenna operates at the sub-6 GHz band and three open waveguide antennas are used for the mm-wave multi-beam radiation. The proposed antenna achieves high gain at both bands with a reused radiating aperture. Mm-wave multi-beam radiation is obtained without an extra feeding network. For demonstration purposes, the central frequencies of the sub-6 GHz and the mm-wave bands are selected at 6 and 27 GHz, respectively. An antenna prototype is fabricated and experimentally verified.

A compact and highly isolated integrated 8-port MIMO antenna for sub-6 GHz and mm-wave 5G-NR applications

A metasurface (MS) antenna that allows polarization reconfigurability is proposed. The MS antenna is formed by a MS and source antenna, separated by a small air gap. The MS consists of 16 identical unit cells on a substrate, where each unit cell used is a corner truncated square patch. A microstrip fed slot antenna (MFSA) is used as the source antenna. The MS converts the linearly polarized (LP) signal generated by the MFSA into a circularly polarized (CP) signal with wider return loss bandwidth(RLBW). By rotating the MS relative to the MFSA, different polarizations could be achieved. For verification of simulation results, the MS antennas are fabricated and measured. Simulated and measured results show good agreements. The MS antenna has an operating frequency of 2.4 GHz, suitable for WLAN applications.

This paper investigates the design and implementation of a novel hybrid metamaterial unit cell to improve a beamforming Wi-Fi antenna’s performance. The proposed metamaterial unit cell is created on an FR-4 substrate (εγ = 4.4) and a thickness of 1.6 mm. The metallization height of the unit cell is maintained at 0.035 mm. The designed metamaterial unit cell is simulated using HFSS Ver. 18.2 to verify the double negative behaviour. The unit cell consists of five Split Ring Resonators (SRR’s) at the bottom and a hexagonal ring of six triangles. Initially, a conventional inset fed microstrip patch antenna is designed then an array of the proposed unit cell is created and used as a superstrate to study the performance. A Three Element Antenna Array (TEAA) is designed to operate at 2.4 GHz Wi-Fi band, and the superstrate created out of the proposed unit cell is used to study its effect. Metamaterial superstrate improved the conventional Single Element Antenna (SEA) gain by approximately 2 dB. Superstrate with TEAA exhibited an improved gain of 1 dB over TEAA.

Millimeter wave (mmW) communications at the 60 GHz unlicensed band is seen as a promising approach for boosting the capacity of wireless local area networks (WLANs). If properly integrated into legacy IEEE 802.11 standards, mmW communications can offer substantial gains by offloading traffic from congested sub-6 GHz unlicensed bands to the 60 GHz mmW frequency band. In this paper, a novel medium access control (MAC) is proposed to dynamically manage the WLAN traffic over the unlicensed mmW and sub-6 GHz bands. The proposed protocol leverages the capability of advanced multi-band wireless stations (STAs) to perform fast session transfers (FST) to the mmW band, while considering the intermittent channel at the 60 GHz band and the level of congestion observed over the sub-6 GHz bands. The performance of the proposed scheme is analytically studied via a new Markov chain model and the probability of transmissions over the mmW and sub-6 GHz bands, as well as the aggregated saturation throughput are derived. In addition, analytical results are validated by simulation results. Simulation results show that the proposed integrated mmW-sub 6 GHz MAC protocol yields significant performance gains, in terms of maximizing the saturation throughput and minimizing the delay experienced by the STAs. The results also shed light on the tradeoffs between the achievable gains and the overhead introduced by the FST procedure.

A multiresonance metasurface antenna is proposed which has wide bandwidth and low-profile. The characteristic mode theory is used to design antenna structure. Three ideal modes are obtained by adjusting the mode currents to optimize the radiation performance of the antenna. The characteristic mode analysis is used to model, analyze, and optimize the antenna, revealing the physical characteristics of the metasurface antenna. The slot is not only used as the feeding structure for exciting characteristic modes but also introduces a slot mode. Combining the slot mode with the metasurface modes, the bandwidth of the antenna is broadened. The antenna element has a relative bandwidth of 43.7%. To obtain higher gain, a 2 × 2 antenna array is proposed. The antenna array is simulated, fabricated, and measured. The results show that the relative bandwidth of the proposed metasurface antenna array is 31.6% with the gain of 12.3–15.8 dBi over the operating bandwidth.

This paper presents a compact artificial magnetic conductor (AMC) reflector integrated with a planar antenna for upper sub-6 GHz wireless communication applications. The proposed radiator is designed with dimensions of 14 × 13 mm on an FR4 substrate with a dielectric constant of ε r = 4.3 and a thickness of 1.56 mm, providing a compact structure suitable for integration into space constrained wireless terminals. To address the inherently low gain and pronounced backward radiation associated with electrically small antennas, a compact AMC reflector composed of 20 × 20 mm unit cells is introduced. The AMC surface is implemented in a 2 × 2 array, resulting in an overall panel size of 42 mm × 42 mm. Experimental results demonstrate that the AMC-backed antenna maintains an impedance bandwidth and operating range comparable to those of the isolated radiator, while achieving a clear enhancement in forward radiation performance. The inclusion of the AMC enhances the maximum antenna gain by approximately 5 dB across the operating band. With its low profile, compact dimensions, and fully FR4-based realization, the proposed AMC-backed antenna represents a candidate for space-limited wireless communication systems, including 5G terminal devices, customer-premises equipment (CPE), and IoT gateways.

In this paper, a fractal inspired metamaterial superstrate is proposed for the gain enhancement of microstrip patch antenna resonating at 2.4 GHz. Fractal structure is used as the metamaterial unit cell, which is designed on a FR4 substrate with a thickness of 1.6 mm. The metamaterial unit cell exhibits near-zero refractive index at 2.4 GHz. The superstrate consists of a 2×2 array of metamaterial unit cells which acts as a partial reflective surface of Fabry-Perot (FP) cavity. The distance between the antenna and the superstrate is optimized by the FP resonance condition. The antenna has a directional radiation pattern more than the microstrip patch antenna. The antenna gives a peak gain of 7 dBi with a gain enhancement of 4 dB and a beamwidth reduction of 23° and 2° along H plane and E plane respectively. The aperture efficiency of the antenna is 80.47%. The whole structure is simulated and analyzed using finite element method. The simulated and the measured results show good agreement.

Due to the worldwide ongoing pressure to massively exploit the Sub-6 GHz spectrum for the deployment of independently-operated and heterogeneous networks, innovative solutions for network coexistence are deeply required. Hence, in this paper, we design a self-organizing strategy with the aim of minimizing the coexistence interference among heterogeneous networks sharing the Sub-6 GHz spectrum. The design is performed under the constraints of promoting selfless network utilization and avoiding any direct communication among the heterogeneous networks. For this, we develop an analytical framework, grounded on the nest-site selection behavior observed in honeybee swarms, to model the coexistence problem among multiple heterogeneous networks. Specifically, first, different heterogeneous networks are mapped into different populations and the allocation of a Sub-6 GHz band to a network is mapped into the population commitment. Then, the evolution of the commitment process is described through a multi-dimensional differential system. We analytically study the stability of such a system at the equilibrium, and we derive the conditions that assure the optimal allocation of the available Sub-6 GHz bands among the different heterogeneous networks. Finally, the proposed strategy is validated through an extensive performance evaluation.

6G wireless communications will be immersed in the future with different applications. It is expected to support all IoT services and satellite communications, and it is expected to support artificial intelligence (AI) and machine learning (ML). The THz frequency band has a vital role in 6G communication. In this study, a new graphene plasmonic two-port Terahertz (THz) MIMO antenna is analyzed by the characteristic mode theory (CMA), which gives a better insight into the physical behavior of the MIMO configurations. The proposed MIMO antenna is compact and designed on a Teflon substrate of 130 × 85 µm2. The antenna provides a wide impedance bandwidth of 0.6 THz (3.2–3.8 THz). The CMA is applied to clarify the position at which the mutual coupling gives a maximum concentrated current distribution. It is mainly used to reveal the preferable MIMO antenna configuration by the usage of the model significant and model current distribution property. To reduce the mutual coupling between the radiating elements, a complementary dumbbell-structure Metamaterial (MTM) unit cell is etched in the ground plane to block the coupling mode without any affection on the dominant mode. The preferred MIMO configuration gives high isolation of −55 dB between the radiating patches. The fundamental characteristics have been discussed in detail. The proposed MIMO design offers several attractive features such as large bandwidth of 0.6 THz, low envelope correlation coefficient (ECC) of 0.000168, compact size, stable radiation, high gain of 7.23 dB, and low channel capacity loss (CCL) of 0.006. The proposed MIMO design is suitable for different applications in the THz band according to the high-performance parameters such as biomedical applications, security scanning, sensing, IoT, and 6G high-speed wireless communication systems.

A 5G rotated frame radiator for multiple applications is presented in the following paper. The presented geometry is capable of radiating the large frequency band from 2.91 to 12.17 GHz, which covers the 5G-(I) sub-6 GHz band, X-band communication with high efficiency. The impedance bandwidth of the radiator is 128%, with an electrical size of 0.24 λ × 0.24 λ × 0.15 λ in lambda. The antenna is simulated with an FR4 substrate using CST Simulator. 06-stages evolution process is also investigated by simulations, and corresponding S-parameter results are presented. Antenna's design comprises a patch in a rotated square fractal-like frame fed by a microstrip line. The proposed structure also demonstrates stable radiation patterns across the operating bandwidth. The proposed radiator has a high gain of 3.8 dBi, and an efficiency of 85%, which claimed that UWB range of the designed antenna. Therefore, it is useful for 5G-(I) sub-6 GHz band, X-band applications, including mobile, radar, and satellite microwave communication.

Rainfall impacts daily activities and can lead to severe hazards such as flooding. Traditional rainfall measurement systems often lack granularity or require extensive infrastructure. While the attenuation of electromagnetic waves due to rainfall is well-documented for frequencies above 10 GHz, sub-6 GHz bands are typically assumed to experience negligible effects. However, recent studies suggest measurable attenuation even at these lower frequencies. This study presents the first channel state information (CSI)-based measurement and analysis of rainfall attenuation at 2.8 GHz. The results confirm the presence of rain-induced attenuation at this frequency, although classification remains challenging. The attenuation follows a power-law decay model, with the rate of attenuation decreasing as rainfall intensity increases. Additionally, rainfall onset significantly increases the delay spread, and slight Doppler effects were also observed following the onset of precipitation. Building on these insights, we propose RainGaugeNet, the first CSI-based rainfall classification model in the sub-6GHz band that leverages multipath and temporal features. Two variants are developed: RainGaugeNet-R using ResNet1D and RainGaugeNet-T using a Transformer encoder. Using only 20 seconds of CSI data, RainGaugeNet-R achieves up to 95% an average classification accuracy in line-of-sight(LoS) scenarios and 85% in non-line-of-sight(NLoS) conditions. RainGaugeNet-T attains 90% accuracy in LoS and 99% in NLoS settings, demonstrating superior robustness. Both models significantly outperform state-of-the-art baselines while maintaining low computational complexity.

The Theory of Characteristic Modes (TCM) is applied to analyze a finite-sized ground plane shape of a circular monopole antenna, providing physical insight into the effect produced by the ground plane. A circular monopole has been designed on FR-4 substrate on the rectangular and circular ground plane. The information yielded by the modal analysis reveals the close influence of the ground plane shape on the impedance behavior of the antenna. Information provided by TCM can help optimize the ground plane’s size and geometry by exciting the desired modes and suppressing the unwanted modes.

This paper presents a analysis of planar double-negative (DNG) metamaterial unit cell, named split ring resonator (SRR), to obtain better miniaturization at microwave frequencies for a given physical cell size. In this study, electromagnetic transmission characteristics of square split ring resonator and circular split ring resonator of same area are investigated in a comparative manner for varying values of gap size of both type ring resonators.

Excessive demands in the sub-6 GHz frequency spectrum are caused by 5G and the Internet of Things, which calls for high-performance antennas. This paper addresses this difficulty by creating and refining a cutting-edge antenna array especially for this band. The single patch antennas used in many modern communication systems have gain and beamwidth limits. Our initiative seeks to obtain better performance by overcoming these constraints with a unique antenna array design. Utilizing various patch shapes, this novel approach optimizes current distribution-a crucial component of traditional array performance-by incorporating antenna elements. Through meticulous selection and integration of these diverse forms, our goal is to attain a more consistent current distribution throughout the array, which will result in increased gain and a reduced beamwidth. With an emphasis on the sub-6 GHz band, this research aims to significantly advance antenna technology by utilizing the benefits of different patch shapes. Future wireless communication systems may benefit from the increased efficiency, dependability, and adaptability of the optimized antenna array that results. Additionally, the academic community will gain important insights from the thorough project documentation. Ultimately, by promoting improvements in sub-6 GHz communication technology via an improved antenna array design, this initiative hopes to have a long-lasting effect.