This paper presents a new liquid metal via-based flexible phase shifter design for reconfigurable antenna applications. The suggested design makes use of 0.8 mm -radius gallium liquid metal vias embedded in a $\mathbf{1. 6 ~ m m}$-thick Rogers RT/duroid 5880 substrate that operates at $3-4 \text{GHz}$ with a 3.5 GHz center frequency. The phase shifter has exceptional mechanical reconfigurability by bending along the X and Y axes, with bending radii that range from 20 to 100 millimeters. Extensive electromagnetic simulations show that the device achieves phase shift variations appropriate for beam steering applications while maintaining acceptable impedance matching ($S_{11}<-10 \mathbf{~ d B}$) across all bending configurations. Phase shifts ranging from 15° to 45° are produced by bending along the $\mathbf{X}$-axis, whereas 10° to 35° phase changes are produced by bending along the $\mathbf{Y}$-axis over the tested bending radii. The suggested liquid metal via technology has several advantages over conventional patch-based phase shifters that use PIN diodes or varactors, such as zero DC power usage, inherent flexibility, simplified biasing networks, and entirely mechanical reconfiguration. Wearable electronics, conformal antenna arrays, and adaptive beam steering systems, where flexibility and low power consumption are crucial requirements, are especially well-suited for this design. The feasibility of liquid metal technology for flexible radio frequency components of the future in 5 G and beyond wireless communication systems is demonstrated by this work.

The widespread availability of consumer drones has introduced new challenges related to safety, security, and privacy, as these platforms are increasingly misused in sensitive or restricted areas., existing counter-drone technologies–such as radar, optical tracking, and multi-sensor fusion–offer reliable performance but are often prohibitively expensive and impractical for large-scale civilian deployment. This work presents a low-cost framework for real-time drone detection and classification that leverages the radio frequency (RF) emissions exchanged between drones and their controllers. The system is built on a software-defined radio (SDR) platform (USRP B210), which captures RF signals and converts them into spectrograms for analysis using deep learning. A labeled dataset of drone and non-drone signals was developed to train and evaluate detection models. Two state-of-the-art architectures, YOLOv5 and Faster R-CNN, were adapted to this task, with evaluation under varying signal-to-noise ratio (SNR) conditions. Results demonstrate that the proposed system achieves high detection accuracy and robustness even in noisy environments, highlighting its potential as a scalable and practical solution for RF-based drone monitoring.

This paper introduces a unified approach for modeling and synthesizing multi-beam radiation patterns in large, strongly-coupled antenna arrays. The method combines Floquet spectral analysis with Fourier-based contour windowing to efficiently handle both regular and arbitrarily-shaped array layouts. Starting from a single unit cell described by periodic (Floquet) boundary conditions, the electromagnetic response of the entire array is reconstructed via spectral modulation and inverse Fourier transformation. The formulation is solver-agnostic and compatible with numerical methods including the Method of Moments, its equivalent circuit variant, the Finite-Difference Time-Domain, and the Finite Element Method. The proposed technique is particularly suited for emerging systems including 6G communication, Massive MIMO, automotive radars, and IoT networks, where beam-forming, beam-steering, and low-cost computation are critical.

This paper introduces a computationally efficient method for angular modulation analysis in 5G/6G systems, significantly reducing numerical complexity and computation time compared to conventional techniques. Inspired by optical spectroscopy, we present novel approaches tailored for 5G/6G applications like reconfigurable intelligent surfaces (RIS) and metasurfaces. Unlike traditional direct methods (Fourier, Jones matrix, Bessel series, orbital angular momentum), our technique employs a modified Fourier method combined with Floquet analysis.

This paper presents a compact, low-cost dual-band antenna design with low specific absorption rate (SAR) for Wireless Body Area Networks (WBAN) and Industrial, Scientific, and Medical (ISM) applications. The proposed antenna operates at 2.4 GHz with linear polarization and 5.8 GHz with circular polarization, fabricated on a 1.52 mm thick RF35 dielectric substrate (28 × 40 mm). The design features a coplanar waveguide (CPW) feed integrated with substrate-integrated waveguide (SIW) technology to enhance bandwidth and return loss characteristics. The antenna has broad bandwidths of 0.5 GHz with a 2.4 GHz center and 1 GHz with a 5.8 GHz center. To mitigate back radiation and reduce SAR, a 4 × 4 electromagnetic bandgap (EBG) structure was incorporated, resulting in significant performance improvements. The EBG implementation increased the maximum gain from 3.66 to 8.56 dB at 2.4 GHz and from 3.97 to 10 dB at 5.8 GHz. Additionally, SAR values decreased from 7.34 to 1.62 W/kg for 1 g of tissue at 2.4 GHz and from 2.18 to 0.91 W/kg at 5.8 GHz. Prototype measurements confirm simulation results, demonstrating the antenna’s suitability for WBAN and wearable ISM applications, including sensor networks and Wi-Fi devices. The design offers advantages of independent band tuning, circular polarization at the higher frequencies, and compliance with safety standards for human exposure to electromagnetic fields.

RF signals are widely used in various applications such as telecommunications, wireless communication systems, and radar systems. These signals can be manipulated using phase shifters that adjust the signal's phase. This adjustment is essential for beam shaping, signal cancellation, and frequency synthesis in antenna arrays. By controlling the phase of the RF signal, phase shifters help manipulate electromagnetic waves for various applications. Therefore, as Gallo points out, phase shifters are essential for manipulating and controlling high-frequency signals. This manipulation and control is essential to improving the performance of wireless communication and radar systems and can improve signal reception and transmission.The study examines different types of phase shifters, conducts a comparative analysis of different phase shifter topologies and technologies, and highlights their respective advantages and limitations in applications. In addition, the review includes a specific study of liquid metal phase shifters. Finally, the article outlines future research directions for liquid metal phase shifters, It emphasizes the need for innovative design strategies to keep pace with the evolving wireless communications and telecommunications fields. Therefore, this article can serve as a reference for the milestones in RF phase shifter research.

Optical fibers are widely used for long links (intercontinental, terrestrial optical backbone) and short scopes (data center, access network). Certain fibers, called optical fibers specialty, also play an essential role in other fields such as medicine (e.g., endoscopy), sensors, laser applications, etc. The constant proliferation of Internet services, combined with the growth in users, makes it necessary to increase the current capacity of networks to optical fiber. Today, the fibers installed and used for transmission at very high-speed use only the fundamental mode (denoted LP) to transmit information: we speak of fiber's single-mode optics. As they now reach the nonlinear limit of Shannon, one of the ideas for increasing the capacity of optical networks is to implement spatial multiplexing (SDM: Space Divison Multiplexing) and to simultaneously use different modes in a so-called slightly multimode fiber (generally supporting a few dozen modes) or different cores in a multicore fiber. Since 2010, several studies have been developed in this direction, mainly on the fibers supporting the LP (Linearly Polarized) modes and, more recently, the OAM (Orbital Angular Momentum) modes, that is, circularly polarized and helical phase modes. In the latter case, the phase and polarization properties limit the coupling between the modes. The design of a suggested circular photonic crystal fibre with support for 18 OAM modes is discussed in this research. The numerical analysis demonstrates that the proposed fibre has very good values for the fibre parameters, including a low containment loss of less than 810–4 dB/m at a wavelength of 1.9 m, a dispersion flat chromatic with a dispersion dissimilarity for the OAM modes that ranges from 75 to 77 ps/nm.km for a wavelength of 1.3 to 1.9 m, and a noteworthy effectual index partition.

A planar MIMO antenna using a modified EBG structure to increase bandwidth is proposed in this work. The antenna is printed on a Rogers RT-5880 dielectric substrate with a 40 × 20 x 0.787 mm size. Two hexagonal patch antennas in a MIMO array are placed in front of an EBG structure. The EBG structure is made using an array of 4 by 4 cells. Each cell resonates at 8 GHz. The measurement shows that the antenna operates over a bandwidth of7.3 GHz GHz (3.69 to 10.99 GHz) with a maximum gain of 10.4 dBi. The EBG structure improved the gain and the radiation pattern. A Good agreement between simulations and measurements was obtained. The proposed antenna could be used for ISM, 5G, IoT, and S-Band (radar and Satellite) applications.

In this paper, two different types of graphene-based rectangular patch antennas are designed for broadband terahertz applications. First, a patch antenna is modeled using copper metal for terahertz applications. The simulation results show a degraded reflection coefficient due to the use of copper. Therefore, the reflection coefficient is above -10 dB at 4.6 THz, then a VSWR is less than 3 dB when we used copper for the top patch. The patch antenna results are improved when graphene material is used, which has good conductivity, as demonstrated through simulations. Furthermore, an increasing band-width of 1 THz instead to 0.8 THz when we used the graphene material, due to a better impedance match. On the other hand, we achieved a slight increase in gain and the VSWR is less than 2 dB inside the available bandwidth.The time-domain solver of CST MWS software is used to evaluate the performance of the SIW (Substrate Integrated Waveguide) patch antennas. The SIW, PBG technology and the graphene material makes the antenna very important due to performance, such as the gain increases to about 7 dB, the bandwidth is about 1.6 THz duo to increase the chemical potential of the graphene material. The results obtained with CST are compared with simulations using HFSS to validate the design further. In addition, the 10 g peak skin SAR values of the antenna are 1.726e7 W/Kg instead of 9.55e5 W/Kg. In these results we conclude the antenna can detect tumor presence.

Futuristic mobile data networks are expected to reach higher data rates per user to accommodate the specifications of emerging services, such as triple play and mobile applications. Researchers are carrying out their works to tackle the drawbacks of traditional orthogonal frequency-division multiplexing by designing new waveforms with high spectral efficiency and low out-of-band emissions. Among many others, filter bank multicarrier (FBMC) is an appealing candidate for beyond 5G that fulfills these constraints. Consequently, it is worth to shed light on the performance of FBMC in multichannel transmission system. The main contribution of our paper is to compensate fiber nonlinearity including self-phase modulation and cross-phase modulation effects using adaptive Volterra equalizer in longhaul FBMC system based on a 6 x 20 Gb/s in wavelength-division multiplexing scheme over 100 km x 30 spans of single-mode fiber (SMF). The impacts of channel spacing, bit rate, and fiber types on system performance are addressed. For a target of bit error rate = 10(-3), the simulations show that this performance can be reached at -12 dBm of launch power when 5-taps third-order Volterra (TOV) equalizer is used for 12.5 GHz of channel spacing and an improvement of approximately 1 dB is obtained for 7 taps compared with the same equalizer with 3 taps. To further enhance the system performance, standard-SMF is replaced by a new class fiber called pure-silica-core fiber with large effective area, which exhibits a gain of almost 1.3 and 1 dB for 3 and 5 taps, respectively. The complexity burden of the TOV filter is also discussed. (C) 2021 Society of Photo-Optical Instrumentation Engineers (SPIE)

In this paper, we propose and investigate a multi-Gigabits-per-second baseband signal over Standard Single-Mode Fiber (SSMF) link using a 16-Quadrature Amplitude Modulation (16-QAM). This architecture can be deployed within the context of fifth-generation (5G) Cloud Radio Access Network (C-RAN). It consists of 4 × 4 Quasi-Orthogonal Space–Time Block Code Generalized Frequency Division Multiplexing (QOSTBC-GFDM) and Orthogonal Frequency Division Multiplexing (QOSTBC-OFDM) waveforms. It is based on the implementation of a third order Volterra Nonlinear Equalizer (VNLE) in the Remote Radio Unit (RRU). The VNLE has been efficiently employed to reduce the impact of the harmful effect of the photonic devices. A Zero Forcing (ZF) equalizer has been used at the User Equipment (UE) to overcome the wireless channel impairments. Our research shows that VNLE can be a promised solution to compensate signal distortions and non-linearity effects. Furthermore, this study shows that QOSTBC-GFDM is more efficient than QOSTBC-OFDM in terms of Out-Of-Band (OOB) emission and Spectral Efficiency (SE). Moreover, a comparable performance between the two waveforms in terms of Bit Error Rate (BER) and Error Vector Magnitude (EVM) is attained.

Abstract. We investigate the performance of 25-Gbps dual-polarized orthogonal frequency division multiplexing (OFDM)-based modulation in a directly modulated distributed feedback (DFB)-laser over 25 km of single-mode fiber. A Volterra equalizer is used to compensate for the nonlinear effects of the optical fiber. The results show that FBMC-OQAM modulation outperforms OFDM, universal filtered multicarrier (UFMC), and generalized frequency division multiplexing (GFDM) waveforms. Indeed, a target bit error rate of ∼3.8  ×  10  −  3 [forward error correction (FEC) limit] for FBMC, UFMC, OFDM, and GFDM can be achieved at −30.5, −26, −16, and −14.9  dBm, respectively. The effect of the DFB laser is also investigated for UFMC, OFDM, and GFDM, and they undergo a Q penalty of 2.44, 2.77, and 4.14 dB, respectively, at their FEC limit points. For FBMC-OQAM, the signal is perfectly recovered when excluding the DFB laser at −30.5  dBm.

For the first time, in this paper, generalized frequency division multiplexing (GFDM) waveform, through multimode fiber (MMF), is proposed and demonstrated for 5G communications at a data rate of 10 Gb/s. Based on the offset launch technique, the MMF fiber is simulated and evaluated for different offsets. Thanks to the GFDM technique, we reduce the out of band (OOB) radiation by 5 dB compared to orthogonal frequency division multiplexing (OFDM) and we reach even lower values of bit error rate (BER). In addition, we prove that increasing the taps of the Volterra equalizer enables us to obtain acceptable performances of BER, with different values of offsets.

In this work, a simulation study of baseband radio over fibre technology for 5G and Beyond technology has been realized. The proposed architecture deploys an Orthogonal Space-Time Block Code Generalized Frequency Division Multiplexing (OSTBC-GFDM) waveforms generated at the central office (CO). The signal is transmitted via a single-mode fibre (SMF) to the cell site. A Volterra non-linear equalizer (VNLE) is implemented into the cell site to improve signal quality by reducing the optical channel effect along with the transmission link. Then, the signal is up-converted to the frequency range 1 (FR1) and transmitted over the air to the user equipment (UE). The system performance is evaluating by measuring error vector magnitude (EVM) and bit error rate (BER).

Radio over is an attractive solution for broadband wireless access. In this paper, the performance of externally and direct intensity modulated RoF links is analyzed in the presence of the group velocity dispersion and third-order dispersion of the optical fiber. An external modulation system with dual electrode lithium niobate Mach–Zehnder modulator (DE-MZM) and direct modulation system with vertical-cavity surface-emitting laser (VCSEL) are considered. Both modulation schemes are tested using Gaussian optical pulses. Simulations are performed with the same values for common global parameters for both schemes. Although external modulation is a generally considered more advanced, our simulations show that the direct modulation technique with VCSEL shows a more robust performance. The performances are compared using performance parameters like Q factor, eye diagram, BER and RF signal amplitude.

Based on a developed analytical model, we demonstrate the feasibility of intensity-modulation direct-detection (IM/DD) optical orthogonal frequency division multiplexing (OOFDM) system over 1 km of multimode fiber (MMF) at data rates up to 64 Gb/s, at 1550 nm. The effect of data rates, number of subcarriers and fiber length are investigated for different number of excited mode groups that can be generated using the offset launch technique. Indeed, we show that when we increase the efficiency of the Volterra equalizer, by raising its input taps from 7 to 9, we can reduce the system impairments of 5.45 dB in terms of Q factor at 800 m. Furthermore, we prove that by exciting more mode groups the MMF bandwidth is reduced potentially. Finally, thanks to the efficiency of Volterra equalizer, we achieve a bit error rate (BER) below the forward error correction (FEC) limit, even in the case of the full excitation technique.

For the first time, we demonstrate in this paper an intensity-modulation direct-detection (IMDD) universal filtered multi-carrier (UFMC) system through several hundred meters of multimode fiber (MMF) that can be adopted for 5G communications and beyond. The proposed system is simulated and evaluated in terms of bit error rate (BER), Q factor, out of band (OOB) emission and Peak-to-Average Power Ratio (PAPR), at a data rate of 10 Gb/s. It is shown that filtering used with UFMC reduces the OOB radiation by 40 dB compared to orthogonal frequency division multiplexing (OFDM). Moreover, we prove that UFMC gives lower values of BER than OFDM, and even if the PAPR ratio of UFMC is higher than OFDM, the gap remains small. The results also show that using a Volterra equalizer with increasing taps enables to obtain acceptable performance through the MMF in terms of BER, even with high number of excited mode groups.

In this paper, the performance of different nonlinear electrical compensation techniques is evaluated. The goal is to enhance the transmission quality of intensity modulation (IM) and direct detection (DD) optical orthogonal frequency division multiplexing (OOFDM). The overall performance results are compared versus linear compensator equalizers. Also, studies here include the looking at the capability of Volterra based electrical equalizers for transmitted signal recovery.