Vehicle-to-everything (V2X) communication systems impose stringent latency and reliability requirements that are difficult to satisfy in highly dynamic wireless environments. Although reconfigurable intelligent surfaces (RISs) and unmanned aerial vehicles (UAVs) have independently demonstrated potential in enhancing wireless coverage, most existing RIS–UAV frameworks rely on idealized assumptions such as perfect channel state information (CSI) and static user scenarios. In this paper, a multi-RIS-assisted UAV-enabled V2X communication framework is proposed that explicitly accounts for vehicular mobility, latency constraints, and mobility-induced CSI aging. Multiple RIS panels are cooperatively deployed to eliminate coverage blind spots and ensure link continuity in realistic V2X environments. A joint UAV mobility and RIS phase optimization approach is proposed under outdated CSI to improve link reliability. Additionally, a time-varying performance analysis is carried out for understanding the dynamic behavior of signal-to-noise ratio (SNR) and average bit error rate (ABER) for mobility-aware CSI aging. Simulation results demonstrate that the proposed framework reduces the ABER by approximately 75% compared to a conventional single-RIS system under outdated CSI at 20 dB SNR (1.07×10−1 vs. 4.32×10−1), while substantially suppressing outage intervals in high-mobility V2X scenarios (v=20 m/s, CSI delay τ=20 ms), confirming the effectiveness of cooperative multi-RIS assistance for safety-critical vehicular communications.

This paper presents a novel and compact $2\times 2$ MIMO antenna design intended for sub-6 GHz 5G applications. The antenna is fabricated on a FR4 based substrate measuring $0.625\lambda _{0} \times 0.625\lambda _{0} \times 0.101\lambda _{0}$ (centered frequency = 2.2 GHz). It consists of four microstrip patch elements arranged orthogonally to one another and each element is fed by a 50- $\Omega $ feed line. To achieve miniaturization, tri-band operation and better isolation, circular complementary split ring resonators (CSRRs) are etched onto both the radiating patches and the underlying ground plane aligned with the patch configuration. The inclusion of CSRRs leads to the emergence of three resonant bands centered at 2.2 GHz, 3.4 GHz, and 4.4 GHz with respective fractional bandwidths of 3.16%, 2.05% and 2.71%. The antenna achieves reflection coefficients (S11) lower than -10 dB across all bands and inter element isolation ( $\vert \mathrm {S}_{\mathrm {ij}}\vert $ ) better than -25dB. It also shows an envelope correlation (ECC) below 0.006, and diversity gain exceeds 9.97dB. With the CSRR-based isolation, no additional decoupling structures are required. The measured results are observed in good agreement with simulated antenna parameters. The proposed design exhibits significant potential for integration into compact wireless devices, delivering robust MIMO performance, minimal mutual coupling, and reliable tri-band operation across the sub-6 GHz 5G frequency range.

This paper presents a novel and compact 2×2 MIMO antenna design intended for sub-6 GHz 5G applications. The antenna is fabricated on a FR4 based substrate measuring 0.625λ0 × 0.625λ0 × 0.101λ0 (centered frequency = 2.2 GHz). It consists of four microstrip patch elements arranged orthogonally to one another and each element is fed by a 50-Ω feed line. To achieve miniaturization, tri-band operation and better isolation, circular complementary split ring resonators (CSRRs) are etched onto both the radiating patches and the underlying ground plane aligned with the patch configuration. The inclusion of CSRRs leads to the emergence of three resonant bands centered at 2.2 GHz, 3.4 GHz, and 4.4 GHz with respective fractional bandwidths of 3.16%, 2.05% and 2.71%. The antenna achieves reflection coefficients (S11) lower than -10 dB across all bands and inter element isolation (|Sij|) better than -25dB. It also shows an envelope correlation (ECC) below 0.006, and diversity gain exceeds 9.97dB. With the CSRR-based isolation, no additional decoupling structures are required. The measured results are observed in good agreement with simulated antenna parameters. The proposed design exhibits significant potential for integration into compact wireless devices, delivering robust MIMO performance, minimal mutual coupling, and reliable tri-band operation across the sub-6 GHz 5G frequency range.

This paper presents a novel and compact 2 x 2 MIMO antenna design intended for sub-6 GHz 5G applications. The antenna is fabricated on aFR4 based substrate measuring 0.625 lambda(0)x 0.625 lambda(0) x 0.101 lambda(0) (centered frequency = 2.2 GHz). It consists of four microstrip patch elements arranged orthogonally to one another and each element is fed by a 50-Q feed line. To achieve miniaturization, tri-band operation and better isolation, circular complementary split ring resonators (CSRRs) are etched onto both the radiating patches and the underlying ground plane aligned with the patch configuration. The inclusion of CSRRs leads to the emergence of three resonant bands centered at 2.2 GHz, 3.4 GHz, and 4.4 GHz with respective fractional bandwidths of 3.16%, 2.05% and 2.71%. The antenna achieves reflection coefficients (S11) lower than-10 dB across all bands and inter element isolation (|Sij|) better than-25dB. It also shows an envelope correlation (ECC) below 0.006, and diversity gain exceeds 9.97dB. With the CSRR-based isolation, no additional decoupling structures are required. The measured results are observed in good agreement with simulated antenna parameters. The proposed design exhibits significant potential for integration into compact wireless devices, delivering robust MIMO performance, minimal mutual coupling, and reliable tri-band operation across the sub-6 GHz 5G frequency range.

This paper presents an efficient method for high-resolution microwave imaging for early-stage breast cancer detection using ultra-wideband (UWB) antenna. A compact UWB decagonal monopole antenna, designed through a step-by-step evolution process, is proposed as the front-end device for the microwave imaging system. The antenna exhibits a fractional bandwidth of 138.06%, a peak gain of 6.18 dBi, and an average efficiency exceeding 90%. A stable UWB performance has been demonstrated in terms of group delay and phase delay, analyzed for both face-to-face and side-by-side configurations. Additionally, lumped circuit model is proposed to get a physical insight into the working principle of an antenna. In this work, a 3D breast phantom is numerically modeled using CST Microwave studio. Subsequently, an UWB antenna is then used to scan the breast phantom at 36 different positions. S11 parameters are collected in both configurations, i.e. with and without a tumor inside the phantom. These parameters are then used to generate a high-resolution 2D microwave image of the breast using confocal microwave imaging (CMI) algorithm to detect the tumor. The designed antenna exhibits a specific absorption rate (SAR) of 1.22 W/kg at 13.08 GHz, which is within safe limits for human exposure. Hence the proposed UWB antenna is found to be a suitable candidate for biomedical applications.

A self-diplexing, full-mode, substrate-integrated waveguide (SIW) rectangular cavity-backed antenna based on an inverted Z-shaped radiating slot with filtering characteristics is investigated in this work. The proposed design allows for individual control through the loading of four different slots, namely, a combination of horizontal and diagonal slots, called inverted Z-shaped slots. The two diagonal slots make 45° angles between them, and this flexible rotation gives the design flexibility regarding control of the bands. By combining these slots into a modified inverted Z-shaped slot, a SIW rectangular cavity is configured and energized with two separate 50 Ω microstrip feed lines to resonate at two different frequencies—11.63 GHz and 13.27 GHz—and TE210 and TE220 modes are obtained for X- and Ku-band wireless purposes. In an experimental analysis, reflection coefficients of S11 < −10 dB were noted for both operating frequencies of 7.4% (11.23–12.09 GHz) and 3.0% (13.15–13.55 GHz), respectively. The average gain of the proposed antenna design in the two different operating conditions is 6.14 and 6.16 dBi, respectively. In addition, the proposed self-diplexing antenna attained high isolation, greater than 28 dB between both operating channels, and showed overall measured efficiency of 87.32%. Moreover, it features a single-layer structure, operates in dual bands, provides broadside linear polarization, and exhibits filtering capabilities.

Metamaterials [MTMs] are usually classified as a class of material which is effectively homogeneous, well – engineered in nature and can offer some unconventional and fruitful properties like negative permittivity, permeability and index of refraction. Due to their unique properties, these materials grab a broad interest of researchers working in the field of microwave antennas, filters and absorbers. In the last few decades, reasonable growth has been observed in the field of MTM antennas, filters and absorbers. In this article a precise report on fundamentals of MTMs and their use for designing compact antennas, filters and ultrathin absorbers has been presented. On the basis of their characteristics, all the applications have been further subdivided into several categories. In this regard, MTM antennas has been categories in four subsections as zeroth order resonant (ZOR) antennas, bandwidth enhanced\wideband MTM antennas, multiband MTM antennas and gain improvement in MTM antennas. The MTM filter section is further subcategorized as single band, wideband and multiband band-pass filters. In this sequence the electromagnetic (EM) absorbers are categories as single band, wideband and multiband MTM absorbers. Further, the increasing demand for user bandwidth necessitates innovative solutions. To address this challenge, the integration of terahertz (THz) technology within MTM structures emerges as a promising approach to expand their application scope. Consequently, this study explores the potential of MTM structures for THz applications, important case studies and challenges in last section. Further, MTM structures for THz application have been discussed. For the better understanding of the readers of this article, sufficient number of examples has been included, wherever it is necessary.

Single or multi-layer graphene has wide applicability in microwave and THz radiating structure designs. Owing to wide frequency tunability with an external bias of graphene, this paper presents a graphene–metal hybrid (GMH) based microstrip patch antenna (MSA) design at terahertz (THz) frequencies. Eight antenna structures with rectangular patches made of copper and GMH are studied and compared. The proposed structures are designed at 0.835 THz for short-distance communication. Polytetrafluoroethylene (PTFE) substrate of the relative permittivity (εr) 2.1, loss tangent 0.0002 and thickness 40 μm is used. By placing the copper metamaterial (CMTM) as a parasitic element on either side of the antenna, adjacent to the microstrip feedline, the impedance matching bandwidth (BW) is improved from 0.761 THz to 1.115 THz with more than 95

A novel and low profile, planar, rectangular cavity-backed self-diplexing substrate integrated waveguide (SIW) antenna with H-shaped slot for dual-band wireless services was designed and demonstrated. The proposed antenna structure radiates from H-shaped slot, which is etched on top of the SIW rectangular cavity, and is excited by two separate 50 Ω microstrip feed lines. The H-shaped slot is a combination of two vertical slots and one horizontal slot; because of that the presented antenna radiates at two distinct frequency bands around 8.95 GHz and 10 GHz, simultaneously. The design methodology results show that the H-shaped slot is significantly more effective than various other slots in the proposed geometry to suppress the unwanted harmonics, attaining good impedance matching and bandwidths and achieving better isolation between these two ports. Hence, the complete design mechanism helped to achieve self-diplexing characteristics. Furthermore, a self-diplexing H-shaped SIW rectangular cavity-backed antenna was fabricated and characterized for the complete demonstration purpose and found good covenants between the simulated one. Measured results show that the presented designed has impedance bandwidths for the lower and upper frequency bands of around 2.0% (8.89–9.03 GHz) and 3.1% (10.01–10.32 GHz), respectively, and obtained maximum measured gain of 5.11 dBi and 5.41 dBi at 8.95 GHz and 10.15 GHz, respectively. The proposed self-diplexing SIW rectangular cavity-backed structure shows that front-to-back ratios (FTBRs) are more than 21 dB, and on the other side, it provides good isolation between the two ports, which is more than 20 dB.

This paper presents the design of a frequency-tunable substrate-integrated waveguide (SIW) band-reject filter, specifically for spectrum underlay cognitive radio operation. The proposed filter has a simple tuning circuit but provides a wide frequency tuning range from 2.9 to 4.4 GHz (41%). The second resonant mode has been suppressed using a simple quadrature coupling; hence, the fundamental mode bandwidth of the filter has been increased from 2.08 GHz to 3.36 GHz. Due to its wide tuning range, simple tuning circuit, and increased fundamental mode bandwidth, the proposed filter is greatly important in underlay cognitive radio construction. The second-order filter has also been developed, and its performance is analyzed with both simulation and measurement. It gives a tunable bandwidth of 41%, an insertion loss of more than 10 dB, and a fundamental mode bandwidth of 3.36 GHz. The filter performance is also analyzed after connecting it to the standard horn antenna. Finally, from the total efficiency plots, it has been concluded that the proposed filter achieves all the above advantages with a low-lossy nature.

This work proposes a wideband rectenna for wireless energy harvesting of small and IoT devices. A redesigned bow-tie antenna with rectangular slots is proposed to achieve scattering parameters at a frequency of 3.89 GHz. In addition, the antenna design is integrated with a rectifying circuit consisting of four single triangular-shaped rectifiers and a voltage stabilization circuit comprising of filters for higher efficiency. Proposed modified bow-tie antenna demonstrates compactness, performance and ease of integration. Key applications of this energy harvester include wireless sensor networks, wearable devices and low power devices for charging.

Spectrum fragmentation has a substantial impact on spectrum utilization, which lowers blocking performance in elastic optical networks (EONs). In this paper, we investigate the spectrum status when a connection request cannot be served via single-path routing and propose a spectrum retuning approach with multi-path routing to address spectrum fragmentation, thus mitigating blocking concerns in EONs. We divide the approach into five stages: Single path routing, Spectrum block selection, Process Mapping, Connection retuning, and Connection splitting. Initially, the connection request is attempted to be served using the k-shortest routing paths in the best possible way. If, the request cannot be served through this process, this approach will first choose the “largest spectrum block” along the shortest path and then employ the “Process Mapping” operation to that block. This process will be repeated for other shortest paths until the required number of frequency slots is obtained (when there are multiple largest spectrum blocks on the shortest path and the “Process Mapping” function returns zero, the system will then analyze the next largest spectrum block in the array for the “Process Mapping” operation). Once the desired number of frequency slots is achieved through “Process Mapping”, the movable connections will be relocated to new spectrum locations, subsequently leading to the division of connection requests along the respective paths. Conversely, if the requested number of frequency slots is not achieved, the request will be declined, and all temporarily reserved spectrum allocations will be released. The simulation results demonstrate that the proposed approach significantly reduces the number of generated spectrum fragments, simultaneously enhancing blocking performance.

This paper presents an innovative algorithm that combines mini-batch gradient descent with adaptive techniques to enhance the accuracy and efficiency of localization in complex environments. The suggested approach utilizes the gradient ascent technique to refine the localization of IoT devices by iteratively refining their estimated positions based on received signal strength (RSS) measurements. By integrating mini-batch processing, the algorithm improves computational efficiency and convergence speed, making it well-suited for real-time applications. Additionally, the adaptive mechanism dynamically modifies the learning rate and batch size based on the current localization error, guaranteeing robust performance even in different signal conditions. The simulation outcomes indicate that the adaptive mini-batch gradient ascent established localization algorithm surpasses conventional techniques in terms of localization precision and convergence rate, especially in complex and rapidly changing indoor IoT networks. The suggested method provides a flexible and effective way to determine precise locations, which is essential for various IoT applications such as indoor, asset tracking, as well as smart home automation.

In this work a frequency selective resonator (FSS) immersed dual band, rectangular slot array has been presented. Two squared shaped ring frequency selective surfaces are interested on sides of travelling slots to obtain dual-band behavior. The presented array have input reflection coefficient ranges from 8.3-8.52 GHz and 11.7-12.12 GHz respectively. The presented array have higher front to back ration and 8-10 dBi gain, which is suitable for X-band application particular in radar.

This paper aims to introduce an approach for the simultaneous deployment of passive reconfigurable intelligent surfaces (PRIS) and active reconfigurable intelligent surfaces (ARIS) in 6G networks to optimize both capital and operational costs while maximizing network performance, energy efficiency, and signal coverage. By analyzing the energy consumption and costs of 5G base stations and comparing the merits of PRIS and ARIS, the study proposes a strategic deployment method: PRIS in urban areas to mitigate signal blockages and ARIS in suburban and rural areas to amplify signals over longer distances. Simulations demonstrate that this cross-deployment significantly enhances network performance, with PRIS reducing blind spots in urban regions, thus requiring fewer base stations for full coverage, and ARIS boosting signal strength in rural areas, extending base station reach and enhancing connectivity. This strategy leads to substantial reductions in costs and improves channel capacity, supporting green technology and sustainable development goals for future 6G networks.