Abstract Achieving the conversion between free-space propagating waves (PWs) and surface waves (SWs) has been a long-standing issue in the application of SWs. Metasurfaces presently exhibit extraordinary capabilities for electromagnetic waves manipulation and have realized efficient SWs directional radiation control. Nevertheless, most existing schemes still suffer from the limited polarization state and bandwidth, which are difficult to satisfy the requirements of diverse wireless applications. Herein, an appealing strategy of the SWs radiation meta-device is proposed to achieve broadband polarization manipulation in SWs directional radiation. Based on the geometric phase manipulation, the phase of two orthogonal circular polarized (CP) waves are independently controlled in a broad bandwidth. Through specialized arrangement of the meta-atoms, four samples of meta-molecules were composed to offer phase gradient modulation for two orthogonal CP radiations and two orthogonal linear polarized (LP) radiations. Then, four polarization states of broadband directional radiation were realized from SWs which were fed and guided by the horn antennas and dielectric plate. Both simulation and experimental results of the proof-of-concept prototype are in good agreement with the theoretical predictions, which verified the feasibility of our proposed methodology. The innovative design with high efficiency, good crosspolarization discrimination and broadband frequency scanning performance offers an excellent platform for flexibly manipulating SWs radiation and possesses tremendous potential in engineering applications.

A Compact CPW-Fed Super-Wideband Antenna on FR4 for 5G, 6G, and Wireless Applications

In this study, a compact dual band 2-element Multiple Input Multiple Output (MIMO) multiband antenna is designed. Two radiating patches make up the suggested antenna, which aims to produce multiband resonance antenna. The 45×33 mm2 two element MIMO antenna is printed on a 1.6 mm thick FR-4 substrate with a dielectric constant of ɛr = 4.3 and a loss tangent of 0.02. An optimized dual band antenna was produced as a result of a parametric research based on the FDTD technique, which improved the structure's performance with regard to operational bandwidth. Additionally, a separate 50Ω-fed two-element MIMO arrangement is taken into consideration. By introducing spatial diversity into the MIMO arrangement, good isolation can be achieved without the need to use well-known techniques of decoupling structures. Results shows that the system has a mutual coupling of less than -15 dB between the various elements and operates on two bands: "3.5GHz WiMAX." and "4.2 GHz " Moreover, an analysis of the Diversity Gain (DG), Envelope Correlation Coefficient (ECC) and Channel Capacity Loss (CCL) parameters shows that they satisfy the practical standards: DG > 9.80, ECC < 0.06, and CCL < 0.4 bits/s/Hz over the relevant bands

The rapid growth of wireless communication demands within Internet of Things (IoT) applications requires antennas that exhibit high efficiency, compact dimensions, and reliable performance in the UHF band. This study aims to design, simulate, fabricate, and evaluate the performance of a helical antenna operating at 435 MHz, with its results compared against a slot antenna. The design process was conducted using CST Studio Suite with parameter optimization to achieve an optimal configuration. The prototype was fabricated using copper wire as the radiating element and an aluminum ground plane. Experimental testing was carried out with a UHF Antenna Demonstrator, followed by validation through a 433 MHz RF module integrated with Arduino. The simulation results indicated that the optimized helical antenna achieved aVoltage Standing Wave Ratio (VSWR) of 1.8 and a gain of 11.5 dBi. In contrast, the measurement results demonstrated improved performance, with a VSWR of 1.05, a return loss of −32.4 dB, and a bandwidth of 41 MHz. Comparative analysis revealed that the helical antenna outperformed the slot antenna in terms of efficiency, directional radiation pattern, and transmission distance, reaching up to 25 m compared to 15 m for the slot antenna. These findings confirm that the helical antenna is a more suitable and effective solution for UHF IoT communication systems, providing reliable performance for modern wireless applications.

This paper presents a flexible and adjustable antenna design that reduces interference in different practical applications. The antenna, shaped like a square with slots and integrated pin diodes, enables frequency adjustment by connecting or disconnecting components. Made of certain substrate material, the antenna operates at five frequency bands commonly used in 5G sub-6 GHz applications. Along with improving the connection with the Metamaterial (MTM) structure by using four PIN diodes without altering the radiation pattern, the new design replaces the via with a fractal technique, which cuts down on energy losses and boosts performance while also lowering costs. Simulation results demonstrate excellent impedance matching, multiple adjustable bands, and significant gain(>10 dBi). The antenna exhibits radiation patterns and achieves an efficiency greater than 75%. Analysis under various conditions shows the antenna’s performance on curved surfaces, making it suitable for adaptable electronic systems. A comparison with prior studies highlights the antenna’s potential within the specified frequency ranges.

High Electron Mobility Transistors (HEMTs) based on wide band gap semiconductors and two-dimensional electron gas (2-DEG) channels are crucial for high power and radio frequency applications. Gallium nitride (GaN)-based HEMTs offer superior breakdown voltage, electron transport characteristics, and thermal conductivity for next-generation power electronics. This study investigates the effect of gate-drain distance (Lgd) on electronic characteristics of a multi-layer graded AlₓGa₁₋ₓN HEMT structure (x = 0.05-0.30) on Si substrate using finite element method simulation through SimuApsys modeling software. The Lgd parameter was systematically varied between 0.8 μm and 30 μm to analyze breakdown voltage (Vbr), on-resistance (Ron), current-voltage char-acteristics, and electric field distribution. Simulation results reveal critical trade-offs: short Lgd (3-6 μm) provides low Ron and high current density (Ids,max ≈ 3.95 mA/mm) but lower Vbr (~135V) due to concentrated electric fields, while long Lgd (24-30 μm) achieves high Vbr (~380V) through distributed electric field profiles but with increased Ron and reduced current capacity (~0.65 mA/mm). Application-specific Lgd optimization guidelines are established: 3-6 μm for 350V. This simulation approach enables effective device design optimi-zation without expensive experimental fabrication.

This work presents a compact printed MIMO antenna specifically designed for portable wireless applications, offering strong isolation between its elements. The antenna consists of two ultra-low-profile inverted-F antenna (IFA) elements placed back to back with a close spacing of just 0.05λ at the resonance frequency (2.4 GHz). To improve isolation, a parasitic structure is strategically positioned between the two IFAs. Additionally, a slot is introduced into the ground plane, which excites an extra resonance, effectively broadening the antenna’s operational bandwidth. The proposed design was successfully fabricated and tested, with measurement results closely matching the simulations. The antenna demonstrates a good impedance bandwidth ranging from 2.28 to 2.85 GHz, maintaining a return loss better than 10 dB, and achieving excellent isolation levels exceeding 40 dB. It also delivers a high peak efficiency of 90% and a realized gain pattern of around 2 dBi over the band of interest. In addition, the inclusion of the parasitic element further enhances the antenna’s performance by promoting pattern diversity and reducing the correlation between radiation patterns, ensuring robust MIMO and diversity characteristics.

ABSTRACT A light-controlled liquid crystal phased array antenna operating at 10.5 GHz is proposed and experimentally validated. Unlike conventional electrically tuned phased arrays that require bias circuits, the proposed design employs an azo-doped liquid crystal whose dielectric constant is tuned via cis-trans isomerization under optical excitation. This method eliminates dependence on external voltage connections, thereby reducing power consumption, electromagnetic interference, and structural complexity. The antenna consists of a 1 × 2 microstrip patch array, a liquid crystal phase shifter, a power-splitting network, and a coupling feed structure. Measurements confirm stable impedance matching with S11 below −10 dB across the operating band. Under optical illumination, the antenna achieves a beam steering range of ±12° and a peak gain of 7.65 dBi. These results demonstrate the feasibility of all optical control in phased arrays, highlighting its potential for compact, reconfigurable, and interference-resistant applications in next-generation wireless communication and adaptive radar systems.

In this study, a new semi-analytical model was developed that can calculate the output voltage of low-power microwave rectifiers as a function of frequency and input power. The model integrates diode rectification characteristics and frequency-dependent impedance mismatches within the same mathematical structure. Defined by second-order polynomial expressions for input power and frequency, the model directly incorporates reflection coefficient (S11) data into the equations to account for frequency-dependent power losses caused by impedance mismatch, thereby improving calculation accuracy under wide-band conditions. To validate the model, a wide-band rectifier prototype with an FR4-based T-type matching network and a voltage doubler structure was designed and manufactured. Model calculations showed over 95% agreement with simulation results and closely followed the measured output voltage trends over the 0.5–3 GHz frequency range and input power levels from −12 dBm to 0 dBm. The proposed model provides a design-oriented and computationally efficient tool for wide-band, low-power RF energy harvesting and wireless power transfer applications, enabling rapid evaluation of impedance matching strategies with reduced reliance on electromagnetic simulations.

Extensive efforts have been undertaken by governments, research institutes, and telecommunications corporations to expand the availability of fifth‑generation (5G) technology. Closely integrated with the Internet of Things (IoT), 5G enables automation and facilitates large‑scale data collection aimed at improving quality of life. This paper presents an overview of 5G and IoT technologies, highlighting common architectural designs, typical IoT deployments, and persistent challenges. Particular attention is given to interference in wireless applications, with a focus on issues specific to 5G and IoT, as well as potential strategies for mitigation. The study underscores the importance of managing interference and enhancing network efficiency to ensure reliable communication among IoT devices, which is essential for the effective operation of enterprise systems. For organizations that rely on these technologies to improve customer satisfaction, reduce downtime, and increase productivity, the findings provide valuable insights. Finally, the paper emphasizes the potential of network convergence and advanced services to enhance internet speed and accessibility, thereby fostering new opportunities for innovative businesses and applications.

Abstract Dynamically tunable terahertz (THz) devices are of great interest for applications in wireless communication, information encryption, and biomedical imaging. In this paper, we propose a dynamic and stretchable THz metasurface lens fabricated via 3D aerosol jet printing. Based on Pancharatnam–Berry phase, eight optical meta-atoms covering the phase shift range of 0–2 π are employed to construct a phase distribution of a lens. Combined with a multi-level quantitative phase compensation, the metasurface lens achieves focus compensation between focal spots during the stretching process. Experimental results show that the metasurface lens can maintain the target focal length under a stretching ratio of up to s = 115%. This work also investigates the feasibility of 3D aerosol jet printing for THz metasurfaces, providing an insight into the development of low-cost THz optical devices.

A multi-channel Gallium Nitride (GaN) based Gate-All-Around (GAA) Nanosheet Field Effect Transistor (NS FET) having 2nm gate underlap wrapping of high-k dielectric spacer are designed, explored and analysed for inclusion in future wireless application systems. The integration of GaN as the channel material provides superior electron mobility and high breakdown voltage, making it extremely suitable for high-frequency applications. The inclusion of the gate underlap region effectively reduces parasitic capacitance while mitigate short channel effects due to its high-k wrapping. High dielectric gate stack is employed to enhance gate channel coupling and reduce leakage currents. Calibration is done utilizing a fabricated GaN FET and further validated by analytical threshold voltage modelling. Further, DC characterization reveals a remarkably low off-current (IOff) of 12 × 10-7nA/µm, a high switching ratio (IOn/IOff) of 5.26 × 1010, subthreshold swing of 60.50mV/decade, and drain induced barrier lowering (DIBL) of 11.92mV/V that superbly outperform the IRDS2028 benchmarks of 1.5nm technology node. The RF analysis demonstrates superior high-frequency performance with cut-off frequency reaching 8.16THz attributing to enhanced transconductance and minimized gate capacitance indicating the GaN NS FET operation in THz frequency regime. The use of multichannel in NS FET significantly boosts carrier transport efficiency and scaling compatibility exhibits enhanced drive current and reduced leakages. This validates and conforms devices' potential for integration into future RF front-end modules and beyond 5G/6G wireless systems. The combination benefits of material innovation, geometric optimization and electrostatic enhancement positioning this device as a strong candidate for post-CMOS ultra-scaled high-performance logic and RF applications in THz frequency regime.

Equivalent Circuit Modeling-Based Frequency and Pattern Reconfigurable Low-Cost Multi-band Multi-purpose Miniaturized Antenna for Wireless Applications

In real-time digital signal processing, the multirate transformation is a commonly used technique for interpolation and decimation. Comb-based decimation filters are used in wireless applications because of their minimal complexity and effective alias suppression. One symmetrical Finite Impulse Response (FIR) filter that may be used as a decimation filter is the cascaded integrator-comb (CIC) filter. Compared to other decimation filters, the CIC filter operates faster and uses less hardware because it does not require multipliers. Efficient digital filtering is critical in modern wireless communication systems, where real-time processing and resource optimization are essential. This paper presents a multi-stage hybrid polyphase CIC filter architecture implemented on a Xilinx Virtex-4 Field-Programmable Gate Array (FPGA) to enhance signal processing performance. The proposed method integrates a polyphase CIC filter with an FIR compensation filter, addressing the passband droop and improving frequency response. By leveraging polyphase decomposition and pipeline optimization, the design reduces computational complexity while maintaining high accuracy. The FPGA-based implementation ensures low latency, high throughput, and efficient hardware utilization, making it ideal for high-speed wireless applications. Experimental results demonstrate that the proposed filter achieves superior filtering performance compared to conventional CIC filters, offering a robust solution for real-time digital signal processing. The proposed method achieves substantial hardware savings, utilizing only 289 Slice Registers, 25 LUTs, 346 Flip-Flops, 63 BRAMs, and 76 DSPs, compared to the highest values from prior works, which consumed up to 628 Registers, 442 LUTs, 654 BRAMs, and 364 DSPs. This represents a reduction of up to 54% in Slice Registers, 94% in LUTs, and 88% in DSPs, highlighting the efficiency of the proposed architecture for SDR-based IoT gateways.

Radio and mm-wavelength astronomical instrumentation systems require anti-aliasing and band-defining filters with sharp band edges, high reproducibility, low thermal variability, and low susceptibility to radiofrequency (RF) interference. As large-scale deployments involving thousands of RF channels become more common, there is an increasing need for filter solutions that balance technical performance, scalability, and cost-efficiency. In this work, we present a practical framework for the design and implementation of high order stripline filters tailored for wideband digital readout systems. Emphasis is placed on achieving low unit-to-unit variation ([Formula: see text]0.5% on frequency response metrics), steep roll-off ([Formula: see text]90dB/GHz), high stopband isolation ([Formula: see text]-60dB), minimal in-band ripple ([Formula: see text]0.5dB) , and environmental stability (thermal drift [Formula: see text]1% across 0-115[Formula: see text]C). These performance targets are realized specifically in stripline filters, which rely on an embedded layout structure, material selection, and electromagnetic shielding. While these filters are complex to design, for low production runs, their precision and process uniformity make them ideal for scalable batch fabrication. Case studies from radio astronomy applications validate the proposed approach against demanding real-world requirements, demonstrating that the combination of careful material stack-up and repeatable design methodology support scalable deployment of high-order filters for next-generation radio telescopes.

Abstract Direction of arrival (DOA) estimation plays a vital role in automotive radar, speech recognition, and wireless communication applications. Most existing DOA estimation algorithms rely on uniform linear arrays (ULA) with equally spaced elements and simple structures. However, in real-world scenarios, random sensor failures occur, causing the ULA to degrade into a randomly sparse linear array (SLA). The missing data from faulty sensors significantly reduces the performance of traditional DOA estimation methods. To address this issue in radar systems, this paper proposes a novel DOA estimation approach called TAPEDOA-Net, which is based on a Transformer Adaptive Positional Encoder (TAPE). This method preserves the spatial array dimension features of the received signals during feature extraction. It scales the standard Transformer positional encoding using array position information. The Transformer encoder effectively integrates signal features with array position information. This integration reduces the impact of antenna faults on DOA estimation performance. The simulation results show that, compared to several existing methods, the proposed TAPEDOA-Net achieves accurate DOA estimation for both intact ULA and ULA with known failure positions. It achieves higher angular resolution and lower angular error in these complex environments.

ABSTRACT In this study, we conducted a comprehensive DC and AC analysis of Gate-All-Around (GAA) devices, focusing on the implications of increased gate capacitance both for wider and narrower device on key performance metrics. Our findings reveal that the elevated gate capacitance due to thin GaN cap layer significantly affects the transconductance (gm), Drain-Induced Barrier Lowering (DIBL), subthreshold swing (SS) and the on/off current ratio (Ion/Ioff). A new analytical linkage is formulated connecting gate capacitance ( C g ) with key DC performance metrics. The results indicated a significant enhancement in both ft and fmax, attributed to the high Ion/Ioff ratio of 1.72 × 10 13 , confirming the superior high-frequency performance of GAA structures. Our analysis underscores the critical role of gate capacitance in optimising the electrical characteristics of GAA devices, paving the way for their application in 5G wireless communication.

The Internet of Medical Things (IoMT) allows wireless devices and applications to operate healthcare information from remote users to send critical data over the internet for edge devices. However, the healthcare system undergoes serious security and privacy threats. Therefore, the artificial intelligence-based privacy-preserving technique, Federated Learning (FL), can be used to address the privacy-related issues in the IoMT system. This work demonstrates the performance of a Fifth-Generation (5G) massive Multiple-Input-Multiple-Output (MIMO) system for the IoMT network with the FL framework. This proposed model builds a highly secured end-to-end system with a high data rate and high accuracy, which is a critical requirement for IoMT systems. Further, the uncertainty in Channel State Information (CSI) is considered, and the performance is realized for Maximum Ratio Combining (MRC) and Zero-Forcing (ZF) decoding techniques. The advantage of less complexity at a low power regime in MRC as compared to ZF in a massive MIMO system makes it more favorable for IoMT devices. Moreover, the above-mentioned system becomes more accurate and secure with the implementation of the FL technique. In addition, the beamforming and channel hardening features in massive MIMO make the IoMT system more robust against nearby interference. Finally, the simulation was performed on a MATLAB dataset using the proposed model. The results of the sum rate and accuracy demonstrate a secured solution with a high data rate and negligible interference for edge devices. The accuracy obtained is approximately 91% to 92%, with an improvement of around 7% to 8% as compared to the baseline approach.

Abstract Commonly, the electromagnetic properties of a microwave metamaterial are defined by its structure rather than by its chemical composition. Due to the nature of microwaves – electromagnetic radiation at frequencies between 300 MHz and 300 GHz – metamaterials are usually composed of a combination of conductive and dielectric materials, with subwavelength patterns defining how a wave interacts with it. A metamaterial which is very thin with respect to the operating wavelength is usually referred to as a metasurface. While the term “metamaterial” was first coined around the turn of the last millennium [1], antennas engineers have been designing engineered structures which would now be called metamaterials since at least the work of Ben Munk in the 1970s [2], and with the broadest definitions since artificial dielectric lenses were developed by Winston E. Kock at Bell Telephone Laboratories in the 1940s [3]. This historic link to telecommunications means similar techniques are used at lower frequencies, so this roadmap also includes metamaterials for other wireless applications.

In this article, a dual-port MIMO antenna has been investigated with stable dual radiation performance for 5G wireless broadband services. Here, two antenna sections, consisting of a pair of monopole strips, are hybridized with independent excitation units, achieving effective bandwidth, good port isolation and dual radiation performance. The design embodiment linked to a cross-coupled ± 45 ∘ radiators at the top and a reflector at the bottom. All independent antenna units are excited by a referential balun, which acts like an impedance transformer and behaves like a dipole resonator. The excitation in each antenna units asserts a stable duality boresight ± 45 ∘ radiation with a maximum backlobe suppression. The performance merits of the proposed antenna design have been validated on a prototype model, which operates at Port-1 from (2.6 to 4.06) GHz with 43.84% 10 dB impedance bandwidth and at Port-2 from (2.6 to 4.04) GHz with 43.37% 10 dB impedance bandwidth, with consistent port isolation >25 dB in the operating band, 9.07 dBi as peak realized gain and radiation efficiency of (87–89)%, which can be leveraged in 5G wireless applications.