Wireless Applications Research Articles

Performance Analysis of a Swastika shaped MIMO Antenna for Wireless Communication Applications

A novel wideband 4-port Multiple-Input Multiple-Output (MIMO) circular patch antenna is presented for operation in a resonant frequency band from 1.76 to 9.06 GHz used for PCs, Wireless Local Area Networks (WLANs) and satellite applications. The structure of the design consists of microstrip fed slot antenna considered on the four corners of the FR-4 substrate. To reduce mutual coupling and enhance the parameters of the MIMO antenna, a swastika-shaped ground is embedded. The simulated and experimental results show that the design achieves good performance, isolation >15 dB and radiation efficiency greater than 85%. The radiation patterns, surface currents, gain and channel capacity are also investigated. This circular shaped patch antenna is applicable to WLAN and satellite communication applications. Each circular patch on the four corners is connected to a 50 Ω microstrip feedline. A ring slot is etched on the circular patch and a small rectangular slot is embedded to the etched circular patch. The design provides good radiation patterns and the operating bands are obtained at 1.76 GHz, 2.4 GHz, 3.5 GHz and 9.06 GHz attaining reflection loss of -16 dB, -22 dB, -24 dB, -15 dB. The structure of the proposed design is simulated and evaluated in High-Frequency Structure Simulator (HFSS) software. The MIMO structure is fabricated on the FR-4 substrate. The minimum proximity between simulated and measured results is observed.

Multi-band reflective metasurface for efficient linear and circular polarization conversion

This paper introduces a novel reflective metasurface for efficient polarization conversion in the X, Ku, and K bands. Through rigorous simulations and experimental validation, high polarization conversion ratios (PCR) exceeding 90% were achieved, even at incidence angles up to 45∘. Superior performance in the axial ratio (AR) and ellipticity values was demonstrated, showcasing the versatility of the designed metasurface in linear-to-linear and linear-to-circular polarization conversions. Comparative analysis against existing metasurfaces revealed the superiority of the proposed design in polarization conversion, particularly in Linear polarization, left-hand circular polarization, and right-hand circular polarization scenarios. The experimental results closely align with simulation outcomes, with minor discrepancies attributed to fabrication imperfections and antenna misalignments. This study advances metasurface-based polarization converters, offering promising applications in wireless communication, radar systems, quantum optics, and sensing technologies.

Field programmable gate array implementation frameworks of a variable-length pseudorandom pattern generator

A pseudorandom pattern generator produces sequences similar to true random sequences. A variable length pseudo-random pattern generator (PRPG), which can be used as a pattern generator for various applications like built-in self-test (BIST) or cryptography, is proposed in this paper. Our work is based on a linear feedback shift register circuit platform. The proposed design can generate patterns corresponding to different characteristic polynomials of any given polynomial degree. These characteristic polynomials are integrated into the linear feedback shift register circuit by providing an option to select the feedback paths of any of these polynomials. This paper implements and evaluates the proposed design for primitive and non-primitive characteristic polynomials of degrees 3 to 15. The circuit generates output patterns of different periods based on user inputs. Compared to other pseudorandom pattern generator circuits, the proposed circuit can generate a large set of patterns and consumes less power. Adequate results from the experiments demonstrate the functionalities and performance of the proposed pattern generator from degrees 3 to 15. The proposed circuit generates pseudorandom patterns that can be used not only for built-in self-test but also for cryptography and wireless communication applications.

Class-F–1 GaN Power Amplifier Integrated Active Antenna With Increased Efficiency for Wireless Power Transmission Applications

Class-<i>F^–1 </i> GaN Power Amplifier Integrated Active Antenna With Increased Efficiency for Wireless Power Transmission Applications

Design of a metasurface loaded with RF varactor and PIN diode integration dual-band reconfigurable antenna for bluetooth, Wi-Fi, WLAN and wireless 5G applications

Abstract This article presents a compact dual-band reconfigurable antenna design utilizing a metasurface integrated with an RF varactor and PIN diode for Bluetooth, Wi-Fi, WLAN, and 5G wireless applications. The results of the study show that using the metasurface reflector (MSR) structure gives a much higher gain than using a decagon antenna without a metasurface reflector. This antenna is designed and fabricated on FR4 epoxy substrate materials with a dielectric constant of 4.4 and the thickness of the substrate is 1.6 mm. The metasurface reflector (MSR) loaded antenna has a total electrical dimension of 0.51λ0 × 0.49λ0 × 0.013λ0, where λ0 represents the resonating wavelength at a 2.6 GHz center frequency. In the proposed work, the slotted decagon patch antenna consists of a complementary split-ring resonator constructed on its ground plane. Moreover, for the frequency reconfiguration, a PIN diode switch and an additional varactor diode switch are used for tuning the frequency band. Furthermore, without affecting the radiator structure, the varactor diode is placed on the upper side of the patch and the PIN diode switch is integrated into the ground plane. The proposed antenna has reconfigurable and tunable operating frequencies of 2.6 GHz and 3.4 GHz. The operational frequency of the band is switched between 2.6 GHz to 3.4 GHz. The switching operation of the dual configuration of 2.6 GHz with the PIN diode ON and 3.4 GHz with the PIN diode OFF. However, simultaneously applying a reverse bias voltage to the varactor diode from 0-10 V shifts its resonance frequency from 2640-2510 MHz and frequency tuning is done in respective bands. The proposed antenna achieved a peak gain of 7.5 dBi, and a radiation efficiency range of 72– 82% in the overall operating bands of interest. The proposed work is used for Bluetooth, Wi-Fi, WLAN, and wireless 5G applications. Performance verification is done by fabricating prototypes and verifying their performance using simulation and testing results.

Defective ground structure loaded polarization reconfigurable ring-shaped patch antenna for multiband applications

ABSTRACT A novel stub-loaded polarization-reconfigurable ring-shaped circular patch antenna designed for multi-band operation and switchable polarization is presented, having advantages such as ease in manufacturing and compact size (20 mm × 20 mm). The circular ring is segmented into four sectors, and two stubs are loaded on the inner side of the ring to disrupt the current distribution and create two orthogonal electric field vectors, generating circular polarization. The antenna supports it in switching three distinct polarization states: linear polarization, left-hand circular polarization, and right-hand circular polarization, selectable with different combinations of diodes. From the measured results, ARBW (<3 dB) is 32.12% and 6.06% for CP bands. Additionally, eight LP bands with IBW of 71.66%, 3.55%, 3.94%, 35.88%, 45%, 45.5%, 34.77%, and 8.2% are achieved. The antenna exhibits satisfactory stable gain across all frequency bands and excellent radiation performance, making it a promising candidate for modern wireless communication applications (C-band, ITS2 fixed, X-band, and Ku-band satellite downlink operations).

Network model and application in wellbore wireless communication of extremely low frequency electromagnetic waves

Abstract To address the limitations of traditional wellbore communication technologies and address the shortcomings in synchronization and channel analysis of electromagnetic waves wellbore communication models, this paper proposes a novel wellbore wireless communication method using Extremely Low Frequency (ELF) electromagnetic waves. A polygonal multiple-delay complex network model for ELF electromagnetic waves propagation in wellbore and strata was established, which was divided into four subnetworks using network splitting theory: the oil tubing subnetwork, the casing subnetwork, the cement subnetwork, and the strata subnetwork. A controller was designed, successfully validating the stability of the model and achieving fast synchronization. The optimal transmitting frequency range was determined to be between 5 and 20Hz through theoretical derivation of attenuation factors and skin depth, combined with finite element simulations. Simulation results indicate that cement and casing are the primary transmission channels, followed by oil tubing and strata, with electric signals exhibiting significantly higher intensity than magnetic signals. Unlike electric signals, magnetic signals are less affected by shielding effects. Two field experiments confirmed the feasibility of using ELF electromagnetic waves for wellbore wireless communication, which can achieve a wireless communication distance of over 1600 meters without relays. This research provides a critical theoretical foundation and experimental validation for the future development of efficient wellbore wireless communication and intelligent wells.

Optically Pumped Ultrafast and Broadband Terahertz Modulation with Scalable Molecular Beam Epitaxy Grown MoTe2/Si Heterostructures

AbstractDespite advancements in terahertz (THz) modulators, achieving a balance between large modulation depth (MD) and fast modulation speed in scalable devices remains a significant challenge. Optically pumped THz modulators with high MD, broad bandwidth, and fast response times are essential for progress in THz technology. Here, scalable MoTe2/Si van der Waals (vdW) heterostructures are grown via molecular beam epitaxy (MBE) as an optically pumped THz modulators, leveraging its favorable band alignment and seamless integration with silicon complementary metal‐oxide semiconductor (CMOS) technology. High‐quality bilayer, 5‐layer, and 7‐layer MoTe2 films are grown on high‐resistivity silicon, with the bilayer modulator achieving a maximum 74.6% modulation depth under 355 nm illumination of 4.8 W mm−2 at 0.25 THz. The bilayer device exhibited fast rise and fall times of 1.8 and 0.6 µs, respectively, and provided broadband modulation across the 0.1 to 1.0 THz range. Furthermore, this work demonstrates that higher modulation depth significantly enhances THz imaging quality with promising applications in detecting pharmaceutical forgeries. Overall, these ultrafast, broadband THz modulators provide a promising route for advancing next‐generation THz technology, enhancing applications in wireless communication, precision detection, and high‐resolution THz imaging, fostering future innovation.

Topologically Streamlined Single Feed Wide Band Circular Polarized Antenna

A single feed circularly polarized (CP) microstrip hexagonal open loop monopole antenna with defective ground plane is introduced in this article. The antenna is made up of an open hexagonal loop excited by a 50Ω microstrip feed line, ground defected by a curved structure with two slots and a “U” shaped slit etched below the microstrip feed line. The optimized designs are verified experimentally for reflection coefficient, axial ratio bandwidth, realized gain and radiation patterns. Results of the measurement indicate that the proposed antenna attains a wide impedance bandwidth of 103% (2.5–7.8 GHz), axial ratio bandwidth of 83% (2.9–7 GHz) and peak gain of 3.5 dBi. The proposed radiator’s novelty stems from the blend of uncomplicated geometry and single-point-fed excitation with broadband CP characteristics having a compact size of only 0.149λ0 at the lowest CP frequency. The suggested antenna is an appropriate one for various wireless communication applications like WLAN, Wi-MAX, Aeronautical Radio Navigation band and C band applications. Exhaustive studies indicate superior performance of the suggested antenna as compared with the state-of-the art designs.

Programmable beam steering and quasi-continuous phase shift on a 2-bit terahertz coding metasurface with HEMT-switched multimodal modulation.

Terahertz reconfigurable intelligent surfaces (RIS) stand out from conventional phased arrays thanks to their unique electromagnetic properties and intelligent interconnect paradigms. They are a vital technology for terahertz wireless communication and radar detection systems. Compared with 1-bit coding metasurfaces, 2-bit coding metasurfaces offer significant advantages such as single beam steering and reduced quantization errors. Electrically controlled switchable coding metasurfaces have been restricted by the switch performance and integration technology, limiting reported devices to 1-bit coding. Additionally, metasurfaces that offer quasi-continuous phase modulation across a 2π range have garnered extensive attention for their higher phase shift precision and regulation freedom. This paper proposes a 2-bit multimodal THz quasi-continuous phase shift coding metasurface based on asymmetrically configured high electron mobility transistor (HEMT)-dipoles. The meta-device consists of two asymmetrically combined HEMT-dipole resonant structures, wherein the versatile density variations of two-dimensional electron gas (2DEG) introduce subtly local-field modulation under different external voltage combinations, rendering the quasi-continuous phase shift of 0° to 350° at 0.376 THz with a minimum incremental step of 6°. Moreover, selecting optimal 2-bit coding states within the quasi-continuous phase shift loop constructed different array phase gradients based on Snell's law, enabling real-time beam steering from 21° to 48° within the 0.365-0.385 THz frequency range. The simulation results align closely with the experimental findings, marking the first achievement of real-time programmable phase shift control and 2-bit beam steering using electrically controlled switches in the terahertz domain. This research provides a practical approach for real-time quasi-optical continuous phase modulation control and programmable single-beam electronic steering, with promising applications in terahertz wireless communication, radar detecting, and computational imaging, among other fields.

Advantages and Challenges of Graphene Transistors for High-Frequency Applications

Graphene is regarded as an ideal material for next-generation high-frequency (HF) electronic devices, attributed to its unique two-dimensional structure, high carrier mobility, and exceptional electrical properties. In recent years, the limitations of conventional silicon-based technologies for high-frequency applications have become increasingly apparent, resulting in heightened interest in graphene transistors, which exhibit significant potential for applications in wireless communications, radar systems, and terahertz technology. These transistors exhibit high cutoff frequency and low noise characteristics, along with favorable bipolar properties, which provide them with significant advantages in radio frequency (RF) applications. However, despite the significant theoretical advantages of graphene materials, their practical application is still restricted by multiple factors. Specifically, insufficient voltage gain from weak current saturation, material uniformity issues, and large-scale production challenges have restricted the widespread adoption of graphene transistors in high-frequency electronic devices. This paper reviews the relevant literature, examines the disparity between the electrical performance and practical applications of graphene transistors, and identifies the key factors influencing their implementation. The results demonstrate that targeted bandgap engineering, innovative device architectures, and the exploration of new materials can help graphene transistors can mitigate existing challenges and position themselves as key components in future HF electronic devices, driving significant advancements and broader integration of related technologies.

Amelioration and Immuno-modulation by Ashwagandha on Wi-fi Induced Oxidative Stress in Regulating Reproduction Via Estrogen Receptor Alpha in Male Japanese Quail.

As global change threatens avian biodiversity, understanding species responses to environmental perturbations due to radiation emitted by enormous increase in the application of wireless communication is very urgent. The study investigates the effect of MW radiation on redox balance, stress level, male fertility and the efficacy of Withania somnifera (WS) root extract (100mg/kg body weight) orally administered in 8weeks old mature male Japanese quail exposed to 2.4GHzMW radiation for 2h/day for 30days with power density = 0.1264 mw/cm2 and SAR = 0.9978 W/Kg. Wi-fi exposure induces a decrease in testicular weight, volume, density and gonado-somatic index (GSI) while Ashwagandha increases them. Oxidative stress parameters increased and activity of SOD, catalase, GSH was reduced in testes of exposed quail while Ashwagandha treatment reinstates the redox balance. Exposure to Wi-fi alters quail reproduction by increase in corticosterone and decreased testosterone with reduced expression of estrogen receptor alpha (ERα) in testis. Wi-fi exposure increases IL1β and reduces IL10 in testis. IL-1β inhibits testicular cell function and promotes apoptosis by increasing NF-κB and decreasing sperm count in exposed quails. Ashwagandha increases expression of ERα, sperm count and immunity in quail testis. Further, decrease in IL1β, NF-κB and increase in IL-10 after administration of Ashwagandha in Wi-fi exposed quail prevents inflammatory damages and enhances gonadal function. Thus, exposure to Wi-fi increases oxidative stress, activates apoptosis, modulates immunity in testis while Ashwagandha reverses them via enhanced ERα expression, increase in sperm count thereby enhancing fertility in male Japanese quail.

A nanocomposite filled compact circular Hexa band radiator from a traditional Yagi antenna structure with enhanced radiation for flexible wireless applications

A nanocomposite filled compact circular Hexa band radiator from a traditional Yagi antenna structure with enhanced radiation for flexible wireless applications

High-performance 38 GHz millimeter wave antenna for 5G wireless application

High-performance 38 GHz millimeter wave antenna for 5G wireless application

Nonpolar P-type Conjugated Small Molecules Enable High-Performance Organic Photodetectors for Potential Application in Optical Wireless Communication.

The high responsivity and broad spectral sensitivity of organic photodetectors (OPDs) present a bright future of commercialization. However, the relatively high dark current density still limits its development. Herein, two novel nonpolar p-type conjugated small molecules, NSN and NSSN, are synthesized as interface layers to enhance the performance of the OPDs, which not only can tune energy alignments and increase the reverse charge injection barrier but also can reduce the interfacial trap density. Moreover, benefiting from the smoother surface morphology and enhanced conductivity, the NSN exhibited superior charge transport and collection properties. Consequently, the OPD with NSN achieved a dark current density of 0.37 nA cm-2 and a high specific detectivity of 2.77 × 1013 Jones at -2 V. More importantly, the optimized OPDs can be successfully integrated into optical communication systems, demonstrating precise digital signal communication without obvious distortion, showing promising application potential in the wireless transmission system.

A compact multiband frequency reconfigurable antenna integrated with sextuple band artificial magnetic conductor for heterogeneous wireless applications

A compact multiband frequency reconfigurable antenna integrated with sextuple band artificial magnetic conductor for heterogeneous wireless applications

Strategies to enhance THz harmonic generation combining multilayered, gated, and metamaterial-based architectures

Graphene has unique properties paving the way for groundbreaking future applications. Its large optical nonlinearity and ease of integration in devices notably makes it an ideal candidate to become a key component for all-optical switching and frequency conversion applications. In the terahertz (THz) region, various approaches have been independently demonstrated to optimize the nonlinear effects in graphene, addressing a critical limitation arising from the atomically thin interaction length. Here, we demonstrate sample architectures that combine strategies to enhance THz nonlinearities in graphene-based structures. We achieve this by increasing the interaction length through a multilayered design, controlling carrier density with an electrical gate, and modulating the THz field spatial distribution with a metallic metasurface substrate. Our study specifically investigates third harmonic generation (THG) using a table-top high-field THz source. We measure THG enhancement factors exceeding thirty and propose architectures capable of achieving a two-order-of-magnitude increase. These findings underscore the potential of engineered graphene-based structures in advancing THz frequency conversion technologies for signal processing and wireless communication applications.

Design and Fabrication of a Patch Antenna for 5G Wireless Communications from a Low-Permittivity LiAlSi2O6-Based Ceramic.

A microwave dielectric ceramic based on lithium aluminum silicate (LiAlSi2O6) with ultralow permittivity was synthesized using the traditional solid-state reaction technique, and its dielectric characteristics at microwave frequencies are presented. The nominal LiAlSi2O6 ceramic exhibited a relative permittivity of 3.95. To enhance the material properties, LiAlSi2O6-x wt % B2O3 microwave dielectric ceramics were fabricated by incorporating a low-melting-point sintering aid (B2O3), achieving a relative density exceeding 94%. The resultant ceramics exhibited a relative permittivity (εr) ranging from 3.95 to 4.42, a microwave quality factor (Q × f) between 24,720 and 28,990 GHz, and a resonant frequency temperature coefficient (τf) varying from -45.9 to -20.6 ppm/°C. Additionally, the introduction of B2O3 broadened the sintering temperature window and effectively lowered the optimal sintering temperature from 1400 to 1200 °C. Furthermore, LiAlSi2O6 ceramics demonstrated a near-zero coefficient of thermal expansion (CTE) of 1.44 ppm/°C, which is advantageous for applications requiring high thermal stability. Based on LiAlSi2O6-2.0 wt % B2O3 ceramics with εr = 4.42, Q × f = 28,990 GHz, and τf = -20.6 ppm/°C, a microstrip patch antenna was designed and fabricated. Testing of the antenna revealed exceptional performance, including a center frequency of 4.98 GHz, a bandwidth of 280 MHz (-10 dB), and a total efficiency reaching up to 93.7%. These findings underscore the promising potential of this material in advanced microwave and wireless communication applications.

Metamaterial based stepped microstrip line fed quad-band dual-sense circularly polarized slot antenna for wireless applications

Abstract This research proposes a low-complexity, low-profile square-shaped quad-band dual-sense circularly polarized (CP) perturbed slot antenna with stepped microstrip feed for C-band radar and satellite applications. The proposed antenna is characterized by characteristic mode analysis. The proposed design has a square-shaped slot with diagonally opposite symmetric rectangular corner extensions. Multiband resonance is achieved by exciting the split ring resonator (SRR), cross strips and annular ring structure using the stepped microstrip line-fed slot radiator. The slot antenna and a metallic ring resonate at 1.64 and 8.2 GHz, respectively, showing left-hand circular polarization response, whereas the SRR and cross strips resonate at 3.6 and 6.6 GHz, respectively, exhibiting right-hand circular polarization radiation at these resonance bands. Hence, the proposed design shows quad-band performance with dual-sense CP behavior. Furthermore, the proposed antenna allows for independent tuning of polarization sense at resonance frequencies. The proposed design uses a low-cost FR-4 material as a substrate of dimensions 60 × 60 × 1.6 mm3. The experimentally measured results are in close agreement with the simulated performance parameters of the prototype.

Wideband rectifying metasurface with enhanced efficiency for wireless power transmission via harmonic feedback design.

We present a wideband rectifying metasurface (RMS) with enhanced system efficiency for wireless power transmission and energy harvesting. The RMS consists of periodic arrays with integrated diodes, with a high input impedance matched with the diodes, thus eliminating the matching network between metasurface (MS) and rectifier. Besides, a unique harmonic feedback network is embedded in each unit cell, rectifying the high-order harmonic generated by the diode repeatedly, improving the total efficiency over a wide bandwidth. The converted DC power is channeled to one single load through the DC-paths formed by the branches of MS and a series of inductors, avoiding additional DC-combination networks. The MS can effectively capture EM energy at an operating band of 2-3.5 GHz, and the simulated radiation-AC efficiency is up to 99% at 2.8 GHz. A finite 8 × 8 array is fabricated and measured. The total conversion efficiency reaches a peak value of 60.5% at 2.7 GHz when the power density is 25dBm/m2, and is greater than 40% from 2.3 GHz to 2.9 GHz, exhibiting a wide bandwidth of 23.1% compared with existing state-of-the-art studies. The integrated MS-based RF energy harvester with the advantages of a simple structure is of great significance for wireless power transfer and energy harvesting applications.