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Öğe Terahertz-Band Integrated Sensing and Communications: Challenges and Opportunities(Institute of Electrical and Electronics Engineers Inc., 2024) Elbir, Ahmet Mete; Mishra, Kumar Vijay; Chatzinotas, Symeon; Bennis, MehdiThe sixth generation (6G) wireless networks aim to achieve ultra-high data transmission rates, very low latency, and enhanced energy-efficiency. To this end, terahertz (THz) band is one of the key enablers of 6G to meet such requirements. The THz-band systems are also quickly emerging as high-resolution sensing devices because of their ultra-wide bandwidth and very narrow beamwidth. As a means to efficiently utilize spectrum and thereby save cost and power, THz integrated sensing and communications (ISAC) paradigm envisages a single integrated hardware platform with a common signaling mechanism. However, ISAC at THz-band entails several design challenges, such as beam split, range-dependent bandwidth, near-field beamforming, and distinct channel model. This article examines the technologies that have the potential to bring forth ISAC and THz transmission together. In particular, it provides an overview of antenna and array design, hybrid beamforming, integration with reflecting surfaces, and data-driven techniques, such as machine learning. These systems also provide research opportunities in developing novel methodologies for channel estimation, near-field beam split, waveform design, and beam misalignment. © 1986-2012 IEEE.Öğe Thermal annealing effects on the structural and electrical properties of Ag2La thin films deposited by thermal evaporation technique(Digest Journal of Nanomaterials and Biostructures Vol. 19, No. 2, April - June 2024, p. 909 - 917, 17.06.2024) Qasrawi Atef Fayez; Zakarneh Wafathermal annealing process. The thermally heated of films at 200 oC increased the crystallite sizes and improved the crystalline structure of the films. For these films the electrical conductivity measurements which were handled in the temperature range of 300- 440 K. The conductivity analyses indicated that the transport of charged particles is dominated by the thermionic emission and by the variable range hopping conduction mechanisms. The annealing of films shifted the impurity levels and decreased; the degree of disorder, the average hopping distance and the average hopping energy.Öğe Thermal annealing effects on the structural and electrical properties of Ag2La thin films deposited by thermal evaporation technique(Digest Journal of Nanomaterials and Biostructures, 17/06/2024) Qasrawi Atef Fayez; Zakarneh Wafathermal annealing process. The thermally heated of films at 200 oC increased the crystallite sizes and improved the crystalline structure of the films. For these films the electrical conductivity measurements which were handled in the temperature range of 300- 440 K. The conductivity analyses indicated that the transport of charged particles is dominated by the thermionic emission and by the variable range hopping conduction mechanisms. The annealing of films shifted the impurity levels and decreased; the degree of disorder, the average hopping distance and the average hopping energy.Öğe Bi2O3 nanosheets- based photodetectors designed for visible light communication technology(Physica Scripta (IOP), 17.03.2025) QAsrawi Atef Fayez; Zanoon Tateq; Alawneh Isam; Khanfar HazemIn this work, n-type bismuth oxide nanosheets deposited onto n-type silicon substrates by a vacuum evaporation technique under a vacuum pressure of 10−5 mbar is fabricated to perform as a daylight photodetectors suitable for visible light and infrared communication technology. The n-Si/n-Bi2O3 heterojunction devices exhibited conduction and valence band offsets of 0.89 eV 0.73 eV, respectively. Two Schottky barriers Pt/n-Si and Pt/Bi2O3 of respective barrier heights of 1.65 eV and 0.76 eV are formed on the sides of the heterojunction devices. Dark electrical characterization on the Pt/n-Si/n-Bi2O3/Pt hybrid structure showed a maximum current rectification ratio of 166. The current transport mechanism in the devices was dominated by the Richardson –Schottky thermionic conduction type and by electric field assisted charge carrier tunneling within a barrier of width and height of 60 nmand 0.83 eV, respectively. On the other hand, electrical measurements handled under the illumination of a daylight mini-lamp have shown that the photodetectors under focus exhibit maximum current responsivity, external quantum efficiency percentage, specific detectivity and linear dynamic range of 30 AW−1, 3000%, 1.7´1012 Jones and 36.4 dB under illumination power of 82 μW, respectively. The features of the bismuth oxide based photodetectors nominate them for visible and infrared lights illumination technology.Öğe Thermal annealing effects on the structural and electrical properties of Ag2La thin films deposited by thermal evaporation technique(Virtual co physics SRL, 2024) Qasrawi, Atef Fayez; Zakarneh, Wafaa AhmadHerein Ag2La thin films are fabricated by a vacuum coating method and subjected to a thermal annealing process. The thermally heated of films at 200 C-o increased the crystallite sizes and improved the crystalline structure of the films. For these films the electrical conductivity measurements which were handled in the temperature range of 300440 K. The conductivity analyses indicated that the transport of charged particles is dominated by the thermionic emission and by the variable range hopping conduction mechanisms. The annealing of films shifted the impurity levels and decreased; the degree of disorder, the average hopping distance and the average hopping energy.Öğe Effects of ZnPc substrates on the electro‑optical properties of MgSe thin films and the applications of Al/ZnPc/MgSe/ (Ag, C, Au) hybrid devices as resonant negative capacitance sources(Optical and Quantum Eletronics, Springer link, 11/07/2024) Qasrawi Atef FayezHerein, polycrystalline magnesium selenide (MgSe) thin films are deposited onto glass and monoclinic-structured zinc phthalocyanine (ZnPc) thin film substrates under high vacuum pressure using the thermal evaporation technique. ZnPc substrates improved the crystallinity of the MgSe films and decreased the stacking faults percentages and defect concentration by 31.57 and 52.49%, respectively. MgSe films deposited onto ZnPc substrates exhibited a notable increase of up to 32% in light absorption within the visible spectrum, while maintaining the energy band gap value of MgSe without significant alteration. In addition, as both the substrate and the epilayer exhibited p-type conductivity, an isotype heterojunction device structure is formed at the ZnPc/MgSe interfaces. The valence and conduction band offsets for this interface are 0.81 and 1.16 eV, respectively. On the other hand, re-fabrication of the ZnPc/MgSe heterojunctions onto Al thin film substrates and forming three Ag/MgSe, C/MgSe, and Au/MgSe Schottky channels on the epilayer surface allowed wide control of the negative capacitance effect and the resonance-antiresonance (RA) peaks in the capacitance spectra of the Al/ZnPc/MgSe/(Ag, C, Au) hybrid devices. These two important RA and NC features of the device can also be engineered by altering the DC biasing of the device. Moreover, Lorentz model analyses on the capacitance spectra showed an increased density of oscillators and increased scattering time constant with decreasing built-in potential at the metal/MgSe interfaces. The features of the hybrid devices presented make the device promising for microwave and electro-optical applicationsÖğe Design and Characterization of Se/Nb2 O5 Interfaces asHigh Infrared- Absorbers and High Frequency Band Filters(Crystal Research and Technology, Wiley, 07/12/2024) QAsrawi Atef Fayez; Daragme B. RanaHerein a new class of optoelectronic devices beneficial for infrared light absorption and high-frequency application in the terahertz frequency domain are designed and fabricated. The devices are formed by coating a highly transparent thin layer of Nb2 O5 onto a selenium-thin film to form Se/Nb 2 O5(SNO) optical interfaces. Although coating of Nb 2 O5 nanosheets decreased the crystallite sizes and increased the strain and defect concentration in the hexagonal structured Se films, they successfully increased the light absorption by ≈148% in the infrared range of light. A blueshift in the energy band gap of Se from 2.02 to 2.30 eV is observed. The coating of the Nb2 O5onto Se suppressed the free carrier absorption in Se and Nb 2 O5 . As dielectric active layers, SNO interfaces showed a major resonance dielectric peak centered at 1.67 eV. The optical conductivity and terahertz cutoff frequency analyses which are handled using the Drude-Lorentz approach revealed the highest drift mobility and free carrier concentration of 17.17 cm 2 Vs−1 and5.0 × 1017 cm−3 when an oscillator of energy of 1.75 eV is activated. In addition, the terahertz cutoff frequency spectra which varied in the range of4.0–131 THz showed the suitability of the SNO devices for terahertz technology and other optoelectronicsÖğe Power regulation of variable speed multi rotor wind systems using fuzzy cascaded control(Nature research, 2024) Benbouhenni, Habib; Çolak, İlhami; Bizon, Nicu; Mosaad, Mohamed I.; Tella, Teshome GoaPower quality is a crucial determinant for integrating wind energy into the electrical grid. This integration necessitates compliance with certain standards and levels. This study presents cascadedfuzzy power control (CFPC) for a variable-speed multi-rotor wind turbine (MRWT) system. Fuzzy logic is a type of smart control system already recognized for its robustness, making it highly suited and reliable for generating electrical energy from the wind. Therefore, the CFPC technique is proposed in this work to control the doubly-fed induction generator (DFIG)-based MRWT system. This proposed strategy is applied to the rotor side converter of a DFIG to improve the current/power quality. The proposed control has the advantage of being model-independent, as it relies on empirical knowledge rather than the specific characteristics of the DFIG or turbine. Moreover, the proposed control system is characterized by its simplicity, high performance, robustness, and ease of application. The implementation of CFPC management for 1.5 MW DFIG-MRWT was carried out in MATLAB environment considering a variable wind speed. The obtained results were compared with the direct power control (DPC) technique based on proportional-integral (PI) controllers (DPC-PI), highlighting that the CFPC technique reduced total harmonic distortion by high ratios in the three tests performed (25%, 30.18%, and 47.22%). The proposed CFPC technique reduced the response time of reactive power in all tests by ratios estimated at 83.76%, 65.02%, and 91.42% compared to the DPC-PI strategy. Also, the active power ripples were reduced by satisfactory proportions (37.50%, 32.20%, and 38.46%) compared to the DPC-PI strategy. The steady-state error value of reactive power in the tests was low when using the CFPC technique by 86.60%, 57.33%, and 72.26%, which indicates the effectiveness and efficiency of the proposed CFPC technique in improving the characteristics of the system. Thus this control can be relied upon in the future.Öğe Barium Oxide Thin Films Designed as Electro-OpticalGigahertz/Terahertz Filters(Crystal Research and Technology, Wiley, 23.02.2025) QAsrawi Atef Fayez; Alharbi Seham; Laila H. GaabourHerein barium oxide thin films are studied as a promising electro-opticalsystem. The deposited films exhibited a polycrystalline tetragonalstructure and are composed of a mixture of BaO and BaO2 . The p-type filmsare highly transparent (80%) with an energy band gap of 3.55 eV containingexponential band tails of widths of 1.22 eV. Analyses using the Drude-Lorentzmodel demonstrated the films suitability for nonlinear optical applications,with optical conductivity parameters revealing a scattering time constantin the range of 0.4–1.8 fs, a free hole concentration of 10 18−10 19 cm−3 anddrift mobility values of 0.70–3.16 cm 2 Vs−1 . Terahertz cutoff frequency spectra calculations indicated the films capability as efficient terahertz band filterswith a cutoff frequency range of 3.2–193.0 THz. Additionally, the nonlinear third-order optical susceptibility increased with decreasing incident photonenergy. Applying an AC signal with a driving frequency of 0.01–1.40 GHz across the terminals of Yb/BaO/Ag devices revealed a high cutoff frequency (≈9 GHz)in the microwave frequency domain. These properties highlight the potential ofBaO films as nonlinear optical filters and microwave waveguides, positioningthem as candidates for gigahertz/terahertz technology applicationsÖğe Electro-optical dynamics in SnO2 designed as negative resistance sources and gigahertz/terahertz band filters(Optical and Quantum Electronics, springer link, Mayis 2024) Qasrawi Atef Fayez; Kmail BayanAmorphous thin films of SnO2, prepared by a vacuum evaporation technique under a pressure of 10− 5 mbar, are employed as electro-optical filters suitable for microwave, infrared, and visible light communication technologies. The filters perform as optical layers, exhibiting optical transitions within an energy band gap of 3.62 eV, with the band gap containing energy band tails of widths of 0.63 eV. In addition, dielectric dispersion analyses on the optical filters show their ideality for high k-gate dielectric applications. Wide tunability in the dielectric response is observed in these films. Moreover, analyses of the optical conductivity and terahertz cutoff frequency spectra have shown that SnO2 films exhibit resonance of optical signals suitable for infrared and visible light communication technology as well. When excited with infrared light of energy of 1.38 eV, the drift mobility and free hole concentration in these films reach 11.72 cm2/Vs and 2 × 1017 cm− 3, respectively. Furthermore, the device exhibits a negative resistance effect in the microwave range of 0.1–1.80 GHz, and terahertz cutoff frequency values in the range of 10 GHz − 48 THz. The features of the SnO2 electro-optical band filter make them attractive for communication technology extending from 5G/6G to IR and reaching visible light communications.Öğe Electro-optical dynamics in SnO2 designed as negative resistance sources and gigahertz/terahertz band filters(Springer, 2024) Kmail, Bayan H.; Qasrawi, Atef FayezAmorphous thin films of SnO2, prepared by a vacuum evaporation technique under a pressure of 10(- 5) mbar, are employed as electro-optical filters suitable for microwave, infrared, and visible light communication technologies. The filters perform as optical layers, exhibiting optical transitions within an energy band gap of 3.62 eV, with the band gap containing energy band tails of widths of 0.63 eV. In addition, dielectric dispersion analyses on the optical filters show their ideality for high k-gate dielectric applications. Wide tunability in the dielectric response is observed in these films. Moreover, analyses of the optical conductivity and terahertz cutoff frequency spectra have shown that SnO2 films exhibit resonance of optical signals suitable for infrared and visible light communication technology as well. When excited with infrared light of energy of 1.38 eV, the drift mobility and free hole concentration in these films reach 11.72 cm(2)/Vs and 2 x 10(17) cm(- 3), respectively. Furthermore, the device exhibits a negative resistance effect in the microwave range of 0.1-1.80 GHz, and terahertz cutoff frequency values in the range of 10 GHz - 48 THz. The features of the SnO2 electro-optical band filter make them attractive for communication technology extending from 5G/6G to IR and reaching visible light communications.Öğe Enhanced electro-optical performance of barium oxide stacked layers via platinum nanosheets designed for wide band light absorption and terahertz technology(Physica Scripta, 18.12.2024) QAsrawi Atef Fayez; Gaabour Laila H.; Alharbi Seham R.In this study, stacked films of barium oxide (BaO) comprising platinum nanosheets in its structure are designed as electro-optical filters applicable in terahertz technology. The layers were fabricated by the thermal evaporation technique. It was shown that insertion of 50 nm and 100 nm thick Pt nanosheets between stacked layers of BaO improves the crystallinity of the layers by reducing the strains and defect concentrations. In addition, the light absorption and optical conduction is enhanced by more than 300%, 900% and 100 % in the ultraviolet (3.5-4.10 eV), visible (1.80-3.10 eV) and infrared (1.10-1.75 eV) ranges of light, respectively. The insertion of Pt nanosheets led to an increase in the dielectric constant (ε_r) values by over 104%. Specifically, ε_r values were initially 1.2–1.5, 1.6–1.8, and 1.8–2.0 in the ultraviolet, visible, and infrared light ranges, respectively. Upon incorporating Pt nanosheets with a thickness of 200 nm, these ε_r values increased to 1.4–1.7 in the ultraviolet, 1.8–3.6 in the visible, and 3.7–3.9 in the infrared ranges. Significant increase in the terahertz cutoff frequency from ~2.5 THz to ~15.35 THz was achieved in the infrared range of light. Moreover, the optical conductivity parameters which were obtained with the help of Drude-Lorentz electro-optical analysis showed remarkable enhancement in the free carrier concentration and in the drift mobility of the BaO optical filters from 5×〖10〗^18 cm-3 and 0.47 cm2/Vs to 7×〖10〗^18 cm-3 and 2.03 cm2/Vs to 9×〖10〗^18 cm-3 and 2.03 cm2/Vs upon insertion of Pt nanosheets of thicknesses of 100 nm and 200 nm, respectively. Furthermore, the temperature dependent electrical conductivity measurements has shown that Pt nanosheets increased the electrical conductivity of BaO by eight orders of magnitude. The features of BaO stacked layers comprising Pt nanosheets are promising for terahertz technology applications as waveguides and wideband optical filters.Öğe Predicting LAN switch failures: an integrated approach with DES and machine learning techniques (RF/LR/DT/SVM)(Elsevier, 2024) Myrzatay, Ali; Rzayevac, Leila; Bandini, Stefania; Shayea, Ibraheem; Saoud, Bilal; Çolak, İlhami; Kayisli, KorhanThis research paper introduces an innovative approach to predicting failures in Local Area Network (LAN) switches, combining Double Exponential Smoothing (DES) with a suite of Machine Learning (ML) algorithms including Random Forest (RF), Logistic Regression (LR), Decision Trees (DT), and Support Vector Machines (SVM). The primary objective of this study is to enhance the accuracy and timeliness of LAN switch failure predictions, thereby facilitating more proactive and effective network management. Our methodology involves the integration of DES for trend analysis and forecasting in time -series data, with the advanced predictive capabilities of the aforementioned ML algorithms. This hybrid approach not only leverages the strengths of DES in identifying underlying patterns in failure data but also capitalizes on the diverse predictive models to handle various aspects of failure prediction more robustly. The paper details the process of data collection, preprocessing, and the specific application of DES and each ML algorithm to the dataset. A notable contribution of this research is the development of a framework that effectively combines the output of DES with ML models, leading to a significant improvement in predictive accuracy as compared to traditional methods. Through rigorous testing and validation; the proposed approach demonstrated a marked increase in the precision and reliability of failure predictions. The results indicate that the integration of DES with ML algorithms can substantially aid in preemptive maintenance and decision -making processes in LAN management. The implications of these findings are profound, suggesting that such a combined approach can greatly enhance network stability and efficiency. While the focus of this study is on LAN switches, the methodology has the potential for broader applications in various fields of network management and predictive maintenance.Öğe Enhanced Performance of Al, Sb and Al/Sb Nanosheets Designed as Dielectric Lenses for Terahertz Applications(Arabian Journal for Science and Engineering, springer, 26.12.2024) Abu Samen LaraHerein, aluminum (Al), antimony (Sb), and aluminum-coated antimony (Al/Sb) nanosheets are fabricated using the thermal evaporation technique under a vacuum pressure of 10−5 mbar. Structural and morphological investigations of these films have shown their amorphous growth, including nanograins embedded in an amorphous medium. Optically, while Al nanosheets exhibited free carrier absorption due to their metallic nature, Sb and Al/Sb nanosheets demonstrated semiconductor characteristics with energy band gaps of 1.10 eV and 0.60 eV, respectively. Additionally, Al nanosheets recorded a sufficiently large dielectric constant and optical conductivity values exceeding 76 and 24 ( cm)−1, respectively, at an incident photon energy (E) of 1.13 eV. Coating Sb nanosheets with Al enhanced the dielectric properties of Sb, increasing the dielectric constant and optical conductivity values from 3.6 to ~ 14.0 and from 0.40 ( cm)−1 to 4.86 ( cm)−1, respectively, at E 1.13 eV. Moreover, the optical conductivity fitting according to the Drude-Lorentz model showed that the nanosheets under study are suitable for plasmonic interactions and performed as terahertz band filters, exhibiting terahertz cutoff frequencies in the range of 0.69–14.95 THz. Although the charge carriers’ drift mobility in Al nanosheets is very low due to the high charge carrier concentration, coating these nanosheets onto Sb increased the drift mobility of charge carriers in Sb nanosheets. The optical and dielectric analyses presented in this work indicate the potential of Al, Sb, and Al/Sb nanosheets for use as dielectric lenses and terahertz band filters.Öğe Enhanced Performance of Al/Nb2O5/Pt/Nb2O5/Ag Microwave Resonators Designed as Bandstop Filters and Negative Capacitance Sources(Materials Research, 09.11.2024) QAsrawi Atef Fayez; Amjad Salamah Mohammad Aljaloud; Latifah Hamad Khalid AlfhaidHerein stacked layers of Nb2O5 coated onto Al substrates are fabricated as microwave resonators. Structural and morphological analyses on these stacked layers have shown the amorphous nature of growth of the stacked layers. Electrically, the resonators showed negative capacitance effect accompanied with series and parallel resonance at three well -distinguished notch frequencies. Additionally, the resonators exhibited bandstop filter characteristics with notch frequency (nf) centered at 1.05 GHz, return loss (LR) value of 9.0 dB and voltage standing wave ratios (VSWR) of 2.12. To enhance the performance of the Nb2O5 microwave resonators, platinum nanosheets of thicknesses of 50 nm were inserted between layers of Nb2O5. Platinum nanosheets successfully decreased the surface roughness and increase the electrical conductivity by five orders of magnitude. Pt nanosheets additionally improved the values of nf, 11S, LR and VSWR to 1.16 GHz, 0.039, 30.3 dB and 1.12, respectively. The features of the microwave resonators comprising Pt nanosheets in its structure are promising for using them in communication technology.Öğe Enhanced Performance of Fe/WO3 Terahertz Dielectric Lenses(Crystal Research and Technology, Wiley, Nisan 2024) Qasrawi Atef Fayez; Hazem KhanfarHerein transparent iron nanosheets deposited by the ionic coating technique onto glass and WO3 dielectric lenses are studied and characterized. The thickness of Fe nanosheets is varied in the range of 70–350 nm. It is observed that the transmittance and reflectance of the Fe nanosheets are highly affected by the layer roughness. Coating of iron nanosheets onto WO3 dielectric lenses increases the light absorption of WO3 by more than 240 times and red-shifts the energy bandgap. Remarkable enhancements in the dielectric constant and in the optical conductivity are achieved via Fe coatings. In addition, iron coated dielectric lenses show higher terahertz cutoff limits varying in the range of 1.0–30 THz. Iron nanosheets remarkably increase the free charge carrier density and plasmon frequency in the infrared range of light. Moreover, the temperature dependent electrical conductivity shows high temperature stability and an increased electrical conductivity by more than 7 orders of magnitude by coating WO3 with 70 nm thick Fe nanosheets. The stability of the electrical conductivity at low temperatures and the wide range of terahertz cutoff limits in addition to the well-enhanced light absorbability makes the iron coated tungsten oxide dielectric lenses promising for multifunction optoelectronic applications.Öğe Enhanced performance of Pb/FeSe2 interfaces designed for electrical applications(Applied Physics A materials science and processing, Mart 2024) Qasrawi Atef Fayez; Seham Alharbi; Sabah E AlgarniIn this work, iron selenide layers are deposited onto glass and lead substrates to perform as terahertz filters. The layers are deposited by the thermal evaporation technique under a vacuum pressure of 10– 5 mbar. Glass/FeSe2 (GFS) and Pb/FeSe2 (PFS) films are structurally, morphologically and electrically characterized. The atomic composition of the GFS films contained excess selenium that reacted with Pb forming a PbSe layer. This layer induced the crystallinity of iron selenide. The preferred crystal structure of FeSe2 was cubic with cell parameters of a = b = c = 3.04 Å and space group Pm3m . Lead substrates increased the room temperature electrical conductivity of GFS films from of 1.52 ×10−5(Ω cm)−1 to 6.88 ×10−2(Ω cm)−1 . Analyses of the electrical conduction mechanism in the temperature range of 25–330 K have shown that coating the films onto Pb substrates shifted the accepter level from 182 to 58 meV, decreased the degree of structural disorder, shorten the average hopping range from 59 to 19 Å and increased the density of localized states near Fermi level by two orders of magnitude. The conductivity of PFS films exhibited degenerate semiconductor characteristics in the temperature range of 120–28 K. This feature is followed by an evidence of exhibiting superconductivity at critical temperatures lower than 24 K. On the other hand the impedance spectroscopy measurements in the driving signal frequency domain of 0.01–1.0 GHz have shown that Pb/FeSe2/Ag interfaces can perform as band filters showing microwave cutoff frequency values reaching 100 GHz at driving signal frequency of 1.0 GHz. These band filters are ideal for 6G technology nominating PFS films for high frequency applications.Öğe Enhanced Quad-Band WO3 Antennas with 1.46 THz Cutoff Frequency via Indium Nanosheets between Stacked Layers(Physica Status Solidi a (Wiley), 12.12.2024) QAsrawi Atef Fayez; Mashael M. Altaiary; Seham R. AlharbiHerein, stacked films of WO3 separated by indium nanosheets are fabricated as quad-band antennas suitable for high-frequency applications. The amorphous WO3 films and indium nanosheets are coated onto each other using the thermal evaporation technique under a high vacuum pressure of 10−5 mbar. The stacked layers of Pt/WO3/In/WO3/Pt are structurally and electrically characterized. The tunneling-type quad-band antennas are tested in the driving frequency domain of 0.01–1.80 GHz and a low signal amplitude of 0.10 V. It is observed that the insertion of indium nanosheets between layers of WO3 remarkably increases the width of the tunneling barrier from 55 to 70 nm without altering the tunneling barrier height. This also enhances the cutoff frequency at a quad-band frequency of 1.80 GHz from 10 GHz to 1.46 THz and increases the return loss values from ≈5 to 21 dB. A widely tunable cutoff frequency extending from 0.30 GHz to 1.46 THz can be obtained based on the selected driving signal frequency. The microwave-controlling features of the Pt/WO3/In/WO3/Pt devices, with their high cutoff frequency and high power transmission ratios at the quad-band frequency, make them attractive for 6G technology.Öğe High gain multi-band circularly polarized wearable leaky wave zipper MIMO antenna(Cell press, 2024) Saeidi, Tale; Saleh, Sahar; Mahmood, Sarmad Nozad; Timmons, Nick; Al-Gburi, Ahmed Jamal Abdullah; Karamzadeh, Saeid; Razzaz, FaroqA miniaturized, multi-band, four-port wearable Multiple Input Multiple Output (MIMO) antenna is proposed, which contains a leaky wave textile antenna (LWTA) on denim (epsilon(r) = 1.6, tan delta = 0.006) as substrate and Shieldit Super Fabric as conductor textile. The concept in this work involves incorporating the metal and plastic zipper into the garment to function as an antenna worn on the body. Simulations and measurements have been conducted to explore this idea. The LWTA has dimensions of 40 x 30 x 1 mm(3). Every two ports are separated by a zipper with two different kinds of materials: Acetal Polymer Plastic (APP) and 90 % brass to improve the isolation, gain, and Impedance bandwidth. The antenna operates in the frequency ranges covering the L, C, S, and X bands. Additionally, diversity performance is evaluated using the Envelope Correlation Coefficient (ECC) and diversity gain (DG). Simulation and measurement findings agree well, with a maximum gain of 12.15 dBi, low Specific Absorption Rate (SAR) based on the standards, DG greater than 9.65 dB, circular polarization (CP), and strong isolation (<-23 dB) between each port. Since the antenna's characteristics do not change significantly under bending and when the zipper is opened, the proposed antenna is a viable candidate for body-centric wireless communications on the battlefield. For example, it can facilitate communication covering wireless local area network (WLAN) and fifth-generation (5G) communications.Öğe High-performance UWB Vivaldi antenna on FR4: A cost-effective solution for wearable technologies(Elsevier B.V., 2025) Saleh, Sahar; Saeidi, Tale; Timmons, Nick; Alali, Bader; Razzaz, Faroq; Althuwayb, Ayman A.This paper introduces a novel Vivaldi Tapered Slot Antenna (VTSA) designed for wearable Ultra-Wideband (UWB) applications, utilizing a cost-effective FR4 substrate with a thickness of 0.8 mm. The proposed design achieves an 18.81 % size reduction (38.3 mm × 27.06 mm × 0.8 mm), a 36.16 % bandwidth (BW) increase, and a 16.63 % gain improvement compared to a VTSA using a Rogers RO4003C substrate (42.9 mm × 28.28 mm × 0.813 mm). The key contributions of this work include the effective use of the affordable FR4 substrate to achieve high performance, improvements in antenna compactness and BW through innovative slot designs, and the enhancement of gain and radiation pattern stability through the addition of directors to the slots. These modifications significantly boost the antenna's performance while maintaining a compact design. The antenna's suitability for wearable applications was validated through testing on flat and curved human phantoms made of skin, fat, and muscle, showing low Specific Absorption Rate (SAR) values across the UWB spectrum, confirming its safety for body-centric use. Measured results include S11 values below -10.56 dB over the 3.66–20.42 GHz range, a peak gain of 8.1 dBi, stable radiation patterns, and an average group delay of 0.83 ns. Simulations using Computer Simulation Technology (CST) were validated by experimental testing, demonstrating the antenna's potential for wearable and body-centric applications. © 2025 The Author(s)
