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Journal articles on the topic 'Low-THz antennas'
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1
Gao, Yanghua, Weidong Lou, and Hailiang Lu. "A Reconfigurable Graphene Nanoantenna on Quartz Substrate." Instrumentation Mesure Métrologie 19, no. 5 (2020): 379–83. http://dx.doi.org/10.18280/i2m.190508.
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In the terahertz (THz) band, conventional metallic antennas are virtually infeasible, due to the low mobility of electrons and huge attenuation. The existing metallic THz antennas need a high power to overcome scattering losses, and tend to have a low antenna efficiency. Fortunately, graphene is an excellent choice of miniaturized antenna in millimeter/THz applications, thanks to its unique electronic properties in THz band. Therefore, this paper presents two miniaturized reconfigurable graphene antennas, and characterizes their performance in terms of frequency reconfiguration, omnidirectional radiation pattern, and radiation efficiency. The proposed graphene antennas were printed on a quartz substrate, and simulated on CST Microwave Studio. The results show that the excellence of the proposed antennas in reflection coefficient, dynamic frequency reconfiguration (DFR), and omnidirectional radiation pattern. The operation frequency of the two antennas varies from 0.74 to 1.26 THz and from 0.92 to 1.15 THz, respectively. The proposed antennas have great prospects in wireless communications/sensors.
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Abbes, Alaeddine, Annick Pénarier, Philippe Nouvel, Arnaud Garnache, and Stéphane Blin. "Multipolar Photoconductive Antennas for THz Emission Driven by a Dual-Frequency Laser Based on Transverse Modes." Electronics 12, no. 22 (2023): 4679. http://dx.doi.org/10.3390/electronics12224679.
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Continuous-wave tunable photonics-based THz sources present limited output power due to the restricted input optical power accepted by photomixers, along with reduced radiation resulting from low paraxial field amplitude. Here, we investigate multipolar antenna designs to increase the available continuous-wave THz output power by incorporating more photomixers. For this purpose, the spatial structures of the optical and THz E-fields are designed to enhance THz power and radiation in the far field. Simulations of 2 to 4 dipole antennas are conducted, demonstrating an improvement in antenna gain compared to standard dipole antennas. This is in addition to a potential increase in THz power and radiation for photomixing applications. Such work also paves the way for functionalizing the spatial structure of THz light for advanced applications.
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Nissanov, Uri, and Ghanshyam Singh. "High directivity microstrip antenna with stopband and passband frequency selective surfaces for 6G at low-THz." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 6 (2022): 6272. http://dx.doi.org/10.11591/ijece.v12i6.pp6272-6283.
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There is still no high-directivity microstrip antenna with directivity beyond 25 dBi, bandwidth (BW) of more than 24%, which can be used for 6G cellular communication at low-THz at a resonance frequency of 144 GHz. So, duo broadband microstrip antennas have been designed at a resonance frequency of 144 GHz with the Taconic TLY-5 laminate in this work. These designs were carried out with the computer simulation technology microwave studio (CST MWS) software. The first antenna simulation results were compared within an Ansys high-frequency structure simulator (HFSS) software, and the obtained simulation results from both software were in fair consent, supporting the proposed designs. The peak directivity, peak gain, total peak efficiency, and BW obtained for the proposed THz microstrip antennas were 27.01 dBi, 25.3 dB, 78.96%, and 34.21 GHz (24.93%), respectively. Therefore, these antennas can be a base for 6G at low-THz.
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Uri, Nissanov, and Singh Ghanshyam. "High directivity microstrip antenna with stopband and passband frequency selective surfaces for 6G at low-THz." International Journal of Electrical and Computer Engineering (IJECE) 12, no. 6 (2022): 6272–83. https://doi.org/10.11591/ijece.v12i6.pp6272-6283.
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There is still no high-directivity microstrip antenna with directivity beyond 25 dBi, bandwidth (BW) of more than 24%, which can be used for 6G cellular communication at low-THz at a resonance frequency of 144 GHz. So, duo broadband microstrip antennas have been designed at a resonance frequency of 144 GHz with the Taconic TLY-5 laminate in this work. These designs were carried out with the computer simulation technology microwave studio (CST MWS) software. The first antenna simulation results were compared within an Ansys high-frequency structure simulator (HFSS) software, and the obtained simulation results from both software were in fair consent, supporting the proposed designs. The peak directivity, peak gain, total peak efficiency, and BW obtained for the proposed THz microstrip antennas were 27.01 dBi, 25.3 dB, 78.96%, and 34.21 GHz (24.93%), respectively. Therefore, these antennas can be a base for 6G at low-THz.
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Yu, Mei, Chun Li, Xiang Gao, et al. "High-Tc Superconducting Josephson Junction Harmonic Mixers with Stub Tuners on Integrated Bowtie Antennas." Applied Sciences 12, no. 24 (2022): 12813. http://dx.doi.org/10.3390/app122412813.
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Ordinary mixers can hardly meet the requirements in terahertz (THz) communications due to the low-power and expensive THz sources. Sensitive harmonic mixers have been widely studied to avoid this problem, owing to the fact that the higher the number of harmonics, the lower the local oscillator (LO) frequency, and the lower the cost. High-Tc superconducting (HTS) Josephson junction (JJ) mixers are performing candidates for THz receiver frontends because of the advantages of excellent sensitivity, wide bandwidth, high harmonic number and low LO power requirement. However, the normal-state resistance of HTS JJ is so low that traditional antennas are difficult to match it. In other words, it is quite a challenge to match the input impedance to a low input impedance for traditional antennas, especially for antennas fed by coplanar striplines (CPSs). In this work, based on the structure of bowtie, two types of stub tuners were integrated to decrease the impedance of the bowtie antenna so as to improve the coupling efficiency between the traditional bowtie antenna and the JJ. Furthermore, HTS YBa2Cu3O7-δ (YBCO) JJ harmonic mixers coupled with the proposed structures and fed by CPSs are fabricated and measured. The measurements show that the JJ mixer coupled with a pair of open-end stubs of the bowtie antenna achieves up to 88 harmonics, with a conversion efficiency of −69.6 dB. In contrast, the JJ mixer coupled with a pair of lumped-element stubs of the bowtie antenna only attains to 30 harmonics, with a conversion efficiency of −73.4 dB. Additional numerical simulations indicate that the coupling efficiency is enhanced when the complex impedance of the antenna is explicitly considered. Compared with other coupled traditional antennas, the JJ mixer with bowtie antenna has the largest harmonic number. This work paves the way for the future application of low-frequency and low-cost LO for THz communications.
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Park, Ikmo. "Application of metasurfaces in the design of performance-enhanced low-profile antennas." EPJ Applied Metamaterials 5 (2018): 11. http://dx.doi.org/10.1051/epjam/2018008.
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This paper presents a review of metasurface-based antennas conducted at the Microwave Communication Laboratory (MCL) of Ajou University in the Republic of Korea. In this paper, profile miniaturization, bandwidth enhancement, multiband operation, and radiation pattern control of metasurface-based antennas are considered. The paper first presents metasurface-based antennas implemented by placing various radiators on top of the metasurface. It then presents antennas implemented by placing the radiators below the metasurface with and without the ground plane. Metasurface-based antennas are not only able to achieve high efficiency with a low profile but they are also able to generate extra resonances from the metasurface structures, which significantly enhances the overall performance of the antennas. These additional resonances were utilized in multiband and/or wideband operations. In addition, the design of a planar compact wide-gain-bandwidth metasurface-based antenna and its radiation characteristics are presented at a terahertz (THz) frequency range. The THz antennas were designed with metasurfaces and a planar leaky-wave feeding structure. Finally, the outlook on future research at the MCL for antenna-related work and their applications using metasurfaces is provided.
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Ozpinar, Hurrem, Sinan Aksimsek, and Nurhan Türker Tokan. "W-Band Transverse Slotted Frequency Scanning Antenna for 6G Wireless Communication and Space Applications." Aerospace 12, no. 6 (2025): 493. https://doi.org/10.3390/aerospace12060493.
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Terahertz (THz) antennas are among the critical components required for enabling the transition to sixth-generation (6G) wireless networks. Although research on THz antennas for 6G communication systems has garnered significant attention, a standardized antenna design has yet to be established. This study introduces the modeling of a full-metal transverse slotted waveguide antenna (TSWA) for 6G and beyond. The proposed antenna operates across the upper regions of the V-band and the entire W-band. Designed and simulated using widely adopted full-wave analysis tools, the antenna achieves a peak gain of 17 dBi and a total efficiency exceeding 90% within the band. Additionally, it exhibits pattern-reconfigurable capabilities, enabling main lobe beam steering between 5∘ and 68° with low side lobe levels. Simulations are conducted to assess the power handling capability (PHC) of the antenna, including both the peak (PPHC) and average (APHC) values. The results indicate that the antenna can handle 17 W of APHC within the W-band and 3.4 W across the 60–160 GHz range. Furthermore, corona discharge and multipaction analyses are performed to evaluate the antenna’s power handling performance under extreme operating conditions. These features make the proposed TSWA a strong candidate for high-performance space applications, 6G communication systems, and beyond.
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Minkevičius, Linas, Liang Qi, Agnieszka Siemion, et al. "Titanium-Based Microbolometers: Control of Spatial Profile of Terahertz Emission in Weak Power Sources." Applied Sciences 10, no. 10 (2020): 3400. http://dx.doi.org/10.3390/app10103400.
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Terahertz (THz) imaging and spectroscopy set-ups require fine optical alignment or precise control of spatial mode profile. We demonstrate universal, convenient and easy-to-use imaging—resonant and broadband antenna coupled ultrasensitive titanium-based—dedicated to accurately adjust and control spatial mode profiles without additional focusing optical components of weak power THz sources. Versatile operation of the devices is shown using different kinds of THz—electronic multiplier sources, optical THz mixer-based frequency domain and femtosecond optoelectronic THz time-domain spectrometers as well as optically pumped molecular THz laser. Features of the microbolometers within 0.15–0.6 THz range are exposed and discussed, their ability to detect spatial mode profiles beyond the antennas resonances, up to 2.52 THz, are explored. Polarization-sensitive mode control possibilities are examined in details. The suitability of the resonant antenna-coupled microbolometers to resolve low-absorbing objects at 0.3 THz is revealed via direct, dark field and phase contrast imaging techniques as well.
9
Клочков, А. Н., Е. А. Климов, П. М. Солянкин та ін. "Терагерцовое излучение фотопроводящих антенн на основе сверхрешеточных структур \LT-GaAs/GaAs:Si\". Журнал технической физики 129, № 7 (2020): 1004. http://dx.doi.org/10.21883/os.2020.07.49574.17-20.
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A multilayer structure based on low-temperature LT-GaAs with crystallographic orientation (111) A is proposed for the fabrication of terahertz (THz) photoconductive antennas. The structures contain active layers of undoped LT-GaAs and high-temperature GaAs:Si layers doped with Si acceptors. At an optical pump power of 19 mW and a bias voltage of 30 V, a photoconductive antenna on an optimized {LT-GaAs / GaAs: Si} (111) A structure emitted THz pulses with an average power of 2.3 μW at a pulse repetition rate of 80 MHz, the conversion efficiency was 1.2 ∙ 10-4. It is shown that the dependence of the integrated power of THz antenna pulses based on {LT-GaAs / GaAs: Si} (111) A structures on the applied voltage is superlinear, and on the optical pump power it has the form of a saturation curve. The possibility of practical application of the obtained antennas for the tasks of terahertz spectroscopy of biological solutions is shown.
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Wang, Kemeng, Jianqiang Gu, Wenqiao Shi, Youwen An, and Weili Zhang. "Terahertz photoconductive antenna with all-dielectric nanopillars." Terahertz Science and Technology 13, no. 3 (2020): 112–18. http://dx.doi.org/10.1051/tst/2020133112.
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Photoconductive antennas (PCAs), as a popular terahertz (THz) radiation source, have been widely used in spectroscopy, material characterization, biological imaging and detection of hazardous materials. However, PCAs have a relatively low energy conversion efficiency from femtosecond laser pulses to THz radiation which often limits the signal-to-noise ratio and bandwidth of THz imaging and spectroscopy systems. To address these limitations, here we report a THz photoconductive antenna emitter with all-dielectric nanopillars integrated on top of the SI-GaAs substrate to increase the generated photocarriers, which achieves a broadband and frequency insensitive THz power enhancement factor around 1.25 at frequencies 0.05 - 1.6 THz. Our results reported here provide a new method for increasing the THz power of PCAs, which paves the way for the subsequent researches of next-generation PCAs.
11
Tofani, Silvia, and Walter Fuscaldo. "Fabry-Perot Cavity Leaky Wave Antennas with Tunable Features for Terahertz Applications." Condensed Matter 5, no. 1 (2020): 11. http://dx.doi.org/10.3390/condmat5010011.
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Terahertz (THz) radiation is a very appealing band of the electromagnetic spectrum due to its practical applications. In this context, the THz generation and manipulation is an essential part of the technological development. The demand of THz antennas is still high because it is already difficult to obtain directive, efficient, planar, low-cost, and easy-to-fabricate THz radiating systems. In this regard, Fabry-Perot cavity leaky-wave antennas are gaining increasing attention at THz, due to their very interesting radiating features: the combination of planar designs with metamaterials and metasurfaces could offer a promising platform for future THz manipulation technologies. In this short review, we focus on different classes of leaky-wave antennas, based on materials with tunable quasi-optical parameters. The possibility of producing directive patterns with particularly good efficiencies, as well as the capability of dynamically reconfiguring their radiating features, are discussed by taking into account the risk of increasing costs and fabrication complexity.
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Zhou, Yifan, Ruoyu Li, Pengpeng Jiang, Xiaowei Guo, and Shaorong Li. "Design of high efficiency cylindrical dielectric resonator antenna based on topological photonic crystals." Journal of Applied Physics 133, no. 8 (2023): 083103. http://dx.doi.org/10.1063/5.0134980.
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Over the last 30 years, various dielectric resonator antennas (DRAs) have been developed for application in portable wireless communications and millimeter wave systems. However, current methods to feed the antennas suffer from radiation leakage and high losses. In this paper, we propose using a topological photonic crystal (TPC) as an effective feeding method, which can effectively suppress the reflecting loss at the feeder/DRA interface. As a demonstration, we numerically design a DRA with a TPC feeder, operating in a high-order resonant mode at 1.5 THz. Simulation results show that the antenna has a return loss as low as 44 dB, an impedance bandwidth of 3.9%, a maximum gain of 7.4 dBi, and 3dB angular widths of 58 degrees. Over 99% radiation efficiency can be achieved at the operating THz band. The proposed all-dielectric antenna can be suitably used for integrated photonic chips, biomedical applications, and 6G.
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Abdelhakim, Boudkhil, Chetioui Mohammed, Benabdallah Nadia, and Benahmed Nasreddine. "Development and Performance Enhancement of MEMS Helix Antenna for THz Applications using 3D HFSS-based Efficient Electromagnetic Optimization." TELKOMNIKA Telecommunication, Computing, Electronics and Control 16, no. 1 (2018): 210–16. https://doi.org/10.12928/TELKOMNIKA.v16i2.8000.
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Interest of Micro-Electromechanical System (MEMS) antennas in Terahertz (THz) applications has rapidly expanded in recent years due to the advent of accurate Computer Aided Design (CAD) tools. The very special needs of newly proposed MEMS antennas, especially with a wide bandwidth range, require advanced optimization procedures of enhancing already established designs. This paper provides a compact design of a wideband MEMS helix antenna optimized using tree-dimensional High Frequency Structure Simulator (3D-HFSS) based on Quasi-Newton (Q-N) and Sequential Non Linear Programming (SNLP) techniques to modify the antenna structure with a high accuracy for the selective band of frequencies by training the samples and minimizing the error from Finite Element Method- (FEM) based simulation tool. The helix antenna is presented using MEMS technology and shows high performance demonstrated by very low return losses of less than -20 to -65 dB for a wide range of frequencies from 2.5 to 5 THz. High antenna geometry precision and efficient performance are finally achieved by rectifying and synthesizing various tunable parameters embedded in silicon substrate including both helix form and feeding line parameters.
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Ashvanth, Balu. "A tunable frequency selective surface integrated high isolation MIMO antenna for THz applications." Engineering Research Express 4, no. 4 (2022): 045001. http://dx.doi.org/10.1088/2631-8695/ac92c6.
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Abstract A novel tunable triple stop band frequency selective surface (FSS) is designed and integrated with the multiple inputs multiple outputs (MIMO) antenna as an isolation structure to verify its validity. The proposed FSS renders excellent isolation characteristics for the reported MIMO system which is verified from the ECC and DG plot. In FSS, the graphene materials are attached at the end of three stubs to realize tuning over the respective bands. The center frequency of the attained triple bands shows an obvious shift from 2.2 to 2.4 THz, 3.15 to 3.5 THz, and 4.6 to 4.9 THz on increasing the chemical potential of graphene from 0 to 1.5 eV. The tuning range can be enhanced by further increasing the applied potential and hence its service might extend to multi or wideband MIMO systems. The proposed FSS unit cell achieves miniaturization to the level of 0.17 λ o. The validity of the proposed FSS is tested with a linear array MIMO antenna. The designed MIMO antenna consists of two linear array antennas separated by 40 μm with each linear array is made up of three individual antenna elements. The introduction of FSS between the linear arrays provides the minimum isolation of 30 dB. The presented highly isolated linear array MIMO antenna realizes maximum efficiency and gain of 83%, 12.2 dBi respectively. The FSS unit cell structure is modeled and their electromagnetic characteristics are simulated by the 3D electromagnetic simulator CST Studio Suite. The auto meshing technology and frequency domain solver are used to acquire S-parameter. This wearable antenna is a significant component in tracking and monitoring systems including the miniaturized multiband antennas exhibiting stable radiation characteristics during bending, stretching, and crumpling conditions to suit military applications. Nowadays, wearable antennas are being designed for military applications by perfectly matching the industry requirements such as thin, low profile, lightweight, low maintenance, robust, conformal, easy integration into clothing without affecting the movement of the soldier.
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Yadav, Vandna, and (Dr.) Gupta Sumit Kumar Prof. "Antenna design Design and Performance Analysis of a Graphene-Based Two-Port MIMO Yagi-Uda Antenna for THz Applications." International Researchers Journal Volume XII, Issue-4 (2025): 13–22. https://doi.org/10.5281/zenodo.15123517.
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<strong>Abstract </strong>The rapid advancements in terahertz (THz) communication demand high-performance antenna solutions with enhanced gain, directivity, and miniaturization. This study presents the design and performance analysis of a graphene-based two-port multiple-input multiple-output (MIMO) Yagi-Uda antenna optimized for THz applications. Graphene, known for its tunable conductivity and superior electronic properties, is employed as the primary radiating material to achieve reconfigurability and high efficiency at THz frequencies. The proposed MIMO Yagi-Uda structure features a compact design with strategically placed directors, reflectors, and driven elements to maximize directivity and minimize mutual coupling.The antenna’s electromagnetic behavior is analyzed using full-wave simulations, demonstrating significant improvements in gain, bandwidth, and radiation efficiency. The performance parameters, including scattering parameters (S-parameters), envelope correlation coefficient (ECC), gain, and radiation pattern, are evaluated to assess its suitability for high-speed THz wireless communication and sensing applications. The results indicate that the proposed design achieves high isolation, low mutual coupling, and excellent directivity, making it a promising candidate for next-generation THz MIMO systems.This study contributes to the ongoing development of THz antennas by providing insights into the advantages of graphene-based materials and MIMO-Yagi-Uda configurations for futuristic wireless communication technologies.
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Sethi, Waleed Tariq, Hamsakutty Vettikalladi, Habib Fathallah, and Mohamed Himdi. "Equilateral Triangular Dielectric Resonator Nantenna at Optical Frequencies for Energy Harvesting." International Journal of Antennas and Propagation 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/589459.
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The last decade has witnessed a remarkable growth in the telecommunication industry. With the introduction of smart gadgets, the demand for high data rate and bandwidth for wireless applications have increased exponentially at the cost of exponential consumption of energy. The latter is pushing the research and industry communities to devise green communication solutions that require the design of energy saving devices and techniques in one part and ambient energy harvesting techniques in the other part. With the advent of nanocomponents fabrication technology, researchers are now able to tap into the THz frequency regime and fabricate optical low profile antennas at a nanoscale. Optical antennas have proved their potential and are revolutionizing a class of novel optical detectors, interconnectors, sensors, and energy harvesting related fields. Authors in this paper propose an equilateral triangular dielectric resonator nantenna (ETDRNA) working at 193.5 THz standard optical frequency. The simulated antenna achieves an impedance bandwidth from 192.3 THz to 197.3 THz with an end-fire directivity of 8.6 dBi, covering the entire standard optical window of C-band. Numerical demonstrations prove the efficiency of the nantenna at the frequencies of interest, making it a viable candidate for future green energy harvesting and high speed optical applications.
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Wang, Feng, and Kewei Cheng. "A space terahertz antenna fabricated by 3d printing technology." Journal of Physics: Conference Series 2569, no. 1 (2023): 012036. http://dx.doi.org/10.1088/1742-6596/2569/1/012036.
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Abstract In this paper, a case of space high-precision THz antennas based on 3D printing technology in engineering has been proposed. The reflectors and the supporting structure have been printed in an integrated way by adopting the structural optimization design method suitable for the high-precision 3D printing process and using the honeycomb structure in the low-stress area. This can avoid the assembly error caused by the assembly of various components of the antenna and achieve the goal of integrated, high-precision, lightweight, and high-thermal stability 3D printing, and manufacturing, which provides an idea for high-precision manufacturing of 3D printing technology in space-borne THz devices.
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Chen, Ruolin, Xuefei Li, Hao Du, et al. "Migration-Enhanced Epitaxial Growth of InAs/GaAs Short-Period Superlattices for THz Generation." Nanomaterials 14, no. 3 (2024): 294. http://dx.doi.org/10.3390/nano14030294.
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The low-temperature-grown InGaAs (LT-InGaAs) photoconductive antenna has received great attention for the development of highly compact and integrated cheap THz sources. However, the performance of the LT-InGaAs photoconductive antenna is limited by its low resistivity and mobility. The generated radiated power is much weaker compared to the low-temperature-grown GaAs-based photoconductive antennas. This is mainly caused by the low abundance of excess As in LT-InGaAs with the conventional growth mode, which inevitably gives rise to the formation of As precipitate and alloy scattering after annealing. In this paper, the migration-enhanced molecular beam epitaxy technique is developed to grow high-quality (InAs)m/(GaAs)n short-period superlattices with a sharp interface instead of InGaAs on InP substrate. The improved electron mobility and resistivity at room temperature (RT) are found to be 843 cm2/(V·s) and 1648 ohm/sq, respectively, for the (InAs)m/(GaAs)n short-period superlattice. The band-edge photo-excited carrier lifetime is determined to be ~1.2 ps at RT. The calculated photocurrent intensity, obtained by solving the Maxwell wave equation and the coupled drift–diffusion/Poisson equation using the finite element method, is in good agreement with previously reported results. This work may provide a new approach for the material growth towards high-performance THz photoconductive antennas with high radiation power.
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Chen, Peiyu, Mostafa Hosseini, and Aydin Babakhani. "An Integrated Germanium-Based THz Impulse Radiator with an Optical Waveguide Coupled Photoconductive Switch in Silicon." Micromachines 10, no. 6 (2019): 367. http://dx.doi.org/10.3390/mi10060367.
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This paper presents an integrated germanium (Ge)-based THz impulse radiator with an optical waveguide coupled photoconductive switch in a low-cost silicon-on-insulator (SOI) process. This process provides a Ge thin film, which is used as photoconductive material. To generate short THz impulses, N++ implant is added to the Ge thin film to reduce its photo-carrier lifetime to sub-picosecond for faster transient response. A bow-tie antenna is designed and connected to the photoconductive switch for radiation. To improve radiation efficiency, a silicon lens is attached to the substrate-side of the chip. This design features an optical-waveguide-enabled “horizontal” coupling mechanism between the optical excitation signal and the photoconductive switch. The THz emitter prototype works with 1550 nm femtosecond lasers. The radiated THz impulses achieve a full-width at half maximum (FWHM) of 1.14 ps and a bandwidth of 1.5 THz. The average radiated power is 0.337 μ W. Compared with conventional THz photoconductive antennas (PCAs), this design exhibits several advantages: First, it uses silicon-based technology, which reduces the fabrication cost; second, the excitation wavelength is 1550 nm, at which various low-cost laser sources operate; and third, in this design, the monolithic excitation mechanism between the excitation laser and the photoconductive switch enables on-chip programmable control of excitation signals for THz beam-steering.
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Zuo, Xinrong, Chenwei Zhu, Chenyu Yao, et al. "High sensitivity HgTe room temperature terahertz photodetector." APL Photonics 8, no. 4 (2023): 046109. http://dx.doi.org/10.1063/5.0144569.
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The advent of topological semi-metals with peculiar band structure and exotic quantum-transport provides novel pathways for upgrading the performance of terahertz (THz) detection. HgTe is among such a candidate with the unique advantages of a negative bandgap, ultra-high mobility, and thermoelectricity, which ignites the possibility of addressing the technical bottlenecks of traditional routes for THz detection. Herein, for the first time, we report large-area (3 in.) growth of high-mobility HgTe thin-film via molecular-beam epitaxial and the implementation of bow-tie antennas based HgTe THz-detector with the abilities of ultrafast response, low noise, and high ambient-stability at room temperature. By exploration of strong light-coupling and superior hot-carrier transport, the bow-tie antenna-based HgTe photodetector can achieve a responsivity of 0.04 A/W and a noise equivalent power of less than 0.6 nW/Hz1/2 at 0.3 THz. Furthermore, the sensitivity can be further improved by nearly an order of magnitude up to 0.36 A/W at 0.3 THz by incorporating a short channel asymmetric cubic resonator. The reported performances allow a realistic exploration of high-mobility bulk states in topological semimetals for large area, fast-imaging applications in the THz band.
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Zhou, Zepeng, Wenqing Li, Jun Qian, et al. "Flexible Liquid Crystal Polymer Technologies from Microwave to Terahertz Frequencies." Molecules 27, no. 4 (2022): 1336. http://dx.doi.org/10.3390/molecules27041336.
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With the emergence of fifth-generation (5G) cellular networks, millimeter-wave (mmW) and terahertz (THz) frequencies have attracted ever-growing interest for advanced wireless applications. The traditional printed circuit board materials have become uncompetitive at such high frequencies due to their high dielectric loss and large water absorption rates. As a promising high-frequency alternative, liquid crystal polymers (LCPs) have been widely investigated for use in circuit devices, chip integration, and module packaging over the last decade due to their low loss tangent up to 1.8 THz and good hermeticity. The previous review articles have summarized the chemical properties of LCP films, flexible LCP antennas, and LCP-based antenna-in-package and system-in-package technologies for 5G applications, although these articles did not discuss synthetic LCP technologies. In addition to wireless applications, the attractive mechanical, chemical, and thermal properties of LCP films enable interesting applications in micro-electro-mechanical systems (MEMS), biomedical electronics, and microfluidics, which have not been summarized to date. Here, a comprehensive review of flexible LCP technologies covering electric circuits, antennas, integration and packaging technologies, front-end modules, MEMS, biomedical devices, and microfluidics from microwave to THz frequencies is presented for the first time, which gives a broad introduction for those outside or just entering the field and provides perspective and breadth for those who are well established in the field.
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Nadar Akila Mohan, P., and K. Indhumathi. "Millimetre wave antenna for biomedical applications-a review." Journal of Physics: Conference Series 2484, no. 1 (2023): 012055. http://dx.doi.org/10.1088/1742-6596/2484/1/012055.
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Abstract Terahertz represents the portion of electromagnetic wave between the microwave and IR region. Recent research has been focused on the application of Terahertz waves in biomedical applications such as cancer detection. The current diagnostic methods in cancer treatment involve imaging to MRI and biopsy. Due to the low photon energy that terahertz possess, there are no health threats caused in contrast to traditional methods. Cancer cells can be detected by monitoring the blood supply to the affected tissues and water level in the local tissues. This can be diagnosed using Terahertz imaging. THz radiation can be generated and detected using various commercialized systems. On analysis of various literatures, it is observed that Meta material antennas will be the suitable candidate to enhance the existing terahertz spectroscopy techniques since it has better focusing capabilities. This paper reviews the various implementation techniques of an antenna in THz range. The design and properties of the antenna are also investigated.
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Fuscaldo, Walter, Paolo Burghignoli, Paolo Baccarelli, and Alessandro Galli. "Efficient 2-D leaky-wave antenna configurations based on graphene metasurfaces." International Journal of Microwave and Wireless Technologies 9, no. 6 (2017): 1293–303. http://dx.doi.org/10.1017/s1759078717000459.
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Different configurations of leaky-wave antennas (LWAs) based on graphene metasurfaces are studied. The electronic properties of a graphene metasurface in the low THz range are investigated in details in order to discuss the reconfigurability features of the presented structures. Simple exact formulas for evaluating the ohmic losses related to the surface plasmon polariton (SPP) propagation along a suspended graphene sheet, and the relevant figures of merit of SPP propagating over a generic metasurface are given. Such formulas allow us to explain the low efficiency of reconfigurable antennas based on SPPs along graphene metasurfaces. Then, the radiative performance and relevant losses of graphene Fabry–Perot cavity antennas (FPCAs) based on non-plasmonic leaky waves (LWs) are investigated and compared with previous solutions based on SPPs. In particular, a single-layer structure, i.e. a grounded dielectric slab covered with a graphene metasurface, and a multilayered structure, i.e. a substrate–superstrate antenna in which the graphene metasurface is embedded at a suitable position within the substrate, are considered in detail. The results show that the proposed LW solutions in graphene FPCAs allow for considerably reducing the ohmic losses, thus significantly improving the efficiency of the proposed radiators.
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Obraztsov, Petr A., Vladislava V. Bulgakova, Pavel A. Chizhov, et al. "Hybrid Perovskite Terahertz Photoconductive Antenna." Nanomaterials 11, no. 2 (2021): 313. http://dx.doi.org/10.3390/nano11020313.
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Hybrid organic–inorganic perovskites, while well examined for photovoltaic applications, remain almost completely unexplored in the terahertz (THz) range. These low-cost hybrid materials are extremely attractive for THz applications because their optoelectronic properties can be chemically engineered with relative ease. Here, we experimentally demonstrate the first attempt to apply solution-processed polycrystalline films of hybrid perovskites for the development of photoconductive terahertz emitters. By using the widely studied methylammonium-based perovskites MAPbI3 and MAPbBr3, we fabricate and characterize large-aperture photoconductive antennas. The work presented here examines polycrystalline perovskite films excited both above and below the bandgap, as well as the scaling of THz emission with the applied bias field and the optical excitation fluence. The combination of ultrafast time-resolved spectroscopy and terahertz emission experiments allows us to determine the still-debated room temperature carrier lifetime and mobility of charge carriers in halide perovskites using an alternative noninvasive method. Our results demonstrate the applicability of hybrid perovskites for the development of scalable THz photoconductive devices, making these materials competitive with conventional semiconductors for THz emission.
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Alibakhshikenari, Mohammad, Bal S. Virdee, Ayman A. Althuwayb, Dion Mariyanayagam, and Ernesto Limiti. "Compact and Low-Profile On-Chip Antenna Using Underside Electromagnetic Coupling Mechanism for Terahertz Front-End Transceivers." Electronics 10, no. 11 (2021): 1264. http://dx.doi.org/10.3390/electronics10111264.
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The results presented in this paper show that by employing a combination of metasurface and substrate integrated waveguide (SIW) technologies, we can realize a compact and low-profile antenna that overcomes the drawbacks of narrow-bandwidth and low-radiation properties encountered by terahertz antennas on-chip (AoC). In addition, an effective RF cross-shaped feed structure is used to excite the antenna from its underside by coupling, electromagnetically, RF energy through the multi-layered antenna structure. The feed mechanism facilitates integration with the integrated circuits. The proposed antenna is constructed from five stacked layers, comprising metal–silicon–metal–silicon–metal. The dimensions of the AoC are 1 × 1 × 0.265 mm3. The AoC is shown to have an impedance match, radiation gain and efficiency of ≤ −15 dB, 8.5 dBi and 67.5%, respectively, over a frequency range of 0.20–0.22 THz. The results show that the proposed AoC design is viable for terahertz front-end applications.
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Li, Wen Tao, Shunlai Sun, Nana Qi, and Xiaowei Shi. "Reconfigurable Graphene Circular Polarization Reflectarray/Transmitarray Antenna." Frequenz 73, no. 3-4 (2019): 77–88. http://dx.doi.org/10.1515/freq-2018-0156.
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Abstract Reconfigurable reflectarray/transmitarray antennas have found broad applications in wireless communication due to their low cost, small size, flexible design, and superior performance. However, one common drawback of most current designs is the complex reconfiguration operation, which restricts their further applications. In this research, a new design strategy for reconfigurable reflectarray/transmitarray antennas is proposed and shown. Specifically, a circularly polarized $11 \times 11$ unit-cell graphene-based reflectarray/transmitarray antenna covering an area of $1.1 \times 1.1$ mm2 is designed, with a graphene-based frequency selective surface (FSS) as a ground. By adjusting the electric field, a dynamic change in the complex conductivity of graphene is achieved, which in turn changes the phase and the resonance point of the reflected or transmitted wave at the element. By tuning the size of the patch and changing the chemical potential of graphene, the element of the reflectarray/transmitarray operated at 1 THz can provide a dynamic phase range of more than ${360^ \circ }$. The simulation results show that the designed antenna can be dynamically reconfigured between the circularly polarized reflectarray/transmitarray antenna of the single structure, and has potential applications in emerging terahertz communication systems.
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Ullah, Zaka, Illani Nawi, Gunawan Witjaksono, et al. "Dynamic Absorption Enhancement and Equivalent Resonant Circuit Modeling of Tunable Graphene-Metal Hybrid Antenna." Sensors 20, no. 11 (2020): 3187. http://dx.doi.org/10.3390/s20113187.
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Plasmonic antennas are attractive optical components of the optoelectronic devices, operating in the far-infrared regime for sensing and imaging applications. However, low optical absorption hinders its potential applications, and their performance is limited due to fixed resonance frequency. In this article, a novel gate tunable graphene-metal hybrid plasmonic antenna with stacking configuration is proposed and investigated to achieve tunable performance over a broad range of frequencies with enhanced absorption characteristics. The hybrid graphene-metal antenna geometry is built up with a hexagon radiator that is supported by the Al2O3 insulator layer and graphene reflector. This stacked structure is deposited in the high resistive Si wafer substrate, and the hexagon radiator itself is a sandwich structure, which is composed of gold hexagon structure and two multilayer graphene stacks. The proposed antenna characteristics i.e., tunability of frequency, the efficiency corresponding to characteristics modes, and the tuning of absorption spectra, are evaluated by full-wave numerical simulations. Besides, the unity absorption peak that was realized through the proposed geometry is sensitive to the incident angle of TM-polarized incidence waves, which can flexibly shift the maxima of the absorption peak from 30 THz to 34 THz. Finally, an equivalent resonant circuit model for the investigated antenna based on the simulations results is designed to validate the antenna performance. Parametric analysis of the proposed antenna is carried out through altering the geometric parameters and graphene parameters in the Computer Simulation Technology (CST) studio. This clearly shows that the proposed antenna has a resonance frequency at 33 THz when the graphene sheet Fermi energy is increased to 0.3 eV by applying electrostatic gate voltage. The good agreement of the simulation and equivalent circuit model results makes the graphene-metal antenna suitable for the realization of far-infrared sensing and imaging device containing graphene antenna with enhanced performance.
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Fernandez Olvera, Anuar, Axel Roggenbuck, Katja Dutzi, et al. "International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors." Photonics 6, no. 1 (2019): 15. http://dx.doi.org/10.3390/photonics6010015.
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A theoretical model for the responsivity and noise-equivalent power (NEP) of photoconductive antennas (PCAs) as coherent, homodyne THz detectors is presented. The model is validated by comparison to experimental values obtained for two ErAs:InGaAs PCAs. The responsivity and NEP were obtained from the measured rectified current, the current noise floor in the PCAs, and the incoming THz power for the same conditions. Since the THz power measurements are performed with a pyroelectric detector calibrated by the National Metrology Institute of Germany (PTB), the experimentally obtained values are directly traceable to the International System of Units (SI) for the described conditions. The agreement between the presented model and the experimental results is excellent using only one fitting parameter. A very low NEP of 1.8 fW/Hz at 188.8 GHz is obtained at room temperature.
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Froberger, Kevin, Benjamin Walter, Melanie Lavancier, et al. "SOI-based micro-mechanical terahertz detector operating at room-temperature and atmospheric pressure." Applied Physics Letters 120, no. 26 (2022): 261103. http://dx.doi.org/10.1063/5.0095126.
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We present a micro-mechanical terahertz (THz) detector fabricated on a silicon on insulator substrate and operating at room-temperature. The device is based on a U-shaped cantilever of micrometric size, on top of which two aluminum half-wave dipole antennas are deposited. This produces an absorption extending over the [Formula: see text] THz frequency range. Due to the different thermal expansion coefficients of silicon and aluminum, the absorbed radiation induces a deformation of the cantilever, which is read out optically using a 1.5 μm laser diode. By illuminating the detector with an amplitude modulated, 2.5 THz quantum cascade laser, we obtain, at room-temperature and atmospheric pressure, a responsivity of [Formula: see text] for the fundamental mechanical bending mode of the cantilever. This yields noise-equivalent-power of [Formula: see text] at 2.5 THz. Finally, the low mechanical quality factor of the mode grants a broad frequency response of approximately 150 kHz bandwidth, with a thermal response time of ∼ 2.5 μs.
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Khusyainov, D. I., C. Dekeyser, A. M. Buryakov, et al. "Ultrafast carrier dynamics in LT-GaAs doped with Si delta layers." International Journal of Modern Physics B 31, no. 27 (2017): 1750195. http://dx.doi.org/10.1142/s0217979217501958.
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We characterized the ultrafast properties of LT-GaAs doped with silicon [Formula: see text]-layers and introduced delta-doping ([Formula: see text]-doping) as efficient method for enhancing the properties of GaAs-based structures which can be useful for terahertz (THz) antenna, ultrafast switches and other high frequency applications. Low temperature grown GaAs (LT-GaAs) became one of the most promising materials for ultrafast optical and THz devices due to its short carrier lifetime and high carrier mobility. Low temperature growth leads to a large number of point defects and an excess of arsenic. Annealing of LT-GaAs creates high resistivity through the formation of As-clusters, which appear due to the excess of arsenic. High resistivity is very important for THz antennas so that voltage can be applied without the risk of breakdown. With [Formula: see text]-Si doping, control of As-clusters is possible, since after annealing, clusters align in the plane where the [Formula: see text]-doping occurs. In this paper, we compare the properties of LT-GaAs-based planar structures with and without [Formula: see text]-Si doping and subsequent annealing. We used pump-probe transient reflectivity as a probe for ultrafast carrier dynamics in LT-GaAs. The results of the experiment were interpreted using the Ortiz model and show that the [Formula: see text]-Si doping increases deep donor and acceptor concentrations and decreases the photoinduced carrier lifetime as compared with LT-GaAs with same growth and annealing temperatures, but without doping.
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Nguyen, Thinh Tien, Dong Ho Kim, Jung Han Choi, and Chang Won Jung. "Circularly Polarized Series Array and MIMO Application for Sub-Millimeter Wave/Terahertz Band." Journal of Electromagnetic Engineering and Science 24, no. 3 (2024): 294–304. http://dx.doi.org/10.26866/jees.2024.3.r.230.
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This article presents a compact, planar, and circularly polarized array antenna operating in the W-band (84.5–110 GHz), with all its prototypes fabricated using a low-cost, traditional, microwave printed circuit board composed of Rogers RT/duroid 5880 (εr = 2.2, tanδ = 0.009). The final design that was fabricated and measured was a 4 × 4 array antenna having an overall size of 9 mm × 20 mm × 0.254 mm that used series feeding to reduce its sidelobes. Measurements of the 4 × 4 patch antenna array showed approximately 6.9% 3-dB axial ratio bandwidth along with 15.2 dBi maximum right-hand circularly polarized (RHCP) antenna gain at 100 GHz. The array antenna yielded RHCP radiation characterized by a low profile, low cross-polarization levels (<−25 dB), low sidelobe levels (≤−10 dB), and high radiation efficiency (>91%). Additionally, a two-port MIMO antenna system was investigated by considering side-by-side and front-tofront configurations, both of which achieved good isolation and considerable envelope correlation coefficient and diversity gain values. Therefore, the proposed series array and MIMO antennas can be reasonable candidates for 6G applications of the sub-THz band (100– 110 GHz) in ultra-high-speed wireless and satellite communication systems.
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Nomoev, Sergey, Ivan Vasilevskii, and Alexander Vinichenko. "The Research for Approaches to Increase Power of the Compact THz Emitters Based on Low-Temperature Gallium Arsenide Heterostructures." Solid State Phenomena 310 (September 2020): 101–8. http://dx.doi.org/10.4028/www.scientific.net/ssp.310.101.
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The design and technological conditions for the manufacture of photoconductive antennas based on low-temperature gallium arsenide (LT-GaAs) have been developed. The optimized photoconductive THz antenna is made based on LT-GaAs with the flag geometry of the contacts and with the interdigitated structure including metal closing through the dielectric of each second period. LT-GaAs samples were obtained by molecular beam epitaxy at temperatures of 210 °C, 230 °C, 240 °C on GaAs substrates (100). Dark and photocurrent were measured depending on the bias voltage of the LT-GaAs heterostructure at the EP6 probe station. Full wave finite element method solver has been used to investigate the proposed plasmon PCA electrical and optical behavior by combining the Maxwell's wave equation with the drift-diffusion/Poisson equations.
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Jiang, Mengjie, Kaixuan Zhang, Xuyang Lv, et al. "Monolayer Graphene Terahertz Detector Integrated with Artificial Microstructure." Sensors 23, no. 6 (2023): 3203. http://dx.doi.org/10.3390/s23063203.
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Graphene, known for its high carrier mobility and broad spectral response range, has proven to be a promising material in photodetection applications. However, its high dark current has limited its application as a high-sensitivity photodetector at room temperature, particularly for the detection of low-energy photons. Our research proposes a new approach for overcoming this challenge by designing lattice antennas with an asymmetric structure for use in combination with high-quality monolayers of graphene. This configuration is capable of sensitive detection of low-energy photons. The results show that the graphene terahertz detector-based microstructure antenna has a responsivity of 29 V·W−1 at 0.12 THz, a fast response time of 7 μs, and a noise equivalent power of less than 8.5 pW/Hz1/2. These results provide a new strategy for the development of graphene array-based room-temperature terahertz photodetectors.
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Nomoev, Sergey, Ivan Vasilevskii, and Erzhena Khartaeva. "Atomic Force Microscopy and EDX Analysis for Investigation Photoconductive LT-GaAs Terahertz Antennas." Solid State Phenomena 271 (January 2018): 92–97. http://dx.doi.org/10.4028/www.scientific.net/ssp.271.92.
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We investigate the influence of the surface properties of a low-temperature-grown GaAs photoconductive antenna on the terahertz (THz) response power. A comparison to the surface roughness which is extracted from an atomic force microscope is given. We used energy dispersive x-ray spectroscopy (EDX) measurements to determine the Ga/As compositional ratio in the LT-GaAs.
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Abdellatif, Ahmed Shehata, Aidin Taeb, Nazy Ranjkesh, Suren Gigoyan, Elizaveta Nenasheva, and Safieddin Safavi-Naeini. "Low-insertion loss phase shifter for millimeter-wave phased array antennas." International Journal of Microwave and Wireless Technologies 8, no. 1 (2014): 33–39. http://dx.doi.org/10.1017/s1759078714001299.
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This paper proposes a compact, low-loss, and low-cost phase shifter for millimeter-wave/sub-THz applications. The basic idea is to perturb the propagation constant of a high resistivity silicon image guide by high-dielectric constant barium lanthanide tetratitanates (BLT) ceramic loading. Three different BLT ceramic samples have been tested. The measured maximum phase-shift variation reaches 150° at 100 GHz with an average insertion loss of 2.85 dB and an insertion loss variation <0.7 dB for a sample of a 5-mm length. The proposed phase shifter has a bandwidth from 95 to 105 GHz. A low-cost fabrication technology has been developed and used to realize this phase shifter.
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Bhasakar Rao, V. Shiva, and B. Suribabu Naick. "Performance Analysis of RIS-Assisted Index Modulation for Terahertz Communications." International Journal of Electrical and Electronics Research 12, no. 4 (2024): 1474–79. https://doi.org/10.37391/ijeer.120442.
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The significance of Terahertz (THz) communication for the upcoming sixth generation (6G) communications, which offers abundant bandwidth for high-speed data transmission. However, THz frequencies face challenges such as propagation attenuation and molecular absorption that limit their coverage range. To address this issue, the use of reconfigurable intelligent surfaces (RIS) and index modulation (IM) has been proposed to extend coverage and reduce bit error rates (BER) at low transmitted power. This paper introduces a novel RIS-assisted IM system for THz communication, employing semi-definite relaxation (SDR) optimization techniques for passive beam forming at the detector. The proposed system, named PRIS-IM, demonstrates superior performance compared to conventional RIS-IM (CRIS-IM) and conventional IM (CIM) without RIS in THz frequencies. Simulation results illustrate a lower BER at a higher signal to-noise ratio (SNR) achieved by increasing the number of passive elements. Furthermore, the mutual information (MI) of the PRIS-IM system is derived and validated with simulation, and the achievable rate of the PRIS-IM system is improved by increasing the number of transmitting antennas and reflecting elements. Moreover, the PRIS-IM system is analyzed in different channel scenarios and distances. Overall, the proposed system exhibits the potential to significantly enhance the BER and MI performance of THz communication, indicating promising prospects for future wireless networks.
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Digiorgio, Valerio, Urban Senica, Paolo Micheletti, Mattias Beck, Jérôme Faist, and Giacomo Scalari. "Surface-emitting THz quantum cascade laser frequency comb with tunable external mirror dispersion compensation." EPJ Web of Conferences 287 (2023): 07028. http://dx.doi.org/10.1051/epjconf/202328707028.
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We present a surface emitting THz quantum cascade laser frequency comb with an adjustable chromatic dispersion compensation via a mechanically tunable GTI cavity. Surface emission and high optical feedback into the laser cavity are achieved by a planarized ridge waveguide design with low reflectivity facets and two broadband patch array antennas for coupling to an external mirror (back side) and for power extraction (front side). We demonstrate direct and reproducible manipulation of the frequency comb state, specifically the comb stability and beatnote frequency tuning, by controlling the position of an external movable mirror.
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Zhang, Yanbo, Xiangdong Li, Xingwen Zhao, Xianzhong Tian, and Zijiang Yang. "Experimental research on terahertz scanning imaging system based on S-parameters." Journal of Physics: Conference Series 2187, no. 1 (2022): 012044. http://dx.doi.org/10.1088/1742-6596/2187/1/012044.
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Abstract Due to the limitations of the detector in the terahertz (THz) scanning imaging process and the problems of low contrast and poor visualization effect of original image, a THz continuous-wave scanning imaging system from 75 to 110 GHz is presented. The system is comprised of vector network analyzer (VNA), spread spectrum module, transmit and receive antennas, scanning stage and host computer. In addition, the automatic acquisition and storage of S-parameters is realized by Virtual Instrument Software Architecture (VISA) protocol, and the gray imaging method based on S-parameters is proposed. High-precision structural resolution test board is designed based on printed circuit board (PCB) method and the imaging experiment for the resolution test board is carried out. By comparing with original imaging results, better imaging quality of the system designed in this paper is obtained and imaging results show that the resolution of 1.8 mm could be achieved.
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Cui, Yiran, and Georgios C. Trichopoulos. "Quasi-Optical Testbed for Wideband THz On-Wafer Measurements." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2019, DPC (2019): 001311–22. http://dx.doi.org/10.4071/2380-4491-2019-dpc-presentation_tha3_031.
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At mmW and THz band, on-wafer testing is very critical for on-wafer electronics devices and circuits as well as spectroscopy. Nevertheless, current measurement capabilities are limited by contact probe technology and vector network analyzers (VNAs). Recently, we proposed a non-contact method to tackle the issue of using expensive and brittle contact probes. Using quasi-optics and on-chip antennas, the signals from the THz VNA are coupled on the device under test (DUT) with low insertion loss and unmatched repeatability. However, the bandwidth and cutoff frequency limitations of VNAs limit the scope of THz measurements and increase the complexity. State-of-the-art VNAs use external frequency multipliers, namely VNA extenders, to up-convert the VNA signal to the THz band. The problem of using such extenders is three-fold: 1) The maximum cutoff barely breaks it into the THz band, 2) they are bandlimited, and 3) they are extremely expensive due to costs associated with waveguide micromachining and sophisticated semiconductor processes for the electronics. Here, we propose the design of a novel quasi-optical on-wafer testbed that is compatible with photonics-based sources and detectors (e.g., photomixers) and use THz optical components instead of traditional waveguide structures to route the THz signals. With photomixers we can implement cost effective THz sources or receivers that can be efficiently integrated with quasi-optics. They feature a relatively simple topology and operate in a very wide bandwidth, typically from less than 100 GHz to more than 3 THz. Since the optical components are frequency independent, by adopting photomixers as THz emitter and detectors, the proposed quasi-optical system has a potential to achieve ultra-wideband on-wafer measurement capabilities. First, we talk about the design of the quasi-optical coupler consists of two beam splitters, which is used to discriminate between the reference and the measurement signals. Through a rigorous theoretical analysis and experiments we verified a minimum 60 dB isolation and less than 3 dB of insertion loss in the 330–500 GHz band. Then, we discuss how to use this quasi-optical coupler to implement one-port free-space measurements. We also discuss the calibration process and present three calibration standards that eliminate the error terms of the one-port free-space measurement topology. The experimental results we collected from our free-space measurements are shown afterwards. The results for two different DUTs show a good agreement between the measurement and the theoretical reflection coefficients. Next, we present the on-wafer testbed, which is constructed by a quasi-optical coupler and a non-contact probe. We also briefly introduce the on-wafer calibration approach and on-wafer standards. We notice that, in order to couple the THz beam to the on-wafer DUT, all the on-wafer standards and DUTs need to be integrated with probing antennas. Finally, we show the experimental results we obtained from one-port on-wafer measurements. For two different on-wafer DUTs, the measurement results agree with the simulations very well. Besides, with multiple measurements, we also verified that the proposed quasi-optical testbed has a good repeatability.
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Hasan, Md Rabiul, S. Ali, and S. A. Emi. "Ultra-low material loss microstructure fiber for terahertz guidance." Photonics Letters of Poland 9, no. 2 (2017): 66. http://dx.doi.org/10.4302/plp.v9i2.679.
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In this letter, we numerically demonstrate a hybrid-core microstructure fiber for low-loss terahertz guidance. Finite element method with circular perfectly matched layer boundary condition is applied to characterize the guiding properties. It is shown that by using a triangular-core inside a square lattice microstructure exhibits ultra-low effective material loss (EML) of 0.169 dB/cm and low confinement loss of 0.087 dB/cm at the operating frequency of 0.75 THz. We also discuss how other guiding properties including power fraction, single mode propagation and dispersion vary with changing of core diameter and operating frequencies. This low-loss microstructure fiber can be effectively used in numerous applications in the THz regime. Full Text: PDF ReferencesJ. J. Bai, J. N. Li, H. Zhang, H. Fang, S. J. Chang, "A porous terahertz fiber with randomly distributed air holes", Appl. Phys. B 103, 2 (2011). CrossRef S. Atakaramians, S. Afshar, B. M. Fischer, D. Abbott, T. M. Monro, "Porous fibers: a novel approach to low loss THz waveguides", Opt. Express 16, 12 (2008). CrossRef K. Wang, D. M. Mittleman, "Metal wires for terahertz wave guiding", Nature 432, 7015 (2004). CrossRef R. Islam, G. K. M. Hasanuzzaman, M. S. Habib, S. Rana, M. A. G. Khan, "Low-loss rotated porous core hexagonal single-mode fiber in THz regime", Opt. Fiber Technol. 24, (2015). CrossRef M. I. Hasan, S. M. A. Razzak, G. K. M. Hasanuzzaman, M. S.Habib, "Ultra-Low Material Loss and Dispersion Flattened Fiber for THz Transmission", IEEE Photon. Technol. Lett. 26, 23 (2014). CrossRef S. F. Kaijage, Z. Ouyang, X. Jin, "Porous-Core Photonic Crystal Fiber for Low Loss Terahertz Wave Guiding", IEEE Photon. Technol. Lett. 25, 15 (2013). CrossRef M. R. Hasan, M. A. Islam, A. A. Rifat, "A single mode porous-core square lattice photonic crystal fiber for THz wave propagation", J. Eur. Opt. Soc. Rapid Publ. 12, 1 (2016). CrossRef M. R. Hasan, M. A. Islam, M. S. Anower, S. M. A. Razzak, "Low-loss and bend-insensitive terahertz fiber using a rhombic-shaped core", Appl. Opt. 55, 30 (2016). CrossRef S. Ali et al. "Ultra-low loss THz waveguide with flat EML and near zero flat dispersion properties", in 9th Int. Conf. on Elect. and Comp. Eng., IEEE, (2016). CrossRef K. Nielsen, H. K. Rasmussen, A. J. Adam, P. C. Planken, O. Bang, P. U. Jepsen, "Bendable, low-loss Topas fibers for the terahertz frequency range", Opt. Express 17, 10 (2009). CrossRef A. W. Snyder, J. D. Love, Optical waveguide theory (London, Chapman & Hall 1983). DirectLink L. Vincetti, A. Polemi, in Antennas and Propagation Society International Symposium, IEEE (2009)G. P. Agrawal, Nonlinear fiber optics (Boston, Academic Press 1989). CrossRef B. S. Williams, "Terahertz quantum-cascade lasers", Nat. Photon. 1, 9 (2007). CrossRef H. W. Hubers et al. "Terahertz quantum cascade laser as local oscillator in a heterodyne receiver", Opt. Express 13, 15 (2005). CrossRef
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Floettmann, Klaus, Francois Lemery, Martin Dohlus, Michaela Marx, Vasili Tsakanov, and Mikayel Ivanyan. "Superradiant Cherenkov–wakefield radiation as THz source for FEL facilities." Journal of Synchrotron Radiation 28, no. 1 (2021): 18–27. http://dx.doi.org/10.1107/s1600577520014058.
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An electron beam passing through a tube of small inner diameter which is lined on the inside with a dielectric layer will radiate energy in the THz range due to the interaction with the boundary. The resonant enhancement of certain frequencies is conditioned by structure parameters such as tube radius and the permittivity and thickness of the dielectric layer. In low-loss structures narrow-band radiation is generated which can be coupled out by suitable antennas. For higher frequencies, the coupling to the resistive outer metal layer becomes increasingly important. The losses in the outer layer prohibit reaching higher frequencies with narrow-band conditions. Instead, short broad-band pulses can be generated with still attractive power levels. In the first section of the paper, a general theory of the impedance of a two-layer structure is presented and the coupling to the outer resistive layer is discussed. Approximate relations for the radiated energy, power and pulse length for a set of structure parameters are derived and compared with numerical results in the following section. Finally, the first numerical result of the out-coupling of the radiation by means of a Vlasov antenna and estimates of the achieved beam quality are presented.
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Verona, Ivan Cedrick Malaluan, Alexander De los Reyes, Hannah Bardolaza, and Elmer Estacio. "Terahertz Quasi-Time Domain Spectroscopy using a 808nm multimode diode laser." Journal of Physics and Its Applications 5, no. 2 (2023): 58–61. http://dx.doi.org/10.14710/jpa.v5i2.17945.
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We report on a terahertz quasi-time domain spectroscopy (QTDS) system based on a low-cost continuous wave multimode diode laser. Commercially available low-temperature grown gallium arsenide (LT-GaAs) based photoconductive antennas (PCAs) with spiral and dipole configurations were used as emitter and detector, respectively. Terahertz pulses spaced at approximately 55 ps with a bandwidth of 400 GHz were obtained. Parametric measurements of the terahertz peak-to-peak intensity were performed by varying the injection current and temperature while maintaining incident laser power. The highest peak-to-peak intensity was obtained at 170mA injection current and 20° C temperature settings. The change in the THz peak-to-peak intensity is attributed to the mode hopping characteristics of the device which in turn, is dependent on injection current and temperature.
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Palma, Fabrizio. "Theoretical Analysis of the Time Transient of the THz Self-Mixing Rectification Voltage in a Semiconductor Barrier." Electronics 12, no. 6 (2023): 1264. http://dx.doi.org/10.3390/electronics12061264.
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THz detection in a silicon structure can be an effective instrument not only for image detection, and material and gas sensing, but also for communications. Next-generation 6G communications assume the possibility of achieving a large-band transmission, using free space propagation with THz carriers. This possibility relies on the availability of an effective, low-cost detector technology. THz detection by self-mixing can provide an effective amplitude demodulation of the incoming carrier, with antennas directly fabricated on the chip. In this case, the speed of the detectors represents a crucial point in the definition of the bandwidth whereby several GHz are indeed required by the communication systems. The self-mixing process is intrinsically very fast, since it depends on the non-linear interaction of the radiation with the majority carriers inside the semiconductor structure. In this paper, we evaluate analytically the time dependence of the onset of the rectified voltage. A potential propagation along the detector channel follows the self-mixing rectification, accompanied by the charging of the parasitic capacitances of the structure. A numerical simulator can easily evaluate the delay due to this propagation along the structure, but the transient of the true origin of the signal, i.e., the establishment of the self-mixing voltage, at the current time, can be only inferred by analytical approach. In this work, we use the model developed for the THz rectification in the depletion region of an MOS capacitance to develop a transient model of the formation of the characteristic self-mixing charge dipole, and of the generation of the rectified potential. Subsequently, we show by TCAD simulations the propagation of the effect on the semiconductor structure, which surrounds the rectifying barrier, and evaluate the overall time response of a detector.
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Hazer Inaltekin, Mark Bowyer, Iain B. Collings, Gunes Karabulut Kurt, Walid Saad, and Phil Whiting. "Future satellite communications: Satellite constellations and connectivity from space." ITU Journal on Future and Evolving Technologies 5, no. 2 (2024): 288–94. http://dx.doi.org/10.52953/pcds7523.
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Satellite communications is currently undergoing a massive growth, with a rapid expansion in Low Earth Orbit (LEO) networks, and a range of new satellite technologies. Until very recently, satellite communication systems and terrestrial 5/6G wireless networks have been complementary distinct entities. There is now the opportunity to bring these networks together and deliver an integrated global coverage multi-service network. Achieving this will require solving some key research challenges, and leveraging new technologies including high frequency phased-array antennas, onboard processing, dynamic beam hopping, physical layer signal processing algorithms, transmission waveforms, and adaptive inter-satellite links and routing. By integrating seamlessly with terrestrial 5/6G networks and low altitude flying access points, future satellite networks promise to deliver universal connectivity on a global scale, overcoming geographical limitations. In this special issue, we focus on the future of satellite communications, exploring topics ranging from beam hopping and design to space routing and THz satellite communications. Our aim is to shed light on the potential of these emerging technologies and their role in reshaping the landscape of global connectivity.
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Qian, Tianwen, Ben Schuler, Y. Durvasa Gupta, et al. "Hybrid Photonic Integrated Circuits for Wireless Transceivers." Photonics 12, no. 4 (2025): 371. https://doi.org/10.3390/photonics12040371.
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Recent advancements in hybrid photonic integrated circuits (PICs) for wireless communications are reviewed, with a focus on innovations developed at Fraunhofer HHI. This work leverages hybrid integration technology, which combines indium phosphide (InP) active elements, silicon nitride (Si3N4) low-loss waveguides, and high-efficient thermal-optical tunable polymers with micro-optical functions to achieve fully integrated wireless transceivers. Key contributions include (1) On-chip optical injection locking for generating phase-locked optical beat notes at 45 GHz, enabled by cascaded InP phase modulators and hybrid InP/polymer tunable lasers with a 3.8 GHz locking range. (2) Waveguide-integrated THz emitters and receivers, featuring photoconductive antennas (PCAs) with a 22× improved photoresponse compared to top-illuminated designs, alongside scalable 1 × 4 PIN-PD and PCA arrays for enhanced power and directivity. (3) Beam steering at 300 GHz using a polymer-based optical phased array (OPA) integrated with an InP antenna array, achieving continuous steering across 20° and a 10.6 dB increase in output power. (4) Demonstration of fully integrated hybrid wireless transceiver PICs combining InP, Si3N4, and polymer material platforms, validated through key component characterization, on-chip optical frequency comb generation, and coherent beat note generation at 45 GHz. These advancements result in compact form factors, reduced power consumption, and enhanced scalability, positioning PICs as an enabling technology for future high-speed wireless networks.
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Rämer, Jan-Martin, Frank Ospald, Georg von Freymann, and René Beigang. "Generation and detection of terahertz radiation up to 4.5 THz by low-temperature grown GaAs photoconductive antennas excited at 1560 nm." Applied Physics Letters 103, no. 2 (2013): 021119. http://dx.doi.org/10.1063/1.4813605.
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Liu, Linsheng, Zhen Deng, Guipeng Liu, et al. "Low-Temperature Migration-Enhanced Epitaxial Growth of High-Quality (InAs)4(GaAs)3/Be-Doped InAlAs Quantum Wells for THz Applications." Crystals 14, no. 5 (2024): 421. http://dx.doi.org/10.3390/cryst14050421.
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This investigation explores the structural and electronic properties of low-temperature-grown (InAs)4(GaAs)3/Be-doped InAlAs and InGaAs/Be-doped InAlAs multiple quantum wells (MQWs), utilizing migration-enhanced epitaxy (MEE) and conventional molecular beam epitaxy (MBE) growth mode. Through comprehensive characterization methods including transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), pump–probe transient reflectivity, and Hall effect measurements, the study reveals significant distinctions between the two types of MQWs. The (InAs)4(GaAs)3/Be-doped InAlAs MQWs grown via the MEE mode exhibit enhanced periodicity and interface quality over the InGaAs/Be-InAlAs MQWs grown through the conventional molecule beam epitaxy (MBE) mode, as evidenced by TEM. The AFM results indicate lower surface roughness for the (InAs)4(GaAs)3/Be-doped InAlAs MQWs by using the MEE mode. Raman spectroscopy reveals weaker disorder-activated modes in the (InAs)4(GaAs)3/Be-doped InAlAs MQWs by using the MEE mode. This originates from utilizing the (InAs)4(GaAs)3 short period superlattices rather than InGaAs, which suppresses the arbitrary distribution of Ga and In atoms during the InGaAs growth. Furthermore, pump–probe transient reflectivity measurements show shorter carrier lifetimes in the (InAs)4(GaAs)3/Be-doped InAlAs MQWs, attributed to a higher density of antisite defects. It is noteworthy that room temperature Hall measurements imply that the mobility of (InAs)4(GaAs)3/Be-doped InAlAs MQWs grown at a low temperature of 250 °C via the MEE mode is superior to that of InGaAs/Be-doped InAlAs MQWs grown in the conventional MBE growth mode, reaching 2230 cm2/V.s. The reason for the higher mobility of (InAs)4(GaAs)3/Be-doped InAlAs MQWs is that this short-period superlattice structure can effectively suppress alloy scattering caused by the arbitrary distribution of In and Ga atoms during the growth process of the InGaAs ternary alloy. These results exhibit the promise of the MEE growth approach for growing high-performance MQWs for advanced optoelectronic applications, notably for high-speed optoelectronic devices like THz photoconductive antennas.
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Palmieri, Beniamino, Maria Vadalà, and Carmen Laurino. "The FIT therapy for the treatment of musculoskeletal and neurological disorders related symptoms: A retrospective observational study." Asian Journal of Medical Sciences 10, no. 5 (2019): 6–12. http://dx.doi.org/10.3126/ajms.v10i5.21230.
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Background: Far Infrared Waves (FIW) with frequency range among few hundreds gigahertz (GHz) and few terahertz (THz) display some positive effects on neurological and musculoskeletal disorders.
 Aims and Objectives: Our retrospective observational study describes the benefits observed by the administration of an infrared –trapping and focusing plaster (FIT-PATCH) in patients affected by different musculoskeletal and neurological symptoms.
 Materials and Methods: 100 patients were retrospectively reviewed through the Second Opinion Medical Network. Each patient sticked a FIT-PATCH every 5 days for 1 month upon the skin in the painful/inflamed area. Quality of life (QOL) assessment was evaluated by the Short Form-36 (SF-36) health survey questionnaire before starting the treatment and after the fourth week and the Visual Analogue Scale (VAS) completed the pre-post treatment subjective pain record.
 Results: SF-36 showed significantly improvement of the pre-post treatment scores (P < 0.03), pain score (P < 0.02), general health score (P < 0.03) and in the emotional component scores (P < 0.03). The VAS pain score was either improved (P < 0.02) after plaster administration. No side effects or allergenic skin reactions were reported along the study.
 Conclusions: The FIT patches improved the symptoms probably through a mechanism involving the sebaceous/sweat glands system spreading the fit irradiating infrared THz waves energy, to the surrounding tissues with both a thermal and electromagnetic putative effect.The occlusive mechanism of the patch on the skin surface increasing the local thermic gradient cannot be adequately supposed to be therapeutically effective, because the FIT patch locally applied induces haemodynamic microvascular modification, not only locally but also remote. Thus, the intrinsic chemical properties of the FIT formulation absorbs and concentrates the endogenous infrared waves amplifying and reverberating them into the underlying tissues near and far, through low-Q-factor helical antennas of the sweat glands spreading the energy all over the body. Hence, the claim is that fit basically absorbs and concentrates the endogenous infrared waves into the affected districts and accelerates symptoms recovery.
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Youn, Janghyuk, Woong Son, and Bang Chul Jung. "Physical-Layer Security Improvement with Reconfigurable Intelligent Surfaces for 6G Wireless Communication Systems." Sensors 21, no. 4 (2021): 1439. http://dx.doi.org/10.3390/s21041439.
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Recently, reconfigurable intelligent surfaces (RISs) have received much interest from both academia and industry due to their flexibility and cost-effectiveness in adjusting the phase and amplitude of wireless signals with low-cost passive reflecting elements. In particular, many RIS-aided techniques have been proposed to improve both data rate and energy efficiency for 6G wireless communication systems. In this paper, we propose a novel RIS-based channel randomization (RCR) technique for improving physical-layer security (PLS) for a time-division duplex (TDD) downlink cellular wire-tap network which consists of a single base station (BS) with multiple antennas, multiple legitimate pieces of user equipment (UE), multiple eavesdroppers (EVEs), and multiple RISs. We assume that only a line-of-sight (LOS) channel exists among the BS, the RISs, and the UE due to propagation characteristics of tera-hertz (THz) spectrum bands that may be used in 6G wireless communication systems. In the proposed technique, each RIS first pseudo-randomly generates multiple reflection matrices and utilizes them for both pilot signal duration (PSD) in uplink and data transmission duration (DTD) in downlink. Then, the BS estimates wireless channels of UE with reflection matrices of all RISs and selects the UE that has the best secrecy rate for each reflection matrix generated. It is shown herein that the proposed technique outperforms the conventional techniques in terms of achievable secrecy rates.
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Yang, Liuxiao, Hongqiang Wang, Yang Zeng, Wei Liu, Ruijun Wang, and Bin Deng. "Detection of Parabolic Antennas in Satellite Inverse Synthetic Aperture Radar Images Using Component Prior and Improved-YOLOv8 Network in Terahertz Regime." Remote Sensing 17, no. 4 (2025): 604. https://doi.org/10.3390/rs17040604.
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Inverse Synthetic Aperture Radar (ISAR) images of space targets and their key components are very important. However, this method suffers from numerous drawbacks, including a low Signal-to-Noise Ratio (SNR), blurred edges, significant variations in scattering intensity, and limited data availability, all of which constrain its recognition capabilities. The terahertz (THz) regime has reflected excellent capacity for space detection in terms of showing the details of target structures. However, in ISAR images, as the observation aperture moves, the imaging features of the extended structures (ESs) undergo significant changes, posing challenges to the subsequent recognition performance. In this paper, a parabolic antenna is taken as the research object. An innovative approach for identifying this component is proposed by using the advantages of the Component Prior and Imaging Characteristics (CPICs) effectively. In order to tackle the challenges associated with component identification in satellite ISAR imagery, this study employs the Improved-YOLOv8 model, which was developed by incorporating the YOLOv8 algorithm, an adaptive detection head known as the Dynamic head (Dyhead) that utilizes an attention mechanism, and a regression box loss function called Wise Intersection over Union (WIoU), which addresses the issue of varying sample difficulty. After being trained on the simulated dataset, the model demonstrated a considerable enhancement in detection accuracy over the five base models, reaching an mAP50 of 0.935 and an mAP50-95 of 0.520. Compared with YOLOv8n, it improved by 0.192 and 0.076 in mAP50 and mAP50-95, respectively. Ultimately, the effectiveness of the suggested method is confirmed through the execution of comprehensive simulations and anechoic chamber tests.