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Optimum chirp for efficient terahertz generation from two-color femtosecond pulses in air
摘要： We compare detailed spatio-temporal propagation simulations with experiments on generation of terahertz (THz) pulses in single ?laments with two-color optical excitation, which elucidates the mechanism whereby positively chirped optical pulses lead to the maximum THz yield. The long-wavelength components in the leading edge of the positively chirped 2x-pulse preserve the overlap with the x-pulse. The THz yield is extremely sensitive to the temporal overlap: for a 35-fs x-pulse, the yield decreases by an order of magnitude upon a x–2x pulse shift of only 5 fs.
关键词： terahertz,chirp,two-color excitation,femtosecond pulses,THz generation
更新于2025-09-04 15:30:14
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[IEEE NAECON 2018 - IEEE National Aerospace and Electronics Conference - Dayton, OH, USA (2018.7.23-2018.7.26)] NAECON 2018 - IEEE National Aerospace and Electronics Conference - Indium Tin Oxide/Barium Strontium Titanate THz Sensor Antenna
摘要： A Bow-Tie ITO/BST and Au/BST antennas were designed and analyzed using the finite element, Multiphysics COMSOLTM program. The study shows that the outputs peak at several modes and ITO antennas allow for the integration of the antenna with optoelectronic devices.
关键词： COMSOL FEM Modelling,THz,Nano-Antenna
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Performance Evaluation of a 220–260 GHz LO Tunable BPSK/QPSK Wireless Link in SiGe HBT Technology
摘要： This paper reports on characterization and performance evaluation of a 1-m 220-260 GHz tunable carrier wireless link with highly-integrated direct-conversion quadrature TX/RX modules implemented in 0.13μm SiGe HBT technology with ft/fmax of 350/550 GHz. Under limited IF bandwidth constraints of 15 GHz, the maximum achieved data rates for BPSK/QPSK modulation schemes are 35 Gbps with an EVM of 28.9 % and 65 Gbps with an EVM of 31.5 %, respectively. It is further found that the current link performance is not limited by the AWGN-related SNR but mainly affected by the RF front-end imperfections related to large operation bandwidth.
关键词： on-chip lens-integrated antenna,direct conversion quadrature receiver,SiGe HBT,THz communication
更新于2025-09-04 15:30:14
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Signal Reduction by tree leaves in Low-THz Automotive Radar
摘要： In this study, the attenuation of 300 GHz signal propagating through a layer of leaves which can built upon the antenna radome is investigated. Three set of leaves (Lauren, Birch, Willow) are chosen in this measurement as likely obscurants which can stick to automotive radar radome and cause signal degradation. Transmissivity through uniform layer of the leaves with different water contents is measured. The water content is estimated in leaves drying gradually. The complex permittivity of the leaves with different water contents is estimated and these values are used to calculate the transmissivity through the uniform layer of leaves. Comparison of transmissivity in equivalent water layer with that of leaves having the same water content is made. Measured transmissivity through leaves is compared with that obtained by theoretical model.
关键词： leaves,Transmissivity,Low-THz wave,automotive
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - 140 GHz Linear to Circular Polarization Convertor Based on Modified Cross Slot Frequency Selective Surface with High Selectivity
摘要： A 140 GHz linear to circular polarization converter based on a frequency selective surface (FSS) with high selectivity is proposed and designed in this paper. The periodic element of the converter includes a square substrate integrated waveguide (SIW) cavity and two cross slots with stubs etched on the top and bottom conductor claddings of the cavity. Based on the SIW cavity, a transmission pole is provided to improve passband characteristics and sideband selectivity. Besides, this THz converter can be easily fabricated using normal PCB process instead of compacted and high-cost technologies.
关键词： high selectivity,frequency selective surface (FSS),circular polarization (CP),Terahertz (THz) technology,substrate integrated waveguide (SIW) cavity
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Low-THz Transmission Through Liquid Contaminants on Antenna Radome
摘要： The effect of a uniform layer of petroleum-based fuels, gasoline and diesel, on wave propagation through a radome at 150 GHz and 300 GHz is studied theoretically and empirically. The measured results are compared with a theoretical calculation and are found to be in good agreement. Transmissivity higher than -2 dB and -5 dB is measured through a 15 mm layer of diesel at 150 GHz and 300 GHz, respectively. Transmissivity through a 15 mm uniform layer of gasoline is recorded to be about -15 dB for both frequencies. However, the antenna radome for outdoor automotive applications is more likely to be covered by diesel than gasoline, due to the weaker dispersion and faster evaporation of gasoline.
关键词： radomes,transmissivity,petroleum-based fuels,low-THz waves
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Suppressing Ghost Images for Synthetic Aperture THz Imaging with Large Sampling Spacing
摘要： This paper presents our study on the ghost images suppression for THz imaging system with large sampling spacing which are achieved by both sparse antenna array (SPA) of large element spacing (>8λ) and mechanical scanning. The ghost images in synthetic aperture imaging algorithm is due to the grating lobes of the array radiation pattern, so we propose a ghost image suppression method based on a weighting function in the traditional imaging algorithm. Therefore, the large sampling spacing between array elements for synthetic aperture THz imaging becomes possible, which can further reduce the cost and data acquisition time. And this study will help to guide the scheme design of SPA for THz imaging system.
关键词： THz imaging,ghost images suppression,sparse antenna array
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Large Aperture Metal-Mesh Lenses for THz Astronomy
摘要： In this paper we present preliminary results of a metal-mesh graded index Fresnel lens. The designed lens has a diameter of 300 mm, a focal length of 1050mm and operates from 70 to 300 GHz. It was not possible to directly scale the design of the previous lenses, so a Fresnel graded index was used. A new testing facility was developed and verified, which allowed us to show that the new lens matches the same performance of a traditional polyethylene lens. Lenses of this diameter are of interest in the astronomy instrumentation community.
关键词： THz,Metamaterials,GRIN Lens
更新于2025-09-04 15:30:14
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Investigation of moments-based transport models applied to plasma waves and the Dyakonov–Shur instability
摘要： Transport models based on balance equations with different degrees of numerical complexity can be derived from the Boltzmann transport equation (BTE). In this paper two different drift-diffusion models based on the first two moments of the BTE as well as two hydrodynamic models based on four moments are derived and analyzed for their accuracy in the THz frequency range with emphasis on the generation of plasma waves. To this end, they are compared to the BTE in the small-signal regime under homogeneous bulk conditions where harmonic waves were assumed, which reveals that the hydrodynamic models provide a higher accuracy. It is also shown that the anisotropy of the distribution function must be taken into account in the closure relations. This leads to convective derivatives in the balance equations, which are very difficult to treat by numerical means in the case of semiconductor devices and are neglected in commercial TCAD suites. But without them a meaningful simulation of the Dyakonov–Shur plasma instability will not be possible.
关键词： Boltzmann transport equation,THz,drift-diffusion,plasma instability,hydrodynamic
更新于2025-09-04 15:30:14
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The instability of terahertz plasma waves in cylindrical FET
摘要： In this paper, the Dyakonov-Shur instability of terahertz (THz) plasma waves has been analyzed in gated cylindrical ?eld effect transistor (FET). In the cylindrical FET, the hydrodynamic equations in cylindrical coordinates are used to describe the THz plasma wave in two-dimensional electronic gas. The research results show that the oscillation frequency of the THz plasma wave is increased by increasing the component of wave in the circumferential direction, but instability increment of the THz plasma wave are increased by increasing the radius of channel.
关键词： oscillation frequency,cylindrical ?eld effect transistor,THz plasma waves
更新于2025-09-04 15:30:14