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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-pass Frequency Selective Surface for a Dual-band Gyro-multiplier Characterized by THz-TDS
摘要： This work investigates the performance of a low-pass frequency selective surface (FSS) fabricated from perforated hole array on a copper plate for the use in a dual-band high power gyro-multiplier. The output beam from the high power gyro-multiplier contains signals at two separating bands carrying peak power up to 2 kW. The frequency separating components therefore are required to stand high power and produce low insertion loss. Metallic perforated array is an ideal option to meet these requirements. Considering the fabrication accuracy, low-pass FSS is selected. The fabrication of the low-pass FSS is based on precision milling technology. The performance of the FSS is evaluated using a terahertz time domain spectroscopy.
关键词： gyro-multiplier,terahertz time domain spectroscopy,quasi-optics,frequency selective surface
更新于2025-09-04 15:30:14
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Room-Temperature Continuous-Wave Frequency-Referenced Spectrometer up?to?7.5?THz
摘要： The lack of coherent room-temperature sources in the whole terahertz spectral window (0.3–10 THz) has significantly hampered the growth of scientific and technological applications in this range. Among them, high-precision frequency measurements of molecular transitions play a central role but remain an open challenge. Here, room-temperature generation and detection of continuous-wave, broadly tunable, narrow-linewidth THz radiation are presented, and their application to high-resolution spectroscopy in the broad 1–7.5 THz spectral range is demonstrated. This result has been achieved by implementing a Cherenkov phase-matching scheme into a channel waveguide in a nonlinear crystal. This simple approach, entirely based on robust telecom technology, unprecedently merges in a single source an ultra-broad continuous-wave spectral coverage and a state-of-the-art accuracy (approximately 10?9) in molecular-transition-center determination.
关键词： terahertz,continuous-wave,frequency-referenced,spectroscopy,Cherenkov phase-matching
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Multi-Color Coherent Smith-Purcell Radiation with Controllable Direction from 2D Rectangular Sub-Wavelength Hole Array
摘要： We proposed a multi-color Smith-Purcell radiation source with controllable emission direction by using a sheet free-electron beam to drive the two-dimensional rectangular sub-wavelength hole array. Each hole is an electromagnetic wave oscillating and radiating unit with specified frequencies. The coherent radiation is generated when the radiation from all units constructively interfere. By adjusting the arrangement of the sub-wavelength hole array, the coherent radiation direction could be steered in the three dimensional space.
关键词： terahertz source,sub-wavelength hole array,free-electron beam,Smith-Purcell radiation,coherent radiation
更新于2025-09-04 15:30:14
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai, China (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - A Frequency Nonlinearity and Fluctuation Correction Method for Terahertz ISAR Imaging
摘要： Due to the high frequency band and wide bandwidth of Terahertz imaging radar, the high frequency generally performs unstable in system. In detail, the linearly frequency modulated (LFM) signal shows nonlinearity and the frequency center fluctuates randomly with time. It will potentially lead to the degradation of Terahertz inverse synthetic aperture radar (THz-ISAR) imaging quality. To address this problem, this paper presents a frequency nonlinearity and fluctuation correction method based on minimum entropy (ME). Following the error model, both the error can be corrected by applying the ME metric to the range and azimuth direction. The feasibility and adaptability of this proposal have been validated by simulation and real data experimental result.
关键词： minimum entropy,Terahertz,error correction,inverse synthetic aperture radar
更新于2025-09-04 15:30:14
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Terahertz rectangular corrugated transmission line with Gaussian mode filtering for DNP-NMR
摘要： Gyrotrons have been developed as terahertz wave sources in dynamic nuclear polarisation (DNP) system to increase the sensitivity of nuclear magnetic resonance (NMR) in the high-magnetic field regime. However, the transmission of the Gaussian beam from the gyrotron output window to the NMR system proves to be a critical challenge. In this study, a terahertz transmission system, composed of a rectangular corrugated waveguide and a back-to-back rectangular corrugated horn for Gaussian mode filtering, is proposed. The attenuation in the optimised 0.33?THz corrugated waveguide remains lower than 0.01 dB/m in a broad frequency range from 280?GHz to 450?GHz. Besides, the coupling coefficient from the electric field in the 0.33 THz mode-filtering horn to the fundamental HE11 mode in the rectangular corrugated waveguide is obtained nearly 99.5%. This terahertz transmission system is potential to be applied in DNP-NMR spectrometer based on continuous wave gyrotrons.
关键词： DNP-NMR,Gaussian mode filtering,terahertz,transmission line,gyrotron
更新于2025-09-04 15:30:14
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Applicability of the thin-film approximation in terahertz photoconductivity measurements
摘要： Thin mesoporous photoconductive layers are critically important for efficient water-spitting solar cells. A detailed understanding of photoconductivity in these materials can be achieved via terahertz transient absorption measurements. Such measurements are commonly interpreted using the thin-film approximation. We compare this approximation with a numerical solution of the transfer function without approximations using experimental results for thin-film mesoporous tin oxide (SnO2) samples which range in thickness from 3.3 to 12.6 mm. These samples were sensitized with either a ruthenium polypyridyl complex or a porphyrin dye. The two sensitizers have markedly different absorption coefficients, resulting in penetration depths of 15 mm and 1 mm, respectively. The thin-film approximation results are in good agreement with the numerical work-up for the short penetration length dye. For the longer penetration length samples, the thin-film formula fails even for thicknesses of only 3 mm (cid:2) k/100. The imaginary part of the conductivity calculated using the thin-film formula was significantly larger in magnitude than the value without approximations. This discrepancy between the commonly used thin-film approximation and the numerical solution demonstrates the need for a careful analysis of the thin-film formula.
关键词： thin-film approximation,terahertz photoconductivity,mesoporous SnO2,ruthenium polypyridyl complex,porphyrin dye
更新于2025-09-04 15:30:14
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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz 2018) - Nagoya (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Experimental Characterization of Artificial Human Skin with Melanomas for Accurate Modelling and Detection in Healthcare Application
摘要： A preliminary investigation is carried out on the artificial human skin tissues with and without metastatic melanomas using Terahertz Time Domain Spectroscopy (THz-TDS). Both the refractive indexes and absorption coefficients of artificial skin with melanomas are higher than the normal artificial skin samples over the entire frequency range between 0.2 THz to 1.6 THz. The reason is that tumour cells degrade the in contraction of fibroblasts causing more water content malignant tissues. This study quantifies the impact of melanomas on the optical parameters of artificial skin tissue and can help in techniques that will diagnose and prevent tumours at the early stage.
关键词： artificial human skin,absorption coefficient,Terahertz Time Domain Spectroscopy,refractive index,melanomas
更新于2025-09-04 15:30:14
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HIGH-RESOLUTION GRID-INDEPENDENT IMAGING FOR TERAHERTZ 2-D SYNTHETIC APERTURE RADAR WITH SPATIAL UNDER-SAMPLING
摘要： For the purpose of two-dimensional (2-D) imaging in the Terahertz (THz) near field through 2-D synthetic aperture radar technology, Fourier transform (FT) is one of the most popular imaging ways. However, FT-based algorithms would encounter performance loss either when spatial sampling is under Nyquist frequency or there are off-grid scatterers in the scene of interest. Therefore, by exploiting the theory of matrix enhancement and continuous parameter estimation, we propose to use matrix enhancement and matrix pencil (MEMP) method and matched filter to deal with arbitrarily located scatterers when spatial under-sampling is adopted. Through constructing a specifically expanded matrix, the information of the scatterers involved in the small data set can be enhanced. Then, high-resolution grid-independence 2-D imaging can be achieved by the combination of MP and matched filter. Simulation results verify the effectiveness of the proposed algorithm.
关键词： Terahertz,matrix pencil,matrix enhancement,synthetic aperture radar,Fourier transform,grid-independent imaging,under-sampling
更新于2025-09-04 15:30:14
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Handbook of Advanced Non-Destructive Evaluation || Terahertz Techniques in NDE
摘要： So far, terahertz measurement technology has rarely been used in industry. This book chapter presents therefore the underlying technologies, the resulting possibilities and exemplary applications. The introduction describes the basic properties of terahertz systems and the advantages of terahertz technology over established techniques such as infrared, X-rays and ultrasound. The two industrially relevant terahertz techniques, time domain spectrometer and FMCW system, are described in detail. In addition, the metrological basics for their main applications are introduced. Imaging is required in many applications. Different approaches are presented. Before the chapter concludes with an outlook on future applications, current application examples are discussed. This concerns applications in the fields of coating thickness measurement, safety, materials research, testing of lightweight materials and inline testing. An extensive reference list provides a deeper insight into the topics addressed.
关键词： lightweight materials,materials research,coating thickness measurement,terahertz,NDE,FMCW,imaging,inline testing,time-domain spectroscopy
更新于2025-09-04 15:30:14