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- 实验方案
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Method to improve degraded range resolution due to non-ideal factors in FMCW radar
摘要： This paper reports a method to improve a degraded range resolution for FMCW radar. The proposed post-processing method can achieve an improved range resolution without increasing a signal bandwidth by eliminating factors that can degrade the range resolution based on the non-negative least-squares method. For an FMCW radar adopting the post-processing method with the center frequency of 76.5 GHz and the signal bandwidth of 200 MHz, simulation results show that the degraded range resolution of 160 cm is improved to 70 cm, and measurements show that two corner reflectors with the radar cross section of 10 dBsm located at 70 cm range intervals can be distinguished.
关键词： FMCW,non-negative least-squares method,radar,range resolution,signal bandwidth
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Analysis of NsRCM in BiForSAR Imagery
摘要： As for the bistatic forward-looking synthetic aperture radar (BiForSAR) imaging, frequency-domain imaging algorithms integrated with autofocus is advisable to get a well focused BiForSAR image in the presence of uncompensated motion errors. Nevertheless, a severe drawback of the autofocus algorithms is that they are only capable of removing one-dimensional azimuth phase errors. In range direction, there exists nonsystematic range cell migration (NsRCM) originated from motion errors and RCM correction procedure in frequency domain imaging algorithms as well. In this paper, the causes of different NsRCM in BiForSAR imaging are analyzed, and the corresponding relationship between different NsRCM is deduced. Based on the analyses, we propose an autofocus NsRCM correction scheme for BiForSAR imagery using frequency domain imaging algorithms, being capable of eliminating the range-dependent NsRCM.
关键词： Bistatic Forward-looking Synthetic Aperture Radar (BiForSAR),autofocus,nonsystematic range cell migration (NsRCM),minimum-entropy,spatially-variant
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - Range-Variant Channel Errors Calibration Algorithm for Multichannel HRWS SAR Imaging
摘要： Azimuth multichannel SAR system can realize high-resolution and wide-swath (HRWS) SAR imaging, which has attracted interests. The azimuth ambiguities of multichannel SAR can be suppressed by digital beamforming (DBF) techniques. However, the presence of inevitable channel errors deteriorates the performance of ambiguity suppression. In this paper, we focus on the research of range-variant channel phase errors. We analyze the effect of radial position errors by using the second order Taylor series to expand the azimuth phase history. It indicates that the radial position errors can be regarded as range-variant phase errors. We divide the raw data into several blocks along range direction. Then we use the azimuth cross-correlation technique to estimate the phase errors of each block data. Compared with the subspace-based calibration techniques, the azimuth cross-correlation technique does not use the information of azimuth ambiguities. Afterwards, the fitting process is employed to estimate the range-variant channel phase errors. Finally, the experiments on real data processing validate the effectiveness of our proposed method.
关键词： channel error calibration,Range-variant,HRWS,cross-correlation,multichannel SAR
更新于2025-09-23 15:22:29
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Electrical Transport Properties of Thin Film Composed of a-ZnO Nanorods
摘要： Background: Due to its wide band gap, high exciton binding energy and high breakdown strength, the nanostructures of ZnO may find applications for electronic, photonic devices, and high-frequency applications. Objective: The aim of the present work is to study electrical transport of thin film composed of a-ZnO nanorods. Method: Physical vapour condensation method was employed to fabricate the nanorods of ZnO. The morphology of these nanorods was investigated with the help of scanning electron microscope. X-ray diffraction pattern of as-prepared thin film was recorded using X-ray diffractometer. For dc conductivity measurements, four-probe method was used. Result: The as-prepared ZnO nanorods have diameter ranging from 10-20 nm and the length is of order of few hundred nanometers. XRD pattern of film composed of ZnO nanorods suggests the amorphous nature. Temperature dependence of dc conductivity has been studied over the temperature range of (297- 4.2K). For the temperature range of 297-120K, Mott’s three dimensional variable range hopping (VRH) is applied to explain the electrical conduction. For lower temperature range (120 - 4.2K), 2D-variable-range hopping in localized states near the Fermi level may be responsible for the transport of carriers. Conclusion: Variable range hopping mechanism (VRH) has been suggested for the entire temperature range (298-4.2K) on the basis of temperature dependence of dc conductivity data, which changes from 3D to 2D on moving to lower temperatures side (below 125K).
关键词： physical vapour condensation technique,variable range hopping,XRD,ZnO nanorods,SEM,Mott’s parameters,electrical conduction mechanism
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - A Temporal Tone Mapping Adaptation: An Application using Logarithmic Camera
摘要： Noise, ?icker, temporal inconsistencies disturb the tone mapping creation for High Dynamic Range image (HDR). A method to alleviate these artifacts in tone mapped HDR video sequences is presented in this paper. A temporal ?ltering is developed in order to minimize undesirable artifacts in the low dynamic range image reconstruction process. In the experiments, tone mapping is applied on video sequences obtained by a logarithmic camera. This temporal process provides visual comfort without any kind of blink and prevents Low Dynamic Range (LDR) videos to be disturbed by some random brightness values of isolated pixels.
关键词： logarithmic sensor,temporal artifacts,high dynamic range video,tone mapping
更新于2025-09-23 15:22:29
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Low Complexity Algorithm for Range-Point Migration-Based Human Body Imaging for Multistatic UWB Radars
摘要： High-resolution, short-range sensors that can be applied in optically challenging environments (e.g., in the presence of clouds, fog, and/or dark smog) are in high demand for various applications. Ultrawideband radar is a promising sensor that is suitable for short-range surveillance or watching sensors. Range-point migration (RPM) has been recently established as a promising imaging approach to achieve accurate and real-time 3-D imaging. However, when objects with many scattering points are dealt with, such as a human body, RPM suffers from high computational costs. In this letter, we propose an algorithm with a lower complexity for an RPM-based 3-D imaging method by introducing a sampling-based scattering center extraction with a simpli?ed evaluation function, in which an ef?cient sample pattern is provided by a golden ratio. The results from a ?nite-difference time-domain-based numerical test, which introduces a realistic human body object, demonstrate that our proposed method remarkably reduces the computational cost without sacri?cing the reconstruction accuracy.
关键词： ultrawideband (UWB) radar,short-range sensor,multistatic observation model,3-D imaging,range-point migration (RPM)
更新于2025-09-23 15:21:21
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Estimation and Removal of Strong Range Ambiguities in Multistatic Synthetic Aperture Radar With Multiple Elevation Beams
摘要： Bistatic and multistatic synthetic aperture radar (SAR) can greatly improve system performance in various aspects, especially in achieving high-resolution wide-swath (HRWS) images. However, the specific system structure may lead to a higher degree of range ambiguities. This letter studies the structure of multistatic multiple elevation beams (MMEB) system which achieves HRWS images with the drawback of more serious range ambiguities compared with the conventional SAR which must be suppressed to get an acceptable system performance. The character that the receivers form, a prospective distributed multichannel system in azimuth, can give a guide in estimating the strong range ambiguities and remove them. An innovative method in estimating and removing (not just smearing) the strong range ambiguities based on this character is proposed. Theoretical analysis and experimental results show the effectiveness of the method. The proposed method considerably improves the range ambiguous performance of the MMEB system without using digital beamforming or pulse coding and makes full use of the system character, and thus improves the applicability of the system.
关键词： multistatic multiple elevation beams (MMEB),high-resolution wide-swath (HRWS),range ambiguities,Bistatic and multistatic,synthetic aperture radar (SAR)
更新于2025-09-23 15:21:21
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ELECTRODELESS MEASUREMENT TECHNIQUE OF COMPLEX DIELECTRIC PERMITTIVITY OF HIGH-K DIELECTRIC FILMS IN THE MILLIMETER WAVELENGTH RANGE
摘要： An electrodeless measurement technique of complex dielectric permittivity of high-K dielectric ?lms is described. The technique is based on a quasi-optic Fabry-Perot resonator and modi?ed for investigation of two-layer dielectric structures — substrate/K-?lm. This procedure is destined to be used for providing a simple intermediate control of parameters of high-K ?lms before the following technological process. Regimes of measurements providing the most sensitive conditions for de?nition of ?lm parameters are considered. The proposed method is tested on two-layer structures with well-known parameters and is used for characterization of ferroelectric (Ba,Sr)TiO3 ?lms in the millimeter wavelength range (～ 50 GHz).
关键词： Fabry-Perot resonator,complex dielectric permittivity,electrodeless measurement,millimeter wavelength range,high-K dielectric films
更新于2025-09-23 15:21:21
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Adaption of an array spectroradiometer for total ozone column retrieval using direct solar irradiance measurements in the UV spectral range
摘要： A compact array spectroradiometer that enables precise and robust measurements of solar UV spectral direct irradiance is presented. We show that this instrument can retrieve total ozone column (TOC) accurately. The internal stray light, which is often the limiting factor for measurements in the UV spectral range and increases the uncertainty for TOC analysis, is physically reduced so that no other stray-light reduction methods, such as mathematical corrections, are necessary. The instrument has been extensively characterised at the Physikalisch-Technische Bundesanstalt (PTB) in Germany. During an international total ozone measurement intercomparison at the Iza?a Atmospheric Observatory in Tenerife, the high-quality applicability of the instrument was verified with measurements of the direct solar irradiance and subsequent TOC evaluations based on the spectral data measured between 12 and 30 September 2016. The results showed deviations of the TOC of less than 1.5 % from most other instruments in most situations and not exceeding 3 % from established TOC measurement systems such as Dobson or Brewer.
关键词： stray-light reduction,direct solar irradiance measurements,array spectroradiometer,total ozone column,UV spectral range
更新于2025-09-23 15:21:21
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An Ellipsometric Technique with an ATR Module and a Monochromatic Source of Radiation for Measurement of Optical Constants of Liquids in the Terahertz Range
摘要： Measuring the optical constants of liquids, especially water-containing solutions, is very difficult in the terahertz range. The well-known methods of measurement of the refractive index and absorption coefficient in this range include time-domain spectroscopy and Fourier-transform spectrometry. We have developed a highly sensitive ellipsometry method for measuring the optical constants of liquids using the tunable monochromatic radiation from the Novosibirsk free-electron laser. The ellipsometer is supplemented with an internal reflection module for the measurement of highly absorbing samples. The angle of incidence on the sample in the silicon prism of the module has been optimized for maximum sensitivity to parameters to measure. Measurements of the optical constants of various liquids have been performed, and a sensitivity of 0.01 has been demonstrated.
关键词： Internal reflection ellipsometry,Free electron laser,Aqueous solution,Terahertz range
更新于2025-09-23 15:21:21