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高精度测距雷达研究 被引量:27
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作者 樊昌元 丁义元 《电子测量与仪器学报》 CSCD 2000年第2期52-56,共5页
本文介绍一种低成本、高精度线性调频连续波 (LFMCW )测距雷达。对雷达中频信号处理 ,文中提出并采用了“双计数器多周期平均倒数测频”(以下简称双频计 )。整个雷达系统以毫米波一体化前端和单片机为核心 ,使其成为一个集检测、处理、... 本文介绍一种低成本、高精度线性调频连续波 (LFMCW )测距雷达。对雷达中频信号处理 ,文中提出并采用了“双计数器多周期平均倒数测频”(以下简称双频计 )。整个雷达系统以毫米波一体化前端和单片机为核心 ,使其成为一个集检测、处理、显示、控制于一体的测控系统。实验表明 ,该雷达系统对近距离 (2~ 5 0m)测量 ,其精度可提高 1~ 3个数量级 ,且对振荡器线性度要求不高 (3%左右 ) 展开更多
关键词 低成本 高精度 LFMCW 测距雷达 双频计 单片机
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S参数标准的研制和网络分析仪检定 被引量:4
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作者 张国华 商晓宇 《宇航计测技术》 CSCD 2000年第3期1-11,共11页
网络分析仪系统是一种宽频段、多参数、并能进行实时测量的大型频域、时域测量系统。主要介绍同轴、波导 S参数标准件的组成、设计方法、研制过程及参数定标的方法。并介绍了双频激光同轴量规计的设计方法、工作原理及利用它对标准件定... 网络分析仪系统是一种宽频段、多参数、并能进行实时测量的大型频域、时域测量系统。主要介绍同轴、波导 S参数标准件的组成、设计方法、研制过程及参数定标的方法。并介绍了双频激光同轴量规计的设计方法、工作原理及利用它对标准件定标的情况。文章中提供了大量的数据 ,详细也列出了标准失配器、标准空气线等 ,S参数标准件在各频率点上定标的数据 ,从各不同方面验证了参数标准的准确性。 展开更多
关键词 S参数标准 网络分析仪 微波 双频激光同轴量规
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EXPERIMENTAL STUDY ON SOIL MOISTURE USING DUAL-FREQUENCY MICROWAVE RADIOMETER 被引量:2
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作者 GUAN Zhi ZHAO Kai SONG Dong-sheng 《Chinese Geographical Science》 SCIE CSCD 2006年第1期83-86,共4页
An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical r... An experiment of measuring soil moisture was carried out by using dual-frequency microwave radiometer designed by the authors. The measured data were analyzed by using statistical regression method and the empirical regression model of retrieving soil moisture in L-band and C-band was developed. The soil moisture in a rainfall event was retrieved using the experiential regression model, which is consistent well with the field sampling value. The results show that when soil moisture is lower than 75%, the brightness temperature is linear with soil moisture. However, when soil moisture is higher than 75%, the brightness temperature is not linear with soil moisture, so it is difficult for microwave radiometer to measure the changes of soil moisture. The experiment verifies the effectiveness and feasibility of microwave remote sensing soil moisture. Although this method for linear regression based on the data measured with the radiometer is simple, and has strong adaptability, generally it has only local application value, and lacks universal applicability for different areas and different conditions. 展开更多
关键词 soil moisture dual-frequency microwave radiometer brightness temperature
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A NOVEL WIDEBAND ANTENNA DESIGN USING U-SLOT 被引量:1
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作者 Chai Wenwen Zhang Xiaojuan 《Journal of Electronics(China)》 2008年第2期192-196,共5页
U-slot patch antennas with П-shaped feed slot are studied, and numerical results based on the FDTD method are presented. The effects of varying physical parameters are investigated with a goal of understanding the co... U-slot patch antennas with П-shaped feed slot are studied, and numerical results based on the FDTD method are presented. The effects of varying physical parameters are investigated with a goal of understanding the coupling among different resonators. It is found that the U-slot patch antenna can be designed to attain 50% impedance bandwidth as well as 30-40% gain bandwidth. By altering the sizes of U-slot and feed slot, the wideband characteristic can be changed into a duai-frequency char- acteristic. 展开更多
关键词 Microstrip antenna Wideband antenna Dual-frequency antenna U-slot Feed slot
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A NOVEL METHOD ON DESIGNING BISPECTRAL WINDOWS
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作者 Yao Wenbing Yao Tianren Han Tao (Huazhong University of Sciece & Technology, Wuhan 430074) 《Journal of Electronics(China)》 2002年第2期192-198,共7页
A novel method on designing bispectral windows is proposed in this letter. Compound functions based on a function with binary quadric form, starting from the symmetry characteristic of three-order moments are used as ... A novel method on designing bispectral windows is proposed in this letter. Compound functions based on a function with binary quadric form, starting from the symmetry characteristic of three-order moments are used as the 2-D windowfunctions. Two approaches on how to find the expressions of the compound functions are discussed in detail. One is to approximate the compound function after being Taylor expanded under the Minimum Mean Square Error (MMSE) criteria. Another is to compound the hyperbolic secant function and the binary quadric function directly. According to theoretical analysis, the first type new windows have been proved as slightly better than the conventional ones, the second type new windows are much better than the conventional ones, and the bispectral estimation mean square error approximates to 0. 展开更多
关键词 Bispectral estimation Bispectral windows 2-D window functions
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A Physics-Based Dual-Frequency Approach for Altimeter Wind Speed Retrieval
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作者 LI Shuiqing ZHOU Liangming +3 位作者 LI Zhanbin MIAO Qingsheng MOU Lin WANG Aifang 《Journal of Ocean University of China》 SCIE CAS 2014年第4期579-583,共5页
The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing ... The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study. 展开更多
关键词 ALTIMETER mean square slope DUAL-FREQUENCY wind speed retrieval
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Phase estimation in bispectral domain based on conformal mapping and applications in seismic wavelet estimation 被引量:8
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作者 Yu Yong-Cai Wang Shang-Xu +1 位作者 Yuan San-Yi Qi Peng-Fei 《Applied Geophysics》 SCIE CSCD 2011年第1期36-47,95,共13页
Seismic wavelet estimation is an important part of seismic data processing and interpretation, whose preciseness is directly related to the results of deconvolution and inversion. Wavelet estimation based on higher-or... Seismic wavelet estimation is an important part of seismic data processing and interpretation, whose preciseness is directly related to the results of deconvolution and inversion. Wavelet estimation based on higher-order spectra is an important new method. However, the higher-order spectra often have phase wrapping problems, which lead to wavelet phase spectrum deviations and thereby affect mixed-phase wavelet estimation. To solve this problem, we propose a new phase spectral method based on conformal mapping in the bispectral domain. The method avoids the phase wrapping problems by narrowing the scope of the Fourier phase spectrum to eliminate the bispectral phase wrapping influence in the original phase spectral estimation. The method constitutes least-squares wavelet phase spectrum estimation based on conformal mapping which is applied to mixed-phase wavelet estimation with the least-squares wavelet amplitude spectrum estimation. Theoretical model and actual seismic data verify the validity of this method. We also extend the idea of conformal mapping in the bispectral wavelet phase spectrum estimation to trispectral wavelet phase spectrum estimation. 展开更多
关键词 conformal mapping higher-order spectra phase wrapping wavelet estimation
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