本文提出一种改进的FM-CW SAR Frequency Scaling算法。FM-CW SAR由于大的脉冲持续时间和100%的信号占空比,使"停-走-停"模式失效。本文针对FM-CW SAR的信号处理特点,如载机在大扫频周期内运动引起的快时间距离走动问题及传...本文提出一种改进的FM-CW SAR Frequency Scaling算法。FM-CW SAR由于大的脉冲持续时间和100%的信号占空比,使"停-走-停"模式失效。本文针对FM-CW SAR的信号处理特点,如载机在大扫频周期内运动引起的快时间距离走动问题及传统算法应用在FM-CW SAR中带来的频谱混叠问题进行深入讨论,改进的算法在校正快时间距离走动的同时,解决了频谱混叠问题,实现了目标精确成像。理论推导和仿真结果表明算法的可行性与正确性。展开更多
A broadband frequency tunable microwave reflectometer system, which has the abil- ity of fast and stable frequency sweeping operation, is applied in the large helical device （LHD） to measure the boundary of the high...A broadband frequency tunable microwave reflectometer system, which has the abil- ity of fast and stable frequency sweeping operation, is applied in the large helical device （LHD） to measure the boundary of the high-temperature plasma. When the microwave is launched, with extraordinary polarization, from the low field side of the magnetic field with its frequency swept from low to high, the microwave of minimum right-hand cut-off frequency is reflected most out- side. We can then estimate the plasma boundary position by measuring the change of the reflected power from the cut-off layer.展开更多
The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The recons...The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The reconstruction suffers a significant immediate error that is not rapidly damped.It is demonstrated that even though no reflections occur inside the hollow region causing the blind area,the higher probing frequencies that propagate through it carry information that can be used to estimate its properties.The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1 D,with special attention paid to the frequency band where they are dominant.A database of perturbation signals was simulated onfive-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge.The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it.展开更多
文摘本文提出一种改进的FM-CW SAR Frequency Scaling算法。FM-CW SAR由于大的脉冲持续时间和100%的信号占空比,使"停-走-停"模式失效。本文针对FM-CW SAR的信号处理特点,如载机在大扫频周期内运动引起的快时间距离走动问题及传统算法应用在FM-CW SAR中带来的频谱混叠问题进行深入讨论,改进的算法在校正快时间距离走动的同时,解决了频谱混叠问题,实现了目标精确成像。理论推导和仿真结果表明算法的可行性与正确性。
基金a Grant-in-Aid for Scientific Research on Priority Areas (Nos.18035015,20026010)a Grant-in-Aid for Young Scientists (A)(No.18686075)the Ministry of Education,Culture,Sports,Science and Technology Japan and also a budgetary Grant-in-Aid (No.NIFS08ULHH508)of National Institute for Fusion Science and the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion
文摘A broadband frequency tunable microwave reflectometer system, which has the abil- ity of fast and stable frequency sweeping operation, is applied in the large helical device （LHD） to measure the boundary of the high-temperature plasma. When the microwave is launched, with extraordinary polarization, from the low field side of the magnetic field with its frequency swept from low to high, the microwave of minimum right-hand cut-off frequency is reflected most out- side. We can then estimate the plasma boundary position by measuring the change of the reflected power from the cut-off layer.
基金carried out with the support of the Brazilian National Council for Scientific and Technological Development(CNPq)under the Science Without Borders programme,within the framework of the French Federation for Magnetic Fusion Studies(FR-FCM)and of the EUROfusion consortium with funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No.633053part-funded by the RCUK Energy Programme grant number EP/P012450/1。
文摘The standard density profile reconstruction techniques are based on the WKB approximation of the probing wave’s phase,making them unable to properly reconstruct blind areas in the cut-off frequency profile.The reconstruction suffers a significant immediate error that is not rapidly damped.It is demonstrated that even though no reflections occur inside the hollow region causing the blind area,the higher probing frequencies that propagate through it carry information that can be used to estimate its properties.The usually ignored full-wave effects were investigated with the use of full-wave simulations in 1 D,with special attention paid to the frequency band where they are dominant.A database of perturbation signals was simulated onfive-dimensions of parameters and an application of the database inversion was demonstrated for a magnetic island in a Tore Supra discharge.The new adapted reconstruction scheme improved the description of the density profile inside the hollow region and also along 10 cm after it.
