衛星訊號閃爍與電離層不規則體飄移-衛星量測與地面觀測之比較; Ionosphere Scintillation and Irregularity Motion-Comparison between In-situ Measurement and Ground Observation

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Title:	衛星訊號閃爍與電離層不規則體飄移-衛星量測與地面觀測之比較;Ionosphere Scintillation and Irregularity Motion-Comparison between In-situ Measurement and Ground Observation
Authors:	吳綱常;Kang-Chang Wu
Contributors:	通訊工程研究所
Keywords:	閃爍理論;飄移速度;不規則體;電離層;ionosphere;irregularity;drift speed;scintillation theory
Date:	2003-06-25
Issue Date:	2009-09-22 11:15:40 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本文藉由地面觀測的閃爍資料以及衛星所量測的電離層不規則體密度與速度資料的分析比較，去驗證閃爍理論中關於閃爍訊號的頻譜特性以及閃爍訊號跟離子密度在頻譜分佈上的關連。透過地面相隔的接收站所觀測到的閃爍訊號變化，所求得不規則體的漂移速度，除了符合衛星觀測的結果外，再以此漂移速度所求出不規則體的Fresnel frequency也符合頻譜分析結果；理論上在weak scintillation時，這頻率代表著頻譜開始roll off的頻率，而在strong scintillation時，頻譜的roll off 頻率則會明顯增大；本文先以S4值的分佈定義閃爍強弱，再以不同強弱的閃爍訊號驗證上述的理論結果。在理論上，離子密度資料與閃爍資料的頻譜分佈，在roll off時會有一斜率上的對應關係，若離子密度資料的斜率為-p，則閃爍資料的斜率為1-p，本文先將中華衛星一號上IPEI（電離層電漿電動效應儀）上的速度資料換算後，找出與地面閃爍資料在相近區域、相近時段、相近速度下的密度分佈資料，進行頻譜分析後，驗證理論上斜率的關係，也驗證-p的值近於理論預測值-4以及尺度上的關係。 The purpose of this dissertation is to compare the analysis of scintillation data obtained from ground receivers and irregularities data of density and velocity obtained from satellite with the scintillation theory. We calculate the drift velocities of the irregularities by cross-correlating the scintillation data of spaced receivers. They compare quite well with drift velocities measured by the satellite .Then we can calculate the Fresnel frequency by the drift velocity. According to the scintillation theory, the spectra will start roll-off at Fresnel frequency in the case of weak scintillation, but there is broadening of the spectra in the case of the strong scintillation. The spectra do not show the starting of the roll-off at the Fresnel frequency. For a power law irregularity spectra with the exponent –p the high-frequency asymptote is of the form . In this investigation, we find that in-situ and ground observations have confirmed in general these theoretical predictions with the value of the exponent near –4 and the relation of the outer scale of the irregularities.
Appears in Collections:	[Graduate Institute of Communication Engineering] Electronic Thesis & Dissertation

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