特高頻雷達技術之應用與研究

Abstract

MST(VHF)雷達技術發展至今 , 已經由多方面研究所得可以證實 , VHF 雷達確實是一個非常有效之遙測工具 , 而且不斷的有新技術 , 新理 論被提出 . FDI (FrequencyDomain Interferometry ), 目的是要利用 VHF 雷達來作存在空氣中穩定層狀結構厚度的測量及其高度的定位 , 此 技術從提出 (Kudeki . E , 1987 ) , 接下來是一些學者 ,利用其理論來 作實際層狀結構觀測 , 但在 (Chu and Franke , 1991) 所作之大氣層狀 結構觀測時 , 發現了觀測之相干值和傳統理論之相干值不吻合(較理論相 干值高) , 進而我們對傳統理論作了波數功率頻譜 (Wavenumber Power Spectrum )及有限之雷達積分(Finite Radar Volume Integration ) 二 項修正 , 其結果和觀測資料非常吻合 , 也就是利用傳統 FDI 理論來作 層狀結構厚度及位置的估算 , 將會產生誤估 , 修正後之結果推翻了傳統 理論 . The frequency domain interferometry (FDI) technique , first developed by Kudeki and Stitt (1987) , provides us with the ability to detect such a thin layer by sending two closely spaced frequencies with this technique , thethickness and the position of the thin layer can be estimated , respectivelyfrom the magnitude ( ie , coherence ) and phase of the normalized complexcross-correlation function calculated from the two radar retuns with slightly different operating frequencies , but experiments have not been successfully .The frequency domain interferometry (FDI) experiment (Chu and Steven , 1991 )have been conducted successfully at various MST radar and the thickness and position of the thin layer are estimated , by considering the wavenumber power spectrum of the refractivity irregularity and the limit of integration to be finite , it show that the frequency domain interferometry (FDI) coherenceis not only the function of layer thickness and the components of radar wavevector but also considering the wavenumber power spectrum of the refractivity irregularity and the limit of integration to be finite.