電機資訊學院: 電信工程學研究所指導教授: 江簡富邱牧民Chiou, Mu-MinMu-MinChiou2017-03-062018-07-052017-03-062018-07-052016http://ntur.lib.ntu.edu.tw//handle/246246/276561本論文分成三個部份。第一部份探討微波通過沙塵暴時產生的功率衰減，並根據衰減值還原沙塵暴的分佈參數。本部份採用拋物線型波動方程式的求解技術來模擬電磁波的傳播過程，包含沙塵的吸收與瑞利(Rayleigh)散射效應，其中沙粒的大小及數量密度分佈皆為高度的函數。模擬中並比較三種不同的指向性天線場型與不同的沙塵暴參數組合。 第二部份提出一組模擬三維沙塵暴的模型，其中沙塵暴近似為軸對稱，沙粒數量密度在軸心處最高，且隨高度增加而減少。本部份採用拋物線型波動方程式及雙射線模型模擬電磁波在沙塵暴中的傳播現象，並考慮地表的曲率與地面反射的效應。最後並根據一組實測場景比對模擬結果與量測結果，以驗證本模型之有效性。 第三部份採用拋物線型波動方程式技術計算沙塵暴的雷達回波強度，其中沙粒的大小及數量密度分佈皆為高度的函數。另提出一個考量地表曲率與散射效應的改良雷達方程式，並將此兩種模型的計算結果與傳統的雷達方程式比較，以驗證本模型的改良程度。The thesis is composed of three parts. In the first part, a parabolic wave equation (PWE) method is proposed to simulate millimeter-wave propagation in an sand and dust storm (SDS), including the effects of absorption and Rayleigh scattering by dust particles with given height profiles of particle size distribution and total number density. Three different aperture fields of the transmitting antenna are also chosen to simulate wave attenuation under different sets of SDS parameters. In the second part, a 3D SDS model is proposed, in which the total number density is height dependent and is circularly symmetric in the horizontal plane. The effects of Earth curvature and ground reflection on microwave wave traversing an SDS are studied by using the PWE method and a two-ray model. A time record of microwave attenuation is also simulated and compared with the measurement data to verify the efficacy of the proposed method. In the third part, a PWE-based radar equation is proposed to compute the backscattered power of millimeter-wave in an SDS, in which the height profiles of particle-size distribution and total number density are accounted for. The conventional radar equation is also improved by incorporating the effects of Earth curvature and beam divergence. The improvement of accuracy by using these two radar equations, especially when the specific attenuation is a function of height, is verified by simulations.2984567 bytesapplication/pdf論文公開時間: 2016/8/24論文使用權限: 同意有償授權(權利金給回饋本人)沙塵暴微波毫米波Sand and dust stormmicrowavemillimeter wavevertical profile of reflectivitythesis10.6342/NTU201602494http://ntur.lib.ntu.edu.tw/bitstream/246246/276561/1/ntu-105-F98942012-1.pdf