Re: [問題] 微波和射頻波之模型的差異

看板comm_and_RF作者vaakaa (我要歐趴)時間11年前 (2013/04/17 21:52)推噓1(1推 0噓 6→)

留言7則, 3人參與討論串2/2 (看更多)

摘錄一本大師寫的講義裡的句子給大大參考: Electromagnetic field is like a chameleon—its physics changes as the frequency changes from static to optical frequencies. Electromagnetics is described by fields— a field is a function of 3D space and time. These fields satisfy their respective PDEs that govern their physics. -------------------------------------------------------- When the object size is much less than the wavelength, the physics of the field around it is dominated by the fact that the time derivative is unimportant compared to the space derivative. The field physics is close to that of static field. In the mid-frequency regime, the space derivative is equally important compared to the time derivative, but the size of the object, and hence the boundary condition, still controls the nature of the solution. In the high-frequency regime, the boundary condition plays a lesser role compared to the equations in shaping the solution. Hence, the solution resembles the homogeneous solutions of electromagnetic equations, which are plane waves. Plane waves are mathematical representation of rays, and hence, ray physics becomes more important in this regime. -INTEGRAL EQUATION METHODS FOR ELECTROMAGNETIC AND ELASTIC WAVES by Weng Cho Chew , Mei Song Tong and Bin Hu A Publication in the Morgan & Claypool Publishers series LECTURES ON COMPUTATIONAL ELECTROMAGNETICS #12 ISSN: 1932-1252 很抱歉我其實是來騙p幣的XD 若有違反版規請板上大大提醒 ※ 引述《saltlake (SaltLake)》之銘言： : 射頻波(radiofrequency)的行為 : 我們可以用電流的觀念去模擬 : 講得更複雜一點就是可以用拉普拉絲方程式去計算 : 而一旦頻率更高到了微波領域 : 我們就必須考慮電磁波的觀念 : 這時候有所謂波的近場和遠場等差別 : 概念上不能再用電流的觀念 : 可是 : 目前看到的書本不幸地都沒有從理論方面更具體解釋 : 為什麼射頻波和微波這兩類電磁波 : 不能都用馬克士威方程式 : 從電磁波的角度去計算或了解? : 或者說 : 有沒有甚麼書或文章 : 有比較清楚詳盡的數學推導 : 從馬克士威方程式出發 : 然後根據電磁波頻率的顯著不同 : 導出射頻波的行為是用拉普拉斯方程式? : 謝謝 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.113.170.133

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