臺灣博碩士論文加值系統

本論文探討線狀偶極子天線及環形天線和三維物體間的電磁耦合之時域有
限差分法(FDTD)數值計算，使用之FDTD邊界吸收條件(ABC)為二階Mur-ABC
及PML-ABC。吾人使用一具有均勻肌肉介電常數及導電系數之圓球體來模
擬人頭，將此一圓球體切割成大小相等之FDTD立方塊，天線為z方向之偶
極子天線和x及y方向性的環形天線，在FDTD時域計算結果經傅立葉轉換成
頻域資料後，計算天線在自由空間及在圓球體旁的幅射特性，如天線輸入
阻抗、幅射功率、圓球物體吸收功率(SAR)分佈、幅射效率以及幅射場型/
功率場型等，計算頻率為無線通訊頻帶之835 MHz(偶極子天線) 及400
、892、948 MHz (環形天線)，其中幅射場型是使用FDTD近場至遠場轉換
技巧所求得，並與天線在自由空間之動差法(MoM)數值結果相互比較之。
由分析計算之結果，將可以幫助瞭解在無線通訊系統上，天線和人體之間
的電磁耦合作用以及人體對天線幅射特性之影響。

Thesis presents finite-difference time-domain (FDTD) computation
of EM interactionbetween wire antennas and 3-D body object.
2nd-order Mur and perfectly-matched layer(PML) absorbing
boundary conditions (ABC) are used for FDTD computation. The
dipole and square loop antennas are considered for wireless
communication applications. The 3-D bodyobject is a homogeneous
lossy muscle-sphere to simulate the human head. The antennas
areproximate to the lossy sphere and the loop antenna can have
different orientation. The focusedfrequencies are 835 MHz
(dipole antenna) and 400, 892, and 948 MHz (loop antennas)
wireless communication bands. After the time-domain FDTD
simulation results are Fourier-transformed to frequency-domain
data, the radiation characteristics of the antenna, such as
thecurrent distribution, input impedance, radiation power, body-
absorption power, radiationefficiency and directive/power gain
patterns can be determined. The far-field patterns areobtained
by using the near- to far-field transformation. The FDTD
numerical results arecompared with that by the method of moments
(MoM) for the antennas in free space. Thecomputed radiation
characteristics of the antenna influenced by the human body
(head) isimportant for RF-circuit/antenna design and
communication link budget consideration.