Z型微帶天線之完整理論推導與特性探討

對於Z型微帶天線，為了補強研究理論公式的不完整以及特性探討多樣化不足的問題，本論文的做法是針對Z形天線現有的理論公式進行修改，而求出共振頻率以及解出待定係數，進而以電磁學概念推導出天線內部的電磁場、磁流以及空間中的輻射電場等完整的理論公式。在理論部份，利用現有的理論公式所進行修改而推導出的電磁場、磁流以及輻射電場這三個公式不僅補完了Z型天線的理論，還有助於更完整天線特性之掌握。而理論與模擬數據對比的結果顯示，長路徑上的電場分佈較為劇烈，短路徑上的電場分佈較為均勻。而且兩個模態的輻射場也都呈現良好的單波束，這些情況皆證實本文針對Z型所推導的理論公式是符合實際情況。在天線特性部份，根據探討的結果，短路徑長度的改變可大幅度的調整兩個模態的共振頻率間距，而天線兩隻支腳的粗細程度改變也可以適當的調整共振頻率間距。而當兩隻支腳的比值不同時，共振頻率並沒有太大的影響，所以路徑全長的調整就可以針對任意的共振頻率設計。而且當兩隻支腳的比值在1:3時，峰值差距不夠大的問題可有效改善。在特定頻率應用設計的部份，長短路徑上的模態數與長度先用來決定共振頻率，Z型天線之特性再用來微調共振頻率。而結果顯示，Z型天線確實可以滿足特定的頻帶需求，而且輻射場型仍可維持可接受的單波束。這個Z型微帶天線提供了設計雙頻天線另一種更具自由度的選擇。

關鍵字

雙頻操作； Z型；微帶天線；理論分析

並列摘要

In order to have completed formulation and various investigation for Z-shape microstrip antenna, this thesis modifies current formulation to obtain resonant frequency and required coefficients. Finally, the electromagnetic field in antenna, magnetic currents and radiation in space are obtained by using electromagnetic concept. In the aspect of theoretical derivation, the modified fields, magnetic current and radiation do not make formulation completed, but also make antenna characteristics easier to handle. As the comparison between theory and simulation, results show that the distribution of electric field along long axis is more abrupt, while the one along short axis is uniformed. The radiations of two modes show single beam distribution. All the results prove that the formation for the Z-shape mictostrip antenna agrees with the reality. In the aspect of antenna characteristics, the length of the short axis can adjust the separation of resonant frequencies of to two modes. The widths of two extension legs can also modify this separation. As the ratio of these two extension legs varies, resonant frequencies are not affected so that the whole length of the axis can be used to design for required frequency band. Moreover, as the ratio of these two legs is 1:3, the peak difference between co-pol and cross-pol radiation can be improved effectively. In the aspect of design for specific frequency band, the mode number and length along long and short axis are first used to decide resonant frequency, then the antenna characteristics are used to adjust. Results show Z-shape microstrip antenna can satisfy with the demand of specific band, and their radiations are acceptable.

並列關鍵字

Dual-Band ； Z-shape ； microstrip antenna ； theory analysis

參考文獻

[1] C.A. Balanis, Antenna Theory Analysis and Design, 3rd Edition, John Wiley & sons, 2005.

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[2] 戴崇倫, 謝東宏, 程心澤, ‘‘T-shape Microstrip Antenna for Dual-Band Operation’’, 2009 全國電信研討會, pp. 193, 國立高雄大學, 台灣, 2009.

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[3] H. Nakano and K. Vichien, ‘‘Dual-Frequency Square Patch Antenna with Rectangular Notch,’’ Electronics Letters, Vol.25, no. 16, pp.1067-1068, Aug. 1989.