第四章 分集式天線
4.3 實做與量測結果
圖4.7 為圖 4.4 分集式天線模擬與實做量測頻率響應圖，操作頻寬以及絕緣 度都整理於表 4-1，模擬與實做結果很類似，圖 4.8 為實體照片圖；因為左右兩 隻天線的結構大小是一樣而對稱的，所以兩隻天線的輻射場型為對稱的，所以吾 人只量測左邊天線的輻射場型，如圖4.9 到圖 4.11，各頻率的各平面最大增益和 平均增益整理如表4-2。
圖4.7 空間分集式天線 S 參數量測結果
表4-1 空間分集式天線共振頻段、頻寬、以及隔離度整理
共振頻率(GHz) 2.33GHz~2.66GHz 4.9GHz~6GHz
頻寬 330MHz 1GHz
絕緣度(S21) <-15dB <-15dB
(a)
(b)
圖4.8 空間分集式天線實體圖 (a)正面 (b)背面
(a)
(b) (c)
圖4.9 2.45GHz 空間分集式天線輻射場型 (a)x-y plane (b)x-z plane (c)y-z plane
E-phi E-theta E-total X
Y
Z
(a)
(b) (c)
圖4.10 5.25GHz 空間分集式天線輻射場型 (a)x-y plane (b)x-z plane (c)y-z plane
E-phi E-theta E-total X
Y
Z
(a)
(b) (c)
圖4.11 5.775GHz 空間分集式天線輻射場型 (a)x-y plane (b)x-z plane (c)y-z plane
E-phi E-theta E-total X
Y
Z
表4-2 不同面耦合餽入開路諧振環單極天線各頻率輻射場型的最大增益(peak gain)和平均增益(average gain)
2.45GHz 5.25GHz 5.775GHz Peak x-y plane 2.6dBi -5.01dBi 3.91dBi -2.62dBi 3.12dBi -1.7dBi x-z plane 0.83dBi -4.25dBi 2.74dBi -0.61dBi -1.03dBi -3.72dBi y-z plane 1.77dBi -1.9dBi 5.62dBi 1.41dBi 2.28dBi -0.7dBi
從圖4.8 到圖 4.10 的輻射場型圖可以清楚看出加在兩天線中間的柺杖狀障礙 物對 X 方向的場型多少還是會有阻擋的作用，但因為還有右邊對稱的天線，所 以在場型上會有互補的作用。此空間分集式天線輻射場型實測時是將此平面印刷 天線實際地放進網卡的外殼中量測，其天線增益會因有外層塑膠殼的關係而比較 小一點。在2.45GHz 的最大增益為 2.6dBi，平均增益最大為-1.9dBi；而在 5.25GHz 和5.775GHz 的平均增益接近 0dBi。圖 4.12 為分集式天線實體照片圖
圖4.12 分集式天線實體照片
第五章 結論(Conclusion)
共振頻率上有很大的方便。本論文是將此雙頻天線設計在WLAN 802.11a/b/g 的 應用上，若是要應用在不同頻段的多頻系統中，也可以輕易的調整到所需的頻段。對此天線實際量測結果，在場型上都有不錯的表現，不論在 2.45GHz、
5.25GHz、或是 5.8GHz 時都近似於全向性，且平均增益最大都接近 0dBi。而為 了改良訊號的收發品質，本論文中也製作了空間分集化天線，我們利用簡單但不 增加天線整體尺寸的方法來降低兩天線間互相耦合的效應，整體空間分集化天線 高度仍維持在13mm 左右。希望能提供現行無線通訊產業在天線設計上正面的幫 助。
參考文獻 (Reference)
[1] W. L. Stutzman and G. A. Thiele, ”Antenna Theory and Design,” 2nd ed. , John Wiley, New York, ch.2 and ch.5 , 1998.
[2] C. Wu, “Printed antenna structure for wireless data communications,” U.S. Patent 6 008 774, Dec. 28, 1999.
[3] T. Y. Wu, S. T. Fang, and K. L. Wong, “Printed diversity monopole antenna for WLAN operation,” Electronics Letter, vol. 38, pp. 1625 – 1626, Dec. 5, 2002.
[4] C. Soras, M. Karaboikis, G. Tsachtsiris, and V. Makios, “Analysis and design of an inverted-F antenna printed on a PCMCIA card for the 2.4 GHz ISM band,”
IEEE Antennas and Propagation Magazine, vol. 44, pp. 37 – 44, Feb. 2002 [5] V. Stoiljkovic, and G. Wilson, “A small planar inverted-F antenna with parasitic
element for WLAN applications,” 10th international conference on Antennas and Propagation, vol.1, pp. 82-85, April 1997
[6] T. Tiehong, and Z. Zheng, “Applications of planar inverted-F antenna for Bluetooth,” in Proc. 2003 International Conference on Communication Technology (ICCT 2003), vol.2, pp. 1230-1233, April 2003
[7] Y. L. Kuo, Y. T. Cheng, and K. L. Wong, “Printed inverted-F antennas for applications in wireless communication,” in 2002 IEEE AP-S Int. Symp. vol.
3, pp.454 – 457, June 2002
[8] I. Chen, and C. M. Peng, “Microstrip-fed dual-U-shaped printed monopole antenna for dual-band wireless communication applications,” Electronics Letters, vol. 39, pp.955 – 956, June 2003
[9] S. H. Yeh, and K. L. Wong, “Dual-band F-shaped monopole antenna for 2.4/5.2 GHz WLAN application,” in 2002 IEEE AP-S Int. Symp. vol.4, pp.72 – 75, June 2002
[10] Y. L. Kuo, and K. L. Wong , “Printed Double-T Monopole Antenna for 2.4/5.2GHz Dual-Band WLAN Operations,” IEEE Transactions on Antennas and Propagation, vol. 51, pp. 2187-2192, Sep 2003
[11] G. P. Karakoussis, A.I. Kostaridis, C. G. Biniaris, and D. I. Kaklamani, “A dual-band inverted-F antenna printed on a PC card for the ISM and UNNI bands,”
2003 IEEE Wireless Communications and Networking (WCNC 2003), vol.
1, pp.88 – 92, March 2003
[12] H. D. Chen, J. S. Chen, and Y. T. Cheng, “Modified inverted-L monopole antenna for 2.4/5 GHz dual-band operations,” Electronics Letter, vol.39, pp.1567–1568, 30 Oct. 2003
[13] D. M. Pozar, ”Microwave Engineering,” 2nd ed. , John Wiley, New York, pp.306-313, 1998.
[14] J. S. Hong, and M. J. Lancaster, “Couplings of microstrip square open-loop resonators for cross-coupled planar microwave filters,” IEEE Transactions on Microwave Theory and Techniques, vol.44, pp.2099 – 2109, Nov.1996