倒F型天線

倒F型天線（英語：inverted-F antenna）是用於無線通訊的一種天線，主要運作於特高頻和微波頻率。構造包含導電的接地平面（英語：Ground plane）以及一個與之平行的單極天線（英語：Monopole antenna）。相對於簡易版的單極天線，此設計有兩個好處：第一，這種天線的長度較短且體積更加小巧，可被安裝在流動裝置中。第二，這種天線無需其他元件即可透過設計與饋電電路達成阻抗匹配，提高效率。

與倒F型天線有關的構想最早出現在1950年代，當時構想的是一個立體的彎折天線。然而，如今倒F型天線最為廣泛的應用形式是平面倒F型天線（英語：planar inverted-F antenna，PIFA）。其接地平面和天線平行於一平面上，大幅節省了立體空間，小巧的尺寸使其能夠融入於行動通訊裝置中。PIFA能被以微帶線形式印刷在電路板上。

PIFA是一種貼片天線（英語：Patch antenna）。許多的貼片天線（包含PIFA）都可實現寬頻和多頻功能，實現方式包含使用耦合諧振器（coupled resonator）或是在天線上打洞。

發展與歷史

倒F型天線是由廣受使用的四分之一波長（quarter-wave）單極天線（英語：Monopole antenna）演變而來，其構造包含一個接地平面以及一個直立於平面上的桿狀天線，天線由底部接受饋電。最早具有F狀造型的天線於1940年代被發明，^[1]這個天線從位於中間位置的分支接受饋電，而其底部則連接到接地平面。從饋電線一直到接地平面這個區段的天線具有短截線的作用。只要調整這個區段的長度，就能夠改變天線的輸入阻抗，因此設計者可以透過改變饋電點位置來達成阻抗匹配。

註腳

^ Waterhouse & Novak, p. 19

參考書目

Ali, M.; Guangli Yang; Huan-Sheng Hwang; Sittironnarit, T., "Design and analysis of an R-shaped dual-band planar inverted-F antenna for vehicular applications", IEEE Transactions on Vehicular Technology, vol. 53, iss. 1, pp. 29–37, January 2004.
Barton, "Nosecone Inverted-F (IFA) for S-Band Telemetry"^{[失效連結]}, DTIC, 2017
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Kin-Lu Wong, Yen-Yu Chen, Saou-Wen Su, Yen-Liang Kuo, "Diversity dual-band planar inverted-F antenna for WLAN operation" （頁面存檔備份，存於互聯網檔案館）, Microwave and Optical Technology Letters, vol. 38, iss. 3, pp. 223–225, 5 August 2003.
King, Ronold W. P.; Harrison, C. W., Jr.; Denton, D. H., Jr., "Transmission-line missile antennas", Sandia Corp Technical Memo 436-58, vol. 14, November 1958.
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Liu, Z. D.; Hall, P. S.; Wake, D., "Dual frequency planar inverted F antenna", IEEE Transactions on Antennas and Propagation, vol. 45, iss. 10, pp. 1451–1458, October 1997.
Petosa, Aldo, Frequency-Agile Antennas for Wireless Communications, Artech House, 2013 ISBN 1608077691.
Prasad, Shiela; King, Ronold W. P., "Experimental study of inverted L-, T-, and related transmission-line antennas" （頁面存檔備份，存於互聯網檔案館）, Journal of Research of the National Bureau of Standards, vol. 65, no. 5, pp. 449–454, September–October 1961.
Sánchez-Hernández, David A., Multiband Integrated Antennas for 4G Terminals, Artech House, 2008 ISBN 1596933984.
Waterhouse, Rod; Novak, Dalma, "Wireless systems and printed antennas", pp. 1–36, in Waterhouse, Rod (ed), Printed Antennas for Wireless Communications, John Wiley & Sons, 2008 ISBN 0470512253.
Yarman, Binboga Siddik, Design of Ultra Wideband Antenna Matching Networks, Springer, 2008 ISBN 1402084188.

[1] Waterhouse & Novak, p. 19

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