倒F型天線

應用於數位增強無線電話系統中的一個倒F型天線
倒F型天線（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Ground plane以及一個與之平行的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，可被安裝在行動裝置中。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（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）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，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**

**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", DTIC, 2017 - Cohen, N.,  Fractal antenna applications in wireless telecommunications", Professional Program Proceedings: Electronics Forum of New England, 1997, pp. 43–49, 6–8 May 1997, IEEE 0780339878.- Hall, Peter S.; Lee, E.; Song, C. T. P., "Planar inverted-F antennas", pp. 197–227, in Waterhouse, Rod (ed), Printed Antennas for Wireless Communications, John Wiley & Sons, 2008 0470512253.- Hall, Peter S.; Yang Hao, Antennas and Propagation for Body-Centric Wireless Communications, 2nd ed., Artech House, 2012 1608073769.- Kervel, Fredrik,  868 MHz, 915 MHz and 955 MHz inverted F Antenna date=20220307223437 , Texas Instruments, Design Note DN023 30 September 2011.- Kin-Lu Wong, Yen-Yu Chen, Saou-Wen Su, Yen-Liang Kuo,  "Diversity dual-band planar inverted-F antenna for WLAN operation" date=20151208001632 , 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.- King, Ronold W. P.; Harrison, C. W., Jr.; Denton, D. H., Jr.,  "Transmission-line missile antennas", IRE Transactions on Antennas and Propagation, vol. 8, iss. 1, pp. 88–90, January 1960.- 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 1608077691.- Prasad, Shiela; King, Ronold W. P.,  "Experimental study of inverted L-, T-, and related transmission-line antennas" date=20220623203231 , 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 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 0470512253.- Yarman, Binboga Siddik, Design of Ultra Wideband Antenna Matching Networks, Springer, 2008 1402084188.