倒F型天線

中的一個倒F型天線]]
倒F型天線（）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。構造包含導電的以及一個與之平行的。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（，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。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）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线的作用。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

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