半導(dǎo)體射頻開關(guān)：小型但高性能電路元件

　　RF開關(guān)用于從多個可用源中選擇所需信號，或者將信號路由到所需信道，例如分集天線系統(tǒng)、雷達(dá)和測試和測量裝置。開關(guān)（有時稱為繼電器）可以使用機電（EM）的設(shè)計類似于一個非射頻開關(guān)，但這些現(xiàn)在已經(jīng)被開關(guān)IC所取代，除了在高功率應(yīng)用在集成電路的不足，以及一些非常特殊的情況下或在開關(guān)需要許多波蘭人（聯(lián)系人）。

　　也有RF開關(guān)基于MEMS技術(shù)復(fù)制的機電設(shè)計，但使用IC制造技術(shù)。本文重點研究基于IC的固態(tài)開關(guān)，有一個單刀雙擲開關(guān)開始（單刀雙擲）排列（圖1），并且通常與FET和PIN二極管為核心的開關(guān)元件的建立。

　　Figure 1： An SPDT RF switch is conceptually simple， with a control signal directing the switch to route the input to either one of two possible outputs. （Courtesy of Skyworks Solutions）

　　These are many parameters which define RF switch performance， and most must be characterized versus supply voltage， temperature， frequency， power level， and other factors. Some are especially critical in a given application， while others may not be as vital. Note that most RF switches are designed for 50 Ω operation， but some are designed for the 75 Ω standard of cable TV. Given the high frequencies at which these switches operate， many vendors now offer S-parameters and Smith charts as parts for their data sheet specifications （for background see the TechZone article “The Smith Chart： An ‘Ancient’ Graphical Tool Still Vital in RF Design”）， to assist engineers in determining overall signal-path performance， matching component impedances for minimal loss， and modeling-system performance.