半導(dǎo)體射頻開(kāi)關(guān)：小型但高性能電路元件

　　RF開(kāi)關(guān)用于從多個(gè)可用源中選擇所需信號(hào)，或者將信號(hào)路由到所需信道，例如分集天線系統(tǒng)、雷達(dá)和測(cè)試和測(cè)量裝置。開(kāi)關(guān)（有時(shí)稱為繼電器）可以使用機(jī)電（EM）的設(shè)計(jì)類似于一個(gè)非射頻開(kāi)關(guān)，但這些現(xiàn)在已經(jīng)被開(kāi)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(kāi)關(guān)需要許多波蘭人（聯(lián)系人）。

　　也有RF開(kāi)關(guān)基于MEMS技術(shù)復(fù)制的機(jī)電設(shè)計(jì)，但使用IC制造技術(shù)。本文重點(diǎn)研究基于IC的固態(tài)開(kāi)關(guān)，有一個(gè)單刀雙擲開(kāi)關(guān)開(kāi)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(kāi)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.