RF Attenuators： For When You Have Too Much of a Good Thing

　　更高的信號電平通常是一個好東西在RF電路。它們會導致增加的信號-噪聲比（SNR），并減少由內部電路元件噪聲和外部信號噪聲所造成的問題。其結果是，更高的信號電平一般簡化了許多挑戰的RF電路設計。

　　然而，在許多系統中，RF信號可以不可避免地具有寬的動態范圍，跨越30，40，或更多的分貝，一些設計必須處理的信號具有超過100分貝的范圍內。例子包括雷達或遠程無線，甚至短程局域網，其中一個或兩個鏈路節點移動和有障礙和干擾。

　　If a system is designed to function properly with lower-level signals， it may not have the headroom for the higher-power signals （in RF， power and signal level are usually closely correlated）。 The result is overload， saturation， and even possible damage to sensitive analog components such as front-end amplifiers. Even if there is no permanent damage， the system cannot function properly as long as elements of the signal chain are “maxed out.” In these cases， it may take a relatively long time for the components to come out of saturation so that the signal chain is once again viable. In other cases， the attenuator matches the maximum value of a signal at one point to the more-limited maximum of another stage in the chain.