用rms探測器測量射頻功率

　　在大多數(shù)無線應(yīng)用電路中，必須監(jiān)控和控制射頻功率的傳輸和接收電平。這是為了盡量減少功率放大器（PA）的電流消耗，控制接收器增益，優(yōu)化性能和效率，并滿足信號(hào)強(qiáng)度監(jiān)管任務(wù)。

　　為了測量射頻功率，使用了三種不同的方法：峰值檢波器/放大器、對(duì)數(shù)（對(duì)數(shù)）放大器和rms轉(zhuǎn)換器。每一個(gè)都滿足不同類型的復(fù)雜RF波形的應(yīng)用程序優(yōu)先級(jí)和需求，以及性能和成本問題。

　　請(qǐng)注意，射頻功率測量可以在兩個(gè)地點(diǎn)完成：無線和有線。無線，實(shí)際輻射功率的變頻器如二極管的目標(biāo)感，從而產(chǎn)生信號(hào)的射頻功率，照射在它的比例。這是一個(gè)真正的“射頻功率”測量。

　　In contrast， when we measure RF power in a wired circuit， we are not really measuring the power directly. Instead， we are determining the RF power by measuring an “analog” of it， in this case， the voltage across or current through a known resistor. Once you know voltage or current and the resistance， you can compute the power. While this is an indirect way to assess RF power， it is quite accurate if done properly， and certainly more convenient and practical.

　　It may seem that the obvious way to compute the power is to digitize the sensed RF voltage or current and then perform appropriate calculations， but this is very impractical for several reasons. The digitization process would require a converter with extraordinarily-high speed and resolution， which is generally not available. Such a converter would also dissipate significant power， while the high-speed， real-time calculation would require considerable processing capacity.