射頻功率測(cè)量技術(shù)

　　射頻功率測(cè)量技術(shù)

　　隨著今天一切無(wú)線化，射頻功率測(cè)量正迅速成為必需品。本文著重介紹了許多用于精確測(cè)量rf信號(hào)電平的有用技術(shù)，以?xún)?yōu)化這些無(wú)線系統(tǒng)的性能。本文討論了改變應(yīng)用程序需求的最佳方法。

　　射頻信號(hào)可以有多種形式，從單載波連續(xù)波（CW）到多載波、QAM（正交幅度調(diào)制），其中包含高波峰因數(shù)波形。測(cè)量這些廣泛變化的信號(hào)的功率水平需要了解它們的特性以及所需的測(cè)量精度。如果信號(hào)是突發(fā)性的，如在TDD（時(shí)分雙工）系統(tǒng)，就有時(shí)域測(cè)量中要考慮的因素更加復(fù)雜。無(wú)論如何，選擇正確的檢測(cè)器類(lèi)型有助于簡(jiǎn)化設(shè)計(jì)任務(wù)。

　　Measuring RF power using peak detection

　　Take the simplest case of a CW waveform measurement. Even if the amplitude can vary， as long as the signal is within a prescribed time interval during which the amplitude is relatively constant， accurate measurement can be made with a peak level detector， such as the LTC5532 from Linear Technology. This device is built with a very fast Schottky detector with on-chip temperature compensation and a 2 MHz bandwidth output buffer. The internal Schottky circuit peak-detects the incoming RF signal and performs a peak-hold filtering， producing a DC output voltage that is proportional to the RF input peak level.

　　The LTC5532 is a very low power device that runs on 500 μA supply current in active mode. Yet its internal Schottky circuit is capable of detecting 7 GHz RF signals. A version of the part， the LTC5532EDC in a 6-lead， 2 mm x 2 mm plastic DFN package， offers low parasitics and can support operation to 12 GHz and higher.