射頻放大模塊的增益

　　“無線電”這個詞現(xiàn)在比過去多了很多。早期的無線電發(fā)射機比振蕩器簡單得多，它只需通過振幅、頻率或相位調(diào)制信號信息到載波上。簡單的單芯片或晶體管發(fā)射器和接收器的設計和使用，功率晶體管可以提供足夠的功率，以滿足大多數(shù)需求。今天，普通人擁有一個通常使用多個射頻收發(fā)器的個人移動設備是司空見慣的事。

　　這些現(xiàn)代無線電攜帶他們的性能和可靠性的高期望水平。我們的無線鏈路必須工作，以及有線鏈路。這意味著在后臺操作的許多子系統(tǒng)需要在接收信號被仔細檢查和解碼的情況下被啟動。

　　隨著數(shù)字時代的到來，即使是模擬信號的數(shù)字形式處理。數(shù)字系統(tǒng)，特別是密集的和多個時鐘，可以是嘈雜的，并增加高功率發(fā)射機也可以降低接收信號的靈敏度。

　　Other requirements， such as frequency hopping， spread spectrum， protocol preambles， CRC， ECC， ACK/NOACK， just to name a few， make simple transistor RF links obsolete. As a result， RF links require more complex chips than ever before. For the engineer， it is like carrying a heavy stone on your back that keeps getting heavier every generation as more complexity is added.

　　The design process has experienced increased levels of complexity， too. Multiple ground planes need to converge. The digital ground plane can be fraught with switching noise. An analog ground plane should be as quiet as possible so sensors can pass reliable levels to sensitive A/D stages of a data acquisition system. The RF ground plane also should strategically protect low-level radio signals while maintaining consistent transmission line impedances. This imposes greater thought in split power and ground plane design as well as in functional partitioning when laying out a circuit board.