射频放大模块的增益

　　射频放大模块的增益

　　“无线电”这个词现在比过去多了很多。早期的无线电发射机比振荡器简单得多，它只需通过振幅、频率或相位调制信号信息到载波上。简单的单芯片或晶体管发射器和接收器的设计和使用，功率晶体管可以提供足够的功率，以满足大多数需求。今天，普通人拥有一个通常使用多个射频收发器的个人移动设备是司空见惯的事。

　　这些现代无线电携带他们的性能和可靠性的高期望水平。我们的无线链路必须工作，以及有线链路。这意味着在后台操作的许多子系统需要在接收信号被仔细检查和解码的情况下被启动。

　　随着数字时代的到来，即使是模拟信号的数字形式处理。数字系统，特别是密集的和多个时钟，可以是嘈杂的，并增加高功率发射机也可以降低接收信号的灵敏度。

　　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.