日: 2026年4月20日

Why Put an Attenuator Before an LNA?

You see a receiver design with an attenuator1 before the LNA2 and it feels wrong. Why reduce a weak signal? This post explains this smart trade-off. An attenuator is placed before an LNA to improve the receiver’s blocking performance3. It prevents strong, out-of-band signals from saturating the LNA. This preserves the amplifier’s linearity and ensures it can properly process the weak, desired signal in a noisy environment. I remember the first time I saw this in a TDD base station diagram. My first thought was, “This must be a mistake. The receiver signal is already weak, we need to amplify it, not attenuate it!” I believe many engineers who are […]