请教一下大家关于射频的问题，估计都比较熟悉的，请进来解答，谢谢

skj33750

你好：这道题和它的解答：
An RF system has a linear throughput gain of +10 dB and an output 3rd-order intercept point (OIP3) of +30 dBm. What is the input 3rd-order intercept point (IIP3)?
a) +20 dBm
A system's 3rd-order intercept points are determined by the components between its input and output. As with the input signal power, the system's gain modifies the output intercept point values. Simply add the gain to the IIP3 to arrive at the OIP3.
+30 dBm - 10 dB = +20 dBm.
请教一下怎么理解的，老是看不懂！！十分感谢

gogo1222

画下图就理解了，可以参考Razavi的射频微电子P21

ZYWANGG11

我是这样理解的，首先要弄清IIP3：Input 3rd order intercept point, OIP3：Output 3rd order intercept point,G：Gain的关系。你的问题是已知线性放大增益G=+10 dB ，OIP3=+30 dBm跟据公式OIP3 (dBm) = IIP3 (dBm) + G (dB)，得IIP3 (dBm)=OIP3 (dBm) - G (dB)，所以IIP3为+30 dBm - 10 dB = +20 dBm 。[em13][em13]