CC2530的观察输出控制器与发射功率的关系

在CC2530中有这样的一个寄存器OBSSEL1 ，OBSSEL2， OBSSEL3， OBSSEL4 ，，不明白他的用途是什么，他在CC2591的配置里面有，我做实验发现他与发射功率有关系，但是一直他是怎么影响发射功率的，求大虾们指教，新手

7.9 Radio Test Output Signals

By using the OBSSELx registers (OBSSEL0–OBSSEL5) the user can output different signals from the RF
Core to GPIO pins. These signals can be useful for debugging of low-level protocols or control of external
PA, LNA, or switches. The control registers OBSSEL0–OBSSEL5 can be used to override the standard
GPIO behavior and output RF Core signals (rfc_obs_sig0, rfc_obs_sig1, and rfc_obs_sig2) on
the pins P1[0:5]. For a list of available signals, see the respective RFC_OBS_CTRLx registers in
Section 23.15.3 for CC253x or Section 24.1 for CC2540 or Chapter 25 for CC2541.

这个我看过，我是想知道他是通过怎么样的途径，或者什么机理去影响功率