My previous problem is solved. Many thanks!
For another question, I set the RF transceiver in manual gain mode. I injected a single tone signal with constant power into the transceiver and then I read back the RSSI register 0x1A7. I got a value with that receiver power.
With the same setting, I only change the input power but I read back the RSSI register 0x1A7. It give me the same value.
Please advise.