help on the theoretical backgroud of RSSI

[sunjiao3]

Hi, friends. I am doubting on the theoretical background of RSSI. There is majorly 2 may to get the logrithmic function for RSSI. First is the piece-wise approximation, used in cascaded amplifiers. Second, which I am not so sure yet, is dependent on the direct power detector which is composed of differential pairs. However, I've found no detailed theoretical reference on the mechanism of these 2 solution. For example, why piece-wise approximation is used? Is it some kind of forula like the Taylor function: ln(1+x)=1+x+.... ?
So, could any one of you please enlight me on this issuse? Or, are there any documents that talk on the methanism on the RSSI? Thank you all in advance.

 

[ccw27]

https://eceserv0.ece.wisc.edu/~sharmav/bluetooth/PowerAmp.pdf

There are other articles from earlier posts, I suggest you search the forum.

 

[sunjiao3]

Thank you very much. I have this materail. But, what I am wondering is, the theoretical explanation of RSSI. Why piece-wise approximation can approximate Logrithmic funcion? And the other method? What is the function behind them? Like the taylor function ln(1+x)=1+X+....?
Could any one of you please enlight me on this question?