Looking for information about RSSI theory and methods

Dear All :
I will design RSSI for RF appliation , But I don't know what the theory of RSSI
Does any can say it ? And There are many implemetation method .What RSSI method is good ? How Do I select it ? Does RSSI need ADC ? Thanks

Attached is the best article I found on Integrated RSSI for RF-IC.
It explains on the various architectures available (progressive compression and paralell amplification).
This article has both theory and simulations.

The attachment is missing now. Can you upload it one more time?
Thank you very much!

You can search detector MMIC for your use.