Antenna (RF) -> Tuner (IF) -> Demod (TS) ->

If the RF strength can not be measured by Tuner (such as XC3028, XC4000, ..., etc.),
"Signal Strength" is the IF strength which is measured by Demod (such as TDA10046, TDA10048, CE6353, ZL10353, MT353, ..., etc.).
The IF signal is amplified by Tuner (such as TDA18271, TDA18211, XC3028, XC4000, XC5000, ..., etc.).
And the driver may
return the IF strength measured by Demod or
return the "Signal Quality" (Quality measured by Demod).