Dear all,
I see that this subject leads to interesting different point of views. As I wrote in my previous message, the purpose remains first "educational", just also highlighted by Herb with its reference to Agilent application note 1316.?
I like the proposal of Erik, i.e. to have coupling between input attenuation and RefLevel, if this last one is set to +20 dBm or higher value. However is it something compatible with AGC strategy ? As an example, I have put a stand-alone carrier at 250 MHz for different levels, and below is what I get for AUTO modes (attenuator and RefLevel) :
RF input level +10 dBm : ATTENUATE 30 dB, REF LEVEL +30 dBm
RF input level 0 dBm : ATTENUATE 20 dB, REF LEVEL +20 dBm
This shows that the attenuation values for these two use cases is 10 dB higher than minimum automatic attenuation of 10 or 20dB proposed by Erik. So it could be difficult to couple the two parameters for getting optimum and safe conditions at same time for the tinySA. If I understand correctly the AGC strategy, the idea seems to keep a displayed value which is always around 20 dB lower (for AUTO modes) compared to RefLevel, which for this last one is driven by the attenuation value.
As a conclusion it seems more careful to keep the existing working mode as it is. Never mind for the coupling theory !
Jean-Roger
