I would like some help quantifying what effect the EVM figures have on the accuracy of this device down at low signal levels. My current setup demodulates the RF signal (1.5GHz) directly down to DC as the LO is at the same frequency. The RF signal will be both amplitude & phase modulated with respect to the LO, but there is no QAM or similar modulation used as my application does not involve comms. I am merely looking at how the signal changes in amplitude & phase as a measurement technique, which is where my confusion lies...
The EVM graphs in the datasheet quote EVM figures when used with 16QAM. Is there anyway to convert these figures so that they could quantify the amplitude/phase accuracy at different signal levels? e.g. a -40dBm EVM would mean +/-0.1dB resolution when the RF input is -50dBm (for example).
What I am basically trying to understand is what would be the lowest signal that this device could "accurately" measure? Would EVM dominate the noise floor or vice versa? or are there other factors to consider?