For I^2+Q^2 , when I am applying -4.7 dBm RF input, below are the max and min value for the conseutive 1,31,072 samples.
Min value (I^2+Q^2) = 0.033015493
Max value (I^2+Q^2) = 0.033976138
Difference in measurement = 0.00096044
For I^2+Q^2 , when I am applying -40 dBm RF input using attenuator of 30 dB at the output of function generator, below are the max and min value for the conseutive 1,31,072 samples.
Min value (I^2+Q^2) = 7.8827*10^-6
Max value (I^2+Q^2) = 2.9508*10^-5
Difference in measurement = 2.1625 *10^-5
FYI: When I have verified function generator output with spectrum analyzer, I have observed that with lower amplitude from the function generator, I am getting unstable output at spectrum. so I am suspecting that function generator itself is providing unstable output at the lower amplitude.