I have a question regarding
noise figure of a direct conversion receiver. (zero
IF frequency with I & Q outputs),
a single sideband or double sideband noise figure
measurement be used for this type of receiver &
what is the logic behind this?
I get as
far as the signal & noise from the desired signal
frequency & its image (another part of the required
band) coming through the mixer and IF signal and
noise powers going up by 3dB due to the 2 adding.
But when the baseband resolves the two signals,
do they both have a 3dB SNR degredation due to the
noise being random & not able to be resolved
- or do I and Q noises somehow cancel?