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Post subject: Noise figure of a direct conversion
Posted: Tue Jul 10, 2007 4:35 am
Joined: Tue Jul 10, 2007
I have a question regarding noise
figure of a direct conversion receiver. (zero IF frequency
with I & Q outputs),
Should 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?