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Post subject: Noise figure of a direct conversion receiver
Posted: Tue Jul 10, 2007 4:35 am
Joined: Tue Jul 10, 2007 4:08 am
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?