Noise at image frequency in heartley/weaver architecture

[Ghost Tweaker]

weaver architecture

Hi everyone,

I was wondering how noise at the image frequency would be rejected in the heartley or weaver architecture. I understand that the image will be rejected but with the noise going through 2 different path (LPF, ADCs), can we state that it will be rejected (3dB NF improvement if yes)???

Thanks for the answers
See ya

 

[AA1LL]

The noise has to have been amplified above kTo (-174dBm/Hz) to appear as uncorrelated crap at the image frequency. And then, you wont get 3dB better noise figure you just wont get 3dB worse.