I think I might have something at my receiver, but I'm not sure how to deal with it. If you take a look at this picture : https://www.dropbox.com/s/sp1hrhl8qgj2xct/Receiver.png?dl=0 , we clearly see 2 spikes centered at + 312.5kHz and - 312.5kHz. That's what I should have. The upper graph is the output of my quadrature demodulator, but i'm not sure if it's supposed to be like this since i've never used it before. From there what should I do ? Here is the link to my actual flowgraph : https://www.dropbox.com/s/6vuyleerbwl3df2/UAT.png?dl=0