I also have the similar problem at the receiver side, why trying to
the constellation of DQPSK.
From constellation sink block, I can obtain much better constellation.
using scope sink, it shows a mess.
As far as I went through the code of constellation sink, it seems like
conducting additional synchronization before plotting the results.
Anyone can explain more about the detail of constellation sink in GRC
And how can we output the data in constellation sink?