IQ data QPSK Demodulation I have an IQ data of QPSK signal , when I apply a PLL loop I obtain constellation in figure below. What is this phenomenon, and how can I obtain the good constellation??



The second figure is about variation angles, is there any idea about the red countoured effect?





after adding symbol syncronisation , i obtain constellation below , but there  is also sommes error that causes incorrect demapping ;; is there any suggestion ????
I suspect you're not doing symbol synchronization. You need to synchronize and then sample the output of your receiver filter at the correct times. Only then will you see the tradiational constellation diagram. Look for "Gardner algorithm" on this website; another well-known algorithm is Mueller and Muller.

One thing you can do to get confidence that your signal is correct is to plot its eye diagram. If the eye is open, then all you need to do is synchronize and sample. If it's closed, you have a different problem.