qpsk costas

On first attached picture is Costas loop which can be used for QPSK carrier regeneration.
After some math, you will get that (for QPSK) e(t) is proportional to phase error (second attached picture).
My question is: can I use this same loop for 8PSK carrier regeneration? If not, how should I modify it?
Thanks in advance.

Good initial coverage of MPSK carrier extraction is given within "Digital Communications" by Proakis. There is given a description of generalized Costas loop, too. If you want just to experiment, you can also try to use a QPSK Costas loop, but first you should square the input signal to reduce nuber of phase stages on 4 and at the end divide the frequency of loop synchronized carrier by 2.

Regards,
D