On Sep 20, 9:16 am, fpga.vhdl.desig...@gmail.com wrote:
> if gardner can't works for QAM what kind of symbol synchronisation
> could we use for QAM ?

You could try applying a nonlinearity such as abs(), sqrt() or half
bit delay-conjugate multiply to the data. This produces a discrete
component at the symbol rate, which can be bandpass filtered to
provide a symbol clock reference.

John