I have done my receiver design with QPSK modulation. I am trying to communication between two systems at L band. My data rate is 1 Mbps. As my data rate is high I have allocated 64 bit for timing recovery.
Timing recovery has farrow interpolation filter followed by Gardner timing recovery, loop filter (2nd order) and interpolation control for the farrow interpolation filter. I am doing 2 samples/symbol analysis.
What I am assuming is the fractional value to the interpolation filter will stabilize once 64 bit allocated for timing recovery is over. But what I observe is the fractional value varies even after the 64 bit allocated is over because of which my data sometimes is wrong.
- can the fractional input to the interpolation filter vary?
- if yes why is the data sometime is wrong even if it is just direct board to board communication?