# Loop Filter Coefficients in Timing Recovery loop in Baseband Receiver

I am trying to design the Symbol timing recovery(#STR) block of #DVBS Receiver. For reference, I am using the following matlab simulink design (NDA timing recovery part within Digital Baseband Receiver)

The design has considered a roll-off factor of 0.5. I need to design for a roll-off factor of 0.2.

All other parameters remaining constant, I believe the only factor that will change in the design would be the loop filter coefficients. But , I am not able to understand how the loop filter coefficients of PI filter are calculated in the design.

The value of the loop filter coefficients are C2 = 1.35e-4, C1 = C2/128.where c2 = proportional filter coefficient, c1 = integral filter coefficient.

C2 depends on k0,kd,zeta(damping ratio), natural frequency (wn),(zeta and wn determine loop bandwidth).

How to calculate kd? From my understanding , it should be the slope of S-CURVE of gardner TED when error tends to zero.

Kindly clarify.

Regards avi

• Your link isn't working. – Gilles May 19 '16 at 7:14