## Loop Filter Coefficients in Timing Recovery loop in Baseband Receiver

Started by 8 years ago2 replieslatest reply 8 years ago560 views

Hi!

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

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Yes, Kd is the slope around the zero-error region.   The units for that slope must be compatible with the units of Ko, the DDS/VCO gain constant, such that the product of KoKd has units of 1/seconds.

This presentation covers the basics and some important details:

http://www.compdsp.com/presentations/Jacobsen/abin...

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