Hi!

Thanks for detailed reply Steve and Kevin. I am now trying to
implement the Interpolator . The simplest form is the Linear
Interpolator defined as:

y[k] = x[m(k)] + u[k]*{ x[m(k)+1] - x[m(k)] }

I have a confusion in understanding the "base-point" index m(k). This
is defined in Gardner's Article (Interpolation in digital Modems
P-I)as:

m= m(k) - i

1) Is x[m(k)+1] the "recent/current" sample and x[m(k)] is
previous/delayed sample of x or vice-versa?

2)Its written in paper that correct set of signals is identified by
m(k) and the current set of filter samples (coefficients) is
identified by u[k]. However, the Farrow structure doesnt show any
detail as to how m(k) is involved in computation. Its just a
combination of tapped delay lines and their sums controleld by u[k],
which is supplied by controller. About m(k) the article says: "The NCO
is operated such that its avarage period is Ti. Recycling the NCO
register indicates that a new interpolant is to be computed, using the
signal samples currently residing in the interpolator's shift
register. Thus, base-point index is identified by flagging the correct
set of signal samples, rather than explicitly computing m(k)". What
does this mean? We have to compute the interpolant on every clock
cycle Ts? If yes, what is the significance of
m(k)?

Regards
Rider