Hi!

I have a query regarding the computation of Gardner Timing Error
detector (TED). Dr. Gardner on his article "A BPSK/QPSK Timing Error
Detector for Sampled Receivers" states that Timing Error (for BPSK)
can be computed as:

U(r) = x(r-1/2)[x(r)-x(r-1)]

He calls the samples x(r) as "STROBE" values and those like x(r-1/2)
as "MIDWAY"
between strobes [like x(r-1/2) is midway between x(r) and x(r-1)].

Its also mentioned that this algorithm uses only 2 samples/symbol to
compute the error. I need to ask that:

1)What he means by these STROBE and MIDWAY values ,x(r) and x(r-1/2) ,
and how to compute them from the available 2 samples/symbol?

2) For the complete timing recovery loop, there is also an
interpolator. If the interpolator is fed with 2 samples/symbol, then
what is it computing? is it computing the midway value x(r-1/2) or
what?

Regards
Rider