Vladimir Vassilevsky <antispam_bogus@hotmail.com> wrote:

>Hello all,
>
>Classic Gardner timing detector:
>
>Gardner(x) = (x2 - x0)*x1
>
>Where x0, x1, x2 are sampled in -1/2, 0, +1/2 of the symbol.
>Essentially this detector finds the derivative of the energy after the
>matched filter.
>
>Let's take a different look at that. Consider the transition waveform
>from one symbol to the next symbol. Take I and Q components of this
>waveform:
>
>I = x2 - x0
>Q = -x0 + 2x1 - x2
>
>Dual angle:
>
>I*Q ~ = x0^2 + 2x1(x2-x0) - x2^2
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>Proposed detector
>
>Which equals to:
>
>== 2*Gardner(x) + x0^2 - x2^2
>
>Apparently (x0^2 - x2^2) averages out to zero assymptoticaly with the
>infinite averaging, so, the whole thing eventually gets equvalent to the
>Gardner detector. However, for the smaller averaging, the data related
>noise of the proposed detector can be up to 2..3 times less then that of
>Gardner. The AWGN behaviour is the similar for both detectors. So, it
>turns out to be possible reducing the data noise without any additional
>information.
>
>What is the name of the wheel that I just reinvented?
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com

The following sounds suspiciously similar from the abstract.
I'll take a look at it next time I'm at the library.

http://ieeexplore.ieee.org/xpl/freea...isnumber=29703


Steve