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Re: [Discuss-gnuradio] Filter delays and direction of time.

From: Achilleas Anastasopoulos
Subject: Re: [Discuss-gnuradio] Filter delays and direction of time.
Date: Fri, 21 Jan 2005 09:02:00 -0500
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax)

Point well taken!

Essentially I am trying to synchronize
two sinusoids, one of which is passing through a
filter and is thus gaining some phase/time over the other.

I think I found a way to solve my problem
by using the "advance" (as opposed to delay)
"block" of GnuRadio, ie, the filter with taps [0,1].


Eric Blossom wrote:

I think there's a bit of an impedance mismatch between how you are
thinking and how GNU Radio works.  GNU Radio is not an isochronous
data flow engine.  We've got lots of implicit buffering between
blocks.  You have virtually no control over the amount of buffering
that's taking place between blocks.  Thus, implementing a delay with the
filter block isn't going to get you what I think you want.  You're
probably noticed that there's no "delay" primitive.  If you've got
something with a feedback loop in it, it needs to be implemented in a
single block.  E.g., PLL's.

What are you really trying to do?  What's the problem you're trying to
solve, or the computation you're trying to make?

FYIW, in the gr_hilbert_fc.{h,cc} block we implement the hilbert filter and
the parallel delay line in the same block, thus ensuring goodness.


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