On Mon, May 11, 2015 at 12:00 PM, Richard Bell <richard.be...@gmail.com> wrote:
> From what I remember, there shouldn't be a functional difference. The > difference is the amount of feedback delay in the loop. You always need to > make sure one delay exists in any feedback path you can take, to avoid race > conditions. After that, you want to minimize the loop delay. The one > accumulator with delay in the feedback path ensures stability. The other > accumulator keeps the delay out of the feedback path because it minimizes > the loop latency. > > Hope that helps. > > Rich > > Sent from my iPhone > Yep, thanks, Richard! Tom > On May 11, 2015, at 8:42 AM, Tom Rondeau <t...@trondeau.com> wrote: > > On Tue, Apr 28, 2015 at 8:50 AM, <ruben.m...@swisscom.com> wrote: > >> Hello, >> >> I've been looking into the design details of the control-loop block. I >> stumbled upon the blog post of Tom ( >> http://www.trondeau.com/blog/2011/8/13/control-loop-gain-values.html >> with the derivation >> https://static.squarespace.com/static/543ae9afe4b0c3b808d72acd/543aee1fe4b09162d0863397/543aee1fe4b09162d08633ac/1313345573084/control_loop_derivation.pdf) >> and also this article from TI: >> http://www.ti.com/lit/an/slyt169/slyt169.pdf. >> >> Now looking at the schematics of the control loop in Tom's post and the >> TI article (figure 5), you notice a slight difference after the loop >> filter. In the TI article, there is delay (z^-1) followed by an >> accumulator. In the schematics of Tom's post, the delay block is directly >> integrated in the loop. Can somebody comment on these differences? >> >> Thanks >> Ruben >> > > Hi Ruben, > > This is a good question, and I don't want to let it drop. I just don't > have a good answer for your right now. If I can find the time, I'll try to > go through things more carefully to understand why there is the added > delay. Just keeping the thread alive in case someone else can jump in and > answer it. > > Tom > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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