Re: [Discuss-gnuradio] Question on control-loop block design

[Tom Rondeau]

On Tue, Apr 28, 2015 at 8:50 AM, <address@hidden> 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