Re: [Discuss-gnuradio] Observation concerning decimation with CIC

[Matt Ettus]

Christoph Thein wrote:
> Hi Matt,
>
> the new image seems to solve the problem. Thank you!
>
> What did you change in the code? 
>
> Cheers,
>
> Christoph & Hanwen

Great news.  The basic issue is that since the halfband decimators 
decimate by 2, they have an internal state (which we call odd or even). 
     The design wasn't syncing this state, so I added a small amount of 
code to resync the filters when they are enabled.  The CIC was already 
doing this, so you didn't see the problem when only using the CIC and 
not the halfbands.

If you want to see exactly what I changed, it is here:

http://gnuradio.org/cgit/matt.git/commit/?h=rx_mimo_hb_sync

You can check the code out from the rx_mimo_hb_sync branch from matt.git 
on gnuradio.org.

Johnathan -- please merge this to the mainline and put up a new image 
for general use.

Thanks to both of you for reporting this bug.  Anybody doing MIMO 
reception should probably update to this new version.

Matt