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

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] Observation concerning decimation with CIC
Date: Thu, 24 Sep 2009 12:43:09 -0700
User-agent: Thunderbird (X11/20090825)

Christoph Thein wrote:
Hi Matt,

the new image seems to solve the problem. Thank you!

What did you change in the code?

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:


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.


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