Re: [Discuss-gnuradio] USRP Gain

[Richard Jaeger]

On Sep 4, 2008, at 12:37 PM, Matt Ettus wrote:

> > Re CIC gain, there's a also a decimation specific shifter involved in
> > the path.  Please take a look at
>
>
> Yes.  You guys have the R^4 formula right, but the shifter takes  
> back most of the gain.  The actual gain from the CIC decimator once  
> you include the shifter is:
>
> R^4 /  ( 2^ ceiling(log2(r^4)))
>
> I hope that is readable.  Basically, if R is a power of 2, then the  
> gain is exactly 1.  If R is not a power of 2 then the gain is in the  
> range of (0.5,1).
>
> Matt

Well, if the gain is really in (0.5, 1), that makes my missing gain  
situation worse.  I would be hunting for more than 20,000 in that case.
Also, it is inconsistent with my measurements that show that the gain  
increases by a total of 26 dB as the decimation rate
is changed from 96 to 256.

---

Where is the shifter you are referring to?   Is it in a non-recursive  
implementation of the CIC filter?

Dick...