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From: | Richard Jaeger |
Subject: | Re: [Discuss-gnuradio] USRP Gain |
Date: | Fri, 5 Sep 2008 16:04:20 -0500 |
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 atYes. 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...
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