[Discuss-gnuradio] Observation concerning decimation with CIC

[Christoph Thein]

Hello,

we have implemented synchronized reception with two USRP2's using a common 
clock and the 1PPS signal to be able to use the two ethernet interfaces. This 
works quite good but we observed one thing. 

When we set the decimation rate to an odd number (5 in our case), the samples 
are aligned perfectly. When we use an even numbered decimation rate, we could 
detect unalignments in some of our test runs with the same setup.

We have the idea that this is related to the way the decimation is performed 
(refer to "Re: [Discuss-gnuradio] USRP2 Filtering/Decimation Question" for 
more details) i.e. if only the CIC is involved it works fine otherwise there 
are some troubles. 

Does anybody have made similar observations or is able to tell more about the 
problem?

Thanks,

Hanwen  & Christoph