LabVIEW
CIC multirate decimation system
Solved!
Hey guys,
maybe some of you read another thread of mine regarding CIC filters: http://forums.ni.com/t5/LabVIEW/cic-fix-point-filter/m-p/3184637#M921820
Now I got a more theoretical question:
What is the benefit of a multirate filter system with CIC filter?
More clearly, why not use one cic filter with a rate factor of 512 but two cic filters with R1=64 and R2=8? (both are one stage CIC filter with differential delay of 1)
As the frequency I am interested in, in my signal, is 0Hz (DC) the aliasing attenuation is more than sufficient.
The Cut off frequency is 1 Hz, so aliasing attenuation after decimating from 48kHz to 750 Hz (R=64) is ~57dB and from 750Hz to 93,75 (R=8) is ~38dB.
f(aliasing) = fs/R - fc ;fs=samplerate, fc=cut off (see Hogenauers paper to CIC filter)
I hope someone can help me here.
kind regards
Slev1n
Ok, I think I found the solution by myself...(I was comparing wrong grpahs 
)
Here the picture for the single rate CIC version. (fs=48kHz and R=512) Aliasing attenuation is only ~39dB...
But I am still listening to other opinions 🙂 or facts why multirate is better/worse 🙂
