sin3 filter for delta-sigma

[Rick C]

On Thursday, September 12, 2019 at 5:34:05 PM UTC-4, Lasse Langwadt Christensen wrote:

torsdag den 12. september 2019 kl. 22.42.44 UTC+2 skrev Rick C:
On Thursday, September 12, 2019 at 4:20:48 PM UTC-4, Lasse Langwadt Christensen wrote:
torsdag den 12. september 2019 kl. 22.01.38 UTC+2 skrev Rick C:


Or it can be done with fewer adders by simply adding in the latest sample and subtracting out the oldest on each iteration.


yep, that is what it does in a clever way that avoids the long delay line
for "oldest"

The delay line is there, it's just not so long and has adders as well. It's the decimation that allows it to be log2(N) long rather than N. Just like in a polyphase FIR filter it saves the calculations you won't be needing to produce a result. If you remove the decimation a polyphase FIR becomes a standard FIR calculated in sections.


https://www.dsprelated.com/blogimages/RickLyons/Multirate_Trans_Func_figure1.PNG

with the rate change moved to before the combs the delays is one sample at the output rate instead of R samples at the input rate

And here I always thought the two were equivalent.

--

Rick C.

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