[Discuss-gnuradio] fractional resampler weird behavior?

2019-07-03 Thread Achilleas Anastasopoulos
Hi all,

I have a 1KHz complex exponential sampled at 10Ksps going through a
fractional resampler with resampling ratio = 10
I display the output on a frequency sink (with sampling rate set to
100Ksps).
I expect to see a 1 KHz tone.
Instead I see only a DC component (see attached grc file)

When I repeat the experiment with the RATIONAL resampler with interpolation
10 and decimation 1 I get the expected result.

Can someone verify this behavior and if yes, am I missing something or is
this a bug?
(gnuradio 3.7.13.5)

thanks
Achilleas


test_resampler.grc
Description: application/gnuradio-grc
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Re: [Discuss-gnuradio] fractional resampler weird behavior?

2019-07-03 Thread CEL
Uh, yeah.

That thing always confuses me, too. The "resampling ratio" is the
inverse of what you'd expect, i.e. to interpolate by 10, set it to 0.1.

Note that for extreme resampling ratios (r << 1 or r >> 1), it might
make sense to split the resampling between a rational resampler and
this MMSE resampler, for both computational performance as well as
signal quality reasons.

Best regards,
Marcus

On Wed, 2019-07-03 at 14:40 -0400, Achilleas Anastasopoulos wrote:
> Hi all,
> 
> I have a 1KHz complex exponential sampled at 10Ksps going through a
> fractional resampler with resampling ratio = 10
> I display the output on a frequency sink (with sampling rate set to
> 100Ksps).
> I expect to see a 1 KHz tone.
> Instead I see only a DC component (see attached grc file)
> 
> When I repeat the experiment with the RATIONAL resampler with
> interpolation 10 and decimation 1 I get the expected result.
> 
> Can someone verify this behavior and if yes, am I missing something
> or is this a bug?
> (gnuradio 3.7.13.5)
> 
> thanks
> Achilleas
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> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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