On 08/01/2013 08:16 AM, embyte wrote:
Hello list,
I have a graph consisting of a modulator mixed with a signal source,
and a USRP sink.
I have it configured with a *sampling rate* of 720KHz.
When I run it, UHD fires the following warning (and transmission seems
fine).
The requested interpolation is odd; the user should expect CIC
rolloff.
Select an even interpolation to ensure that a halfband filter is
enabled.
interpolation = dsp_rate/samp_rate -> 89 = (64.000000
MHz)/(0.719101 MHz)
What is this about? Thanks.
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Two problems:
(1) 720Khz is not an exact integer fraction of 64MHz (the sampling rate
of the device)--so it rounded
(2) It's warning you that you'll get a "humped" frequency response with
more rolloff than you'd like, due to the rounded-down sample rate
requiring an interpolation rate that is not divisible by two.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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