Forum: GNU Radio Requested decimation is odd

Hi all,



I am using USRP N200 with LFRX daughter board. The newest version of 
images
has been loaded.

The sampling rate is set as 4 MHz. There is constantly a UHD warning:



The requested decimation is odd; the user should expect CIC rolloff.

Select an even decimation to ensure that a halfband filter is enabled.



How do I change the decimation value?

And what value should I set it?



Thanks!



Ting Wu

>
> How do I change the decimation value?
>
> And what value should I set it?
>
> Thanks!
>
> Ting Wu
>
100e6 / 4e6 = 25

Which is odd value which changes the "line up" of filtering in the FPGA.

Select a sample rate that results in an even decimation value, unless
you can live with the edge roll-off for an odd value.

Thank you for your response!



We need to use the sampling rate of 4 MHz. How can I deal with this 
problem?

Actually we have been running the same application on several USRPs 
(N200
and N210), and there was no such warning.



Any suggestions?



Ting Wu



From: Marcus D. Leech [mailto:mleech@ripnet.com]
Sent: Monday, November 12, 2012 11:29 AM
To: Ting Wu
Cc: Discuss-gnuradio@gnu.org
Subject: Re: [Discuss-gnuradio] Requested decimation is odd



Hi all,



I am using USRP N200 with LFRX daughter board. The newest version of 
images
has been loaded.

The sampling rate is set as 4 MHz. There is constantly a UHD warning:



The requested decimation is odd; the user should expect CIC rolloff.

Select an even decimation to ensure that a halfband filter is enabled.



How do I change the decimation value?

And what value should I set it?



Thanks!



Ting Wu

100e6 / 4e6 = 25

Which is odd value which changes the "line up" of filtering in the FPGA.

Select a sample rate that results in an even decimation value, unless 
you
can live with the edge roll-off for an odd value.

On 11/11/12 09:42 PM, Ting Wu wrote:
>
> *From:*Marcus D. Leech [mailto:mleech@ripnet.com]
>
>
>
>
>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
The warning is new.  But nothing else has changed.   If your application
has been running fine, it will continue
  to run fine.

I see.

Thanks a lot!



Ting Wu



From: Marcus D. Leech [mailto:mleech@ripnet.com]
Sent: Monday, November 12, 2012 12:05 PM
To: Ting Wu
Cc: Discuss-gnuradio@gnu.org
Subject: Re: [Discuss-gnuradio] Requested decimation is odd



On 11/11/12 09:42 PM, Ting Wu wrote:

Thank you for your response!



We need to use the sampling rate of 4 MHz. How can I deal with this 
problem?

Actually we have been running the same application on several USRPs 
(N200
and N210), and there was no such warning.



Any suggestions?



Ting Wu



From: Marcus D. Leech [mailto:mleech@ripnet.com]
Sent: Monday, November 12, 2012 11:29 AM
To: Ting Wu
Cc: Discuss-gnuradio@gnu.org
Subject: Re: [Discuss-gnuradio] Requested decimation is odd



Hi all,



I am using USRP N200 with LFRX daughter board. The newest version of 
images
has been loaded.

The sampling rate is set as 4 MHz. There is constantly a UHD warning:



The requested decimation is odd; the user should expect CIC rolloff.

Select an even decimation to ensure that a halfband filter is enabled.



How do I change the decimation value?

And what value should I set it?



Thanks!



Ting Wu

100e6 / 4e6 = 25

Which is odd value which changes the "line up" of filtering in the FPGA.

Select a sample rate that results in an even decimation value, unless 
you
can live with the edge roll-off for an odd value.








--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

The warning is new.  But nothing else has changed.   If your application 
has
been running fine, it will continue
  to run fine.