Requested decimation is odd

GNU Radio
1

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

2

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.

3

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:[email protected]]
Sent: Monday, November 12, 2012 11:29 AM
To: Ting Wu
Cc: [email protected]
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.

4

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

*From:*Marcus D. Leech [mailto:[email protected]]

–
Marcus L.
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.

5

I see.

Thanks a lot!

Ting Wu

From: Marcus D. Leech [mailto:[email protected]]
Sent: Monday, November 12, 2012 12:05 PM
To: Ting Wu
Cc: [email protected]
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:[email protected]]
Sent: Monday, November 12, 2012 11:29 AM
To: Ting Wu
Cc: [email protected]
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 L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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