Empathy List Archives

AM

Andrea Mariani via USRP-users

Tue, May 20, 2014 8:18 AM

Dear all,

I'm getting started with some transmission test using USRP2+WBX daughterboard, based on simple OFDM like signals.
I'm experiencing a DC offset in the transmitted signal, which I think is caused by a LO leakage problem.
How could I remove it?
Is there an alternative to "manually" removing the DC offset?

Thanks in advance.

PS: regarding WBX documentation I didn't find so much on the ettus website, where can I found it? Thanks!

Dear all, I'm getting started with some transmission test using USRP2+WBX daughterboard, based on simple OFDM like signals. I'm experiencing a DC offset in the transmitted signal, which I think is caused by a LO leakage problem. How could I remove it? Is there an alternative to "manually" removing the DC offset? Thanks in advance. PS: regarding WBX documentation I didn't find so much on the ettus website, where can I found it? Thanks!

MJ

Mike Jameson via USRP-users

Tue, May 20, 2014 9:18 AM

Put the following line in the "Center Freq" box of the "UHD Source" block
in GRC:

uhd.tune_request(center_freq, rf_freq=(center_freq +
lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL)

You must define the variables 'center_freq' and 'lo_offset'. lo_offset
should be outside the passband i.e. (samp_rate/2) * 1.25

Mike

--
Mike Jameson M0MIK BSc MIET
Ettus Research Technical Support
Email: support@ettus.com
Web: http://ettus.com

On Tue, May 20, 2014 at 9:18 AM, Andrea Mariani via USRP-users <
usrp-users@lists.ettus.com> wrote:

Dear all,

I'm getting started with some transmission test using USRP2+WBX
daughterboard, based on simple OFDM like signals.
I'm experiencing a DC offset in the transmitted signal, which I think is
caused by a LO leakage problem.
How could I remove it?
Is there an alternative to "manually" removing the DC offset?

Thanks in advance.

PS: regarding WBX documentation I didn't find so much on the ettus
website, where can I found it? Thanks!

USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

Put the following line in the "Center Freq" box of the "UHD Source" block in GRC: uhd.tune_request(center_freq, rf_freq=(center_freq + lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL) You must define the variables 'center_freq' and 'lo_offset'. lo_offset should be outside the passband i.e. (samp_rate/2) * 1.25 Mike -- Mike Jameson M0MIK BSc MIET Ettus Research Technical Support Email: support@ettus.com Web: http://ettus.com On Tue, May 20, 2014 at 9:18 AM, Andrea Mariani via USRP-users < usrp-users@lists.ettus.com> wrote: > Dear all, > > I'm getting started with some transmission test using USRP2+WBX > daughterboard, based on simple OFDM like signals. > I'm experiencing a DC offset in the transmitted signal, which I think is > caused by a LO leakage problem. > How could I remove it? > Is there an alternative to "manually" removing the DC offset? > > Thanks in advance. > > PS: regarding WBX documentation I didn't find so much on the ettus > website, where can I found it? Thanks! > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >

MB

Martin Braun via USRP-users

Tue, May 20, 2014 11:40 AM

On 20.05.2014 10:18, Andrea Mariani via USRP-users wrote:

Dear all,

I'm getting started with some transmission test using USRP2+WBX daughterboard, based on simple OFDM like signals.
I'm experiencing a DC offset in the transmitted signal, which I think is caused by a LO leakage problem.
How could I remove it?
Is there an alternative to "manually" removing the DC offset?

Thanks in advance.

PS: regarding WBX documentation I didn't find so much on the ettus website, where can I found it? Thanks!

Our general d'board manual page is here:

http://files.ettus.com/uhd_docs/manual/html/dboards.html

And you can find the schematics here:

http://files.ettus.com/schematics/wbx/

Cheers,
Martin

On 20.05.2014 10:18, Andrea Mariani via USRP-users wrote: > Dear all, > > I'm getting started with some transmission test using USRP2+WBX daughterboard, based on simple OFDM like signals. > I'm experiencing a DC offset in the transmitted signal, which I think is caused by a LO leakage problem. > How could I remove it? > Is there an alternative to "manually" removing the DC offset? > > Thanks in advance. > > PS: regarding WBX documentation I didn't find so much on the ettus website, where can I found it? Thanks! Our general d'board manual page is here: http://files.ettus.com/uhd_docs/manual/html/dboards.html And you can find the schematics here: http://files.ettus.com/schematics/wbx/ Cheers, Martin

MD

Marcus D. Leech via USRP-users

Tue, May 20, 2014 1:13 PM

On 05/20/2014 05:18 AM, Mike Jameson via USRP-users wrote:

Put the following line in the "Center Freq" box of the "UHD Source"
block in GRC:

uhd.tune_request(center_freq, rf_freq=(center_freq +
lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL)

You must define the variables 'center_freq' and 'lo_offset'.
lo_offset should be outside the passband i.e. (samp_rate/2) * 1.25

Mike

Or, even simpler:

uhd.tune_request(target_frequency_in_hz, desired_lo_offset)

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

On 05/20/2014 05:18 AM, Mike Jameson via USRP-users wrote: > Put the following line in the "Center Freq" box of the "UHD Source" > block in GRC: > > uhd.tune_request(center_freq, rf_freq=(center_freq + > lo_offset),rf_freq_policy=uhd.tune_request.POLICY_MANUAL) > > You must define the variables 'center_freq' and 'lo_offset'. > lo_offset should be outside the passband i.e. (samp_rate/2) * 1.25 > > Mike Or, even simpler: uhd.tune_request(target_frequency_in_hz, desired_lo_offset) -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org

usrp-users@lists.ettus.com

USRP2+WBX LO leakage TX