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Discussion and technical support related to USRP, UHD, RFNoC
View all threadsLO offset effect on passband
Hello,
I have some follow-up questions to the LO offset discussion. Some quick
background, I've been characterizing and calibrating the rx of the
B205-i for several months now and I am trying to squeeze every bit of
performance out of it. In general, the calibration works quite well.
However, I'm always looking for tips and tricks to improve the
performance. It was mentioned that one should use an offset of at least
+/-6MHz for optimal performance. In spirit of this I wanted to
investigate the flatness of the passband with the two options (no
offset, -8MHz offset). According to this
https://files.ettus.com/manual/page_usrp_b200.html 56MHz is the max
master clock so I set mine to 40MHz to enable a 20MHz sample rate. My
rx_bandwidth is set according to rate+abs(LO_OFFSET). The test is
performed in the following way:
- Set B205 rx freq to 2.4G, gain to 35, rate to 20M, (10db external
pad connected) - Generator sweeps a tone from 2.4G-30M to 2.4G+30M in 50kHz steps at
constant -20dBm output power. - Fetch 50k samples per sweep point, flat top window, FFT, extract
largest tone and put it in dBm.
The plots linked below are the results of the two sweeps (0 offset,
-8MHz offset). Note that the y-axis scale has an arbitrary x-dBm offset
that is not interesting for this test.
I noticed that the flatness and shape of the two options are quite
different. Some things I expected like the image being mixed in at the
lower frequencies for the -8MHz offset, however, I was hoping the
passband would look more similar. For example, at +4MHz tone freq, there
is 1dB of difference. My question is as simple as, is this expected or
am I configuring something incorrectly? Also, what procedure would you
recommend for equalizing the passband?
cheers,
Dominik
--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233
Fax: +49 (0) 351 7958019 232
Email: dominik.eyerly@konrad-technologies.de
mailto:dominik.eyerly@konrad-technologies.de
Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzell
www.konrad-technologies.de http://www.konrad-technologies.de
www.abexstandard.org http://www.abexstandard.org
Support Telefon: +49 (0) 7732 9815 100
support@konrad-technologies.de mailto:support@konrad-technologies.de
sig
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
Hi Dominik,
I believe you need to set the rx_bandwidth to rate + abs(2*lo_offset).
Regards,
Michael
On Thu, Feb 23, 2017 at 7:02 AM, Dominik Eyerly via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hello,
I have some follow-up questions to the LO offset discussion. Some quick
background, I've been characterizing and calibrating the rx of the B205-i
for several months now and I am trying to squeeze every bit of performance
out of it. In general, the calibration works quite well. However, I'm
always looking for tips and tricks to improve the performance. It was
mentioned that one should use an offset of at least +/-6MHz for optimal
performance. In spirit of this I wanted to investigate the flatness of the
passband with the two options (no offset, -8MHz offset). According to this
https://files.ettus.com/manual/page_usrp_b200.html 56MHz is the max
master clock so I set mine to 40MHz to enable a 20MHz sample rate. My
rx_bandwidth is set according to rate+abs(LO_OFFSET). The test is
performed in the following way:
1. Set B205 rx freq to 2.4G, gain to 35, rate to 20M, (10db external
pad connected)
2. Generator sweeps a tone from 2.4G-30M to 2.4G+30M in 50kHz steps at
constant -20dBm output power.
3. Fetch 50k samples per sweep point, flat top window, FFT, extract
largest tone and put it in dBm.
The plots linked below are the results of the two sweeps (0 offset, -8MHz
offset). Note that the y-axis scale has an arbitrary x-dBm offset that is
not interesting for this test.
I noticed that the flatness and shape of the two options are quite
different. Some things I expected like the image being mixed in at the
lower frequencies for the -8MHz offset, however, I was hoping the passband
would look more similar. For example, at +4MHz tone freq, there is 1dB of
difference. My question is as simple as, is this expected or am I
configuring something incorrectly? Also, what procedure would you recommend
for equalizing the passband?
cheers,
Dominik
--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233 <+49%20351%207958019233>
Fax: +49 (0) 351 7958019 232 <+49%20351%207958019232>
Email: dominik.eyerly@konrad-technologies.de
Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzellwww.konrad-technologies.dewww.abexstandard.org
*Support Telefon: +49 (0) 7732 9815 100 <+49%207732%209815100>*support@konrad-technologies.de[image: sig]
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
USRP-users mailing list
USRP-users@lists.ettus.com
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Hi Michael,
Thanks for getting back to me. Unfortunately, this does not improve the
plots. Even settings the bandwidth to max (56e6) still produces a
lopsided passband. Do you have any other recommendations I could try?
cheers,
dominik
On 02/25/2017 10:48 PM, Michael West wrote:
Hi Dominik,
I believe you need to set the rx_bandwidth to rate + abs(2*lo_offset).
Regards,
Michael
On Thu, Feb 23, 2017 at 7:02 AM, Dominik Eyerly via USRP-users
<usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com> wrote:
Hello,
I have some follow-up questions to the LO offset discussion. Some
quick background, I've been characterizing and calibrating the rx
of the B205-i for several months now and I am trying to squeeze
every bit of performance out of it. In general, the calibration
works quite well. However, I'm always looking for tips and tricks
to improve the performance. It was mentioned that one should use
an offset of at least +/-6MHz for optimal performance. In spirit
of this I wanted to investigate the flatness of the passband with
the two options (no offset, -8MHz offset). According to this
https://files.ettus.com/manual/page_usrp_b200.html
<https://files.ettus.com/manual/page_usrp_b200.html> 56MHz is the
max master clock so I set mine to 40MHz to enable a 20MHz sample
rate. My rx_bandwidth is set according to rate+abs(LO_OFFSET).
The test is performed in the following way:
1. Set B205 rx freq to 2.4G, gain to 35, rate to 20M, (10db
external pad connected)
2. Generator sweeps a tone from 2.4G-30M to 2.4G+30M in 50kHz
steps at constant -20dBm output power.
3. Fetch 50k samples per sweep point, flat top window, FFT,
extract largest tone and put it in dBm.
The plots linked below are the results of the two sweeps (0
offset, -8MHz offset). Note that the y-axis scale has an arbitrary
x-dBm offset that is not interesting for this test.
http://imgur.com/a/laDFy
I noticed that the flatness and shape of the two options are quite
different. Some things I expected like the image being mixed in at
the lower frequencies for the -8MHz offset, however, I was hoping
the passband would look more similar. For example, at +4MHz tone
freq, there is 1dB of difference. My question is as simple as, is
this expected or am I configuring something incorrectly? Also,
what procedure would you recommend for equalizing the passband?
cheers,
Dominik
--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233 <tel:+49%20351%207958019233>
Fax: +49 (0) 351 7958019 232 <tel:+49%20351%207958019232>
Email: dominik.eyerly@konrad-technologies.de
<mailto:dominik.eyerly@konrad-technologies.de>
*Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzell*
www.konrad-technologies.de <http://www.konrad-technologies.de>
www.abexstandard.org <http://www.abexstandard.org>
*Support Telefon: +49 (0) 7732 9815 100 <tel:+49%207732%209815100>*
support@konrad-technologies.de <mailto:support@konrad-technologies.de>
sig
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
_______________________________________________ USRP-users mailing
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--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233
Fax: +49 (0) 351 7958019 232
Email: dominik.eyerly@konrad-technologies.de
mailto:dominik.eyerly@konrad-technologies.de
Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzell
www.konrad-technologies.de http://www.konrad-technologies.de
www.abexstandard.org http://www.abexstandard.org
Support Telefon: +49 (0) 7732 9815 100
support@konrad-technologies.de mailto:support@konrad-technologies.de
sig
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
Hi Dominik,
The +/-6 MHz minimum is a red herring. There is no need to shift that
much. That was my misunderstanding. I thought the frontend bandwidth was
getting adjusted automatically and it wasn't. You can use any LO offset as
long as you set the bandwidth correctly.
I believe what you are seeing is expected. You will only have a
symmetrical response (or as close to symmetrical as possible) and the best
flatness at an LO offset of zero. As you apply more of an LO offset, you
will see more roll off. Which way the roll off slopes is determined by
whether the LO offset is positive or negative.
Regards,
Michael
On Mon, Feb 27, 2017 at 4:06 AM, Dominik Eyerly <
d.eyerly@konrad-technologies.de> wrote:
Hi Michael,
Thanks for getting back to me. Unfortunately, this does not improve the
plots. Even settings the bandwidth to max (56e6) still produces a lopsided
passband. Do you have any other recommendations I could try?
cheers,
dominik
On 02/25/2017 10:48 PM, Michael West wrote:
Hi Dominik,
I believe you need to set the rx_bandwidth to rate + abs(2*lo_offset).
Regards,
Michael
On Thu, Feb 23, 2017 at 7:02 AM, Dominik Eyerly via USRP-users <
usrp-users@lists.ettus.com> wrote:
Hello,
I have some follow-up questions to the LO offset discussion. Some quick
background, I've been characterizing and calibrating the rx of the B205-i
for several months now and I am trying to squeeze every bit of performance
out of it. In general, the calibration works quite well. However, I'm
always looking for tips and tricks to improve the performance. It was
mentioned that one should use an offset of at least +/-6MHz for optimal
performance. In spirit of this I wanted to investigate the flatness of the
passband with the two options (no offset, -8MHz offset). According to this
https://files.ettus.com/manual/page_usrp_b200.html 56MHz is the max
master clock so I set mine to 40MHz to enable a 20MHz sample rate. My
rx_bandwidth is set according to rate+abs(LO_OFFSET). The test is
performed in the following way:
1. Set B205 rx freq to 2.4G, gain to 35, rate to 20M, (10db external
pad connected)
2. Generator sweeps a tone from 2.4G-30M to 2.4G+30M in 50kHz steps
at constant -20dBm output power.
3. Fetch 50k samples per sweep point, flat top window, FFT, extract
largest tone and put it in dBm.
The plots linked below are the results of the two sweeps (0 offset, -8MHz
offset). Note that the y-axis scale has an arbitrary x-dBm offset that is
not interesting for this test.
I noticed that the flatness and shape of the two options are quite
different. Some things I expected like the image being mixed in at the
lower frequencies for the -8MHz offset, however, I was hoping the passband
would look more similar. For example, at +4MHz tone freq, there is 1dB of
difference. My question is as simple as, is this expected or am I
configuring something incorrectly? Also, what procedure would you recommend
for equalizing the passband?
cheers,
Dominik
--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233 <+49%20351%207958019233>
Fax: +49 (0) 351 7958019 232 <+49%20351%207958019232>
Email: dominik.eyerly@konrad-technologies.de
Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzellwww.konrad-technologies.dewww.abexstandard.org
*Support Telefon: +49 (0) 7732 9815 100 <+49%207732%209815100>*support@konrad-technologies.de[image: sig]
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
_______________________________________________ USRP-users mailing list
USRP-users@lists.ettus.com http://lists.ettus.com/mailman
/listinfo/usrp-users_lists.ettus.com
--
--
i.A. Dominik Eyerly
Software
Tel: +49 (0) 351 7958019 233 <+49%20351%207958019233>
Fax: +49 (0) 351 7958019 232 <+49%20351%207958019232>
Email: dominik.eyerly@konrad-technologies.de
Konrad GmbH — Fritz-Reichle-Ring 12 — D-78315 Radolfzellwww.konrad-technologies.dewww.abexstandard.org
*Support Telefon: +49 (0) 7732 9815 100 <+49%207732%209815100>*support@konrad-technologies.de[image: sig]
Geschäftsleitung: Michael Konrad
Handelsregisternr: HRB 550593 in Freiburg
Ust-Id-Nr. DE 206693267
VERTRAULICHKEITS-INFORMATION: Dieses e-Mail und alle anhängenden Dokumente, enthalten Informationen der Konrad GmbH und sind nur für die adressierte Person bestimmt. Diese können vertraulich und/oder von Veröffentlichungen ausgenommen sein. Das Kopieren und die Weitergabe an nicht autorisierte Dritte sind verboten. Für Zuwiderhandlungen können Sie haftbar gemacht werden. Falls Sie nicht der Empfänger sind, benachrichtigen Sie den Absender bitte umgehend. Danke
CONFIDENTIALITY NOTICE: This e-mail and any documents which may accompany it, contains information from Konrad GmbH, which is intended only for the use of the individual or entity to which it is addressed, and which may contain information that is privileged, confidential, and/or otherwise exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, any disclosure, dissemination, distribution, copying or other use of this communication or its substance is prohibited. If you have received this communication in error, please contact us immediately. Thank you.
