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Today's Topics:
1. 1/f shaped noise floor on SBX - is this a normal feature?
(Rickard Radio)
2. Re: 1/f shaped noise floor on SBX - is this a normal feature?
(Marcus Leech)
3. Re: 1/f shaped noise floor on SBX - is this a normal feature?
(Rickard Radio)
4. Re: 1/f shaped noise floor on SBX - is this a normal feature?
(Marcus Leech)
5. Re: 1/f shaped noise floor on SBX - is this a normal feature?
(Rickard Radio)
6. Re: 1/f shaped noise floor on SBX - is this a normal feature?
(Marcus Leech)
7. AGC and UHD "peak" stream argument questions (Rickard Radio)
8. Re: AGC and UHD "peak" stream argument questions (Marcus Leech)
9. UHD protocol specifications (Giulio Mazzoleni)
10. Re: UHD protocol specifications (Matt Ettus)
----------------------------------------------------------------------
Message: 1
Date: Wed, 29 May 2013 18:17:12 +0200
From: Rickard Radio <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] 1/f shaped noise floor on SBX - is this a normal
feature?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=windows-1252
Hi USRP users,
I have a (rather strong ?) 1/f shaped noise floor with the SBX daughterboards
(rev 4 I think, acquired end of 2012).
Running the uhd-calibration utilities does not give any visible difference, see
links to pics below.
As a comparison, the noise floor on the RFX2400 db is rather flat. Maybe
generally a little higher but without the strong 1/f peak.
Q1: Is this a normal and expected (1/f colored) noise floor with the SBX db?
If I pump up the uhd gain (>0 dB) the 1/f shaped noise floor remains and gets
amplified correspondingly.
I know 1/f noise is a common notorious feature in electronics so perhaps it is
included with the SBX too.
Q2: Should I see (or not) a visible improvement with the uhd-calibration
enabled (i.e., with the calibration values in .uhd/cal/) ?
With the calibration enabled the gr-application tells me that the appropriate
cal values are "loaded", which sounds reassuring? but maybe I do something
wrong.
Link to picture of PSD without calibration:
https://www.dropbox.com/s/vl7x8c8i7qn3ueh/UHD_uncalibrated_SBX.png
Link to picture of PSD with calibration (its identical to my eyes):
https://www.dropbox.com/s/ngc98l71ugifqs4/UHD_calibrated_SBX.png
Thanks for any comments,
Rickard
------------------------------
Message: 2
Date: Wed, 29 May 2013 16:26:02 +0000 (UTC)
From: Marcus Leech <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: [USRP-users] 1/f shaped noise floor on SBX - is this a
normal feature?
Message-ID: <1518858532.79826.1369844764026.JavaMail.mail@webmail02>
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Message: 3
Date: Wed, 29 May 2013 18:36:09 +0200
From: Rickard Radio <[email protected]>
To: Marcus Leech <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] 1/f shaped noise floor on SBX - is this a
normal feature?
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"
OK, thanks! However, I want to utilize all the bandwidth I can get so the
passband need to stay in the centre. As a consequence then also the 1/f noise
peak has a relatively small total power, except when the received signal is
very weak which leads me to another related question I have...
On May 29, 2013, at 6:26 PM, Marcus Leech <[email protected]> wrote:
> The SBX is a direct-conversion receiver, so you'll see some 1/f noise. You
> can use offset tuning to move DC out of your passband, and as a happy
> consequence, move the 1/f noise out of your passband as well.
>
>
>
> on May 29, 2013, Rickard Radio <[email protected]> wrote:
> Hi USRP users,
>
> I have a (rather strong ?) 1/f shaped noise floor with the SBX daughterboards
> (rev 4 I think, acquired end of 2012).
> Running the uhd-calibration utilities does not give any visible difference,
> see links to pics below.
> As a comparison, the noise floor on the RFX2400 db is rather flat. Maybe
> generally a little higher but without the strong 1/f peak.
>
> Q1: Is this a normal and expected (1/f colored) noise floor with the SBX db?
> If I pump up the uhd gain (>0 dB) the 1/f shaped noise floor remains and gets
> amplified correspondingly.
> I know 1/f noise is a common notorious feature in electronics so perhaps it
> is included with the SBX too.
>
> Q2: Should I see (or not) a visible improvement with the uhd-calibration
> enabled (i.e., with the calibration values in .uhd/cal/) ?
> With the calibration enabled the gr-application tells me that the appropriate
> cal values are "loaded", which sounds reassuring? but maybe I do something
> wrong.
>
> Link to picture of PSD without calibration:
> https://www.dropbox.com/s/vl7x8c8i7qn3ueh/UHD_uncalibrated_SBX.png
>
> Link to picture of PSD with calibration (its identical to my eyes):
> https://www.dropbox.com/s/ngc98l71ugifqs4/UHD_calibrated_SBX.png
>
> Thanks for any comments,
> Rickard
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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Message: 4
Date: Wed, 29 May 2013 16:39:16 +0000 (UTC)
From: Marcus Leech <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: [USRP-users] 1/f shaped noise floor on SBX - is this a
normal feature?
Message-ID: <1425797148.80057.1369845556876.JavaMail.mail@webmail02>
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Message: 5
Date: Wed, 29 May 2013 19:00:21 +0200
From: Rickard Radio <[email protected]>
To: Marcus Leech <[email protected]>
Cc: [email protected]
Subject: Re: [USRP-users] 1/f shaped noise floor on SBX - is this a
normal feature?
Message-ID: <[email protected]>
Content-Type: text/plain; charset="windows-1252"
All I can get, i.e. 25 MHz 16 bit or 50 MHz 8 bit.
I am not sure what you mean. Do you mean that with a certain wanted analog
carrier (center) frequency, fc, which is what I normally use but then also with
this "offset tuning", I still receive/transmit the whole bandwidth centered
around fc in RF (analog domain in the air) but have just (circularly) shifted
the whole spectrum after sampling in the digital domain which I can then just
undo in digital domain by the DDC with the uhd? Or maybe I got this totally
wrong?
Is "offset tuning" equivalent to the "lo_off" parameter to use with the
"uhd.tune_request(fc, lo_off)" ?
I never really understood that parameter until perhaps now? I will try that
tomorrow!
On May 29, 2013, at 6:39 PM, Marcus Leech <[email protected]> wrote:
> How much bandwidth are you using?
>
> With offset tuning, your desired center frequency is still slap-dab in the
> middle, but UHD has arranged to tune the analog hardware differently, and
> then use the DDC to move DC to somewhere else, and still have your desired Fc
> exactly where you want it.
>
> on May 29, 2013, Rickard Radio <[email protected]> wrote:
> OK, thanks! However, I want to utilize all the bandwidth I can get so the
> passband need to stay in the centre. As a consequence then also the 1/f noise
> peak has a relatively small total power, except when the received signal is
> very weak which leads me to another related question I have...
>
> On May 29, 2013, at 6:26 PM, Marcus Leech <[email protected]> wrote:
>
>> The SBX is a direct-conversion receiver, so you'll see some 1/f noise. You
>> can use offset tuning to move DC out of your passband, and as a happy
>> consequence, move the 1/f noise out of your passband as well.
>>
>>
>>
>> on May 29, 2013, Rickard Radio <[email protected]> wrote:
>> Hi USRP users,
>>
>> I have a (rather strong ?) 1/f shaped noise floor with the SBX
>> daughterboards (rev 4 I think, acquired end of 2012).
>> Running the uhd-calibration utilities does not give any visible difference,
>> see links to pics below.
>> As a comparison, the noise floor on the RFX2400 db is rather flat. Maybe
>> generally a little higher but without the strong 1/f peak.
>>
>> Q1: Is this a normal and expected (1/f colored) noise floor with the SBX db?
>> If I pump up the uhd gain (>0 dB) the 1/f shaped noise floor remains and
>> gets amplified correspondingly.
>> I know 1/f noise is a common notorious feature in electronics so perhaps it
>> is included with the SBX too.
>>
>> Q2: Should I see (or not) a visible improvement with the uhd-calibration
>> enabled (i.e., with the calibration values in .uhd/cal/) ?
>> With the calibration enabled the gr-application tells me that the
>> appropriate cal values are "loaded", which sounds reassuring? but maybe I do
>> something wrong.
>>
>> Link to picture of PSD without calibration:
>> https://www.dropbox.com/s/vl7x8c8i7qn3ueh/UHD_uncalibrated_SBX.png
>>
>> Link to picture of PSD with calibration (its identical to my eyes):
>> https://www.dropbox.com/s/ngc98l71ugifqs4/UHD_calibrated_SBX.png
>>
>> Thanks for any comments,
>> Rickard
>> _______________________________________________
>> USRP-users mailing list
>> [email protected]
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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Message: 6
Date: Wed, 29 May 2013 17:06:33 +0000 (UTC)
From: Marcus Leech <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: [USRP-users] 1/f shaped noise floor on SBX - is this a
normal feature?
Message-ID: <182273289.80468.1369847193539.JavaMail.mail@webmail02>
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------------------------------
Message: 7
Date: Wed, 29 May 2013 19:33:44 +0200
From: Rickard Radio <[email protected]>
To: [email protected]
Subject: [USRP-users] AGC and UHD "peak" stream argument questions
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
Hi USRP users,
Q: Is there any way to accomplish true AGC with UHD and GR that affects the
analog gain with the UHD or do I have to adjust that analog UHD gain manually
(which I currently do) ?
I could of course have missed something obvious. The AGC functions in GR seem
to only affect the gain in the digital domain, after ADC. Correct? Or is it
somehow possible to feed back digital AGC values to the UHD to affect the
analog gain setting?
Q: Similarly, is it possible to affect the "peak" stream arg value in the UHD
during runtime with GR as a way to adapt the ADC range to the incoming signal?
Adjusted at least at a slow rate by preferably monitoring the received signal
values in GR. That is, can the "peak" stream argument to UHD somehow be updated
during runtime with GR? This is almost the same question but especially with
sc8 (8 bits) its really important to tune the ADC range to the incoming analog
signal and I would like to accomplish that automagically, and even better If I
can save those AGC values that affect the analog gain via UHD for possible post
processing!
Rickard
------------------------------
Message: 8
Date: Wed, 29 May 2013 17:47:04 +0000 (UTC)
From: Marcus Leech <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: [USRP-users] AGC and UHD "peak" stream argument questions
Message-ID: <913342627.80996.1369849624180.JavaMail.mail@webmail02>
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Message: 9
Date: Thu, 30 May 2013 10:58:23 +0200
From: Giulio Mazzoleni <[email protected]>
To: [email protected]
Subject: [USRP-users] UHD protocol specifications
Message-ID: <[email protected]>
Content-Type: text/plain
Dear USRP users,
I am new to this mailing list, so greetings to everyone.
I was looking at SDR support for GNU radio and Simulink and seems that
USRP2/UHD is the most widely used and supported.
I've been experimenting with the UHD driver in the last few days since I
would like to create a compatible UHD endpoint (at least for a minor
subset of functions, mostly related to rx and tx).
I took a look at the driver implementation and at the host code, even if
it seems a bit complex to understand at first and could accomplish some
basic single channel transfers in gnu radio.
The real problem is that the PC driver is doing many error checking
based on data coming from I2C and FPGA registers and the data flow is
somewhat difficult to follow in case of errors.
Is there any formal specification of the UHD protocol? Or the source
code is the only real source of information publicly available, as I
guess?
I see that this very question has alreaduy been posted in the past
http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2012-March/003871.html
but got no answer at that time.
Thank you very much for any suggestion you could think of and best
regards,
Giulio
------------------------------
Message: 10
Date: Thu, 30 May 2013 08:55:23 -0700
From: Matt Ettus <[email protected]>
To: Giulio Mazzoleni <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] UHD protocol specifications
Message-ID:
<CAN=1kn8y6dBk4d-60cqQmCP1SJroR_XNS=maq86nrncs0jh...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Giulio,
The protocol itself is only documented through the code. It is in rapid
development, and any documentation would quickly become out of sync with
the code.
The use of UHD with Matlab is governed by a separate license agreement
between Ettus Research and The Mathworks. Use of UHD with Simulink (or
Matlab or any other proprietary program) with radio hardware other than
Ettus Research hardware would be a direct violation of that license. If
you would like to discuss this further, please contact me off list.
Matt Ettus
President, Ettus Research LLC
On Thu, May 30, 2013 at 1:58 AM, Giulio Mazzoleni <
[email protected]> wrote:
> Dear USRP users,
> I am new to this mailing list, so greetings to everyone.
>
> I was looking at SDR support for GNU radio and Simulink and seems that
> USRP2/UHD is the most widely used and supported.
>
> I've been experimenting with the UHD driver in the last few days since I
> would like to create a compatible UHD endpoint (at least for a minor
> subset of functions, mostly related to rx and tx).
>
> I took a look at the driver implementation and at the host code, even if
> it seems a bit complex to understand at first and could accomplish some
> basic single channel transfers in gnu radio.
>
> The real problem is that the PC driver is doing many error checking
> based on data coming from I2C and FPGA registers and the data flow is
> somewhat difficult to follow in case of errors.
>
> Is there any formal specification of the UHD protocol? Or the source
> code is the only real source of information publicly available, as I
> guess?
>
> I see that this very question has alreaduy been posted in the past
>
> http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2012-March/003871.html
> but got no answer at that time.
>
> Thank you very much for any suggestion you could think of and best
> regards,
> Giulio
>
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
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