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Today's Topics:
1. Re: USRP EMI Solution (John McInnes)
2. Re: Sending data to USRP2 with Simulink, without Buffer
Overflow (Mike McLernon)
----------------------------------------------------------------------
Message: 1
Date: Mon, 20 May 2013 12:33:11 +0000
From: John McInnes <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP EMI Solution
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
What exactly are you looking for in terms of interference
rejection/suppression? The boxing as it stands provides pretty much what most
people care about in terms of EMI in that it reduces the probability of
spurious emission/coupling. If you're looking for double figure suppression on
some specific band that is leaking somewhere other than the antenna port, it
likely isn't an issue generic enough that someone has already developed an
isolation solution.
From: [email protected]
To: [email protected]
Date: Sun, 19 May 2013 01:11:45 +0100
Subject: Re: [USRP-users] USRP EMI Solution
The requirements are different, but how much EMI/RFI shielding do you think the
box provides?
I can tell you now it would be around 1dB, if even that. It really is as
effective as tissue paper. It may couple some near-field effects but not much.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 19:24:04 -0400
Subject: Re: [USRP-users] USRP EMI Solution
From: [email protected]
To: [email protected]
The requirements of TEMPEST and the requirements of ordinary commercial EMC are
very, very different.
Because a box doesn't meet TEMPEST says essentially *zero* about its
suitability for ordinary commercial
applications in the EMC realm.
I've been inside the photon-locked shielded room at NRAO, and other similar
rooms. Ordinary commercial gear
*does not* need to meet those requirements. At all. Ever.
Open up a standard commercial-grade or ham-radio grade receiver/transceiver
sometime. You'll find that there's
no extensive RF gasketting (if any at all). Just a metal box that is bonded,
in several places to the system
ground, and the RF connector grounds are common with the cabinet. They
aren't "tissue paper", but they aren't
TEMPEST-qualified either.
I've been involved in radio since 1986. Installed a crap-ton of RF equipment,
done system designs, etc, etc.
For ordinary commercial and amateur-radio applications. NONE of it was
TEMPEST-qualified, because, well,
for ordinary commercial purposes, it didn't need to be.
On Sat, May 18, 2013 at 6:38 PM, Mark McCarron <[email protected]> wrote:
Hilbert,
I've designed EMI/RFI solutions and TEMPEST secure rooms to protect computing,
comms and humans. That box may as well be tissue paper.
Grounded means nothing other than general electrical safety (even then there
are caveats to this). An EMI/RFI shield extends a ground reference around an
object. That's not as easy as it sounds.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 18:24:30 -0400
Subject: Re: [USRP-users] USRP EMI Solution
From: [email protected]
To: [email protected]
The metal is *grounded*. It doesn't matter whether it's painted, or not. The
paint issue is along the seams in
any type of cabinet. Ideally, you want all the seams to be one continuous
ground, and if you have a cabinet
that fits-together mechanically, that's where you'll typically find RF gasket
material between two non-painted
surfaces. But the paint, in and of itself, is irrelevant.
Certainly, if you're going to be operating any kind of RF device like this in a
*very high* EMI environment, you might
want to build yourself a faraday cage with welded seams, and improved RF
choking on all non-RF
ingress/egress points.
The existing cabinetry is more than adequate for most applications. Hardly
"transparent".
For RX, you only have to get the "RF leakage through the cabinet" to
significantly below "RF I would have received
from the antenna in the same EM field".
And the secondary emissions from the device itself are required to pass
various tests, as far as I know,
like FCC and CE testing. Again, in order to pass those tests, the cabinet
can't possibly be "transparent".
That's just absurd.
On Sat, May 18, 2013 at 5:58 PM, Mark McCarron <[email protected]> wrote:
That's not an EMI shield. The metal is painted and would be effectively
transparent to EMI/RFI. What is required is a continuously conducting surface
with proper sealed inputs and EMI gaskets.
Its incredibly hard to properly seal anything from EMI/RFI.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 17:42:09 -0400
From: [email protected]
To: [email protected]
Subject: [USRP-users] USRP EMI Solution
Mark writes:
>Has anyone considered constructing an EMI shield box for the USRP?
>
>Regards,
>
>Mark McCarron
You mean, other than the one that comes with it? The box is metallic,
grounded, and most of the perforations in it are a tiny fraction of a
wavelength up to a few GHz. If I were
operating in high RF fields above about 3GHz, I might replace the fan grille
with
some steel mesh.
The USB cable Ettus supplies includes a common-mode choke, as does the power
cable.
For lower frequencies (below 50Mhz) adding more common-mode chokes to those
cables will likely help, and they're available on eBay reasonably cheaply.
But, as far as I know, the existing steel cabinet was engineered to provide EMI
isolation, and given its material and construction, it can't help but do so,
due to physics...
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
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--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
_______________________________________________
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--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
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Message: 2
Date: Mon, 20 May 2013 14:59:03 +0000
From: Mike McLernon <[email protected]>
To: Kehinde Ogunyanda <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Sending data to USRP2 with Simulink, without
Buffer Overflow
Message-ID:
<e3879be9a282cb45aab7ce258a9ae48f21a31...@exmb-01-ah.ad.mathworks.com>
Content-Type: text/plain; charset="us-ascii"
Hi Ken,
If you havent already downloaded the MathWorks USRP support package, you can
follow the instructions at http://www.mathworks.com/hardware-support/usrp.html
to download and install for R2013a. Note that the page has a link to help you
download the support package for previous releases, at
http://www.mathworks.com/support/solutions/en/data/1-M28V7O/index.html?solution=1-M28V7O.
Once you download and install the support package, you can type help sdru at
the MATLAB command prompt to find essential functions, objects, Simulink
models, and examples. Specifically, click on the Help and Examples link to
open example models. You should start with the FM mono receiver example model.
Hth,
Mike
From: Kehinde Ogunyanda [mailto:[email protected]]
Sent: Sunday, May 19, 2013 12:50 PM
To: Mike McLernon
Cc: [email protected]
Subject: Re: [USRP-users] Sending data to USRP2 with Simulink, without Buffer
Overflow
Hello Mike,
I actually thought I respondedto your question. Yes, I intend using Simulink
for the OFDM -USRP system. I found some Matlab (".m" files) from cgran webpage,
but I must confess, I don't know what to do with the ".m" files. I am hoping to
see some simulink blocks connected togehter, and may be press the "Run" button
to see it work. Forgive me, I don't know how it really works, but I think the
simulink blocks are more or less like GUI, which will be a little bit
understandable for people like us. Kindly help out.
Ken
On Thu, May 16, 2013 at 4:33 AM, Mike McLernon <[email protected]>
wrote:
Hi Ken,
Do you plan to use GNU Radio or MATLAB/Simulink?
Mike
________________________________________
From: USRP-users [[email protected]] on behalf of Ken
[[email protected]]
Sent: Wednesday, May 15, 2013 6:02 PM
To: [email protected]
Subject: Re: [USRP-users] Sending data to USRP2 with Simulink, without Buffer
Overflow
Mike McLernon <Mike.McLernon@...> writes:
>
> Hi Vlad,
>
> Some questions to make sure I understand your working environment:
> 1. What version of MATLAB/Simulink are you using? R2010b?
> 2. What frame size(s) are you using?
> 3. What is your USRP decimation factor on the Rx side?
> 4. Have you confirmed buffer overflow with the 'overrun' port on the
USRP Rx block?
> 5. Have you tried running in Rapid Accelerator mode?
>
> Once we get that info, we can diagnose a bit better.
>
> Hth,
> Mike
>
> -----Original Message-----
> From: usrp-users-bounces@...
> [mailto:usrp-users-bounces@...] On Behalf Of Vlad Stoica
> Sent: Wednesday, April 13, 2011 5:19 AM
> To: USRP-users@...
> Subject: [USRP-users] Sending data to USRP2 with Simulink, without Buffer
Overflow
>
> Hello guys
>
> I have implemented an OFDM transmitter and receiver modell in Simulink.
> It should work at 10.7MHz with the LF daughterboards.
>
> I use frame based computing, and one frame lasts 46.6msec. My signal has a
width of 40kHz.
>
> My first tests have been to write the OFDM modulated signal into a wave
file, output it via soundcard, with a
> SMIQ Modulator do a vector modulation to 10.7MHz and then give that signal
to the RX.
>
> On the computer i ran the receive modell (with frequency and time synchro)
and it worked fine !
>
> Now instead of writing a wave file i directly send the data to the USRP2.
> But it seems that some packets get lost, and i guess there is a buffer
overflow at the USRP2 input.
>
> Do you know how i can synchronize my transmitter modell with the buffer in
USRP2 ?
>
> I'm thinking about using UHD drivers, and Embedded Matlab "load libraries"
> and transmit the files with the UHD.
>
> Thanks for ideas and hints !
>
> Greetz
> Vlad
> --
> NEU: FreePhone - kostenlos mobil telefonieren und surfen!
> Jetzt informieren: http://www.gmx.net/de/go/freephone
>
> _______________________________________________
> USRP-users mailing list
> USRP-users@...
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
Hello to anyone who can help me out. I am a total stranger, when it comes to
using GNU and SDR. I am interested in playing with a complete transmit and
receive OFDM model that can be ported into USRP. I don't mind giving my e-
mail. I would also like to put convolutional or permutation codding in the
model.
Ken
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--
Sincerely Yours,
Alex.
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