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Today's Topics:
1. Question about Future Products (Robert Palumbo)
2. MIMO Reference Problem (Brian Heilig)
3. Re: Noise Floor issue? ([email protected])
4. Explanation about GPSDO Module? (Count Zero)
5. Re: Explanation about GPSDO Module? (Ian Buckley)
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Message: 1
Date: Sat, 28 Apr 2012 12:59:05 -0400
From: Robert Palumbo <[email protected]>
To: [email protected]
Subject: [USRP-users] Question about Future Products
Message-ID:
<cakwzk9z4jxwehv-2runkngfev5mcss_+-qum9obxncc_mmx...@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hello,
I would like to start off by saying that you guys sell a great line of
products. I've been using the N200/N210 series for my applications
extensively, and their performance has been superior thus far,
especially in terms of flexibility and reliability.
I was wondering if Ettus Research has any upcoming plans to develop
another USRP-product, similar in performance to the N210, but with a
larger FPGA (i.e., Virtex family)? The N210 works perfectly for my
application, but the only limitation right now is the size of the
DSP3400A FPGA.
Thanks for any info you can give,
Rob
--
Robert A Palumbo
[email protected]
------------------------------
Message: 2
Date: Sat, 28 Apr 2012 16:30:30 -0400
From: Brian Heilig <[email protected]>
To: [email protected]
Subject: [USRP-users] MIMO Reference Problem
Message-ID:
<CALLWv_=p-ywlunnhaod+mpajprug+a1szudmxjt0pjbwi+h...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Dear List,
I have a pair of USRP2 radios with RFX900 daughterboards. Both are HW rev
4. I'm having a very difficult time getting the two radios to synchronize
to the same reference clock. I've tried both an external reference and the
MIMO reference. I'm transmitting from USRP2 B and receiving from USRP2 A,
and I'm (attempting to) lock B to A's reference. Unfortunately I'm seeing
about a 10KHz difference in the received frequency at A.
I've taken some pictures of what I believe to be the root of the problem.
By the way I have my own FPGA and firmware images. The troubleshooting is
pretty close to the hardware.
In order to ensure the two radios were synchronized I used the 10 MHz
output of A to trigger an oscilloscope. I then measured the various clocks
on B. If the two clocks were synchronized we would see a nice clean signal
without aliasing. But I don't...
Here are some pictures of what I'm seeing.
http://imgur.com/a/0rw3K
The first image is of the 10 MHz signal from radio A, measured at the
output of the clock switch U18 on radio B. This shows that a clean
reference clock is arriving at the AD9510 U9 ref input. This measurement is
triggered to itself.
The next image is of the 100 Mhz output of the VCO of USRP2 B. It's also
triggered to itself.
The next image is of the 10 MHz from radio A used as a trigger, and 100 Mhz
output of the VCO from radio A. This is a sanity check, and shows what the
display should look like if the two clocks are frequency aligned. Note that
there is some interference on the 10 MHz signal from the 100 Mhz signal.
This is because the probe measuring the 10 MHz signal is not the greatest.
The last image is of the 10 MHz from radio A (same as image #1) used as a
trigger, and 100 MHz output of the VCO from radio B. If the two clocks were
synchronized I'd expect to see nice clean clocks. I don't, which indicates
there is a (non-integer) frequency drift between them due to aliasing.
Please help! I can't go any further until this is resolved.
Thanks,
Brian
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Message: 3
Date: Sun, 29 Apr 2012 14:25:57 +1200
From: "[email protected]" <[email protected]>
To: Tim Newman <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] Noise Floor issue?
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
On 28/04/12 23:37, Tim Newman wrote:
> I believe there was a bug that was fixed the the 003.004.000 release
> firmware. Which firmware are you running?
>
> Tim
>
> On Saturday, April 28, 2012, [email protected]
> <mailto:[email protected]> wrote:
>
> I have two N200 with SBX and have a similar antenna on both units
> and am running uhd_fft with parms :
>
> uhd_fft -s 2e6 -f .804e9 -a addr=192.168.n0.2 -g 30
>
> as you can see from the screenshot, the analogue tv sound channel
> at 804.75 MHz is observable in both FFTs but the noise floor
> appears to be quite a bit higher in ..20.2 than in 10.2 ( the
> latter has a GPSDO ) by ~ 25 "dB"
>
> When I switch the antennas over, the issue remains.
>
> When I moved the DB to a USRP1, I get the 2nd-screen_shot. This
> might imply there is an issue with the base N200?
>
> Any ideas about what might be wrong?
>
> Kind Regards,
>
> John
>
Thanks for the response Tim. I downloaded the latest UHD and GNURadio
circa April 22nd (NZ date
) using Marcus' script.
The version of UHD is 003.004.001-43-g81e2262c. I downloaded the fw and
fpga to both N200s at that time.
Kind Regards,
John
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Message: 4
Date: Sat, 28 Apr 2012 22:41:36 -0400
From: Count Zero <[email protected]>
To: [email protected]
Subject: [USRP-users] Explanation about GPSDO Module?
Message-ID: <[email protected]>
Content-Type: text/plain; charset="utf-8"
I have a USRP N210 with a GPSDO module. I understand that the internal clock
and the GPSDO clock are both producing a 10MHz base clock frequency (please
correct me if I'm wrong).
This is slightly confusing for me, because in some online documentation I read
the USRP is producing a 64MHz clock, which is not suitable when used as a GSM
base station. Is there an explanation somewhere about how this module is used
to clock the N210 to a frequency other than 64MHz (such as 52MHz).
I understand that there may be a clock multiplier within the USRP which takes
the internal 10MHz signal and multiplies it to achieve any other frequency
required. But how is the GPSDO different?
Thanks!
--
Count Zero
P.S. I would like to express how grateful I am about this mailing list. I have
read some really interesting posts, and I feel I have learned quite a lot from
those posts.
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Message: 5
Date: Sat, 28 Apr 2012 20:34:03 -0700
From: Ian Buckley <[email protected]>
To: Count Zero <[email protected]>
Cc: [email protected]
Subject: Re: [USRP-users] Explanation about GPSDO Module?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
You're getting a few data points mixed up ...first the 64MHz is only applicable
to the USRP1, it had no flexibility in clocking unless you modified the H/W, as
indeed people interested mainly in GSM did. The N210 is a whole bunch more
powerful and flexible w.r.t clocking. If you look at the schematic (Page 4)
you'll see that U18 multiplexes the 2 sources of 10MHz (VCXO and GPSDO) and
then feeds them to U9 which is a combined PLL and clock signal buffer, which
performs frequency multiplication and distribution to the various components
(ADC/DAC/FPGA). The default configuration of N210/N200/USRP2 is to use a 100MHz
clock internally for all DSP, and a 50MHz clock that is phase aligned (divide
by 2 done in the FPGA) to the 100MHz to drive the microprocessor and some of
the peripherals. U9 (Analog devices AD9510) is programable and you are
encouraged to read the datasheet if you wish to extrapolate what custom
clocking might be possible.
-Ian
On Apr 28, 2012, at 7:41 PM, Count Zero wrote:
>
> I have a USRP N210 with a GPSDO module. I understand that the internal clock
> and the GPSDO clock are both producing a 10MHz base clock frequency (please
> correct me if I'm wrong).
>
> This is slightly confusing for me, because in some online documentation I
> read the USRP is producing a 64MHz clock, which is not suitable when used as
> a GSM base station. Is there an explanation somewhere about how this module
> is used to clock the N210 to a frequency other than 64MHz (such as 52MHz).
>
> I understand that there may be a clock multiplier within the USRP which takes
> the internal 10MHz signal and multiplies it to achieve any other frequency
> required. But how is the GPSDO different?
>
> Thanks!
>
> --
> Count Zero
>
> P.S. I would like to express how grateful I am about this mailing list. I
> have read some really interesting posts, and I feel I have learned quite a
> lot from those posts.
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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