On 08/21/2020 08:47 AM, Koyel Das (Vehere) wrote:
Hi Marcus,
In order to see if single channel of usrp is giving correct phase, I
will transmit a qpsk signal using one usrp and receive using the usrp
under test. The qpsk signal should appear same in receiver as in
transmitter and that will confirm if single channel is working fine.
Attached is the flowgraph for qpsk signal generator. I have a doubt
that “Random Source” block is not accepting any datatype other than
“byte” else the connection is getting red and “USRP Sink” is not
accepting anything other than “complex float”. In between is the
“Constellation Modulator” block. The connections are showing
compatible (please refer the attached flowgraph). Perhaps
"Constellation Modulator" is sending out data as "complex float" to
"USRP Sink" otherwise how can the two blocks be compatible?
So can I expect usrp sink will get correct data and not deform the
data out of “Constellation Modulator” to some incorrect data, since
"Random Source" is sending "Byte" and "USRP Sink" is receiving
"complex float"? Means is the flowgraph correct taking all datatypes
into consideration?
I am also attaching the grc files of transmitter and receiver.
Regards,
Koyel
Neither of your attached .grc files have anything useful in them...
When I said "check sanity of individual channels", I wasn't concerned
with phase--only that they were grossly "sane". When you inject
a signal in to them, do the resulting signals have the correct
attributes? Is the SNR roughly correct, etc?
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------------------------------------------------------------------------
*From:* USRP-users <usrp-users-boun...@lists.ettus.com> on behalf of
Koyel Das (Vehere) via USRP-users <usrp-users@lists.ettus.com>
*Sent:* Monday, August 17, 2020 10:07:05 AM
*To:* Marcus D. Leech <patchvonbr...@gmail.com>;
usrp-users@lists.ettus.com <usrp-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
Ok Marcus I will try to figure out if individual channels are working
fine.
Regards,
Koyel
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*From:* Marcus D. Leech <patchvonbr...@gmail.com>
*Sent:* Sunday, August 16, 2020 10:52 PM
*To:* Koyel Das (Vehere); usrp-users@lists.ettus.com
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
On 08/16/2020 01:15 PM, Koyel Das (Vehere) wrote:
I am not observing one individual channel but phase difference
between two channels. I very well know individual channel would show
random phases but not the phase difference when same signal is
injected in two channels. I hope you are aware that phase difference
= 2pi/lambda* path_difference. Path difference is constant as that’s
the difference between two paths of two daughterboards and hence this
phase difference is constant. Remember same signal is injected so
initial phases would be same for two channels and only the difference
in the signal path lengths bring the difference which is constant
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Yes, I fully understand that. I'm simply suggesting some simple
diagnostics to determine whether, as individual channels, the
receivers are
working correctly.
------------------------------------------------------------------------
*From:* Marcus D. Leech <patchvonbr...@gmail.com>
<mailto:patchvonbr...@gmail.com>
*Sent:* Sunday, August 16, 2020 10:39 PM
*To:* Koyel Das (Vehere); usrp-users@lists.ettus.com
<mailto:usrp-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
On 08/16/2020 12:46 PM, Koyel Das (Vehere) wrote:
The measurement is not initial phase but the phase difference
between two channels
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Are you using an external reference, or using the internal clock in
the X310?
If you observe an individual channel, is it "sane" ? That is,
apparently on-frequency, and with correct amplitudes and low distortion?
------------------------------------------------------------------------
*From:* Koyel Das (Vehere) <koyel....@vehere.com>
<mailto:koyel....@vehere.com>
*Sent:* Sunday, August 16, 2020 10:15:48 PM
*To:* Marcus D. Leech <patchvonbr...@gmail.com>
<mailto:patchvonbr...@gmail.com>; usrp-users@lists.ettus.com
<mailto:usrp-users@lists.ettus.com> <usrp-users@lists.ettus.com>
<mailto:usrp-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
the phase difference between two channels of USRP as a function of
frequency and time, when measured by splitting the same signal and
feeding two channels of usrp, are wandering around wrt one another
which was not happening before. I had given demo more than 30 times
based on this principle and tested previously more than 50 times and
I got correct result every time. Now only suddenly it started
happening. The frequency is 2.4 GHz and bandwidth I tried from 1 MHz
to 100 MHz. Previously the whole bandwidth was showing similar
values but then suddenly started behaving abnormally giving near to
correct result sometimes and sometimes junk.
Regards,
Koyel
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*From:* Marcus D. Leech <patchvonbr...@gmail.com>
<mailto:patchvonbr...@gmail.com>
*Sent:* Sunday, August 16, 2020 10:05 PM
*To:* Koyel Das (Vehere); usrp-users@lists.ettus.com
<mailto:usrp-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
On 08/15/2020 11:59 PM, Koyel Das (Vehere) wrote:
No it doesn’t look better again after reducing gain. Sometimes the
phase differences are closeby but not so same as we were getting
before and most of the times they are totally incorrect. Strength
of the signal when we tried with maximum gain was near -40 dbm.
Regards,
Koyel
To clarify some things.
(A) The phase errors are just the initial phases--they don't wander
around with respect to one another during a run?
(B) What frequency range?
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*From:* USRP-users <usrp-users-boun...@lists.ettus.com>
<mailto:usrp-users-boun...@lists.ettus.com> on behalf of Marcus D.
Leech via USRP-users <usrp-users@lists.ettus.com>
<mailto:usrp-users@lists.ettus.com>
*Sent:* Sunday, August 16, 2020 12:25:37 AM
*To:* usrp-users@lists.ettus.com
<mailto:usrp-users@lists.ettus.com> <usrp-users@lists.ettus.com>
<mailto:usrp-users@lists.ettus.com>
*Subject:* Re: [USRP-users] Incorrect data from usrp 2955
On 08/15/2020 01:16 PM, Koyel Das (Vehere) via USRP-users wrote:
Hi,
We are using USRP 2955. Something has gone wrong. Before we were
getting constant phase difference across channels for limited
bandwidth and with time when we split single antenna signal using
splitter and fed two channels of USRP but now it is not doing so.
This happened on Friday that after getting a series of correct
results : constant phase difference across channels by feeding
signal using splitter as mentioned above, we suddenly started to
receive wrong data: random phase across channels and with time
using the same setup with splitter. The thing we did was setting
gain to near maximum and receiving 100 MHz sample rate. But I
don't think amplifier has damaged because in this usrp we have
four independent channels and when we connected the splitter to
unused channels then also we got wrong data. What can go wrong
that USRP is streaming data but phases are wrong? What do you
think? Please let me know.
Regards,
Koyel
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Does it look better again when you reduce the gain?
What is the magnitude of the signals going to the RX ports?
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