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Today's Topics:
1. self-interference with wbx (Francois Quitin)
2. self interference with wbx (Francois Quitin)
----------------------------------------------------------------------
Message: 1
Date: Thu, 20 Dec 2012 16:40:08 -0800
From: "Francois Quitin" <[email protected]>
To: <[email protected]>, <[email protected]>
Subject: [USRP-users] self-interference with wbx
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
Dear List,
I am using a USRP-2 with a WBX daughterboard that is operating in full
duplex mode. Both the Tx and Rx gain are cranked up to their maximum values
(tx gain 25 dB, rx gain 30 dB). The Tx and Rx frequencies are about 70 MHz
apart (Tx->964 MHz and Rx->892MHz). I'm having a little trouble with the
self-interference:
- when the Tx chain is sending periodic packets (with 0s in
between), this creates very high noise in my Rx chain (up to 0.01 on
gnuradio companion scope)
- when the Tx chain is sending a continuous pilot tone, there is no
noise in my Rx chain (noise is lower than 0.0005 on gnuradio companion
scope)
I would like that, when transmitting periodic packets, the noise would be as
low as when transmitting a continuous pilot tone. I understand that periodic
packets would create noise in a wider band than the periodic tone, but
still, my Tx and Rx frequencies are very far apart. Is there some automatic
gain in the USRP that is playing tricks here? If so, is there a way to solve
this?
Any input is appreciated,
Thanks a lot,
Francois
PS: for our application, we had to turn the DUC cordic off. But even with
the DUC cordic enabled, I still observe similar trends, so I don' suppose
that would matter. We also had to put the Clock source to "external" to
avoid the automatic clock correction (but again, putting it to "Default"
didn't change a thing).
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Message: 2
Date: Thu, 20 Dec 2012 16:44:34 -0800
From: "Francois Quitin" <[email protected]>
To: <[email protected]>
Subject: [USRP-users] self interference with wbx
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
Dear List,
I am using a USRP-2 with a WBX daughterboard that is operating in full
duplex mode. Both the Tx and Rx gain are cranked up to their maximum values
(tx gain 25 dB, rx gain 30 dB). The Tx and Rx frequencies are about 70 MHz
apart (Tx->964 MHz and Rx->892MHz). I'm having a little trouble with the
self-interference:
- when the Tx chain is sending periodic packets (with 0s in
between), this creates very high noise in my Rx chain (up to 0.01 on
gnuradio companion scope)
- when the Tx chain is sending a continuous pilot tone, there is no
noise in my Rx chain (noise is lower than 0.0005 on gnuradio companion
scope)
I would like that, when transmitting periodic packets, the noise would be as
low as when transmitting a continuous pilot tone. I understand that periodic
packets would create noise in a wider band than the periodic tone, but
still, my Tx and Rx frequencies are very far apart. Is there some automatic
gain in the USRP that is playing tricks here? If so, is there a way to solve
this?
Any input is appreciated,
Thanks a lot,
Francois
PS: for our application, we had to turn the DUC cordic off. But even with
the DUC cordic enabled, I still observe similar trends, so I don' suppose
that would matter. We also had to put the Clock source to "external" to
avoid the automatic clock correction (but again, putting it to "Default"
didn't change a thing).
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