[USRP-users] looping the USRP2 in Simulink

Sacha Vrazic vrazic at free-impulse.com
Mon Nov 29 04:39:02 EST 2010

Hello everyone!

I am using one USRP2 board with LFRX and LFTX daughter boards inside.
I want to check if the symbols I sent are well received. For that purpose I
made 2 simulink models (one for transmitter and one for receiver), I use a
QPSK modulation and a carrier frequency of 2 MHz.
I also connect the Tx out to the Rx In with a coaxial cable.

Unfortunately I cannot get the correct at the receiver the symbols I
transmitted. When I observe the receive constellation (under simulink), it
looks like there a phase problem or fading. But I do not understand because
in that case the channel is reduced to a 20 cm coaxial cable.
So I come with several questions:

* Is the Rx output baseband or at an Intermediate frequency?
* Is the power of the signal enough at the entrance of the receiver when
* Could it be a phase problem between transmitter and receiver?

If you have any idea or suggestions how to solve this issue, I would be

Thank you!


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