Re: [Discuss-gnuradio] Using the USRP LFRX daughterboard to receive a complex baseband signal (I+Q)

[Josh Blum]

The current USRP API does not support receiving complex signal (I on RXA 
and Q on RXB) from LFRX and BasicRX boards. At least not in an easy way...

In the future, the USRP API will support complex samples, and 
"usrp_dual_source_x" will have an option called antenna: "RXAB"

Any word on this from developers?

Einar Thorsrud wrote:
> Hi all,
>
> I am having difficulties understanding how to combine the two signals on 
> the RXA and RXB connectors on the same LFRX-daughterboard to one single 
> complex signal (I+Q) using the "usrp_dual_source_x" block.
>
> The best would be to receive a float from each, and then combine the two 
> signals to a complex signal using the "gr_float_to_complex" block. 
> However it seems it is only possible to get the samples as short or 
> complex, so my idea is to take the real part of each of the two 
> “complex” signals (as they in reality are real), and combine those to 
> complex using the above mentioned block.
>
> This method involves some seemingly unnecessary conversions, so I am 
> guessing that there is another way?

Its not ideal, but thats the way to do it for now.

USRP dual source -> 2 convert complex to float -> combine 2 floats with 
"gr_float_to_complex"

:-(

-Josh

> - Einar
>
>
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