Understanding usrpe3xxToneReceiverML.m example

Hallo, I can not understand the above mentioned SDR example. They use a DDS inside the FPGA for the creation of the TX signal. From my point of view the dds signal is send to the tx front end and is received by the rx frontend. So actually I need a connection between the tx and rx front end. But when I test this example on my E312 device I can also see a correct spectrum and wave plot with terminated front ends. How is that possible? Is the produced DDS signal send to the rx signal stream path inside the FPGA without using the rf card? Thanks for your answer! Regards, Tobias

[Jan]

I assume you are talking about https://mathworks.com/examples/matlab-communications/mw/usrpembeddedseriesradio_product-usrpe3xxToneReceiverML-reception-of-a-tone-signal-using-usrp-reg-e310 .

[Tobias Störch]

Yes, thats right. Sorry when I was a little bit imprecisly.

Answer 1

[Nick Choi]

In the 'Transmit a Tone Signal from the FPGA' section of the example, there is a line that says "Note that the simultaneous transmission and reception of data from MATLAB to RF card (duplex) is currently not supported. Therefore, for this example the data is generated in FPGA using DDS and transmitted directly to the RF card. MATLAB is only used for signal reception"

https://www.mathworks.com/help/supportpkg/usrpembeddedseriesradio/examples/reception-of-a-tone-signal-using-usrp-r-e310.html?s_tid=answers_rc2-1_p4_MLT#d118e2939

Based off of this description, I would say that the data signal would be going from the FPGA to the RX of the RF card.

[Tobias Störch]

Hey, thanks for your answer! I interpret this statement in a way that the data generated by the DDS are send to the TX stream of the RF card and the DDS on the FPGA is used for transmitting because MATLAB is not able to transmit and receive at the same time. Furthermore, also the following statement in the hardware description part of the example implies that: "... Connect an loopback cable with attenuation between TRx-A and RX2-A or attach appropriate antenna suitable for 2.4 GHz band." So my suggestion is that there is a possibility to switch the data stream of the DDS in a way, that it is streamed directly to the RX or to the TX signal path on the RF card. Any ideas?