Hello All,

I have a USRP x300 and I want to build my custom image. I would like to
drive an array of 4 Tx/Rx antennas in the HF band for ionospheric research,
i.e beam steering monostatic pulse radar.

This is my idea for a custom built:

Since I will use 4 daughterboards 2 LFTX and 2 LFRX mounted on the X300.
Each LFTX or LFRX have 2 port that can be used independently or as a single
I/Q input. I will use it independently. Then, I will have available 4 Rx
ports and 4 Tx ports. The Radio connections would be the following:

For the receiver chain: Radio 0 port 0, Radio 0 port 1, Radio 0 port 2 and
Radio 0 port 3 would be connected to an adder, the output of the adder to a
DDC chain, and the output of the DDC chain to a streamer. In that way all 4
Rx signal would be summed before passing through the DDC chain and I would
save space in FPGA.

For the transmitter chain the only difference is that I would connect the
output of the DUC to a delay line filter and from there extract the 4
outputs to the 4 Tx ports available on the daughterboards. This delay line
should be configurable since from there I would change the steering of the
beam.

Also I would like to use only one 1Gb Ethernet and not both, so I could
save FPGA space. In summary this would be the rfnoc blocks: 2 Radio
interfaces, 1 DDC, 1DUC, 1 custom delay line block, and only 1Gb interface.
I think this may occupy less space than the default image.  One of the many
doubts that I have is about the radio interfaces, in the default image
these radio interfaces have only 2 port, for example Radio 0:0 and Radio
0:1, but I would need also Radio 0:2 and Radio 0:3. The same for Radio 1: 0
to 3. Because I will use all the ports availables in the doughterboards.

I know this is a general and tricky question and I apologize in advance.
But any any help would be very appreciated.

Best,
German

Hi,

It may help to review "Table 2 - Ettus Research Daughterboard Characteristics” at https://kb.ettus.com/Selecting_a_RF_Daughterboard

In short, BasicRX/LFRX can be configured for dual Rx. I’ve done this using the existing UHD image in an X310 to get 4 channel phase coherent reception in GNU Radio. But, LFTX and BasicTX boards can do only 1 Tx, so max of 2 Tx in an X310. Someone who knows RFNoC and Ettus gear could comment on what would need to change to accomplish your goal for Tx.

HTH,
Richard

On Dec 18, 2023, at 12:51, German Farinas german.farinas@gmail.com wrote:

Hello All,

I have a USRP x300 and I want to build my custom image. I would like to drive an array of 4 Tx/Rx antennas in the HF band for ionospheric research, i.e beam steering monostatic pulse radar.

This is my idea for a custom built:

Since I will use 4 daughterboards 2 LFTX and 2 LFRX mounted on the X300. Each LFTX or LFRX have 2 port that can be used independently or as a single I/Q input. I will use it independently. Then, I will have available 4 Rx ports and 4 Tx ports. The Radio connections would be the following:

For the receiver chain: Radio 0 port 0, Radio 0 port 1, Radio 0 port 2 and Radio 0 port 3 would be connected to an adder, the output of the adder to a DDC chain, and the output of the DDC chain to a streamer. In that way all 4 Rx signal would be summed before passing through the DDC chain and I would save space in FPGA.

For the transmitter chain the only difference is that I would connect the output of the DUC to a delay line filter and from there extract the 4 outputs to the 4 Tx ports available on the daughterboards. This delay line should be configurable since from there I would change the steering of the beam.

Also I would like to use only one 1Gb Ethernet and not both, so I could save FPGA space. In summary this would be the rfnoc blocks: 2 Radio interfaces, 1 DDC, 1DUC, 1 custom delay line block, and only 1Gb interface. I think this may occupy less space than the default image.  One of the many doubts that I have is about the radio interfaces, in the default image these radio interfaces have only 2 port, for example Radio 0:0 and Radio 0:1, but I would need also Radio 0:2 and Radio 0:3. The same for Radio 1: 0 to 3. Because I will use all the ports availables in the doughterboards.

I know this is a general and tricky question and I apologize in advance. But any any help would be very appreciated.

Best,
German

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