Set sub-device specification

[Bernhard_S]

Dear all,

I'm using my USRP with a LFRX daughterboard. For some tests I would like to configure the system to use one of the RF connectors with the IF interface, instead of using both connectors with the IQ interface. I tried to change the "Active Antenna" Property but this doesn't show any reaction. As far as I have seen in the documentations, the LFRX Daughterboard uses the sub-device specification to establish the routing of ADC/DAC samples to the DSP chain within the FPGA, instead of using the antenna specification, which could be the reason for this.

Does anyone know if there is a possibility to define the sub-device specification using LabVIEW?

Thank you,

Bernhard

[Sarah_Y]

Hey Bernhard,

You are correct, there is not a way to define the sub-device in LabVIEW.  The antenna name won't change the data being collected.  The driver will always collect both sub channels, storing the data in the form x + jy, where x is the data from one sub channel and y is the data from the other sub channel.  If you are only interested in looking at one sub channel of data, it is easy to do.  You can split the received signal up and look at each channel by itself.  Here is a block diagram that I have used to do this with BasicRX boards:

[Anthony_F]

That's a great idea Sarah,

I would image transmitting would be a similar process, correct?

[Sarah_Y]

Yup!  Anthony's image above will work if you have a BasicTX and only want to transmit on one sub channel.

[Bernhard_S]

Hi Sarah,

Thanks for your responce. This sounds like a really good solution and I'm sure that it can be quite usefull for me in the future. But for my current problem I actually would like to measure a signal on one of the SMA connectors, independendly from the signal that is present on the second SMA connector of the LFRX. I think this is not possible with the solution you provided to me. Do you maybe have any idea how to solve this?

Thank you,

Bernhard

[Sarah_Y]

Hey Bernhard,

I attached a pdf file with 3 images.  The images were saved from the 3 FFT plots being generated using the block diagram that I posted above.  I input a 21 MHz tone into RX_B on my BasicRX (same idea as the LFRX).  There is no signal being input on RX_A.  You can see that I am collecting the data from RX_B independently from RX_A.  It is possible that there will be interference from one channel to the other, but this is how you can use the driver to collect your data.  Let me know if I am misunderstanding what you are trying to accomplish and I'll do what I can to get you up and running!

[Bernhard_S]

Hi Sarah,

In my application I'm receiving two signals operating on the same carrier frequency. The basic idea is to use the received IQ data for further signal processing. In addition to this I would like to measure the peak voltage of the signal that is received by RX_B. I tried the block diagram you suggested to receive the data independently from each other but this doesn't seem to work. I attached a pdf that shows the output of the three FFT plots from an example signal I have input to RX_A. There is no input on RX_B. Anyhow the spectrum for CHA and CHB looks quite similar to me.

Kind regards,

Bernhard

[giube]

Hi all,

I re-open an old thread because I'm currently beginning to work in a similar case.

Thank you for your posts.

I'm using a USRP2 board with a LFRX-LF daughterboard for receiving a signal with only one RF port connected.

To me is not clear if there are strings (which ones?) to use to set the correct parameters of LFRX-LF through the "Configure Signal.vi".

I currently use "RX-A" but I'not sure there is a difference if I use other strings, such as "RXA" or "A" or "A:A" in order to acquire the signal from the only RF port I use...

Could anyone help me please?