USRP Carrier Frequency

[kman0111]

Hello, I am using USRP-2954R, and I am testing transmission and reception using the example of Labview 2023 version. (niUSRP EX QAM Tx.vi / niUSRP EX QAM Rx.vi)

If I set the transmission carrier frequency in 'niUSRP EX QAM Tx.vi' to 500MHz or less, the Carrier frequency I entered is the same as the Actual Carrier Frequency, but if I set it to 500MHz or more, the frequency lowered by 2GHz is set as the Actual Carrier Frequency. (0.5GHz -> -1.5GHz, 2GHz -> 0Hz, 4GHz -> 2GHz)

I hope you guys can give me an answer as to what is causing the above phenomenon. The UBX-160, the daughter board included in the 2954R, seems to change its circuit path starting on 500MHz. I wonder if this is the reason, but it is not clear.

[mikiofuku]

I tried it and had no problems on LabVIEW 2022 Q3 and NI-USRP 2022 Q4.

Which version of LabVIEW and NI-USRP did you use?
What's the difference between the setting value and the read back value?

[kman0111]

I use Labview 2023 Q3, and NI-USRP 2023 Q3. and I confirmed that UBX-160 daughter board is connected with 2954r.

If I set setting frequency to 500MHz or more, the frequency lowered by 2GHz is set as the Actual Carrier Frequency. (0.5GHz -> -1.5GHz, 2GHz -> 0Hz, 4GHz -> 2GHz)

Under 500 MHz of setting frequency, the actual frequency is same with the setting frequency. 

I attached the capture file for three cases. (400MHz, 1GHz, 3GHz)

[mikiofuku]

Hi

I've been involved with USRP for over 10 years, but this is the first time I've seen this problem.

It may be a bug in NI-USRP 2023 Q3. Why not try downgrading to NI-USRP 2022 Q4?

[kman0111]

Thank you so much for suggesting the solution. I'll try it.

I am beginner in usrp and labview... If I just install the NI-USRP driver as an older driver, will it automatically downgrade?

[mikiofuku · Accepted solution]

Uninstall NI-USRP 2023 and then install the new one. For uninstallation, use NI Package manager.

[kman0111]

Labview 2023 Q3 + NI-USRP 2022 Q4 => USRP example VIs are missing in Functions tab (which can be opened by right click in block diagram) (I think the reason should be that the version of NI-USRP is older than the Labview...)

Labview 2021 SP1 + NI-USRP 2022 Q4 => Works

Really thank you for providing the solution.

[mikiofuku]

Good!

NI-USRP Examples are here.

click "Windows Start button"=>search "NI-USRP Examples"

or

C:\Program Files (x86)\National Instruments\LabVIEW 2022\examples\instr\niUSRP

or

C:\Program Files\National Instruments\LabVIEW 2022\examples\instr\niUSRP

[SorenF]

Hi,

I am facing the same problem with a different setup.

I am on a Linux machine and hardware is an X300 with a UBX160.

When I am above 500 MHz the actual carrier freq becomes about 2000 MHz smaller. I checked it with the uhd example script  tx_waveforms that comes with the uhd install. Below is the output. Note that actual frequency is negative. There is no output at 915 MHz on a spectrum analyser. Below 500 MHz everything is fine.

Is there a way to downgrade the firmware to test? Is NI aware of the problem?

Thanks

Soren

$ ./tx_waveforms --freq 915e6 --rate 5e6 --gain 0

Creating the usrp device with: ...
[INFO] [UHD] linux; GNU C++ version 13.1.0; Boost_107400; UHD_4.4.0.0+ds1-4
[INFO] [X300] X300 initialization sequence...
[INFO] [X300] Maximum frame size: 1472 bytes.
[INFO] [X300] Radio 1x clock: 200 MHz
Using Device: Single USRP:
Device: X-Series Device
Mboard 0: X300
RX Channel: 0
RX DSP: 0
RX Dboard: A
RX Subdev: UBX RX
RX Channel: 1
RX DSP: 1
RX Dboard: B
RX Subdev: Unknown (0xffff) - 0
TX Channel: 0
TX DSP: 0
TX Dboard: A
TX Subdev: UBX TX
TX Channel: 1
TX DSP: 1
TX Dboard: B
TX Subdev: Unknown (0xffff) - 0

Setting TX Rate: 5.000000 Msps...
Actual TX Rate: 5.000000 Msps...

Setting TX Freq: 915.000000 MHz...
Setting TX LO Offset: 0.000000 MHz...
Actual TX Freq: -1085.000002 MHz...

Setting TX Gain: 0.000000 dB...
Actual TX Gain: 0.000000 dB...

[WARNING] [0/Radio#0] Attempting to set tick rate to 0. Skipping.
Setting device timestamp to 0...
Checking TX: TXLO: locked ...
Press Ctrl + C to stop streaming...

[mikiofuku]

Hi

You can upgrade or downgrade your UHD.
Using pybombs is convenient because multiple versions of UHD can coexist. Please see the URL below.

https://files.ettus.com/manual_archive/n310_release-0.1/html/page_build_guide.html#build_pybombs

You may also get better results if you post your questions regarding UHD to the USRP Users mailing list.

https://kb.ettus.com/Mailing_Lists