Invalid IQ Rate in RFmx Soft Front Panel Measuring a 5G NR Signal

Updated Feb 15, 2022

Reported In

Hardware

  • PXIe-5840

Software

  • RFmx
  • RFmx NR

Issue Details

I am using my PXIe-5840/1 with the RFmx soft front panel to take several measurements of a 5G NR signal. I am taking ACP and EVM measurements. When I configure the NR setting of Bandwidth to the value of 400 MHz, I receive the following error message:
 
NationalInstruments.RFmx.NRMX: -1074097882:
Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.
 
Property: IQ Rate
Requested Value: 1475350000
Minimum Value: 19073.4863281
Maximum Value: 1250000000
Error code: -1074097882
 
Why am I getting this error and how can I resolve it?

Solution

This device cannot run an ACP measurement in parallel with the EVM measurement when these settings are selected. However, if you disable the EVM measurement by going to Measurements -> ADD / REMOVE (see image below), the error goes away and the ACP measurement can be configured with 400 MHz bandwidth.
 


This happens because the RFmx driver has the capability of running several measurements at the same time. However, when two or more measurements run in parallel, the driver must ensure that the measurements are configured with a set of settings that is compatible with all the measurements running in parallel. Also, measurements can be configured with several sets of settings to allow them more flexibility. The ACP measurement can only accept 400 MHz bandwidth with a specific configuration of the task, but that configuration is not compatible with the EVM measurement. Therefore, when both measurements run in parallel, the driver will never configure the ACP measurement in a way it accepts this setting. Disabling the EVM measurement allows the driver to select the configuration compatible with the 400 MHz bandwidth option.
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