Unexpected Frequency Spectrum From NI USRP 2945

Updated May 1, 2023

Reported In

Hardware

  • USRP-2945
  • USRP-2955

Issue Details

I am using NI USRP 2945 to receive a single tone from the Agilent RF waveform generator and observing the received signal frequency spectrum using the example available in the default NI-USRP Simple Streaming project. However, instead of showing a single tone, the spectrum is showing various frequencies and elevated noise floors.
 

Solution

If the received signal is undergoing a (external link) clipping effect, the spectrum will have a number of harmonics instead of a single tone. Reducing the power from the RF generator and/or the preamplification gain of the USRP will bring the power levels within the ADC range and resolve the clipping of the input signal.
 

Additional Information

Very high input power levels can also damage the analog signal path of an RF device. Please check the device datasheet for the maximum input power range. If necessary, use the attenuators to lower the power levels of the input signal before it enters the device receive chain.
 

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