CFR Configurations

NI-RFmx Waveform Creator 3.0 Help

Edition Date: January 2019

Part Number: 377064E-01

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The following controls are available in CFR tab.

CFR Apply: Specifies whether to apply crest factor reduction (CFR).

Note Note   CFR is only supported in LTE, NR, and Multi Carrier plugin.

CFR is applied per carrier set.

CFR Method: Specifies the method used to perform CFR when you select the CFR Apply checkbox.

NI-RFmx Waveform Creator supports two CFR methods, Clipping and Peak Windowing. The default value is Clipping.

Clipping

When the Clip Using control is set to Level, the I and Q values of a waveform are clipped.

With clipping enabled, the I and Q values will be clipped depending on the settings specified.

  • If the clipping type is Circle, the overall IQ Vector will be clipped to the percentage specified.
  • If the clipping type is Square, the I and Q values will be individually clipped to the percentage specified.

There is an option to apply the clipping parameters before filtering has been applied, or after.

Note Note  Clip using level behavior is the same as clipping function under IQ Impairments tab. Only for LTE, NR, and multi carrier plugin, clipping is available in CFR tab.

When the Clip Using control is set to Target PAPR, the signal is hard clipped such that the target PAPR is achieved.

Target PAPR: Specifies the target peak-to-average power ratio when you select the CFR Apply checkbox. This value is expressed in dB. The default value is 8.00 dB. Valid values are 1 dB to 100 dB.

Max Iterations:Specifies the maximum number of iterations allowed to converge waveform PAPR to target PAPR, when you select the CFR Apply checkbox. The default value is 10. Valid values are 1 to 1000.

Filter Enabled: Specifies whether to enable the filtering operation when you select the CFR Apply checkbox. The default value is Disabled.

Note Note  CFR filter is applied per sub block. Sub Block parameters as specified in Multi-Carrier tab are considered for computations.
In Multi Carrier plugin, CFR filter is applied per input waveform. Frequency Offset and Bandwidth specified per carrier(input waveform) are considered for computations.

Peak Windowing

Peak windowing scales the peaks in the signal using weighted window function to get smooth peaks and achieve the target PAPR.

Window Type: Specifies the window type to be used when you select the CFR Apply checkbox and set CFR Method control to Peak Windowing.
The default value is Kaiser-Bessel Window.

  • Flat Top Window - Uses the flat top window function to scale peaks.
  • Hanning Window - Uses the Hanning window function to scale peaks.
  • Hamming Window - Uses the Hamming window function to scale peaks.
  • Gaussian Window - Uses the Gaussian window function to scale peaks.
  • Blackman Window - Uses the Blackman window function to scale peaks.
  • Blackman Harris Window - Uses the Blackman-Harris window function to scale peaks.
  • Kaiser Bessel Window - Uses the Kaiser Bessel window function to scale peaks.

Window Length: Specifies the maximum window length to be used when you select the CFR Apply checkbox and set CFR Method control to Peak Windowing. The default value is 10. Valid values are 1 to 1024.

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