NI-RFSA Express (Spectrum)

NI RF Vector Signal Analyzers

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NI-RFSA Express (Spectrum)

Configures and acquires data from National Instruments RF signal analyzers using NI-RFSA in Spectrum mode.

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
Configuration Contains the following options:
  • Device—Specifies the RF signal analyzer used. This ring control lists all NI RF signal analyzers installed on this computer that can be used by this Express VI. If you relaunch the VI and the selected RF signal analyzer is dimmed, it is no longer available.
  • Resolution bandwidth (Hz)—Specifies the resolution bandwidth of the spectrum. Resolution bandwidth controls the width of the frequency bins in the power spectrum computed by NI-RFSA. A larger value means the frequency bins are wider, thus you get fewer bins or spectral lines.

    Resolution bandwidth is calculated as the 3 dB bandwidth of the window frequency response.

  • Units—Specifies the units of the acquired spectrum.
  • Reference level (dBm)—Specifies the maximum expected power of the RF signal to be acquired.
  • Attenuation—Specifies whether the attenuation is automatically determined or user-specified.
    • Attenuation (dB)—Specifies the downconverter's overall attenuation of the input RF signal.
  • Specification method—Specifies whether the acquisition frequencies are defined in terms of a start and stop frequency or a center frequency and span.
  • Start frequency (Hz)—Specifies the start frequency of the acquired RF signal. The acquisition consists of a span of data from the start frequency to the stop frequency.
  • Stop frequency (Hz)—Specifies the stop frequency of the acquired RF signal. The acquisition consists of a span of data from the start frequency to the stop frequency.
  • Center frequency (Hz)—Specifies the center frequency of the acquired RF signal. The acquisition consists of a span of data surrounding the center frequency.
  • Span (Hz)—Specifies the span of the acquired RF signal. The acquisition consists of a span of data surrounding the center frequency.
Timing Contains the following options:
  • Reference clock source—Specifies the source of the reference clock signal.
  • PXI Chassis Clk10 source—Specifies the signal driven to the 10 MHz reference clock on the PXI backplane. Only certain combinations of Reference clock source and PXI Chassis Clk10 source are valid.
Advanced Spectrum Contains the following options:
  • Averaging mode—Specifies the averaging mode. Select from RMS, Vector, Peak Hold, or None.
  • Number of averages—Specifies the number of acquisitions to average.
  • Window type—Specifies the FFT window type.
Autoscale graphSpecifies whether to autoscale the Y scale of the graph.

Checked—The Y scale of the graph is autoscaled every time the graph is updated.
Unchecked—The Y scale of the graph remains unchanged when the graph is updated.

Block Diagram Inputs

ParameterDescription
closeDetermines whether the instrument session remains open when the VI finishes execution. Use this parameter for loop optimization by setting it to FALSE on all iterations except the last. The default is TRUE.

Note: This input is not intended for sharing the session between Express VIs. If a loop contains multiple Express VIs that use the same device, you must wire in TRUE for this input.

error inDescribes error conditions that occur before this Express VI runs.

Block Diagram Outputs

ParameterDescription
dataContains the data acquired by the device.
spectral info Contains properties of the acquired spectrum. This output is used by VIs in the Spectral Measurements Toolkit.
error outContains error information. If error in indicates that an error occurred before this Express VI runs, error out contains the same error information. Otherwise, it describes the error status that this Express VI produces.


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