National Instruments NI Spectral Measurements Toolkit, User Manual

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NI Spectral Measurements Toolkit User Guide 8 ni.com
The averaging parameters cluster specifies the following settings:
• Averaging type, such as vector averaging, RMS averaging,
or peak hold
• Weighting type, such as linear or exponential
• Averaging size
The linear weighting mode parameter specifies a type of linear weighting.
The SMT Zoom Power Spectrum VI, located on the SMT Advanced
palette, returns the spectrum in units of V
2
rms
.
The unit conversion settings parameter specifies the units in which to
display the spectrum. For example, you can set units to dBm , peak scaling
to RMS , and psd? to
on
to view the power spectrum as power spectral
density (PSD).
The spectrum parameter is a waveform graph that shows the spectrum of
the simulated signal, which is a 12.00 MHz sine wave with added white
noise. The center of the spectrum appears at 12.00 MHz, the center
frequency, and the spectrum spans from 9.523 MHz to 14.483 MHz.
Use the
peak search settings parameter to find the peaks in the example
spectrum. In the parameter, specify whether to find Single Max Peak or
Multiple Peaks , and enter the threshold level value above which a peak is
valid. The peak threshold level uses the same unit of measurement as the
spectrum.
The number of peaks parameter shows the number of peaks that meet the
threshold criteria, and the peaks parameter shows the frequency and Y-axis
values for these peaks.
SMT ACP (simulated)
The SMT ACP (simulated) VI demonstrates how to use SMT VIs
to perform measurements on a spectrum. This VI is located in the
Simulation
folder. The example shows one specific measurement, the
adjacent channel power (ACP). You can also perform other measurements,
such as power in band and occupied bandwidth (OBW).
The example uses the SMT Config Zoom FFT VI to configure the zoom
FFT. The
SMT zoom settings parameter from the SMT Config Zoom FFT
VI is wired to the SMT zoom settings parameter of the SMT Zoom Power
Spectrum VI. The example performs the ACP measurement on the raw
power spectrum before the unit conversion.
Note Perform the adjacent channel power measurement on an unscaled power spectrum
before calling the SMT Spectrum Unit Conversion VI.