National Instruments NI Spectral Measurements Toolkit - Manual (Page 7)

© National Instruments Corporation 7 NI Spectral Measurements Toolkit User Guide
For an averaged power spectrum with zoom, use the SMT Zoom Power
Spectrum VI. For an averaged FFT spectrum, which has a complex
output for magnitude and phase calculations, use the SMT Zoom FFT VI
first and then the SMT Averaged FFT Spectrum VI. If you have two
channels of input time-domain data and want cross power spectrum or
frequency-response measurements, use the SMT Zoom FFT Spectrum VI
first and then the SMT Averaged Cross Spectrum VI or the SMT Averaged
Frequency Response VI.
Using LabVIEW Spectral Measurements Examples
This section describes some of the examples located in the < LabVIEW>\
examples\Spectral Measurements Toolset folder. If you are
programming in C, refer to the Using LabWindows/CVI Spectral
Measurements Examples section.
SMT Simulation Examples
The Simulation folder contains examples that are hardware-independent
and use a simulated signal generated by the host computer. All examples
contain the word “simulated” in their names.
SMT Spectrum Analyzer (simulated)
The SMT Spectrum Analyzer (simulated) VI demonstrates how to
use SMT VIs to build a spectrum analyzer with zoom and averaging
capabilities. This VI is located in the
Simulation folder inside the
Spectral Measurements Toolset folder.
The SMT Config Zoom FFT VI specifies the zoom settings, returning
the SMT zoom settings cluster. This cluster is wired to the SMT zoom
settings parameter of the SMT Zoom Power Spectrum VI. The spectral
info cluster that the SMT Zoom Power Spectrum VI returns is wired to the
spectral info parameter on the SMT Spectrum Unit Conversion VI.
In this example, the spectrum settings parameter specifies the zoom
settings in terms of center frequency, span, and RBW. The example uses the
default value for the resolution bandwidth, –1.00,
which implies that the
software calculates the RBW value based on other inputs to the
configuration VIs. The SMT Config Zoom FFT VI, located on the SMT
Advanced palette, uses these settings to recommend an acquisition size.
This VI also returns the actual spectrum settings, which appear directly
below the spectrum graph. In the example, the SMT Config Zoom FFT VI
calculates span as 4.96 MHz and the resolution bandwidth as 30.88 kHz.