National Instruments Toolkit Using LabVIEW Spectral Measurements Examples

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.

The Simulation folder contains examples that are hardware-independent

and use as imulated signal generated by the host computer. All examples

contain the word “simulated” in their names.

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

defaultvalue 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 30.88kHz.