National Instruments NI Spectral Measurements Toolkit User Manual Page 1

USER GUIDENI Spectral Measurements ToolkitThis document explains how to use the NI Spectral Measurements Toolkit (SMT) in LabVIEW and LabWindows™/CVI™

NI Spectral Measurements Toolkit User Guide 10 ni.comCross Power Spectrum MeasurementThe Cross Power Spectrum Measurement example is located at sample

© National Instruments Corporation 11 NI Spectral Measurements Toolkit User GuideFigure 2. Zoom FFT TechniqueFFT algorithms usually perform baseband

NI Spectral Measurements Toolkit User Guide 12 ni.comContinuous Zoom FFTContinuous zoom FFT is a technique for quickly analyzing data as it arrives. A

© National Instruments Corporation 13 NI Spectral Measurements Toolkit User GuideThe continuous zoom FFT technique is sometimes called the real-time z

NI Spectral Measurements Toolkit User Guide 14 ni.comBlock Zoom FFTUse a block zoom FFT in situations when you cannot access data until the data acqui

© National Instruments Corporation 15 NI Spectral Measurements Toolkit User GuideThe block zoom FFT is a general-purpose technique that works best as

NI Spectral Measurements Toolkit User Guide 16 ni.comFigure 5. Spectrogram Process ExampleThe SMT Config Zoom STFT VI specifies the spectrogram in te

© National Instruments Corporation 17 NI Spectral Measurements Toolkit User Guideeffective band specification. If you leave the default advanced param

NI Spectral Measurements Toolkit User Guide 18 ni.comConfiguring Zoom FFT VIsWhen using Spectral Measurements Toolkit VIs, you must enter several valu

© National Instruments Corporation 19 NI Spectral Measurements Toolkit User GuideThe left side of Figure 7 shows examples of the four combinations of

NI Spectral Measurements Toolkit User Guide 2 ni.comAveraged Cross Spectrum ...28Averaged

NI Spectral Measurements Toolkit User Guide 20 ni.comthat is outside the effective band, the span changes to the default value, which is the center of

© National Instruments Corporation 21 NI Spectral Measurements Toolkit User GuideFigure 8 shows the shape of the equivalent filter corresponding to a

NI Spectral Measurements Toolkit User Guide 22 ni.comThe acquisition size comes from the following basic relationship:df = fs/N = 1/Twhere N is equal

© National Instruments Corporation 23 NI Spectral Measurements Toolkit User GuideFigure 9 shows the spectrum of a multitone signal calculated using tw

NI Spectral Measurements Toolkit User Guide 24 ni.comSpectral Domain AveragingAveraging is an important part of spectrum-domain measurements because o

© National Instruments Corporation 25 NI Spectral Measurements Toolkit User GuideThe averaging VIs require that you enter an FFT spectrum as a complex

NI Spectral Measurements Toolkit User Guide 26 ni.comAveraging OptionsFigure 10 illustrates the options available for spectrum averaging.Figure 10. S

© National Instruments Corporation 27 NI Spectral Measurements Toolkit User Guideemphasis on the most recent data. The averages sofar parameter stops

NI Spectral Measurements Toolkit User Guide 28 ni.comAveraged Power SpectrumThe following equations describe the averaging methods you can apply to a

© National Instruments Corporation 29 NI Spectral Measurements Toolkit User GuideAveraged Frequency ResponseIf you have a stimulus to a system with sp

© National Instruments Corporation 3 NI Spectral Measurements Toolkit User GuideUsing the Spectral Measurements ToolkitThe Spectral Measurements Toolk

NI Spectral Measurements Toolkit User Guide 30 ni.comSpectrum scaling options are combinations of the following options:• RMS or peak—An FFT returns a

© National Instruments Corporation 31 NI Spectral Measurements Toolkit User GuidePeak Search and Amplitude/Frequency EstimationThe SMT Spectrum Peak S

NI Spectral Measurements Toolkit User Guide 32 ni.comPower in BandThe SMT Power in Band VI, located on the SMT Measurements palette measures the total

© National Instruments Corporation 33 NI Spectral Measurements Toolkit User GuideFigure 12 illustrates a typical ACP measurement and the three paramet

NI Spectral Measurements Toolkit User Guide 34 ni.comFigure 13 shows an example of an OBW measurement. The logarithmic amplitude scale gives the appea

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NI Spectral Measurements Toolkit User Guide 4 ni.comIntegrating the Spectral Measurements ToolkitYou can use the Spectral Measurements Toolkit for the

© National Instruments Corporation 5 NI Spectral Measurements Toolkit User GuideSMT Programming Flow DiagramProgramming flow diagrams are flowcharts t

NI Spectral Measurements Toolkit User Guide 6 ni.com2. Enter the output power spectrum into an SMT measurement VI and/or use the SMT Spectrum Unit Con

© National Instruments Corporation 7 NI Spectral Measurements Toolkit User GuideFor an averaged power spectrum with zoom, use the SMT Zoom Power Spect

NI Spectral Measurements Toolkit User Guide 8 ni.comThe averaging parameters cluster specifies the following settings:• Averaging type, such as vector

© National Instruments Corporation 9 NI Spectral Measurements Toolkit User GuideThe channel specification parameter specifies the center frequency, ba