USER GUIDE NI Spectral Measurements Toolkit This document explains how to use the NI Spectral Measurements Toolkit (SMT) in LabVIEW and LabWindows measurements. Contents Conventions ... 2 Using the Spectral Measurements Toolkit ... 3 SMT Programming Flow Diagram ... 5 Using LabVIEW Spectral Measurements Examples ...
Italic text in this font denotes text that is a placeholder for a word or value monospace italic that you must supply. NI Spectral Measurements Toolkit User Guide Averaged Cross Spectrum ...28 Averaged Frequency Response ...29 Unit Conversion...29 Peak Search and Amplitude/Frequency Estimation ...31...
LabVIEW. Analog modulation—The Spectral Measurements Toolkit supports analog modulation to perform amplitude, frequency, and phase modulation and demodulation. Functions and VIs are included to perform upconversion and downconversion on baseband and passband signals. NI Spectral Measurements Toolkit User Guide...
For more information about supported hardware, refer to the NI Spectral Measurements Toolkit Readme, located at Start»All Programs»National Instruments» Spectral Measurements. For simplicity, this document pertains only to using VIs in the LabVIEW...
Enter the time-domain data into the SMT Basic Zoom Power Spectrum VI. This VI specifies the zoom settings in terms of only center frequency and span. The VI performs zoom FFT processing and returns a power spectrum in units V NI Spectral Measurements Toolkit User Guide...
Complete the following steps when using the advanced-level VIs of the programming flow diagram in the SMT Programming Flow VI: NI Spectral Measurements Toolkit User Guide Enter the output power spectrum into an SMT measurement VI and/or use the SMT Spectrum Unit Conversion VI as follows:...
Perform the adjacent channel power measurement on an unscaled power spectrum Note before calling the SMT Spectrum Unit Conversion VI. NI Spectral Measurements Toolkit User Guide Averaging type, such as vector averaging, RMS averaging, or peak hold Weighting type, such as linear or exponential...
The standard FFT, shown in the upper graph, indicates a single peak, and the zoom FFT, shown in the lower graph, indicates the presence of two separate tones in the signal. NI Spectral Measurements Toolkit User Guide samples\ ni.com...
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Figure 2. Zoom FFT Technique df = f /N = 1/T is the frequency of the sampled signal T is the time duration N is the number of samples or increase N to improve df. NI Spectral Measurements Toolkit User Guide...
The continuous zoom FFT shifts a high-frequency signal into the baseband before adjusting the sample rate. NI Spectral Measurements Toolkit User Guide /M. The antialias filter has a cutoff /(2 × M) because the Nyquist frequency has decreased by...
VI, either reduce the acquisition rate or use the block zoom technique. NI Spectral Measurements Toolkit User Guide updates like a block zoom FFT and waits for the VI by reusing the last half of the...
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The VI also has advanced parameters for specifying the spectrogram, including window, resolution bandwidth, RBW definition, frequency points, time points, and NI Spectral Measurements Toolkit User Guide Time Span Time (µ s ) Figure 5.
• • • NI Spectral Measurements Toolkit User Guide center frequency must fall within the effective band of the input signal. The effective band is the frequency band in which the data from the input signal is valid. You can use the effective band to exclude the roll-off region of an analog antialiasing filter from consideration.
The default value of RBW definition is 3 dB. NI Spectral Measurements Toolkit User Guide Figure 8. Main and Side Lobes of a 7-Term Blackman-Harris Window ni.com...
The choice of RBW depends on a number of factors, such as the spacing between the two tones that you want to identify and the amplitude of these tones. NI Spectral Measurements Toolkit User Guide df = f /N = 1/T...
When you apply a zoom FFT VI to a signal, you receive the complex FFT spectrum. The spectrum domain averaging functions can operate on the FFT spectrum to return different types of spectra, such as averaged FFT spectrum, power spectrum, cross spectrum, and frequency response. NI Spectral Measurements Toolkit User Guide ni.com...
X and its averaged output Y. Each complex frequency of spectrum X in magnitude to its counterpart in Y is retained. The result is a real spectrum. Complex conjugate. is compared . The larger value NI Spectral Measurements Toolkit User Guide...
For linear weighting, For exponential weighting, where N is a user-specified constant that determines how much weight is given to recent data relative to older data. Small values of N place more NI Spectral Measurements Toolkit User Guide Peak-Hold Linear Auto Restart...
Moving average—Average the most recent N measurements. Continuous—Average all measurements taken with equal weight. Table 2. FFT Averaging Methods and Equations Averaging Method Equation = <X> <X conj X ( )> = max(X k – 1 NI Spectral Measurements Toolkit User Guide...
A cross spectrum has no peak-hold average. NI Spectral Measurements Toolkit User Guide Table 3. Averaged Power Spectrum Averaging Methods and Equations Averaging Method = conj(X) × Y = <...
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----------- - ⎝ ⎠ NI Spectral Measurements Toolkit User Guide RMS or peak—An FFT returns an amplitude spectrum scaled such that a frequency bin represents the RMS value of a sine wave at that frequency. A bin can also represent the peak value if you scale the spectrum by Amplitude or power—The power spectrum is the squared magnitude...
You can use the SMT Adjacent Channel Power (Advanced) VI to measure power for an arbitrary number of adjacent channels at user-specified bandwidths and offsets from the center frequency. NI Spectral Measurements Toolkit User Guide . Perform this measurement before ∑...
1% of the signal power is actually located there. Where to Go for Support The National Instruments Web site is your complete resource for technical support. At troubleshooting and application development self-help resources to email and phone assistance from NI Application Engineers.
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Instruments trademarks. Other product and company names mentioned herein are trademarks or trade names of their respective companies. For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software, the patents.txt file on your media, or ni.com/patents.