Calculates the power spectrum of a signal that is unevenly spaced in time. Details
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XTime is the discrete- and unevenly-spaced times. |
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X represents the data material at times XTime. There is a one-to-one relation between XTime and X. |
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Power Spectrum FFT {X} Frequency are the frequency points at which the power spectrum is calculated. |
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Power Spectrum FFT {X} is the power spectrum, in the sense of the Lomb normalized periodogram. |
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error returns any error or warning from the VI. Refer to Signal Processing Error Codes for more information about these conditions. |
The algorithm used is based on the Lomb normalized periodogram. Let the data be given at the time points
. In other words,
and
.
Furthermore,
and
.
Then the Lomb normalized periodogram is defined as
,
with
The following diagram shows the Fourier transform of length 256 of a signal that has been sampled at unequal intervals of time. The signal is a combination of sine waves of frequencies 20, 40, 60, and 80 Hz. The duration of the signal is 1 sec. The sampling frequency was chosen as 256 Hz, giving the frequency resolution of 1 Hz.