Table Of Contents

Power and Frequency Estimator (G Dataflow)

Version:
    Last Modified: March 15, 2017

    Computes the estimated power and frequency around the peak frequency in the power spectrum of a time-domain signal.

    This node achieves good frequency estimates for measured frequencies that lie between frequency lines on the spectrum. This node also makes corrections for the window function you use.

    connector_pane_image
    datatype_icon

    power spectrum

    The power spectrum of a time domain signal.

    datatype_icon

    peak frequency (max)

    The frequency, usually in Hz, of the frequency peak around which to estimate the frequency and power.

    If you do not wire this input, this node automatically searches for the maximum peak in the power spectrum array and estimates the frequency and power around it.

    Default: -1

    datatype_icon

    window constants

    The window constants for the selected window.

    You obtain window constants from the Window Properties node. You need this input only when you use the spectral density output formats, the last four output unit selections.

    datatype_icon

    eq noise BW

    The equivalent noise bandwidth (ENBW) of the window that was used. You can use this value to divide a sum of individual power spectra of the power spectrum or to compute the power in a given frequency span.

    Default: 1.0

    datatype_icon

    coherent gain

    The inverse of the scaling factor applied to the window.

    Default: 1.0

    datatype_icon

    span

    The number of frequency lines (bins) around the peak to be included in the peak frequency and power estimation.

    Default: 7—which means that the power in three frequency lines before the peak frequency line, the peak frequency line itself, and the three frequency lines after the peak are included in the estimation. This number is adequate for most windows.

    datatype_icon

    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

    datatype_icon

    df

    The frequency interval of the power spectrum.

    Default: 1.0

    datatype_icon

    estimated frequency peak

    The estimated frequency of the peak in the input power spectrum.

    Algorithm for Calculating the estimated frequency peak

    The following equation computes the estimated frequency peak:

    estimated frequency peak = Σ ( Power Spectrum ( j ) * ( j * df ) ) Σ ( Power Spectrum ( j ) )

    for j = i span 2 , ... , i + span 2

    where

    • i is the peak index
    • Power Spectrum (j) is the power in bin j
    • df is the frequency bin width
    datatype_icon

    estimated power peak

    The estimated power of the peak in the input power spectrum.

    Algorithm for Calculating the estimated power peak

    The following equation computes the estimated power peak:

    estimated power peak = Σ ( Power Spectrum ( j ) ) ENBW

    for j = i span 2 , ... , i + span 2

    where

    • i is the peak index
    • Power Spectrum (j) is the power in bin j
    • ENBW is the equivalent noise bandwidth of the window
    datatype_icon

    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: This product does not support FPGA devices


    Recently Viewed Topics