TFA Time Varying Filter VI

LabVIEW 2014 Advanced Signal Processing Toolkit Help

Edition Date: June 2014

Part Number: 372656C-01

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Owning Palette: Time Frequency Transform VIs

Requires: Advanced Signal Processing Toolkit

Performs time-varying filtering on a signal. Wire data to the signal input to determine the polymorphic instance to use or manually select the instance.

Note  This VI does not support the LabVIEW Real-Time Module.

Details  Example

Use the pull-down menu to select an instance of this VI.

TFA Time Varying Filter (Waveform)

signal specifies the input signal.
threshold settings specifies the parameters to process the Gabor coefficients. You can change the front panel values of threshold settings. If open front panel? is TRUE, threshold settings specifies the initial settings for the time-varying filter. If open front panel? is FALSE, this VI uses threshold settings to generate the specifications of the time-varying filter.
threshold specifies the amplitude of the threshold for the Gabor coefficients. This VI sets all the coefficients whose amplitudes are less than the amplitude of the threshold, (Cmax – Cminthreshold, to 0, where Cmax is the maximum amplitude of the Gabor coefficients, and Cmin is the minimum amplitude of the Gabor coefficients.
noise level removes the small particles in the joint time-frequency representation plot. The functionality to remove small particles requires NI Vision. If you do not have NI Vision installed, this VI ignores this input. This VI removes from the joint time-frequency domain all the particles whose areas are smaller than row×column×noise level, where row and column are the row size and the column size of the Gabor coefficients. Refer to the TFA Discrete Gabor Transform VI for information about how the sizes of Gabor coefficients relate to dM (time steps) and N (frequency bins).
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
open front panel? specifies to display the Time Varying Filter dialog box, where you can set the parameters for the time-varying filter and see the results. If open front panel? is FALSE, this VI uses threshold settings to generate the specification for the time-varying filter. The default is TRUE, which means this VI displays the Time Varying Filter dialog box so you can set the parameters for the time-varying filter and see the results.
filtered signal returns the filtered signal.
threshold settings out returns the actual parameters to threshold the Gabor coefficients in this VI.
threshold returns the actual threshold.
noise level returns the actual noise level.
error out contains error information. This output provides standard error out functionality.

TFA Time Varying Filter (Real)

signal specifies the input signal.
threshold settings specifies the parameters to process the Gabor coefficients. You can change the front panel values of threshold settings. If open front panel? is TRUE, threshold settings specifies the initial settings for the time-varying filter. If open front panel? is FALSE, this VI uses threshold settings to generate the specifications of the time-varying filter.
threshold specifies the amplitude of the threshold for the Gabor coefficients. This VI sets all the coefficients whose amplitudes are less than the amplitude of the threshold, (Cmax – Cminthreshold, to 0, where Cmax is the maximum amplitude of the Gabor coefficients, and Cmin is the minimum amplitude of the Gabor coefficients.
noise level removes the small particles in the joint time-frequency representation plot. The functionality to remove small particles requires NI Vision. If you do not have NI Vision installed, this VI ignores this input. This VI removes from the joint time-frequency domain all the particles whose areas are smaller than row×column×noise level, where row and column are the row size and the column size of the Gabor coefficients. Refer to the TFA Discrete Gabor Transform VI for information about how the sizes of Gabor coefficients relate to dM (time steps) and N (frequency bins).
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
open front panel? specifies to display the Time Varying Filter dialog box, where you can set the parameters for the time-varying filter and see the results. If open front panel? is FALSE, this VI uses threshold settings to generate the specification for the time-varying filter. The default is TRUE, which means this VI displays the Time Varying Filter dialog box so you can set the parameters for the time-varying filter and see the results.
filtered signal returns the filtered signal.
threshold settings out returns the actual parameters to threshold the Gabor coefficients in this VI.
threshold returns the actual threshold.
noise level returns the actual noise level.
error out contains error information. This output provides standard error out functionality.

TFA Time Varying Filter (Complex)

signal specifies the input signal.
threshold settings specifies the parameters to process the Gabor coefficients. You can change the front panel values of threshold settings. If open front panel? is TRUE, threshold settings specifies the initial settings for the time-varying filter. If open front panel? is FALSE, this VI uses threshold settings to generate the specifications of the time-varying filter.
threshold specifies the amplitude of the threshold for the Gabor coefficients. This VI sets all the coefficients whose amplitudes are less than the amplitude of the threshold, (Cmax – Cminthreshold, to 0, where Cmax is the maximum amplitude of the Gabor coefficients, and Cmin is the minimum amplitude of the Gabor coefficients.
noise level removes the small particles in the joint time-frequency representation plot. The functionality to remove small particles requires NI Vision. If you do not have NI Vision installed, this VI ignores this input. This VI removes from the joint time-frequency domain all the particles whose areas are smaller than row×column×noise level, where row and column are the row size and the column size of the Gabor coefficients. Refer to the TFA Discrete Gabor Transform VI for information about how the sizes of Gabor coefficients relate to dM (time steps) and N (frequency bins).
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
open front panel? specifies to display the Time Varying Filter dialog box, where you can set the parameters for the time-varying filter and see the results. If open front panel? is FALSE, this VI uses threshold settings to generate the specification for the time-varying filter. The default is TRUE, which means this VI displays the Time Varying Filter dialog box so you can set the parameters for the time-varying filter and see the results.
filtered signal returns the filtered signal.
threshold settings out returns the actual parameters to threshold the Gabor coefficients in this VI.
threshold returns the actual threshold.
noise level returns the actual noise level.
error out contains error information. This output provides standard error out functionality.

TFA Time Varying Filter Details

The time-varying filter is suitable for transient signals whose frequency evolves over time. This VI converts the time-domain signal to the joint time-frequency domain with the Gabor transform, removes noise in the joint time-frequency domain, and then reconstructs the time-domain signal with the Gabor expansion by using the Gabor coefficients after thresholding.

Example

Refer to the Time Varying Filter VI in the labview\examples\Time Frequency Analysis\TFAFunctions directory for an example of using the TFA Time Varying Filter VI.

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