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AFT Update Coefficients VI

LabVIEW 2013 Adaptive Filter Toolkit Help

Edition Date: June 2013

Part Number: 372357B-01

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Owning Palette: Adaptive Filters VIs

Requires: Adaptive Filter Toolkit

Updates the coefficients of an adaptive filter point by point. Use this VI with the AFT Filter Signal VI to update the coefficients of an adaptive filter. You must use the least mean squares (LMS) or recursive least squares (RLS) algorithms to create the adaptive filter. Wire data to the e(n) input to determine the polymorphic instance to use or manually select the instance. The data type of the adaptive filter that you wire to the adaptive filter in input must match the instance of the AFT Update Coefficients VI.

Note  Do not use the AFT Update Coefficients VI with the AFT Create FIR Fast Block LMS and AFT Create FIR QR-RLS VIs.

Examples

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

AFT Update Coefficients (Real, PtByPt)

adaptive filter in specifies the adaptive filter that you create.
e(n) specifies the error signal e(n) of the adaptive filter. The error signal is the difference between the input signal d(n) and the output signal y(n). Use the AFT Filter Signal VI to obtain y(n).
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
step size specifies the step size for the adaptive filter. If this value is less than zero, this VI ignores this parameter and uses the step size that you specify when you create the adaptive filter. If this value is zero, this VI processes the input signal without updating the coefficients of the adaptive filter. If this value is greater than zero, this VI uses this value as the step size to update the coefficients of the adaptive filter. The default is –1.
Note  This parameter is valid only if the adaptive filter uses a least mean squares (LMS) algorithm. If the adaptive filter uses the normalized LMS or normalized leaky LMS algorithm, the value must be less than 2.
adaptive filter out returns the adaptive filter in unchanged.
error out contains error information. This output provides standard error out functionality.

AFT Update Coefficients (Complex, PtByPt)

adaptive filter in specifies the adaptive filter that you create.
e(n) specifies the error signal e(n) of the adaptive filter. The error signal is the difference between the input signal d(n) and the output signal y(n) of the adaptive filter. Use the AFT Filter Signal VI to obtain y(n).
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
step size specifies the step size for the adaptive filter. If this value is less than zero, this VI ignores this parameter and uses the step size that you specify when you create the adaptive filter. If this value is zero, this VI processes the input signal without updating the coefficients of the adaptive filter. If this value is greater than zero, this VI uses this value as the step size to update the coefficients of the adaptive filter. The default is –1.
Note  This parameter is valid only if the adaptive filter uses a least mean squares (LMS) algorithm. If the adaptive filter uses the normalized LMS or normalized leaky LMS algorithm, the value must be less than 2.
adaptive filter out returns the adaptive filter in unchanged.
error out contains error information. This output provides standard error out functionality.

Examples

Refer to the following VIs for examples of using the AFT Update Coefficients VI:

  • Adaptive Channel Equalization VI: labview\examples\Adaptive Filters\Applications\Adaptive Channel Equalization
  • Control Coefficients Updating for Adaptive Filter VI: labview\examples\Adaptive Filters\Getting Started

 

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