IIR Filter VI

Owning Palette: Advanced IIR Filtering VIs

Requires: Full Development System

Filters the input sequence X using the direct form IIR filter specified by Reverse Coefficients and Forward Coefficients. Wire data to the X input to determine the polymorphic instance to use or manually select the instance.

Details  Example

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

Select an instance IIR Filter (DBL)IIR Filter (CDB)

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IIR Filter (DBL)

	init/cont controls the initialization of the internal states. The default is FALSE. The first time this VI runs or if init/cont is FALSE, LabVIEW initializes the internal states to 0. If init/cont is TRUE, LabVIEW initializes the internal states to the final states from the previous call to this instance of this VI. To process a large data sequence that consists of smaller blocks, set this input to FALSE for the first block and to TRUE for continuous filtering of all remaining blocks.
	X is the input array of samples to filter.
	Reverse Coefficients is the reverse coefficients of the filter design. This VI does not place any restrictions on the coefficient arrays. If both coefficient arrays are empty, the VI performs no filtering and sets Filtered X to the value of X.
	Forward Coefficients is the forward coefficients of the filter design.
	Filtered X is the output array of filtered samples.
	error returns any error or warning from the VI. You can wire error to the Error Cluster From Error Code VI to convert the error code or warning into an error cluster.

IIR Filter (CDB)

	init/cont controls the initialization of the internal states. The default is FALSE. The first time this VI runs or if init/cont is FALSE, LabVIEW initializes the internal states to 0. If init/cont is TRUE, LabVIEW initializes the internal states to the final states from the previous call to this instance of this VI. To process a large data sequence that consists of smaller blocks, set this input to FALSE for the first block and to TRUE for continuous filtering of all remaining blocks.
	X is the input array of samples to filter.
	Reverse Coefficients is the reverse coefficients of the filter design. This VI does not place any restrictions on the coefficient arrays. If both coefficient arrays are empty, the VI performs no filtering and sets Filtered X to the value of X.
	Forward Coefficients is the forward coefficients of the filter design.
	Filtered X is the output array of filtered samples.
	error returns any error or warning from the VI. You can wire error to the Error Cluster From Error Code VI to convert the error code or warning into an error cluster.

IIR Filter Details

The IIR Filter VI obtains the elements of Filtered X using the following equation.

,

where Y is Filtered X, N_b is the number of Forward Coefficients, b_j is Forward Coefficients, N_a is the number of Reverse Coefficients, and a_k is Reverse Coefficients.

Note  You can use the IIR Filter VI to implement the FIR filtering operation by leaving Reverse Coefficients unwired and by wiring the FIR filter coefficients to Forward Coefficients.

Example

Refer to the Zero Phase Filtering VI in the labview\examples\Signal Processing\Filters directory for an example of using the IIR Filter VI.

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