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Applies a zero phase filter to an input sequence X. The data type you wire to the X input determines the polymorphic instance to use.

Details  Example

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

Select an instance Zero Phase Filter (DBL)Zero Phase Filter (CDB)

Zero Phase 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 a real vector.
	Reverse Coefficients specifies the reverse coefficients of the zero phase filter.
	Forward Coefficients specifies the forward coefficients of the zero phase filter.
	Filtered X returns the filtered signal.
	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.

Zero Phase 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 complex valued input sequence.
	Reverse Coefficients specifies the reverse coefficients of the zero phase filter.
	Forward Coefficients specifies the forward coefficients of the zero phase filter.
	Filtered X returns the filtered signal.
	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.

Zero Phase Filter Details

This VI filters the input sequence X as shown in the following figure:

g_–n is the reverted sequence of g_n. H(z) is an IIR filter whose coefficients are specified by Reverse Coefficients and Forward Coefficients.

You must specify the Reverse Coefficients and Forward Coefficients in direct form. Use the IIR coefficient design VIs on the Advanced IIR Filtering palette to get cascade form IIR filter coefficients. Then use the Cascade to Direct Coefficients VI to convert the resulting IIR Filter Cluster to direct form.

With a zero phase filter, the output sequence Filtered X has no phase distortion. Although the zero phase filter is non-causal, it is useful in offline applications such as filtering a sound file saved on disk.

Example

Refer to the Zero Phase Filtering VI in the labview\examples\analysis\fltrxmpl.llb for an example of using the Zero Phase Filter VI.