Zero Phase Filter VI

Owning Palette: Filters VIs

Requires: Full Development System

Applies a zero phase filter to an input sequence X. 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 Zero Phase Filter (DBL)Zero Phase Filter (CDB)Zero Phase Filter (Cascade, DBL)Zero Phase Filter (Cascade, CDB)

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Zero Phase Filter (DBL)

	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)

	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 (Cascade, DBL)

	X is a real input signal.
	IIR Filter Cluster contains the cascaded form of IIR filter coefficients. This cluster is the output from one of the IIR coefficient design VIs: Butterworth Coefficients, Bessel Coefficients, Chebyshev Coefficients, Elliptic Coefficients, or Inv Chebyshev Coefficients. filter structure selects IIR second-order or fourth-order filter stages. 0 IIR 2nd Order 1 IIR 4th Order Reverse Coefficients is the reverse coefficients of the IIR cascade filter. Forward Coefficients is the forward coefficients of the IIR cascade 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 (Cascade, CDB)

	X is a complex valued input signal.
	IIR Filter Cluster contains the cascaded form of IIR filter coefficients. This cluster is the output from one of the IIR coefficient design VIs: Butterworth Coefficients, Bessel Coefficients, Chebyshev Coefficients, Elliptic Coefficients, or Inv Chebyshev Coefficients. filter structure selects IIR second-order or fourth-order filter stages. 0 IIR 2nd Order 1 IIR 4th Order Reverse Coefficients is the reverse coefficients of the IIR cascade filter. Forward Coefficients is the forward coefficients of the IIR cascade 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 illustration:

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\Signal Processing\Filters directory for an example of using the Zero Phase Filter VI.

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