IIR Filter with I.C. 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. You can use this VI to process blocks of continuous data. This VI is similar to the IIR Filter VI except that you specify the initial conditions for this VI. Wire data to the X input to determine the polymorphic instance to use or manually select the instance.

Details  

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

Select an instance IIR Filter with I.C. (DBL)IIR Filter with I.C. (CDB)

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IIR Filter with I.C. (DBL)

	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.
	Initial X Conditions contains the most recent inputs. The most recent prior input should be the last element in the array. The number of elements in this array should be one less than the number of elements in the Forward Coefficients array.
	Initial Y Conditions contains the most recent outputs. The most recent output should be the last element in the array. The number of elements in this array should be one less than the number of elements in the Reverse Coefficients array.
	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.
	Final X Conditions contains the most recent inputs. You can use Final X Conditions as Initial X Conditions on the next call to this VI.
	Final Y Conditions contains the most recent outputs. You can use Final Y Conditions as Initial Y Conditions on the next call to this VI.

IIR Filter with I.C. (CDB)

	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.
	Initial X Conditions contains the most recent inputs. The most recent prior input should be the last element in the array. The number of elements in this array should be one less than the number of elements in the Forward Coefficients array.
	Initial Y Conditions contains the most recent outputs. The most recent output should be the last element in the array. The number of elements in this array should be one less than the number of elements in the Reverse Coefficients array.
	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.
	Final X Conditions contains the most recent inputs. You can use Final X Conditions as Initial X Conditions on the next call to this VI.
	Final Y Conditions contains the most recent outputs. You can use Final Y Conditions as Initial Y Conditions on the next call to this VI.

IIR Filter with I.C. Details

The IIR Filter with I.C. 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.

The filter initialization uses the following equations.

y_i = y_ic[N_a + i – 1]    for i < 0

x_i = x_ic[N_b + i – 1]    for i < 0,

where y_ic is the array of Initial Y Conditions and x_ic is the array of Initial X Conditions.

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