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Equi-Ripple HighPass VI

LabVIEW 2013 Help

Edition Date: June 2013

Part Number: 371361K-01

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Owning Palette: Filters VIs

Requires: Full Development System

Generates a highpass FIR filter with equi-ripple characteristics using the Parks-McClellan algorithm and the # of taps, stop freq, high freq, and sampling freq: fs. The Equi-Ripple HighPass VI then applies a linear-phase, highpass filter to the input sequence X using the Convolution VI to obtain Filtered X. 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.

Equi-Ripple HighPass (DBL)

X is the input signal to filter.
# of taps must be greater than 2. The default is 33. If # of taps is less than or equal to 2, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
Note  The Parks-McClellan algorithm introduces a large error when designing a highpass filter for an even number of taps. To avoid this error, the Equi-Ripple HighPass VI adjusts the number of taps to the next higher odd value if # of taps is even.
stop freq must be greater than zero and observe the Nyquist criterion. The default is 0.2 Hz. If stop freq is less than or equal to zero or does not meet the Nyquist criterion, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
high freq must be greater than stop freq and observe the Nyquist criterion. The default is 0.3 Hz. If high freq is less than or equal to stop freq or does not meet the Nyquist criterion, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
sampling freq: fs is the frequency in Hz at which you want to sample X and must be greater than 0. The default is 1.0 Hz.
Filtered X contains the result of filtering the input sequence X by convolution. This VI calculates the number of elements, k, in Filtered X using the following equation:

k = n + m – 1,

where n is the number of elements in X and m is the number of taps.

This VI also calculates the delay associated with the output sequence using the following equation:

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.

Equi-Ripple HighPass (CDB)

X is the input signal to filter.
# of taps must be greater than 2. The default is 33. If # of taps is less than or equal to 2, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
Note  The Parks-McClellan algorithm introduces a large error when designing a highpass filter for an even number of taps. To avoid this error, the Equi-Ripple HighPass VI adjusts the number of taps to the next higher odd value if # of taps is even.
stop freq must be greater than zero and observe the Nyquist criterion. The default is 0.2 Hz. If stop freq is less than or equal to zero or does not meet the Nyquist criterion, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
high freq must be greater than stop freq and observe the Nyquist criterion. The default is 0.3 Hz. If high freq is less than or equal to stop freq or does not meet the Nyquist criterion, the VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.
sampling freq: fs is the frequency in Hz at which you want to sample X and must be greater than 0. The default is 1.0 Hz.
Filtered X contains the result of filtering the input sequence X by convolution. The number of elements, k, in Filtered X is given by the following equation.

k = n + m – 1,

where n is the number of elements in X and m is the number of taps.

A delay is also associated with the output sequence, as given by the following equation.

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.

Equi-Ripple HighPass Details

The stopband of the filter goes from zero (DC) to the stop freq. The transition band goes from the stop freq to the high freq. The passband goes from the high freq to the Nyquist frequency.

The values for stop freq and high freq must observe the following relationship.

0 < f0 < f1 < 0.5fs

where f0 is stop freq, f1 is high freq, and fs is sampling freq: fs. If you violate any of these conditions, this VI sets Filtered X to an empty array and returns an error through the Parks-McClellan VI.


 

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