DFD Bessel Design VI

	filter type specifies the type of filter that this VI creates. 0 Lowpass (default) 1 Highpass 2 Bandpass 3 Bandstop
	order specifies the digital filter order. The value of order must be greater than zero. The default is 2. If you set filter type to Lowpass or Highpass, the digital filter order you specify must equal the analog prototype filter order. If you set filter type to Bandstop or Bandpass, the digital filter order you specify must be an even number that equals two times the analog prototype filter order. Increasing the value can narrow the transition band.
	high cutoff freq specifies the high cutoff frequency in hertz. The value must be greater than low cutoff freq. The default is 0.45. This VI uses this input for bandpass and bandstop filter designs only. The cutoff frequency specifies the passband, or the region of an approximately linear phase response.
	low cutoff freq specifies the low cutoff frequency in hertz. The default is 0.12. The cutoff frequency specifies the passband, or the region of an approximately linear phase response.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	fs specifies the sampling frequency in hertz. The value must be greater than zero. The default is 1, which is the normalized sampling frequency.
	filter out returns a new filter.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

DFD Bessel Design Details

Bessel filters have maximally flat response in both the passband and the stopband. The phase response in the passband of Bessel filters, which typically is the region of interest, is nearly linear. However, Bessel filters require high-order filters to provide a good approximation of the ideal filter response.

To achieve linear phase response without a Bessel filter, use FIR filter designs or use the DFD Group Delay Compensator VI to compensate the IIR filter group delay.

Examples

Refer to the following VIs for examples of using the DFD Bessel Design VI:

• IIR Filter Design - DFD VI: labview\examples\Digital Filter Design\AALXMPL

   Open example  Browse related examples

• Bessel IIR Filter Design VI: labview\examples\Digital Filter Design\Floating-Point Filters\Conventional

   Open example  Browse related examples