Table Of Contents

Filter Design (Bessel) (G Dataflow)

Version:
    Last Modified: March 15, 2017

    Designs an IIR cascade filter as specified by the Bessel filter model.

    Programming Patterns

    To filter a sequence of data, wire the filter output to the Filtering node.

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    filter structure option

    The order of the IIR cascade filter.

    Name Value Description
    IIR 2nd Order 0 Returns IIR second-order filter stages.
    IIR 4th Order 1 Returns IIR fourth-order filter stages.
    Auto Select 10 Returns either IIR second-order or IIR fourth-order filter stages according to filter type. If filter type is Lowpass or Highpass, this node returns IIR second-order filter stages. If filter type is Bandpass or Bandstop, this node returns IIR fourth-order filter stages.

    Default: Auto Select

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    filter type

    The passband of the filter.

    Name Description
    Lowpass

    Uses a lowpass filter.

    Highpass

    Uses a highpass filter.

    Bandpass

    Uses a bandpass filter.

    Bandstop

    Uses a bandstop filter.

    Default: Lowpass

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    low cutoff frequency

    The low cutoff frequency in Hz. This value must observe the Nyquist criterion.

    When filter type is Bandpass or Bandstop, this value must be less than high cutoff frequency.

    Default: 0.125

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    high cutoff frequency

    The high cutoff frequency, in Hz. This value must observe the Nyquist criterion.

    The node places the following restrictions on this parameter according to filter type:

    filter type Restrictions
    Lowpass or Highpass The node ignores this input.
    Bandpass or Bandstop This value must be greater than low cutoff frequency and less than half of sampling frequency.

    Default: 0.45

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    order

    The order of the IIR filter.

    This value must be greater than zero.

    Default: 2

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    sampling frequency

    The sampling frequency, in Hz.

    sampling frequency must be greater than zero. If this input is less than or equal to zero, this node returns an error as well as an empty array for reverse coefficients and forward coefficients.

    Default: 1

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    filter

    Output IIR cascade filter.

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    filter structure

    Structure of the output filter.

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    forward coefficients

    The forward coefficients of the IIR cascade filter.

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    reverse coefficients

    The reverse coefficients of the IIR cascade filter.

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    sampling frequency

    The sampling frequency in Hz.

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: This product does not support FPGA devices


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