Notch Coefficients Express VI

LabVIEW 2018 FPGA Module Help


Edition Date: March 2018
Part Number: 371599P-01
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Owning Palette: Scaling VIs

Requires: FPGA Interface

Generates filter coefficients for the Notch Filter Express VI.

Note  Large changes to inputs during run time cause invalid states and instability in the Notch Filter Express VI. Change the inputs gradually or reset the filter after changing the inputs.
Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
Filter SpecificationsContains the following options:
  • Notch frequency (Hz)—Specifies the center frequency for the notch filter to attenuate.
  • Expected sample rate (S/s)—Specifies the sample rate of the input signal. This Express VI uses the rate you specify to calculate the normalized notch frequency, which is Notch frequency/Expected sample rate.
    Caution  The actual sample rate is specified elsewhere in the FPGA application. If the sample rate changes, you must change the Expected sample rate in this VI. Otherwise, this VI might not behave as expected.
  • Specify quality—Allows you to configure the Q factor of the notch filter.
    • Q factor—Specifies the quality factor of the notch filter. This option is available only when you select Specify quality.
  • Specify bandwidth—Allows you to configure the Notch width (Hz) of the notch filter.
    • Notch width (Hz)—Specifies the 3-dB bandwidth of the filter, which is the frequency range for which the filter attenuates the signal energy by a factor of two or more. This option is available only when you select Specify bandwidth.
ImplementationContains the following options:
  • Number of channels—Specifies the number of channels to process. The number of channels must match the number of channels specified in the configuration dialog box for corresponding filter Express VI.
  • FPGA clock rate (MHz)—Specifies the clock rate at which the compilation tools compile the FPGA VI.
Filter ResponseDisplays the actual magnitude response of the filter.

Block Diagram Inputs

ParameterDescription
notch frequency (Hz)Specifies the center frequency for the notch filter to attenuate. The default is 1000 hertz.
notch width (Hz)Specifies the 3-dB bandwidth of the filter, which is the frequency range for which the filter attenuates the signal energy by a factor of two or more. The default is 200 Hz. This option is available only when you select the Specify bandwidth option.
Q factorSpecifies the quality factor of the notch filter. The default is 5. This option is available only when you select the Specify quality option.
sample rate (S/s)Specifies the sampling rate of the signal in samples per second. The default is 50000 S/s.
error inDescribes error conditions that occur before this node runs.
channel indexSpecifies the index of the channel for the scaled coefficients configuration. This parameter is available only if the Number of channels option is greater than 1.

Block Diagram Outputs

ParameterDescription
scaled coefficientsReturns single-channel filter coefficients to load at run time.

Scaled coefficients is a fixed-size array of 32-bit signed integers. The size of the array depends on the order you specify. If the filter order is one, the array contains two elements. If the filter order is two, the array contains three elements. If the filter order is four, the array contains six elements.

The filter coefficients must correspond to the filter type and order you specify using the Type and Order options in the Notch Filter Express VI. You cannot alter the order or type of the filter at run time.
configurationReturns the scaled coefficients to load at run time for the channel index you specify using the channel index element of this cluster. This parameter is available only when you configure the VI such that Number of channels is greater than one.
error outContains error information. This output provides standard error out functionality.

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