Table Of Contents

Filter Design (Inverse f) (G Dataflow)

Last Modified: December 18, 2017

Designs an IIR filter whose magnitude-squared response is inversely proportional to frequency over a specified frequency range. You can use the inverse-f filter to colorize spectrally flat, or white, noise.

Programming Patterns

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

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exponent

Exponent of the desired inverse-f spectral shape. This node designs a digital filter with the desired magnitude-squared response of 1/frequencyexponent.

Default: 1

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low cutoff frequency

Lower frequency edge of the operating frequency range of the filter.

Default: 0.1

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high cutoff frequency

Higher frequency edge of the operating frequency range of the filter.

Default: 100

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order

Number of first order stages of the inverse-f filter.

Increasing order improves the inverse-f spectral shape but requires more computation time during the filter operation.

Default: 5

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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 design sample rate in samples/second.

Default: 1000

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unity gain frequency

Frequency, in radians per second, at which the ideal inverse-f filter response has unity gain.

The actual inverse-f filter is designed to approximate the ideal filter over the frequency range defined by low cutoff frequency, high cutoff frequency, and order. Therefore, the actual gain of the filter at unity gain frequency is near unity only if unity gain frequency is within the design frequency range specified in low cutoff frequency, high cutoff frequency, and order.

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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filter information

Magnitude and phase of the frequency response of the designed inverse-f filter.

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magnitude (dB)

Magnitude of the frequency response of the designed inverse-f filter in dB.

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frequency (Hz)

Frequencies of the frequency response of the designed inverse-f filter in Hz.

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magnitude (dB)

Magnitudes of the frequency response of the designed inverse-f filter in dB.

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phase (deg)

Phase of the frequency response of the designed inverse-f filter in degrees.

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frequency (Hz)

Frequencies of the frequency response of the designed inverse-f filter in Hz.

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phase (deg)

Phases of the frequency response of the designed inverse-f filter in degrees.

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magnitude error

Magnitude of the deviation of the actual inverse-f filter, in decibels, when measured against the ideal inverse-f filter.

The ideal filter has a magnitude-squared response proportional to 1/f exponent over the frequency range specified by low cutoff frequency, high cutoff frequency, and order.

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frequency (Hz)

Frequencies of the magnitude error in Hz.

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magnitude (dB)

Magnitudes of the magnitude error in dB.

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noise bandwidth

Expected noise bandwidth of the designed inverse-f filter.

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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

Web Server: Not supported in VIs that run in a web application


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