Moving FFT block
This block calculates a moving fast fourier transform for a selected target input field.
Moving FFT block
Description
The block contains three output ports. The first output port contains the values of the frequencies specified for the selected target field (configured in the block property page). The second output port contains the index for the topmost or highest frequency values contained in the first port. The third output port contains the value(s) of the topmost frequency value(s) in the first port. FFT Frequency values are calculated over a moving time window. The size of the time window is dynamically calculated by the FFT block as a function of the configured output samples and the sampling period as specified by the user. FFT frequency value calculations can be triggered by an external field or calculated on every execute. Each FFT block will calculate FFT frequency values for one target field only.
Moving FFT block
Block Type
Statistical block (Moving window)
Input port
The input port may contain only double type fields and must contain the target field for which FFT frequency values are required.
Output ports
Output
This port will contain the FFT frequency values for the output fields configured in the block property page. Output field values are always of type double.
Top frequencies
This port will contain the indices for the highest FFT frequecy value(s) contained in the Output port. (View the property page and output field names to relate index information to frequency information). This port will always contain integer type fields.
Top values
This port will contain the highest values for the FFT fequency values contained in the Output port. This port will always contain fields of type double.
Runnability
Minimum requirements for runnability on the FFT block:
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Selected input field
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Configured number of Output samples
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Configured sampling period
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Selected Calculation method
NOTE: If the calculation method is set to "On value change" a properly configured trigger must be selected from the connected parameter port.
Parameter port
The parameter port must contain (if connected) fields of type double, integer or string. Fields in the parameter ports are made available in the calculation trigger selection. Should the calculation method be set to "On value change" a field from the parameter must be selected as the calculation trigger. When the field value changes, FFT frequency values in the Output port will be calculated and updated. BAD_QUALITY input samples are ignored for calculation triggers. Calculation will be triggered if and only if the value of the selected field changes from one GOOD_QUALITY sample to the next GOOD_QUALITY sample.
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