1. Purpose
This app is used to create and apply an FIR (Finite Impulse Response) digital filter.
2. Installation
Download the FIR Filter.opx file, and then drag and drop it onto the Origin workspace. Then an icon will appear in the Apps gallery panel.
3. Operation
Select a column with the signal data to be filtered from a worksheet, and then click the app icon from the Apps gallery panel. Then the dialog will pop up for creating and applying an FIR filter. Change the settings in the dialog accordingly to design an FIR filter, and when the design done, click OK button to apply this designed FIR filter to the input signal to get the results.
4. Dialog Setting
4.2. Response Type
- Lowpass: Allow low frequency components to pass.
- Highpass: Allow high frequency components to pass.
- Bandpass: Allow frequency components within a specified range to pass.
- Bandstop: Allow frequency components outside a specified range to pass.
4.3. Method
- Least Squares: Design least squares linear-phase FIR filter.
- Window: Design window-based FIR filter.
4.4. Filter Order
Specify an integer value as the filter order. For window-based FIR filter, it allows to use the Kaiser window to calculate the filter order automatically by checking the Minimum checkbox.
4.5. Window
Available windows include: Bartlett, Bartlett-Hanning, Blackman, Blackman-Harris, Bohman, Chebyshev, Flat Top, Gaussian, Hamming, Hanning, Kaiser, Nuttall, Parzen, Rectangle, Taylor, Triangular, and Tukey. It also allows user-defined window by providing Window Data.
4.6. Scale Passband
If checked, the coefficients will be normalized, so that, at the center of the passband, the magnitude response of the filter is 1 (that is 0 dB).
4.7. Frequency Specification
Specify the frequency specification for designing the FIR filter.
- Unit: Specify the unit used to customize the frequency specification.
- Hz: Use Hz as the unit when customize the frequency specification.
- Normalized to (0, 1): Frequency is normalized to the region from 0 to 1. It is calculated by Frequency(Hz)/(SampleFrequency(Hz)/2), where SampleFrequency(Hz)/2 is the Nyquist frequency.
- Sampling Frequency (Fs): Specify the sample frequency of the signal (Unit is Hz). By default (Auto is checked), Origin will detect the sample frequency according to the associated X column (if such column exists).
- Pass, Stop and Cutoff Frequencies: Varies by Response Type, Method and Unit.
4.8. Magnitude Specification
Specify the magnitude specification.
- Weight of Passband and Stopband: Specify weight of passband and stopband. Available for Least Squares method.
- Unit: Specify the unit for customizing passband ripple and stop attenuation. Available for window-based filter with Minimum filter order.
- dB: Use dB as unit of the specified passband ripple and stop attenuation.
- Linear: : The specified passband ripple and stop attenuation is by linear unit.
- Passband Ripple: Specify the passband ripple. Available for window-based filter with Minimum filter order.
- Stop Attenuation: Specify the stopband attenuation. Available for window-based filter with Minimum filter order.
4.9. Forward-Backward Filtering
Perform both forward and backward filtering on the input signal.
4.10. Output Results
- Coefficients: Output the coefficients of the transfer function of the designed filter.
- Output Signal: The output signal after filtering by the designed FIR filter.
5. Preview
- Filter Specification: This preview will be changed according to different dialog settings, so to make it easy to see the filter specification for designing the FIR filter.
- Magnitude and Phase Response: Show the graph of the magnitude and phase response for the current FIR filter design.
- Impulse Response: Show the graph of the impulse response for the current FIR filter design.
- Apply Filter: Show the results after using the designed FIR filter on the original signal. The upper plot shows the original signal and the filtered signal. And the lower plot shows the frequency distribution. It also allows to specify the filtering frequency manually in the lower plot by dragging the rectangle or vertical line.