Adams Basic Package > Adams View > Adams View > Dialog box - F1 help > A - D > Create Butterworth Filter

Create Butterworth Filter

(Adams PostProcessor)

Curve Edit toolbar → Filter Curve Tool → Right-click Filter Name text box → filter_function → Create → Create from Butterworth Filter
Creates a Butterworth filter to define the coefficients of a transfer function when creating a curve filter function. The first four options in the dialog box are the same as when you are creating a Butterworth filter directly. See Create/Modify Filter Function dialog box help. To generate these options based on Passband and Stopband options, select the Generate Filter Order _ Frequency checkbox.
Learn about Filtering Curve Data.
 
For the option:
Do the following:
Digital/Analog
Select analog or digital filtering.
Filter Type
Select the type of filter:
■Low Pass - Removes frequencies above the cutoff frequency.
■High Pass - Removes frequencies below the cutoff frequency.
■Band Pass - Removes frequencies outside the two cutoff frequencies.
■Band Stop - Removes frequencies between the two cutoff frequencies.
Order
Set how much the filter will have damped the signal at the cutoff frequency, often referred to as how sharp the filter is.
■First-order filter damps 3dB at the cutoff frequency.
■Second-order filter damps 6dB.
■Third-order filter damps 9dB.
Scaled Cutoff Frequency
Set the frequency of cutoff.
■For a digital filter - Determines the cutoff frequency as a ratio of the Nyquist frequency (half the sample frequency). Therefore, for a signal sampled (simulated) with 100 Hz, the Nyquist frequency is 100/2=50Hz. A scaled cutoff frequency=0.3 then has a cutoff frequency=0.3*50=15 Hz.
Note that if the same filter is applied to a signal sampled at 200 Hz, the filter cutoff is at 30 Hz. If you selected Band Pass or Band Stop for Filter Type, you must provide two cutoff frequencies.
■For an analog filter - Enter the cutoff frequency in the current units (rad/s or Hz). If you selected Band Pass or Band Stop for Filter Type, you must provide two cutoff frequencies.
Generate Filter Order _ Frequency
Select to enable more options to define the Butterworth filter, and use those options to define the order and cutoff frequency above.
If you selected Generate Filter Order _ Frequency, the options listed below appear.
Using the notation Passband Corner Frequency=fp and Corner Frequency=fs, the following rules apply for the options below:
■To create a low-pass filter, give one value each for fp and fs, and fp < fs.
■To create a high-pass filter, give one value each for fp and fs, and fp > fs.
■To create a bandpass filter, specify two values each for fp and fs, such that fs1< fp1< fp2 < fs2.
You cannot create a bandstop filter using the options below.
Passband Corner Frequency (Wp) (Hz - for analog)
Enter the frequency where the damping is at least Passband Ripple dB.
Stopband Corner Frequency (Ws) (Hz - for analog)
Enter the frequency outside of which the damping is at least Stopband Attenuation dB.
Passband Ripple (Rp) (Hz - for analog)
Enter the passband ripple.
Stopband Attenuation (Rs) (Hz - for analog)
Enter the stopband attenuation.
Generate Order _ Frequency
Calculates the appropriate order and cutoff frequency (frequencies) based on the values in the lower portion of the dialog box and loads them in the upper portion. It does not transfer them to the Create Filter Function dialog box until you select OK or Apply.