18.2.1 The FFT Filters Dialog Box

See Recalculating Analysis Results.

Specifies the input signal. See Specifying Your Input Data.

Specifies the filter type.

• Low Pass: This is an ideal low-pass filter that removes all frequencies above the cut-off frequency while keeping other frequencies unaltered.
• High Pass: This is an ideal high-pass filter that removes all frequencies below the cut-off frequency while keeping other frequencies unaltered.
• Band Pass: This is an ideal band-pass filter that removes all frequencies that are below the lower cutoff frequency or above the upper cutoff frequency while keeping other frequencies unaltered.
• Band Block: This is an ideal band-block filter that removes all frequencies that are between the lower cutoff frequency and the upper cutoff frequency while keeping other frequencies unaltered.
• Threshold: This is a threshold filter that allows only frequency components whose amplitudes are greater than the threshold to pass.
• Low Pass Parabolic: This is a parabolic low-pass filter.

This option is available only when Filter Type is either Band Pass or Band Block.

This option is available only when Filter Type is either Band Pass or Band Block.

This option is available only when Filter Type is either Low Pass or High Pass.

Amplitude threshold. This option is available only when Filter Type is Threshold.

This option is available only when Filter Type is Low Pass Parabolic. All frequencies below this value will be kept unchanged after being filtered.

This option is available only when Filter Type is Low Pass Parabolic. All frequencies above this value will be removed completely.

This option is available only when Filter Type is High Pass, Band Pass or Band Block. If this check box is selected, the DC offset will remain unchanged during the filtering.

Specifies the output. See Output Results.