Signal Processing Toolbox

Editing the Filter Using the Pole/Zero Editor

You can edit a designed or imported filter's coefficients by moving, deleting, or adding poles and/or zeros using the Pole/Zero Editor panel. Click the Pole/Zero Editor button in the sidebar or select Pole/Zero Editor from the Edit menu to display this panel.

Poles are shown using x symbols and zeros are shown using o symbols.

Plot mode buttons.   Plot mode buttons are located to the left of the pole/zero plot. Select one of the buttons to change the mode of the pole/zero plot.

The Pole Zero editor has these buttons from left to right: move pole, add pole, add zero, and delete pole or zero.

The following plot parameters and controls are located to the left of the pole/zero plot and below the plot mode buttons.

• Filter gain--factor to compensate for the filter's pole(s) and zero(s) gains
• Coordinates--units (Polar or Rectangular) of the selected pole or zero
• Magnitude--if polar coordinates is selected, magnitude of the selected pole or zero
• Angle--if polar coordinates is selected, angle of selected pole(s) or zero(s)
• Real--if rectangular coordinates is selected, real component of selected pole(s) or zero(s)
• Imaginary--if rectangular coordinates is selected, imaginary component of selected pole or zero
• Section--for multisection filters, number of the current section
• Conjugate--creates a corresponding conjugate pole or zero or automatically selects the conjugate pole or zero if it already exists.
• Auto update--immediately updates the displayed magnitude response when poles or zeros are added, moved, or deleted.

The Pole-zero Editor on the Edit menu has items for selecting multiple poles/zeros, for inverting and mirroring poles/zeros, and for deleting, scaling and rotating poles/zeros.

Items in the lower half of the Edit menu are grayed unless one or more poles or zeros are selected.

Moving one of the zeros on the vertical axis produces the following result:

• The selected zero pair is shown in green.
• When you select one of the zeros from a conjugate pair, the Conjugate check box and the conjugate are automatically selected.
• The Magnitude Response plot updates immediately because Auto update is active.

Displaying the Response in FVTool

Converting the Filter Structure

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