IFDL 4 Filter Designs

With the Igor Filter Design Laboratory you can design lowpass, highpass, bandpass, notch, differentiator, Hilbert, window, and arbitrary Finite Impulse Response (FIR) filters and "analog prototype" Infinite Impulse Response (IIR) filters.

The IFDL panel provides access to most of IFDL’s features.

IIR design GUI

FIR Filter Designs

IFDL 4 can design FIR filters using the following techniques:

For example, the MPR 2 Band Design graph implements either a low pass or high pass filter using the McClellan-Parks-Rabiner ("MPR") equiripple technique:

FIR design GUI

IIR Filter Designs

IFDL 4 can design IIR filters using a bilinear transform of these classical analog filter designs:

IIR design GUI IIR pole-zero plot

IIR filters can be implemented using a Direct Form I or Cascaded Bi-Quad Direct Form II filter:

graph showing gains of each IIR cascade section

Instant Evaluation

IFDL automatically applies the current filter design to ideal or real data you select, whenever you request it or whenever you change a filter design parameter for instant feedback on how the filter will affect the data.

Comparing Filters

IFDL graphically compares two FIR filter’s frequency, impulse, and step responses:

graph showing responses of two different filters overlaid

Applying Filters

You can apply the designed filters in other experiments by importing the saved filter coefficients and combining them with your data.

dialog for selecting data and filter to apply