FIR Filter Design Methods

The LabVIEW Digital Filter Design Toolkit provides the following FIR filter design methods:

  • Kaiser Window
  • Dolph-Chebyshev Window
  • Equi-Ripple

The Kaiser Window method and the Dolph-Chebyshev Window method allows you to get the filter coefficients directly from the analytical equations, so these methods are easier to use than the Equi-Ripple FIR method, which also is known as the Remez design method, but the Equi-Ripple FIR method yields optimal filters and often produces the best results for most FIR filter design problems.

IIR Filter Design Methods

The LabVIEW Digital Filter Design Toolkit provides the following IIR filter design methods:

  • Buttersworth
  • Chebyshev
  • Inverse Chebyshev
  • Elliptic

The following figure illustrates the magnitude responses of a typical lowpass filter designed by the four IIR filter design methods. Each filter has the same numerator and denominator order values:

Figure 5. Variance in the Magnitude Response of a Lowpass Filter Based on the IIR Filter Design Method Used

The following table summarizes the main features of the four IIR-based design methods so you can determine the IIR filter design method to use:

Table 2. Features of the IIR-Based Filter Design Methods
IIR Filter Ripple in Passband? Ripple in Stopband? Transition Bandwidth for a Fixed Order Order for Given Filter Specifications
Butterworth No No Widest Highest
Chebyshev Yes No Narrower Lower
Inverse Chebyshev No Yes Narrower Lower
Elliptic Yes Yes Narrowest Lowest