Infinite Impulse Response (IIR) Filters

IIR Forms

• Direct Form I - the literal implementation of the transfer function. Numerator applies to inputs (b coefficient) and denominator applies to outputs (a coefficients).
• Direct Form II - reorganized to minimize delays/operations.
• Cascaded Second-Order Sections Form I - Used to improve numerical stability of the IIR realization. Filter coefficients are broken into groups of 6.
• Cascaded Second-Order Sections Form II - Reorganized to reduce the number of delays.