Positioning of group delay sections with an LC ladder and the effects of transformations

The problem of group-delay specification and approximation in computer-aided filter design is considered. The author illustrates some of the necessary extensions required to the Z-plane approach to cover the extraction of complex quartets. The extended procedure evaluates the input immittance at a complex frequency, finds the component values for the complex section, and calculates the remaining immittance to a sufficiently good accuracy. The transformation to the bridged-tee form is described.<>