This text opens up completely new vistas in basic analog and digital IIR filter design—regardless of the technology. By introducing exceptionally elegant and creative mathematical stratagems (e.g., accurate replacement of Jacobi elliptic functions by functions comprising polynomials, square roots, and logarithms), optimization routines carried out with symbolic analysis by Mathematica, and the advanced filter design software of MATLAB, it shows students how to design many types of filters that cannot be designed using conventional techniques. The filter design algorithms can be directly programmed in any language or environment such as Visual BASIC, Visual C, Maple, DERIVE, or MathCAD.