Design of signal flow graph (SFG) active filters

A systematic procedure is presented for the design of active filters obtained as operational simulations of LC ladder prototypes. The method is based on the signal-flow graph (SFG) approach, but allows one to obtain the final circuit without ever considering signal-flow graphs. Practical design problems, namely, scaling for maximum dynamic range, stabilizing the reciprocator amplifiers, predistorting the prototype to compensate for the parasitic reactances introduced by reciprocators, eliminating the inherent dc offsets, and tuning are solved and illustrated by examples. Complete design and experimental results are given for a twelfth-order bandpass channel bank filter.