Synthesis of delay networks for an analogue computer

The merits and limitations of simulating a time delay by means of active RC networks are considered. The various methods of determining transfer functions which approximate to that of a pure delay, are discussed. Optimum all-pass and low-pass transfer functions based on a minimum-mean-square-error criterion are derived and compared to the Padé functions and equal-ripple envelope delay functions. The relative merits of the low-pass and all-pass approximations are discussed. Some methods of implementing the optimum transfer functions on an analogue computer are described.