Filters with real or imaginary transfer functions
E. G. Gilbert, J. Otterman · Electrical Engineering · 1960
SYNTHESIS of real or imaginary transfer functions — that is, the synthesis of filters with even (symmetric) or odd (antisymmetric) impulse responses — has both theoretical interest and practical value. Realization is possible only within a time lag T, and requires a delay element filter with a finite memory of 2T.