Finite band approximation for distributed and digital selective linear phase transfer functions

Using the recently derived formula which interpolates to a linear phase response at equidistant frequency intervals in a distributed variable, transfer functions are constructed which exhibit flat amplitude and linear phase characteristics over a finite band. Reciprocal realizations for the implementation in distributed structures are derived, together with a non‐reciprocal version ideally suited for recursive digital filter design. Their superiority over the corresponding maximally flat solutions is also illustrated.