On adaptors for wave digital filters

The adders and multipliers of a wave digital filter (WDF) can be grouped into n-port building blocks called adaptors. Various aspects concerning the realization of adaptors are discussed. These include the minimization of the number of adders, the replacement of parallel adaptors by series adaptors and vice versa, possibilities for combining ideal transformers with adaptors without requiring inverse multipliers, and the realization of adaptors with arbitrary numbers of ports by means of elementary adaptors.