Computer-aided analysis of wave digital filters

Abstract

An original computer-aided analysis package of the Swamy-Thyagarajan wave digital filter structures has been developed, by the authors, on the minicomputer PDP 11/45 GT-44 Graphics System. The package utilizes the chain matrices of the digital two-ports of the Swamy-Thyagarajan wave digital filter structures which are expressed in terms of the coefficient multipliers of the digital two-ports and the Z variable. The elements and values of a doubly terminated LC ladder can be entered on a cathode ray tube display by utilizing the interactive graphics capability of a light pen. The ladder is then transformed into the Swamy-Thyagarajan wave digital filter structures. Port resistances, coefficient multipliers, chain matrices, the coefficients of the digital filter transfer function, transformed lowpass, highpass, bandstop and bandpass filters can be obtained. The package provides numerical values of the amplitude and phase responses, and plots the responses on the cathode ray tube display.