A general-purpose computer program for the design of two-dimensional recursive filters — 2DFil

Abstract

A general-purpose interactive computer program for the design of linear causal shift-invariant two-dimensional recursive filters is presented in terms of its organization and operation. Narrow-band fan filters and circularly symmetric low-pass and high-pass filters for many useful image-processing applications can be designed using this program. The design is by numerical optimization of a guaranteedstable analog transfer function which is derived from a general two-dimensional passive prototype network. Corresponding discrete transfer functions are obtained by the double bilinear transformation. In using the program, selection of one code from a menu of predefined design codes provides the designer with various design features; these include the use of a doubly-terminated network to eliminate erroneous gain spikes, the use of a network particularly suited to circularly symmetric functions, and a facility for designing filters potentially useful for high-speed parallel processing. Design examples of a low-order highly selective fan filter and a circularly symmetric low-pass filter are included.