Scattering and immittance type tabular stability tests for 2-D discrete-time systems and their simplification by telepolation

Two recently proposed efficient tabular procedures for testing stability of two-dimensional (2-D) discrete linear shift invariant (LSI) system polynomials are further simplified. The simplification is achieved by telescoping the last 1-D polynomial of the table by interpolation. It also shows that testing stability of a 2-D system amounts to a finite collection of designated 1-D stability tests. The proposed procedures determine the stability of a 2-D polynomial in an apparently unprecedented low count of operations.