Theory of discrete time SISO linear (L,M) shift invariant system

We have characterized the discrete time single input single output (SISO) linear (L,M) shift invariant system by a two-dimensional kernel function and a filter bank structure. Based on the characterization, we have investigated the conditions for the stability, the invertibility, the causality and the finite response properties of a discrete time SISO linear (L,M) shift invariant system. The advantages of the analysis is that a linear time varying system can be analyzed and designed through a finite number of one-dimensional kernel functions and linear time invariant (LTI) filters. Hence, it facilitates the analysis and the design of a linear time varying system, such as an L/M rate changer used in digital image processing and digital video processing.