On finite word effects in two-dimensional multirate periodically time-varying filters

Two-dimensional multirate digital filters, that have explicit periodic variations of the filter coefficients, are defined. Linear time-invariant mathematical models are introduced to describe the effect of finite computer wordlength in such systems. Input quantisation, internal product quantisation, and coefficient quantisation are all considered. Direct-form and state-space structures are examined, with examples given to illustrate the theory.