On orthogonal digital filter structures for 2-D first-order transfer functions

Two-dimensional first-order transfer functions are dealt with, and the necessary and sufficient conditions are given for the corresponding. Roesser state-space model to be orthogonal, i.e., K=W=I, where K and W are the covariance matrix and the unit noise matrix, respectively. Some properties of the orthogonal realization are also given.<
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