![F1: x_{i+1,j+1} = Q_R[ax_{i+1,j}+bx_{i,j+1}+cx_{i,j}]](/images/tex/10741.gif) and
 and ![F2: x_{i+1,j+1} = Q_R[ax_{i+1,j}]+Q_R[bx_{i,j+1}]](/images/tex/10742.gif) is studied. Here
 is studied. Here  is the rounding operator, and fixed-point arithmetic is used. Sufficient conditions for the stability of
 is the rounding operator, and fixed-point arithmetic is used. Sufficient conditions for the stability of  and necessary and sufficient conditions for the stability of
 and necessary and sufficient conditions for the stability of  are derived. For the more general case of higher order two-dimensional (2-D) digital filters, sufficient conditions for the nonexistence of separable 2-D limit cycles are derived by extending the results of Claasen et al. [1].
 are derived. For the more general case of higher order two-dimensional (2-D) digital filters, sufficient conditions for the nonexistence of separable 2-D limit cycles are derived by extending the results of Claasen et al. [1].