On 2D proper transfer functions†
John Chiasson, STEPHEN D. BRIERLEY, Stanisław H. Żak, E. Bruce Lee · International Journal of Control · 1982
The idea of column reduction of a 2D polynomial matrix is defined and related to the properness of a transfer function matrix. In particular, for a 2D transfer function matrix H(z 1, z 2) = N(z 1, z 2)D −1(z 1, z 2), some conditions are given on N(z 1, z 2) and D(z 1, z 2) to ensure that H(z 1, z 2) is proper.