A new class of 2‐D digital filters composed of all‐pass subfilters

This paper proposes a new construction method for 2‐D IIR digital filters with all‐pass subfilters as components. Recently, numerous studies have been made to construct digital filters by combining all‐pass characteristics. This paper is based on the construction by a parallel connection of an all‐pass subfilter and delay element, which can realize approximately the linear phase characteristic. First, the basic design for 1‐D digital filters as well as its properties are described. Then the theory for the 1‐D case is extended to the 2‐D case, and a new construction method for 2‐D digital filters with low‐pass characteristics with circular symmetry is shown. The proposed method features the following. The phase characteristic is approximately linear in the passband. The filter can be realized with a smaller number of multipliers than in the traditional method. The coefficient sensitivity is low.