A closed form design method for recursive 3-D cone filters

A closed form design method for recursive 3-D cone filters is presented. The filters are realized by concrete passive 3-D wave digital filter (WDF) structures leading to the associated desirable properties of multidimensional WDF. The proposed method is accomplished analytically without the need for time consuming numerical optimization techniques. In contrast to previously reported methods, which are based on cascading 2-D or 3-D fan or wedge shaped filters the proposed method establishes nonseparable transfer functions which offer an excellent approximation to the required circular symmetry