Comparing 2-D recursive and nonrecursive least-square-error approximation filters

Seventy-two 2-D recursive and nonrecursive filters of varying order are designed to approximate, in the least-squares sense, four circularly-symmetric unit-pulse responses, corresponding to four lowpass filters. The approximation error obtained for a given number of filter coefficients is then used as the basis for comparing the efficiency of the designed 2-D recursive and nonrecursive filters.