Further results on 4-fold rotational symmetry in 2-D functions
The presence of various types of symmetries in the frequency responses of a two-dimensional filter function reflects as constraints on its coefficients. The exploitation of these constraints leads to considerable reduction in the design and implementation complexities of two-dimensional filters. In this paper, some new constraints resulting from 4-fold rotational symmetry in frequency responses of two-dimensional filters are derived. The class of McClellan transformations that could be used in the generation of 2-D FIR filters possessing 4-fold rotational symmetry in their frequency responses is also obtained.