Comments on "Minimal multiplier realization of 2-D all-pass digital filters" by K. Manivannan and C. Eswaran
Points out an error in the above paper (see ibid., vol.CAS-35, p.480-482, 1988) and also shows that the realization as such is not valid for filters of order greater than 1. The comments show that the method can be made to work for any order N, provided the delay network is modified by introducing a few more delay elements. >