Implementable orthogonal signal projections based on multirate filters

In this paper we explore how to implement realizable orthogonal projection operators for real signals. Using some of the ideas developed in the area of multirate filter banks we find it possible to implement orthogonal projections onto spaces that are approximately bandlimited, using very efficient operators. These represent a considerable improvement over linear shift-invariant approximations, which are neither bandlimited nor exact projections. A main application is for use with the algorithm of projection on convex sets, which is used, for example in image deblurring, bandlimited extrapolation and in reconstruction in oversampled A/D conversion