A Moulding Technique for the Design of 2-D Nearly Orthogonal Filter Banks

We propose a two-stage method for designing nonseparable nearly orthogonal 2-D two-channel filter banks. The first stage consists of solving a convex optimization problem, obtained by relaxing the paraunitarity constraint to a bound on the polyphase matrix norm. The solution of the first stage is used as initialization for the second stage standard optimization. The resulting filters have good passband phase linearity and reconstruction error and compare favorably with previous designs.