Study of filter properties for the directional filter bank

There are two possible real FIR implementations for the directional filter bank (DFB), namely a polyphase structure and a ladder structure. Despite the fact that DFB has been applied for various applications such as image denoising and texture classification, no study has been performed in comparing these two structures. In this paper, filter properties such as perfect reconstruction, biorthogonality and orthogonality will be studied for these two structures. It is shown that these properties are related to the structure framework as well as selection of a prototype filter. Besides mathematical analysis, simulations have been carried out to see the effect of finite filter length on filter properties for these two structures.