Windowed All Phase DFT Digital Filter
Nini Xu · Journal of Tianjin University Science and Technology · 2005
Based on the architecture of the all phase discrete Fourier transform (APDFT) digital filter, a new type of zero-phase digital filter called the windowed all phase DFT (WAPDFT) digital filter is brought out by windowing the input and/or output data of the DFT/IDFT blocks in the APDFT filter network. The frequency characteristics are improved greatly while the frequency response of the filters still passes or approaches the desired frequency samples. It has much less pass-band and stop-band ripple, and sharp transition. The WAPDFT filter can be implemented with common convolution structure and the frequency domain direct network like the APDFT filter, it can also be realized with a simplified structure. This paper gives the network of the new structure and the associate algorithm. Compared with the traditional frequency sampling structure, this network is not sensitive to finite word length effect. It has real-time self-design function and may constitute a time-variant system. It can be easily integrated into a universal zero-phase digital filter with frequency response and length programmable.