Implement Even and Odd Stacked Frequency Bins in Cascade Non-Maximally Decimated Analysis and Synthesis Filter Banks
fred harris, Elettra Venosa, Xiaofei Chen, Chris Dick · 2018
A variable bandwidth filter is formed by a cascade of non-maximally decimated analysis and synthesis filter banks connected by an adjustable binary mask. The mask selects a subset of baseband output ports from the analysis bank to be merged to a single wider bandwidth super filter by the synthesis filter bank. To form a real symmetric spectral response matching negative and positive frequency channels filters are processed by the synthesis filter bank. Two options, called even and odd channel stacking, place channel centers at even integer multiples or odd integer multiples of fs/(2M). The frequencies of the even stacking set match the center frequencies of the IDFT while the frequencies of the odd stacking set are offset to the midpoints of the even stacked frequencies. The algorithms for the even and odd stacked versions of the polyphaser filters differ in significant ways which makes it difficult to switch between the two versions. In this paper we first review the architectures of the two filter stacking options and then present a new architecture which permits seamless switching between the two stacking modes.