Short Time DFTヒルベルト変換にもちいられるプロトタイプフィルタの最適化

Abstract

Superior characteristics of the short time DFT Hilbert transformer is yielded through employing ideal proto-type filter of infinite frame number. From practical application of view, it becomes to be important to reduce frame number of this proto-type filter and the processing amount in Short Time DFT Hilbert transformers. Optimization of proto-type filters are discussed in this paper to realize small frame number filters equal to the infinite frame number filter in the functional facilities via both non-linear programming and functional analysis. The proto-type filters are optimized in the meanings of minimizing the ripples both on the pass-and elimination-bands and of getting the sharpness of the mainlobe. Optimized proto-type filters are verified with analyzing output signals through Hilbert transformers, which employ these filters, to yield both exactly unity in amplitude and half π radian in phase-shifting even if shorten frame number filters being employed.