Feed-Forward Syllabic Companderの特性とその最適化

Abstract

The syllabic compander is inevitable in improving speech quality through suppressing such noise as fading over poor radio channel or thermal noise in the transmission facilities. The feed-back loop is previously seemed to play fundamental role in existing companders of improving speech quality. However according to employing these feed-back loops, the companded signals are become to be unstable and to be degraded when such impulsive fading noise being added. The feed-forward syllabic compander (ab. in FF compander) is newly proposed here to successfully discuss elimination of the feed-back loop without any loss of generalities from existing syllabic compander if the root-operator and FIR filter are merely employed in the envelope detector. The FF compander is improved to quickly converge in transient response by shortening the FIR filter length of its envelope detector. The shorter FIR filter is adopted to FF compander, the sever harmonic distortions are introduced. Optimized structure of the FF compander is shown to solve this contradiction in the meanings of deciding the filter length, and to be examined through computer simulations.