Short Time DFTを用いたマルチチャネルコンパンダの高調波歪みと混変調歪み特性

Abstract

Reducing the spectrum occupancy over radio channel is as well known as important to prevent finite radio resources from exhausting. The syllabic compander provides indispensable function both to improve speech quality and to reduce fading noise in the cases of saving transmission power and of narrowing spectrum occupancy. Detailed analysis of previously reported multi-channel compander is shown with harmonic distortion and intermodulations based on the short time DFT. This compander is realized with three major functions to avoid envelope detectors, which mainly has caused any distortions in companding. All the input signals are analyzed into instantaneous spectrum via a short time DFT analyzer, then the magnitude of each spectrum component is manipulated by multiplying or dividing to yield companded spectrum, the companded signals are finally given by inverse Fourier transforming from the companded spectrum.